This 100% correct that a full exhaust system will work better than open headers. I did this same experiment at the race track by putting a capable cutouts on my headers. When I took the caps off the headers the car slowed down 2/10 of a second in the 1/8. Put the caps back on and the car picked up and ran where it had previously. Glad to see the myth of 1 7/8 headers busted, I had long wondered about that. Thanks Richard.
I'm absolutely thrilled to see you running low rpm tests with exhaust! This is real world driving data. I would love to see all your tests run this way.
Really cool test and probability highlights how camshafts and headers work in conjunction, with headers often reducing the negative effects of extra duration down low, showing more improvement since there is more to "clean up"
I'll be that guy and ask why no results with a crossover pipe or balance pipe? V8s benefit a lot in that scavenging rev range . And do boosted engines benefit?wether power or economy/fuel efficiency. Love the testing Richard. Playing with a 454 and a 250 blower pulled out for a freshen up
From what I've heard the Gains are very minimal, but I've also heard that you lose low end torque with headers lol. so we need Richard to test it haha.
Belt driven power adders and nitrous benefit from headers and crossovers and stuff because they have normal exhaust pulses that still scavenge normally. Turbos, not so much. Having a free flowing system that helps organize exhaust pulses going into the turbo is somewhat beneficial, but too much volume/pipe length pre turbo hurts performance, and anything after the turbo is just an obstruction.
@@Cowboy.underwater thanks not going to mess with the beautiful stainless steel exhaust under the 57 yep fabricated hi flow x pipe in there too looks mad . So just a freshen up for the bb head's bit of bowl work, new total seal ring's
I was asking myself what size header do I need for my 402 and I just knew you had already tested it and made a video about it. 1 3/4 will be my path forward after I refill my argon.
Now let’s see 1-3/4” vs 1-7/8” vs 2” on a bigger cube motor say a 6.2 ls. I was not expecting these results but then again that’s why I watch your videos to see real world testing. So many people get wrapped up in peak power but under the curve is what matters.
I'd really love to see a taper tube header from 1.75in to 1in at the collector. I know on rotaries it makes a huge difference. Rule of thumb I was always told was 1inch = 100hp of flow. Don't see many 800hp na v8s lol
Remember a 1 7/8 header with a 3 inch exhaust and X pipe into simular mufflers may give you the same or even better results than the 1 3/4 did in this test I'm pretty sure it would help with low speed torque
NO YOU CANT !!!!!.........love this no nonsense in your face type comparisons. keep up the great videos, i like when you do these types without making any internal mods, takes all of the "YEAH BUTS" outta the comments !!!
I wish he would try more Tri-Y setups. These are designed for mid-range 2,500 - 5,500 where all of this testing is being done. Another I have not seen here anywhere is Megaphone type collector setups.
Fascinating. Wish I got paid to do header R&D. Pretty sure with enough fabricating, you could erase most of those mid rpm dips. Little bigger here, little smaller there.... Header setups would be exclusive to the engine setup though lol
Just in time. I've been surfing the web for info on which one of these headers would benefit my lc9 on my truck. I'm running beehive springs, a CompCams camshaft (dur. 214/228 lift .559/.571 lsa 114 ), and 799 ported heads. Thank you so much Richard. With this info i will go with 1 3/4 and magnaflow muffler with a beside cut through exhaust!! Especially knowing that this test was done on a bored out 5.3, which is my plan for the future. I really thought i would miss out if i didn't go with 1 7/8, but for a offroad truck, i'd much rather have low end torque than high end RPM. Thanks again Richard!
If your running a 3000-5000 stall converter the reason for it is so your engine when at full throttle doesn't spend much time from idle to where the stall converter starts to catch so more torque below that say idle to 3000 would benefit street cruising but not so much full throttle now a heavy truck or SUV with a stock stall converter would benefit greatly with more torque from idle to 3000rpm
Looks like I chose the right size for a street 6.0 in a heavy car with a not yet installed 217/225 cam, 1 3/4 tri-y's should do good Thank You Richard Holdener !!!
Thx, I just figured primary size for a 660cid @ 5700rpm power, to be 2.125. A 572cid 6800rpm piece. That's what I want in a heavy SUV, making crazy power.
Well this is good knowledge because some of us with LS7s have a clearance issue with 2” as opposed to 1-7/8” . I’ve always read guys will lean towards 2” headers but rarely speak of the collector length on the LS7s.
Ahhh, the perfect example of exhaust pulse frequency dynamics. There is a bunch to learn on this subject. Quite the bit of information on SpeedTalk about this. I find it interesting that everyone wants to get air in, but then just leave it to chance to get air out. A well designed exhaust system lets you have both torque and horsepower. It is of my opinion that torque is the more valuable of the two.
@Foghorn Leghorn, in my case, a tow vehicle, it is everything. I need grunt down low. My cattle get scared if I'm using all the HP to haul ass. But, they are well fed, so I need torque to move them.
@@harperjmichael Not sure how that would be remotely relevant, NASCAR stuff is designed to rarely go below 7000rpm - above what 98% of his tests peak at.
Torque is of no value for other purposes than engine development and finding out what forces different parts might experience (pistons, rods, axels, tires etc). The vehicles movement, no matter if it's acceleration or a steady speed will always be (average) horsepower, as that's the unit that includes time. But sure, on the dyno you would be more inclined to look at torque during tests of something like headers, as that will tell you the amount you combust on a single cycle (vs hp that let you look at the amount combusted over a certain time). :)
I am more interested to see this test with a 600-650+ hp engine , to see the difference between 1 3/4" and 1 7/8" headers . 450-500 HP just isn't moving enough air for 1 7/8" headers. Thank you sir.
I’ve been waiting for 1 7/8 to get back in stock based on some tests on Engine Masters (not LS) but good to know I can go 1 3/4 with an LS swap and put the $100+ in savings elsewhere in the build. Thank you for the valuable data!
Hi , Seems its all about cams and cubic inches. A good strong street cam on BB 427 can use either 1 7/8 or upto 2 inch and still make power . Need to try on a N/A stroked LS or Sbc at 400 cu. inches . Thats an interesting test. Do the header calcs and 400cu.in is the minimum u would use 1 7/8 . With a strong street cam the requirement is somewhere between 1 3/4 and 1 7/8 tubes .
Richard, my man. Can you do a test on the BTR torque cam? In either a 5.3 or 6L that would be cool to see. I want a better low speed cam in my 2500hd without the chop or need for a looser stall. Maybe even some other cams that can be classified as “stealthy daily driver cams” not everyone wants the “chop chop”
G'day Richard. Thanks for another great video, but your results are not a great surprise to me. I learned a long time ago that dips in an engine's torque curve are a result of a bad exhaust for the RPM range of the dip. This issue is more common with 2-stroke motorcycles than 4-stroke cars & bikes, and much more common on with aftermarket products than with factory products. Whilst the original exhaust system on a motorcycle prevents the engine from making its peak power, compared to an aftermarket system, the original system gives a smoother torque curve. Obviously the manufacturer has the opportunity & ability to test & refine an exhaust system, & they use that to create a well rounded system - from airbox to exhaust tip. However, I do have a few questions for you. Have you considered trying a step design, say from 1 1/2"-1 3/4"-1 7/8"? Also, have you ever tried a cross-over design, where the outer 2 cylinders of 1 bank are collected with the inner 2 cylinders from the opposite bank? Finally, are the 1 7/8" extractors built with more anti-reversion than the 1 3/4" extractors? Once again, thanks for a great video - I enjoy watching shows that encourage thought. Andrew
Motorcycles quite simply cannot be compared to cars in regards to exhaust, because a factory exhaust on a motorcycle IS a header. There aren't the packaging constraints like there are under a car, and motorcycles aren't treated as much of appliances to the manufacturers as passenger cars are to their respectful manufacturers so performance is first and foremost on the agenda.
Hi Richard, I love the videos and keep them coming! I think it's great that with this round of testing, we see that if you have a full exhaust plus headers, that this will positively improve power and torque production at a lower rpm. I wonder if this is because the camshaft manufacturers do their cam grind testing with full exhausts?
Nice vid.. I'm sure there's going to be way to many bad replys My chevy 2 with a 385 ci small block with hooker fenderwell headers only changed a 1/10 of secoond in my 60 times. And that only from weight of exhaust. Still pull front wheel off the ground. Vs open headers
I wish I would have watched this video before buying my headers. I bought 17/8" headers and probably should of got the 13/4"s since my car will see alot more street miles then passes at the track. The 1/34" headers probably fit a little better also.
I think the size difference is very situational and dependant on heads flow and the operating range. i.e. stock engine vs blueprinted. My head porter runs 2in+ headers on his 416+ strokers running out to 7600-8000rpm high compression builds. That is what he recommends
@@richardholdener1727 Hoping to hear back. Do you have an explanation for the up tick in below 2200rpm for the 1 7/8 headers? Below 2200rpm is was higher then all the 1 3/4 runs. Wondering what the results would be for 1000-2200rpms Range as i have a c5 corvette and the gearing really utilizes sub 2k rpms alot on the highways
It would be really interesting to quantify the effect of a cat, especially if we could see it on a couple of engines, like NA making 450ish and an FI making 600-700ish.
So fat what I'm getting is 1 3/4 header with a electric cutout so you can go from open free flowing for higher rpm loudness to daily driving and good down low response with it closed. I can def tell a diff just driving around in my t56 4th gen fbody with cut out closed down low.
Richard I spend way too much time watching these videos 😃 keep em coming. Also have you done a comparison for LS/LT engines on equal length headers vs non-equal length? I know there is a sound change but is there a performance benefit on one vs the other?
Very interesting, I didn't think the 1-3/4 would gain anywhere in the powerband. I'm curious what would happen with a larger displacement and a more aggressive cam revving to 7000 or higher.
Hi Richard I was wondering if you’ll be able to do more back to back testing on 8 into 1 headers, 180 degree headers, and long tube tri y headers similar to what nascar would use. Comparing them to what most people use 4 into 1 headers. Love all the videos you do cheers
Id bet a 2 3/4 collector extension would really bump up that lower speed torque getting its acceloration up better . Especially if this was a 4.8 tested . Torque is king getting that jump and it takes Alot more hp to run that down !!! Towing youll definately feel it !!!
Mark let me know what you think: Hey guys I am doing a efi 331 stroker just a nice weekend street car only, no track. My builder suggests that I do a 1 1/2 inch header and the rest of the combo will be an edelbrock performer rpm 2 intake, Brodix 20 degree 171 cc head, cam around .525 lift 108 lobe separation (that could change and be slightly larger), 70 mm tb, 80 mm maf, dyno tuned with 42 lb injectors. I can find 1 5/8 headers or there are more options anyway but have found the 1 1/2's in Headman as I looked briefly. Just curious as to your thoughts on the 1/4" making a difference either way positively or negatively for what I'm doing with the car. I'm going to expect for a minimum of around 350 rwhp. Thanks
@@dennisrobinson8008 let me know what you think as well: Hey guys I am doing a efi 331 stroker just a nice weekend street car only, no track. My builder suggests that I do a 1 1/2 inch header and the rest of the combo will be an edelbrock performer rpm 2 intake, Brodix 20 degree 171 cc head, cam around .525 lift 108 lobe separation (that could change and be slightly larger), 70 mm tb, 80 mm maf, dyno tuned with 42 lb injectors. I can find 1 5/8 headers or there are more options anyway but have found the 1 1/2's in Headman as I looked briefly. Just curious as to your thoughts on the 1/4" making a difference either way positively or negatively for what I'm doing with the car. I'm going to expect for a minimum of around 350 rwhp. Thanks
I spent a few days reading the views of Calvin Elston on how he does headers and exhaust. Very interesting stuff and a bit unusual to what most might think. Would be an interesting test to see one of his system. But kinda impossible since theyd be custom made for the heads and engine..
@@motorosso3349 Yes that and the head-to-header flange transition. He (Calvin) says the first part of the header is as important as the last part of the intake runner and that the trnsition from the port to the header is very critical. Correctly designed stepped headers seem like a godd idea also. The thing that might surprise most is that he use smaller size on everything than what is otherwise used. He suggest people use the Burns Stainless calculations for the overall dimensions. Its all up on Speed-Talk forum.
@@magnusdanielsson2749 Yes, using the smallest diameter without hurting HP is the way to go as it keeps the gas speed up. I agree on the Burns Stainless calculation for header dimensions.
Is the gain subject to displacement. Will a 4.8 ls or ford 4.6 have similar gains? Or even say an Audi 4.0 V8. I’m sure it’s a factor of many different variables and displacement is one of them. Another great video
@@richardholdener1727 I’m slow so when we add new data and the colors change I’m looking around to take it in while trying to listen to you is all 😄 like if one setup was red on one layout and you add another data file, the color changes from red to something else.
Would you have any content between the 1/34 and 1/78 longtube headers on a 2017 Gen 2 Ford Mustang Cayote engine, with just a 114mm cold air kit . Thanks for the awesome test always.😎💪🇨🇦
With both header diameters bigger than what is needed from both configurations, maybe a set of 1 5/8" diameters would of made things more obvious how to choose header size?
Great video as usual. I feel this particular video would be more relevant in the 2002 era where guys were putting bolt ons on their F bodys and vetts, but considering headers. So I can see the little change in power vs these 2 header sizes at this lever/rpm range This is 2022 and most guys using LS engines for power are wanting to make some big numbers. Im talking NA, N2O, Boosted. I would love to see you do a comparison of say a N/A (6.2 based) Rec head, 416ci , 11.5:1, 650hp, 7000rpm power peak with these 2 header sizes. Let me know. Thanks for your time and effort in all your videos!
What are your thoughts about the 2-in headers for a 5.3 l ? I saw that these were offered by speed engineering for the 5.3 l. In your opinion, are these worth buying?
This is what I tell everyone that’s under 700 hp to get 1 3/4 headers. 1 7/8 headers limit your plug wire selection because they tend to burn certain brands.
Not with the stock camshaft do Under the same circumstances with the exhaust was it tested with the same headers with the same collector extension? I know the test was done to see the difference between these two camshaft but what they saying modifications help the stock camshaft possibly even more and it would outperform the aftermarket camshafts in the RPM ranges that it does. So down around that 2000rpm Mark would it gain torque at the same places as the Chuck Norris cam in the sloppy cam
Hey guys I am doing a efi 331 stroker just a nice weekend street car only, no track. My builder suggests that I do a 1 1/2 inch header and the rest of the combo will be an edelbrock performer rpm 2 intake, Brodix 20 degree 171 cc head, cam around .525 lift 108 lobe separation (that could change and be slightly larger), 70 mm tb, 80 mm maf, dyno tuned with 42 lb injectors. I can find 1 5/8 headers or there are more options anyway but have found the 1 1/2's in Headman as I looked briefly. Just curious as to your thoughts on the 1/4" making a difference either way positively or negatively for what I'm doing with the car. I'm going to expect for a minimum of around 350 rwhp. Thanks
@@richardholdener1727 definitely not using 1 3/4 with my combo and for what I want to do. Why would you say not 1 1/2? Do you have any personal experience with them or know of anyone who has with a similiar combo? I have 1 5/8 LT's on my 302 now with performer 2, TF 170, the same cam mentioned above ( I'm sure he'll grind a little bigger for the 331), 70 tb, 75 maf, x pipe, pypes bomb free flowing catback, 24 lb'ers, and the car is tuned making around 286 rwhp. I previously had shorties with the same combo and flowmasters with an X. When I put the engine in the 94 with that current combo it seemed I lost some down low going from same size shorties to Lt's. I think had I had 1 1/2's on the 302 setup it would definitely feel more torquy down low for sure. With the 331 from my builder's opionion and I'll have to have another convo with him while the engine is being done, but he initially said 1 1/2. I do want to ask him overall why he would say those over the 1 5/8. He builds dirt cars in Tx and dude is like a mad scientist in a lab when he talks about building an engine and the combustion side of things as well as the intake side. I just realized you look like the guy from the video lol so you should know what you are talking about too
Can you do a 4.0 jeep h.o., renix, amc, stroker. Ive had a few and have always wanted to build one but there are no real informational on what and no test so dont know which way would be the best to go.
At the moment i have a 4.0 with a . 030 over bore with a . 060 crack and a . 030 cam ported and decked h.o.head and intake, but stock h.o. ex.manifold. thing is a deffently drives different then a stock 4.0.
I have a 5.3 with 1 7/8 speed engineering headers. The collectors are 3". I am going to be running a 2.5" exhaust. Should I go right to 2.5 at the collector or run it a few feet before reducing it. Thanks for opinions!
Okay. Cool. So now my questions is which of the 2 sound better? I like the idea of 1 3/4” headers in my Tahoe but what about the sound. How does it affect the sound
I wish the testing was done on a specific 2004 5.7 LS1 aluminum that is an LS1 53 cast iron turned into a 57 and you did pick up power by going with the 1 inch 3/4 but a lot of us now have to run a high-flow cat high flow cat has some kind of restriction if you haven't punched it out I wonder what the difference would have been between these exhaust test with an added high flow cat for some of us do have on our modded cars for stickers so what I'm basically saying is inch and 3/4 flows plenty in the beginning that's why you saw the increase with them down low now put a restriction on that flow and you might want the one in in 1 inch and 7/8 header Yes sounds like a dumb scenario but exhaust flow just liking this video has to do with numbers how someone runs this setup but throws a high-flow cat numbers are going to be a little different right... so this is a test with no cat and no Muffler
@Richard Holdener I understand that wave Scavenging is where the powers at but at the same time.. so ain't flow and I know Richard that you know a lot more than I ever will..lol.. you've been planning this for a long time.. so now all that matters an exhaust is the Scavenging.. so putting on a resonator and a Cadillac converter after will make no difference on power I figured adding a high-flow cat would squeeze some numbers off your chart.... I did notice my comment is kind of hard to read up above LOL... sorry about that
What I meant to say was.. after you do your test on your headers Etc and get your HP numbers if you add a set of high-flow cats won't the numbers change from a restriction another words adding the high-flow cats to the test you just did ..wont it bring the numbers down.. I always thought more restriction on the exhaust less flow which meant less flow less air into engine less air out
Would it be accurate to say that scavenging was being affected because of the resonance pulse changing with size and length of the exhaust? BTW I'm looking forward to the 2.2 turbo colab with DV
Back in the day I had a 70 as big block nova. I built a 427 ,about 600 crank. I had hooker super competition 2 18th headers on it. I hit an obstinate in the road and smashed the right header. I put hooker competition 1 78th headers on it and lost noticable power. I think the tube size needed correlates with the amount of ex the engine is making.
@@I_like_turtles_67 no I never dynoed the motor. It had closed chamber oval port heads, with 2.19 and 1.88 valves. The car had 3.73 gears a 4000 stall converter with a manual valve body. I would hit high gear at around 100,and it would do the wild thing. I prefer the 427 to the 454. I run a n ly6 now. Ls engines make cheap power, but so do big block Chevys.they make the cars nose heavy
Are those 1 3/4 QuickTime performance headers? I remember back in he day they were known for having higher torque at low rpms compared to others headers. They were due to the merge collector. That's why I ran those on my ls1.
@@richardholdener1727 I figured they were QTP by the tag being welded to the header. I had done some research and showed up to 35 ft pounds of torque around the 2500 rpm range vs other headers. Thanks Richard awesome work.
Can you run a test with whatever engine you can where you test different pipe lengths after the collectors? Put like a 5ft length of whatever diameter seems to suite and keep cutting a few inches off after each pull to see at what point the corresponding pipe length helps and then starts to hurt scavenging. I'm wondering how accurate my text books were at tech school
@@andrewmontgomery1763 id like to see the results, I know based on sheer volume from displacement, rpm, and other factors it will vary drastically. I know there's a ton of things at play. It would be cool to different displacements from 1 liter up to 10+liters
How is this affected by boost, as in a centrifugal supercharged application? Is the 1-3/4" still fairly equal? Is the 1-7/8" preferred at higher HP levels above 600?
@@richardholdener1727 thank you for your response. I'm targeting north of 750whp on a Dart 363, and finding 1 3/4" headers with a 3" collector has been a real chore. Seems that 1 7/8" is becoming the norm.
Have you done any testing with the gm inline 5cyl? The 4200s cousins brother, I'm curious to know how it would hold up(boost/nitrous) and knowing since it's a shorter package than the 4200 what percentage gains/loses does the 1 extra cylinder bring to the table
@@richardholdener1727 just curious, I have a h3 laying abandoned at our shop. Still runs, frame rotted out and customer doesn't want it... Maybe I'll pull the engine and build it and see what it will do, just wish I had access to an engine dyno...
@@Brother2Jis_27s4 I've wondered about the 2.9 I4 version of the Atlas. It's kinda anemic in its application but it's a pretty big inch I4 with a nice head, I think it could be a solid performer in certain cases.
@@DrewLSsix itd be cool to line the whole family of them up and do a side by side by side... See if going from 4cyl to 6 gives a proportionate increases in power as you add cylinders
The correct header diameter is 115% of the area of the exhaust valve(s). This is a fixed formula that hasn't changed in dog's years. You don't want the headers to be too large, because then you slow down the exhaust too much, harming your scavenging.
Any idea of the max temperature difference between the 2 headers with mufflers? Trying to keep under hood temps down thinking 1-7/8 might help even though I would prefer the low end torque of the 1-3/4
I learned more in 2 weeks watching your old videos than i did watching power block tv. Great work again man
This 100% correct that a full exhaust system will work better than open headers. I did this same experiment at the race track by putting a capable cutouts on my headers. When I took the caps off the headers the car slowed down 2/10 of a second in the 1/8. Put the caps back on and the car picked up and ran where it had previously. Glad to see the myth of 1 7/8 headers busted, I had long wondered about that. Thanks Richard.
I'm absolutely thrilled to see you running low rpm tests with exhaust! This is real world driving data. I would love to see all your tests run this way.
Would have liked to see the 1 7/8” headers with a “ full exhaust” also keep the dyno runs the same color it’s confusing lol
Really cool test and probability highlights how camshafts and headers work in conjunction, with headers often reducing the negative effects of extra duration down low, showing more improvement since there is more to "clean up"
Head bang with the intro is an absolute must
These tests are priceless, I'd love to see you do a comparison of collector styles possibly including a tri-Y style.
Richard's Mustang 5.0 dyno tests book is literally the bible of the fox body Mustang enthusiast. Absolutely awesome!
thnx
I'll be that guy and ask why no results with a crossover pipe or balance pipe? V8s benefit a lot in that scavenging rev range . And do boosted engines benefit?wether power or economy/fuel efficiency. Love the testing Richard. Playing with a 454 and a 250 blower pulled out for a freshen up
From what I've heard the Gains are very minimal, but I've also heard that you lose low end torque with headers lol. so we need Richard to test it haha.
Belt driven power adders and nitrous benefit from headers and crossovers and stuff because they have normal exhaust pulses that still scavenge normally. Turbos, not so much. Having a free flowing system that helps organize exhaust pulses going into the turbo is somewhat beneficial, but too much volume/pipe length pre turbo hurts performance, and anything after the turbo is just an obstruction.
@@Cowboy.underwater thanks not going to mess with the beautiful stainless steel exhaust under the 57 yep fabricated hi flow x pipe in there too looks mad . So just a freshen up for the bb head's bit of bowl work, new total seal ring's
Cats probably change things up is say.
@@timothythomas1737 HAHAHA don't run cats just dogs hot dogs!!sorry couldn't resist lol but yep they do
I was asking myself what size header do I need for my 402 and I just knew you had already tested it and made a video about it. 1 3/4 will be my path forward after I refill my argon.
Now let’s see 1-3/4” vs 1-7/8” vs 2” on a bigger cube motor say a 6.2 ls. I was not expecting these results but then again that’s why I watch your videos to see real world testing. So many people get wrapped up in peak power but under the curve is what matters.
I'd really love to see a taper tube header from 1.75in to 1in at the collector. I know on rotaries it makes a huge difference. Rule of thumb I was always told was 1inch = 100hp of flow. Don't see many 800hp na v8s lol
Throw on 1 5/8” too, may as well test the limits.
Remember a 1 7/8 header with a 3 inch exhaust and X pipe into simular mufflers may give you the same or even better results than the 1 3/4 did in this test I'm pretty sure it would help with low speed torque
I know you want the bigger header-it's not needed
I'm regretting getting 1-7/8 for my 6.5 stroker now. Guess I'll have to try and sell them and hope whoever buys them hasn't seen this video....
NO YOU CANT !!!!!.........love this no nonsense in your face type comparisons. keep up the great videos, i like when you do these types without making any internal mods, takes all of the "YEAH BUTS" outta the comments !!!
I wish he would try more Tri-Y setups. These are designed for mid-range 2,500 - 5,500 where all of this testing is being done. Another I have not seen here anywhere is Megaphone type collector setups.
Fascinating. Wish I got paid to do header R&D. Pretty sure with enough fabricating, you could erase most of those mid rpm dips. Little bigger here, little smaller there.... Header setups would be exclusive to the engine setup though lol
Just in time. I've been surfing the web for info on which one of these headers would benefit my lc9 on my truck. I'm running beehive springs, a CompCams camshaft (dur. 214/228 lift .559/.571 lsa 114 ), and 799 ported heads. Thank you so much Richard. With this info i will go with 1 3/4 and magnaflow muffler with a beside cut through exhaust!! Especially knowing that this test was done on a bored out 5.3, which is my plan for the future. I really thought i would miss out if i didn't go with 1 7/8, but for a offroad truck, i'd much rather have low end torque than high end RPM. Thanks again Richard!
Love your comparisons. They get right to the point.
If your running a 3000-5000 stall converter the reason for it is so your engine when at full throttle doesn't spend much time from idle to where the stall converter starts to catch so more torque below that say idle to 3000 would benefit street cruising but not so much full throttle now a heavy truck or SUV with a stock stall converter would benefit greatly with more torque from idle to 3000rpm
Looks like I chose the right size for a street 6.0 in a heavy car with a not yet installed 217/225 cam, 1 3/4 tri-y's should do good
Thank You Richard Holdener !!!
Tri Ys?
@@richardholdener1727 Yes
@@richardholdener1727 What do you think of them ?
Thx, I just figured primary size for a 660cid @ 5700rpm power, to be 2.125. A 572cid 6800rpm piece. That's what I want in a heavy SUV, making crazy power.
Well this is good knowledge because some of us with LS7s have a clearance issue with 2” as opposed to 1-7/8” . I’ve always read guys will lean towards 2” headers but rarely speak of the collector length on the LS7s.
So much great data! Thanks Richard for the awesome videos.
Big if you need them. Just like intake, peak power increases from exhaust will only go as far as the engine requires.
that's what it's all about, great work. you worked hard for that info, thank you
Ahhh, the perfect example of exhaust pulse frequency dynamics. There is a bunch to learn on this subject. Quite the bit of information on SpeedTalk about this. I find it interesting that everyone wants to get air in, but then just leave it to chance to get air out. A well designed exhaust system lets you have both torque and horsepower. It is of my opinion that torque is the more valuable of the two.
Perhaps Richard could fab up some NASCAR style headers and boom tubes to see if there's still an advantage to be made.
@Foghorn Leghorn, in my case, a tow vehicle, it is everything. I need grunt down low. My cattle get scared if I'm using all the HP to haul ass. But, they are well fed, so I need torque to move them.
@@harperjmichael Not sure how that would be remotely relevant, NASCAR stuff is designed to rarely go below 7000rpm - above what 98% of his tests peak at.
Torque is of no value for other purposes than engine development and finding out what forces different parts might experience (pistons, rods, axels, tires etc). The vehicles movement, no matter if it's acceleration or a steady speed will always be (average) horsepower, as that's the unit that includes time.
But sure, on the dyno you would be more inclined to look at torque during tests of something like headers, as that will tell you the amount you combust on a single cycle (vs hp that let you look at the amount combusted over a certain time). :)
I am more interested to see this test with a 600-650+ hp engine , to see the difference between 1 3/4" and 1 7/8" headers . 450-500 HP just isn't moving enough air for 1 7/8" headers. Thank you sir.
I’m with you!
100%
That into is just so awesome. 😎
Congratulations... I belive you found the origin of the back pressure myth!!
Can you also do the same with 2” headers ? Thank you. You’re probably the best who makes videos comparing stuffs.
no need for 2-inch headers on most LS motors
@ Thank you!! 🙏🏻
It would be very interesting to see how the stock cam responded to the exhaust changes. Apples to apples.
agreed
Best channel on YT.
I’ve been waiting for 1 7/8 to get back in stock based on some tests on Engine Masters (not LS) but good to know I can go 1 3/4 with an LS swap and put the $100+ in savings elsewhere in the build. Thank you for the valuable data!
There is a good build in Australia on a Holden Commodore ss with an l77, similar results but backed up on the drag strip as a gain with smaller
Hi , Seems its all about cams and cubic inches. A good strong street cam on BB 427 can use either 1 7/8 or upto 2 inch and still make power . Need to try on a N/A stroked LS or Sbc at 400 cu. inches . Thats an interesting test.
Do the header calcs and 400cu.in is the minimum u would use 1 7/8 . With a strong street cam the requirement is somewhere between 1 3/4 and 1 7/8 tubes .
Richard, my man. Can you do a test on the BTR torque cam? In either a 5.3 or 6L that would be cool to see. I want a better low speed cam in my 2500hd without the chop or need for a looser stall. Maybe even some other cams that can be classified as “stealthy daily driver cams” not everyone wants the “chop chop”
THE BTR TORQUE CAM WAS TESTED IN THE TRUCK NORRIS VS SLOPPY BEST CAM VIDEO
The curves converge at 3000 rpm. If you could raise the values at 3000, you’ve found more power.
Great stuff.
G'day Richard. Thanks for another great video, but your results are not a great surprise to me.
I learned a long time ago that dips in an engine's torque curve are a result of a bad exhaust for the RPM range of the dip. This issue is more common with 2-stroke motorcycles than 4-stroke cars & bikes, and much more common on with aftermarket products than with factory products. Whilst the original exhaust system on a motorcycle prevents the engine from making its peak power, compared to an aftermarket system, the original system gives a smoother torque curve. Obviously the manufacturer has the opportunity & ability to test & refine an exhaust system, & they use that to create a well rounded system - from airbox to exhaust tip.
However, I do have a few questions for you. Have you considered trying a step design, say from 1 1/2"-1 3/4"-1 7/8"? Also, have you ever tried a cross-over design, where the outer 2 cylinders of 1 bank are collected with the inner 2 cylinders from the opposite bank? Finally, are the 1 7/8" extractors built with more anti-reversion than the 1 3/4" extractors?
Once again, thanks for a great video - I enjoy watching shows that encourage thought.
Andrew
Motorcycles quite simply cannot be compared to cars in regards to exhaust, because a factory exhaust on a motorcycle IS a header. There aren't the packaging constraints like there are under a car, and motorcycles aren't treated as much of appliances to the manufacturers as passenger cars are to their respectful manufacturers so performance is first and foremost on the agenda.
Great work sir. This has been proven over and over and hot rod guys can't stand it. If you're not twisting a motor over 7K, huge headers don't help.
Unless the Engine itself is huge.. 500ci +.. even at 5,000 rpm, a 500ci engine would be choked by 1 3/4 " headers.
Hi Richard, I love the videos and keep them coming! I think it's great that with this round of testing, we see that if you have a full exhaust plus headers, that this will positively improve power and torque production at a lower rpm. I wonder if this is because the camshaft manufacturers do their cam grind testing with full exhausts?
Nice vid.. I'm sure there's going to be way to many bad replys
My chevy 2 with a 385 ci small block with hooker fenderwell headers only changed a 1/10 of secoond in my 60 times. And that only from weight of exhaust. Still pull front wheel off the ground. Vs open headers
So where is the limits on either side? What does 2” or 1 5/8” or even 1 1/2” do?
Interesting findings, but time to min/max the crap out of this topic!
I wish I would have watched this video before buying my headers. I bought 17/8" headers and probably should of got the 13/4"s since my car will see alot more street miles then passes at the track. The 1/34" headers probably fit a little better also.
I think the size difference is very situational and dependant on heads flow and the operating range. i.e. stock engine vs blueprinted. My head porter runs 2in+ headers on his 416+ strokers running out to 7600-8000rpm high compression builds. That is what he recommends
ask him if he ran a back to back test ever on 1 7/8 headers
@@richardholdener1727
Hoping to hear back.
Do you have an explanation for the up tick in below 2200rpm for the 1 7/8 headers? Below 2200rpm is was higher then all the 1 3/4 runs.
Wondering what the results would be for 1000-2200rpms Range as i have a c5 corvette and the gearing really utilizes sub 2k rpms alot on the highways
Can you test with and without high flow catalytic converter?
It would be really interesting to quantify the effect of a cat, especially if we could see it on a couple of engines, like NA making 450ish and an FI making 600-700ish.
@@natesaforverk166 I'm curious for my blown LS2
So fat what I'm getting is 1 3/4 header with a electric cutout so you can go from open free flowing for higher rpm loudness to daily driving and good down low response with it closed. I can def tell a diff just driving around in my t56 4th gen fbody with cut out closed down low.
Richard I spend way too much time watching these videos 😃 keep em coming.
Also have you done a comparison for LS/LT engines on equal length headers vs non-equal length? I know there is a sound change but is there a performance benefit on one vs the other?
Very interesting, I didn't think the 1-3/4 would gain anywhere in the powerband. I'm curious what would happen with a larger displacement and a more aggressive cam revving to 7000 or higher.
2 inch ftw
Pretty sure you'd need more than 1-3/4.
13/4 is big already sbc is 1.5- 1-5/8
Hi Richard I was wondering if you’ll be able to do more back to back testing on 8 into 1 headers, 180 degree headers, and long tube tri y headers similar to what nascar would use. Comparing them to what most people use 4 into 1 headers.
Love all the videos you do cheers
would be cool-but not very practical since most of those can't be used in a vehicle
Id bet a 2 3/4 collector extension would really bump up that lower speed torque getting its acceloration up better . Especially if this was a 4.8 tested . Torque is king getting that jump and it takes Alot more hp to run that down !!! Towing youll definately feel it !!!
So interesting ! I'll bet going to 1 5/8 or even dropping down to 1 1/2 headers would get you even more low end torque
On that size engine if you were 2000-4500 RPM most of the time a 1 5/8" would probably be better than a 1 3/4".
Mark let me know what you think: Hey guys I am doing a efi 331 stroker just a nice weekend street car only, no track. My builder suggests that I do a 1 1/2 inch header and the rest of the combo will be an edelbrock performer rpm 2 intake, Brodix 20 degree 171 cc head, cam around .525 lift 108 lobe separation (that could change and be slightly larger), 70 mm tb, 80 mm maf, dyno tuned with 42 lb injectors. I can find 1 5/8 headers or there are more options anyway but have found the 1 1/2's in Headman as I looked briefly. Just curious as to your thoughts on the 1/4" making a difference either way positively or negatively for what I'm doing with the car. I'm going to expect for a minimum of around 350 rwhp.
Thanks
@@dennisrobinson8008 let me know what you think as well: Hey guys I am doing a efi 331 stroker just a nice weekend street car only, no track. My builder suggests that I do a 1 1/2 inch header and the rest of the combo will be an edelbrock performer rpm 2 intake, Brodix 20 degree 171 cc head, cam around .525 lift 108 lobe separation (that could change and be slightly larger), 70 mm tb, 80 mm maf, dyno tuned with 42 lb injectors. I can find 1 5/8 headers or there are more options anyway but have found the 1 1/2's in Headman as I looked briefly. Just curious as to your thoughts on the 1/4" making a difference either way positively or negatively for what I'm doing with the car. I'm going to expect for a minimum of around 350 rwhp.
Thanks
Cool. Thx Richard
thank you again i very appreciate your video compared parts
I spent a few days reading the views of Calvin Elston on how he does headers and exhaust. Very interesting stuff and a bit unusual to what most might think.
Would be an interesting test to see one of his system. But kinda impossible since theyd be custom made for the heads and engine..
Collector outlet sizing is important.
@@motorosso3349 Yes that and the head-to-header flange transition. He (Calvin) says the first part of the header is as important as the last part of the intake runner and that the trnsition from the port to the header is very critical.
Correctly designed stepped headers seem like a godd idea also. The thing that might surprise most is that he use smaller size on everything than what is otherwise used.
He suggest people use the Burns Stainless calculations for the overall dimensions.
Its all up on Speed-Talk forum.
@@magnusdanielsson2749 Yes, using the smallest diameter without hurting HP is the way to go as it keeps the gas speed up. I agree on the Burns Stainless calculation for header dimensions.
I would estimate that if you run a header with a diameter close to that of your exhaust valve you will b very close to optimized.
Thanks Richard.
Be cool to see what stock truck manifolds with these set-ups
same differences
Is the gain subject to displacement. Will a 4.8 ls or ford 4.6 have similar gains? Or even say an Audi 4.0 V8.
I’m sure it’s a factor of many different variables and displacement is one of them.
Another great video
Great information but it would be really helpful if the file names correlated to the setup a little bit better.
not really an issue
@@richardholdener1727 I’m slow so when we add new data and the colors change I’m looking around to take it in while trying to listen to you is all 😄 like if one setup was red on one layout and you add another data file, the color changes from red to something else.
You should do a test with ls swap s10 hedman long tubes with 1 1/2 primaries compared to the 1 3/4 long tubes
Would you have any content between the 1/34 and 1/78 longtube headers on a 2017 Gen 2 Ford Mustang Cayote engine, with just a 114mm cold air kit . Thanks for the awesome test always.😎💪🇨🇦
NO SIR
@@richardholdener1727 Hopefully if you are willing to bring the content for the Cayote engine it will be much appreciated.👍
I have some Coyote testing vids up-but all Gen 1
@@richardholdener1727 Much appreciated!
I hope inch 3 quarter is enough for my 408 windsor 220 afr super Victor 850carb 680 healthy cam
With both header diameters bigger than what is needed from both configurations, maybe a set of 1 5/8" diameters would of made things more obvious how to choose header size?
Can you show the final results of the 2 cams, truck Norris vs sloppy stage 2 with 1-3/4 headers with exhaust?
I been looking at these 2 cams for my ls2 corvette.
it doesn't change the results
I wanted to see the results together so I can see the power difference's between the 2 cams@@richardholdener1727
Great video as usual.
I feel this particular video would be more relevant in the 2002 era where guys were putting bolt ons on their F bodys and vetts, but considering headers. So I can see the little change in power vs these 2 header sizes at this lever/rpm range
This is 2022 and most guys using LS engines for power are wanting to make some big numbers. Im talking NA, N2O, Boosted.
I would love to see you do a comparison of say a N/A (6.2 based) Rec head, 416ci , 11.5:1, 650hp, 7000rpm power peak with these 2 header sizes.
Let me know.
Thanks for your time and effort in all your videos!
You are mistaken about the market-you (and others) might want to make big power, the vast majority are not building high-hp race motors
Could you do a 8 to 1 header to prove if they add torque? Then add a supercharger. Curious of actual torque gains.
What would the same comparison look like on a 6.2 L versus the 5.7 or 5.3?
Crazy how 1/8” difference make such a change in scavenging
Thanks richard for your video's, do you have any dyno comparisons on dual 2.5 vs dual 3 inch exhausts on a ls?
yes-that exhaust test video is up
Im waiting for the AR 2 1/8 Race headers test.
What are your thoughts about the 2-in headers for a 5.3 l ? I saw that these were offered by speed engineering for the 5.3 l. In your opinion, are these worth buying?
maybe the next evolution in power is testing full exhaust systems
This is what I tell everyone that’s under 700 hp to get 1 3/4 headers. 1 7/8 headers limit your plug wire selection because they tend to burn certain brands.
Not with the stock camshaft do Under the same circumstances with the exhaust was it tested with the same headers with the same collector extension? I know the test was done to see the difference between these two camshaft but what they saying modifications help the stock camshaft possibly even more and it would outperform the aftermarket camshafts in the RPM ranges that it does. So down around that 2000rpm Mark would it gain torque at the same places as the Chuck Norris cam in the sloppy cam
I wish I would have tested that but removed the stock cam then decided to do the header test
Curious to know if a centrifugal would change this at all??? Make it say 800hp blown engine and swap the headers.
Hey guys I am doing a efi 331 stroker just a nice weekend street car only, no track. My builder suggests that I do a 1 1/2 inch header and the rest of the combo will be an edelbrock performer rpm 2 intake, Brodix 20 degree 171 cc head, cam around .525 lift 108 lobe separation (that could change and be slightly larger), 70 mm tb, 80 mm maf, dyno tuned with 42 lb injectors. I can find 1 5/8 headers or there are more options anyway but have found the 1 1/2's in Headman as I looked briefly. Just curious as to your thoughts on the 1/4" making a difference either way positively or negatively for what I'm doing with the car. I'm going to expect for a minimum of around 350 rwhp.
Thanks
use 1 5/8 or 1 3/4
@@richardholdener1727 definitely not using 1 3/4 with my combo and for what I want to do. Why would you say not 1 1/2? Do you have any personal experience with them or know of anyone who has with a similiar combo? I have 1 5/8 LT's on my 302 now with performer 2, TF 170, the same cam mentioned above ( I'm sure he'll grind a little bigger for the 331), 70 tb, 75 maf, x pipe, pypes bomb free flowing catback, 24 lb'ers, and the car is tuned making around 286 rwhp. I previously had shorties with the same combo and flowmasters with an X. When I put the engine in the 94 with that current combo it seemed I lost some down low going from same size shorties to Lt's. I think had I had 1 1/2's on the 302 setup it would definitely feel more torquy down low for sure. With the 331 from my builder's opionion and I'll have to have another convo with him while the engine is being done, but he initially said 1 1/2. I do want to ask him overall why he would say those over the 1 5/8. He builds dirt cars in Tx and dude is like a mad scientist in a lab when he talks about building an engine and the combustion side of things as well as the intake side. I just realized you look like the guy from the video lol so you should know what you are talking about too
Can you do a 4.0 jeep h.o., renix, amc, stroker. Ive had a few and have always wanted to build one but there are no real informational on what and no test so dont know which way would be the best to go.
At the moment i have a 4.0 with a . 030 over bore with a . 060 crack and a . 030 cam ported and decked h.o.head and intake, but stock h.o. ex.manifold. thing is a deffently drives different then a stock 4.0.
I have a 5.3 with 1 7/8 speed engineering headers. The collectors are 3". I am going to be running a 2.5" exhaust. Should I go right to 2.5 at the collector or run it a few feet before reducing it. Thanks for opinions!
I have a 5.3 Silverado with true dual exhaust 2.5 piping. Should I go with the 1 3/4?
Okay. Cool. So now my questions is which of the 2 sound better? I like the idea of 1 3/4” headers in my Tahoe but what about the sound. How does it affect the sound
they sound very similar
I wish the testing was done on a specific 2004 5.7 LS1 aluminum that is an LS1 53 cast iron turned into a 57 and you did pick up power by going with the 1 inch 3/4 but a lot of us now have to run a high-flow cat high flow cat has some kind of restriction if you haven't punched it out I wonder what the difference would have been between these exhaust test with an added high flow cat for some of us do have on our modded cars for stickers so what I'm basically saying is inch and 3/4 flows plenty in the beginning that's why you saw the increase with them down low now put a restriction on that flow and you might want the one in in 1 inch and 7/8 header Yes sounds like a dumb scenario but exhaust flow just liking this video has to do with numbers how someone runs this setup but throws a high-flow cat numbers are going to be a little different right... so this is a test with no cat and no Muffler
headers don't add power based on flow restrictions-they add power from wave scavenging
@Richard Holdener I understand that wave Scavenging is where the powers at but at the same time.. so ain't flow and I know Richard that you know a lot more than I ever will..lol.. you've been planning this for a long time.. so now all that matters an exhaust is the Scavenging.. so putting on a resonator and a Cadillac converter after will make no difference on power I figured adding a high-flow cat would squeeze some numbers off your chart.... I did notice my comment is kind of hard to read up above LOL... sorry about that
What I meant to say was.. after you do your test on your headers Etc and get your HP numbers if you add a set of high-flow cats won't the numbers change from a restriction another words adding the high-flow cats to the test you just did ..wont it bring the numbers down.. I always thought more restriction on the exhaust less flow which meant less flow less air into engine less air out
Did you ever test the truck norris with stock exhaust manifolds vs headers before I thought you had but searching for that wasn't very useful
I have tested them both ways-(not surprisingly) they work with both
@@richardholdener1727 I was wondering if the gains were worth it because I believe or assume it's over lap that affects how much headers help
That was really cool. But, Truck Norris needs a Shanghai Sushi Slicer and some E85. For Science. It's what the People need 🤘🏻🇺🇸
If I had to guess-the curve would be the same shape-just higher power
@@richardholdener1727 #turbocam😎
How about a 4 into 1, 4 into 2 into 1 and a 180 degree header shootout.......then add turbo
Would it be accurate to say that scavenging was being affected because of the resonance pulse changing with size and length of the exhaust? BTW I'm looking forward to the 2.2 turbo colab with DV
I'd love to see a similar test on a 427 or 454 in the future. I mean, does 20-30% more displacement make the bigger headers worthwhile?
👍
AT some point, yes
Back in the day I had a 70 as big block nova. I built a 427 ,about 600 crank. I had hooker super competition 2 18th headers on it. I hit an obstinate in the road and smashed the right header. I put hooker competition 1 78th headers on it and lost noticable power. I think the tube size needed correlates with the amount of ex the engine is making.
@@davidreed6070 about 600?
Did you ever dyno the motor. What did the heads flow?
@@I_like_turtles_67 no I never dynoed the motor. It had closed chamber oval port heads, with 2.19 and 1.88 valves. The car had 3.73 gears a 4000 stall converter with a manual valve body. I would hit high gear at around 100,and it would do the wild thing. I prefer the 427 to the 454. I run a n ly6 now. Ls engines make cheap power, but so do big block Chevys.they make the cars nose heavy
Awesome content Richard. It doesn't make that much difference. Depends where you want your power . 🆒👏🤟💯🔥
hola richard tenes pruebas con escapes mas largos aun ? pierden en alta rpm y ganan potencia a 1000 rpm ?
Do a big block chevy header test. I'm using 1 3/4 on my mild 496
That's tiny for that many cubes. I'd want 1 7/8" minimum for a big block. 2" and up for stuff with a good head.
pretty small for a BBC
Yes they do....problem solved
Need 1-7/8 tri-Y header with a chambered muffler
How much compression did the 5.7 ci engine have with the aftermarket heads?
Are those 1 3/4 QuickTime performance headers? I remember back in he day they were known for having higher torque at low rpms compared to others headers.
They were due to the merge collector. That's why I ran those on my ls1.
QTP
@@richardholdener1727
I figured they were QTP by the tag being welded to the header. I had done some research and showed up to 35 ft pounds of torque around the 2500 rpm range vs other headers. Thanks Richard awesome work.
It would have been nice to see the mufflers on the 1 7/8 headers too....jusssayin😁
WE DID DO THAT
@@richardholdener1727 ok...i thought you only had the mufflers on the 1 3/4 and just the header extensions on the 1 7/8
Watched it again....no 1 7/8 header with the longer extension
Richard, you didn't mention what sort of tuning changes were made with the exhaust changes, if any.
each was run with an optimized tune to get every last ounce of power out of it
@@richardholdener1727 Yes, I assume it was optimized, but were tuning changes needed in the lower rpm range where you saw power differences?
Can you run a test with whatever engine you can where you test different pipe lengths after the collectors? Put like a 5ft length of whatever diameter seems to suite and keep cutting a few inches off after each pull to see at what point the corresponding pipe length helps and then starts to hurt scavenging. I'm wondering how accurate my text books were at tech school
He's actually tested this already. Hopefully he'll comment with the specific video, but I remembering him doing it.
@@andrewmontgomery1763 id like to see the results, I know based on sheer volume from displacement, rpm, and other factors it will vary drastically. I know there's a ton of things at play. It would be cool to different displacements from 1 liter up to 10+liters
@richard So how much of a collector extension did you use and do we even need one if were running full exhaust?
your full exhaust is already an extension
What if you did a X pipe and more normal mufflers
How is this affected by boost, as in a centrifugal supercharged application?
Is the 1-3/4" still fairly equal? Is the 1-7/8" preferred at higher HP levels above 600?
I like bigger headers with high hp blower applications
@@richardholdener1727 thank you for your response. I'm targeting north of 750whp on a Dart 363, and finding 1 3/4" headers with a 3" collector has been a real chore. Seems that 1 7/8" is becoming the norm.
Have you done any testing with the gm inline 5cyl? The 4200s cousins brother, I'm curious to know how it would hold up(boost/nitrous) and knowing since it's a shorter package than the 4200 what percentage gains/loses does the 1 extra cylinder bring to the table
not yet
@@richardholdener1727 just curious, I have a h3 laying abandoned at our shop. Still runs, frame rotted out and customer doesn't want it... Maybe I'll pull the engine and build it and see what it will do, just wish I had access to an engine dyno...
@@Brother2Jis_27s4 I've wondered about the 2.9 I4 version of the Atlas. It's kinda anemic in its application but it's a pretty big inch I4 with a nice head, I think it could be a solid performer in certain cases.
@@DrewLSsix itd be cool to line the whole family of them up and do a side by side by side... See if going from 4cyl to 6 gives a proportionate increases in power as you add cylinders
The correct header diameter is 115% of the area of the exhaust valve(s). This is a fixed formula that hasn't changed in dog's years. You don't want the headers to be too large, because then you slow down the exhaust too much, harming your scavenging.
THE CALCULATION TELLS YOU NOTHING ABOUT WHAT HAPPENS AT 2000 RPM
Any idea of the max temperature difference between the 2 headers with mufflers? Trying to keep under hood temps down thinking 1-7/8 might help even though I would prefer the low end torque of the 1-3/4
I doubt the header size changes exhaust temps much
E-85 is what you want to reduce under hood temps.
How would that low end power change with a turbo set up ?
more low speed torque equals better turbo response