SBC Chevy - Testing 6 Rocker Arm ratios 1.5 VS 1.6 actual and advertised. 👀
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- เผยแพร่เมื่อ 11 ก.พ. 2023
- This is a test of rocker arm ratio, to see how accurate the advertised ratio is.
Tested are, GM Performance, Scorpion, Crane, and OEM GM. The tests were performed on a SBC Chevrolet, with a minimum of 3 trials to prove accuracy.
The results will surprise you.
Today, March 16 I have just published a follow up video where I measure the valve lift at every 10 degrees of crankshaft rotation from -20BTDC to 106 degrees ATDC, the full sweep of lift. I then calculate the average lift over the entire cycle.
Best to worse is a difference of .046" average lift. - ยานยนต์และพาหนะ
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Excellent video. I was recently having a discussion with a friend and fellow old car nut about roller rockers vs stamped steel rockers. Your video taught me things about rocker arms that I didn't previously know and also corrected a couple of misconceptions I had regarding their performance. Thanks for furthering my understanding of engine design.
Yes Interesting tests. Thanks.
Thank you!
Very informative and great video.
Glad it was helpful! AG
Great info! I really appreciate your scientific testing and comparison.
Thanks Kiss, glad you appreciate it. AG
David Vizard also has a good video on rocker arms
Thanks for the information. I think I have watched it. AG
david vizard has a great video on dang near anything go faster run better auto he probably has forgotten more automotive knowledge than i can hope to gain
and i would be happy knowing that much
You should have included the ratio at .150-.200" lifter lift.
Some rockers are a better off-the-seat ratio giving more area under the curve.
Back to back dyno tests show 12-20 hp better.
Thanks for the question Ray. i have another video where I compare lifts every 10 degrees through the entire lift range if you want to check it out. AG
The effective ratio actually changes as the valve opens due to geometry changes as the contact area on the valve moves, etc.
It would be even more interesting to see the results taken at, say 5-6 different points along the valve lift cycle, then show a graph of them overlaid for additional insight on the analysis.
Thanks for the suggestion drussell. I will need a second dial indicator so I can measure cam lift and valve lift at the same time, or just record cam lift at incremental points, document that, then record valve lift at the same points. It will be easier and more accurate with the crankshaft in the engine so I can use my degree wheel to record the points. As soon as I receive the crankshaft I will try to mock it up so look for a follow up video.
@@goldsgarage8236 Yeah, it is probably simplest to just measure the lobe lifts at incremental points using a degree wheel, then measure the actual lift at the valve at those same points.
This is one of those things where the overall geometry matters, and it is significantly more complex than it appears at first glance. For example, for those of us with shaft-mounted rockers on our Mopars, you can even change the effective ratio just by using longer pushrods and shimming the rocker shafts up a bit so that the face of the stamped steel rocker contacts the valve stem tip "further out" on the rocker. This is one situation where the difference between the shaped tip of a classic stamped rocker vs. roller makes a difference too, the stamped one slides across the valve more and can change effective ratio wildly depending on the shape of that tip and where it is in that part of the rocking-motion. The guys that run in various "stock parts" classes have been exploiting things like this for decades. It's all very interesting. 😀
Thanks for your input. I will do the test as soon as I get a crankshaft in the engine. Watch for it.
I know this is old, but you're right about the varying ratio as the rocker goes through it's lift. ....kinda. What you said is true IF you have improper rocker arm geometry from the wrong length pushrods.
Usually when people use pushrods that are too short to put the contact patch in the middle. (or a stock shoe type rocker where the rockers contact point moves to the outside as the rocker opens the valve). That includes using that plastic tool that has no idea how many degrees of rotation the rocker is going to see (I.E. the amount of lift the valve will see)
If you set up a roller tip rocker with correct geometry, the contact area pushes almost straight down through the entire lift/close cycle. (and it is straight down at the middle of the lift). Don't that will make the witness mark as thin as a needle.
...and if it's not in the middle, you have the wrong rockers. Not the wrong length pushrods.
I'm really curious how close those varying amounts of ratio would have been on that test if they were set up with correct mid-lift geometry.
Good info !
Thanks Sam, glad it was helpful. I am still planning a follow up to demonstrate ratio over the full cam cycle from lifting the valve off the seat to full lift.
@@goldsgarage8236 Insightful :)
Great information. I think manufacturers should have to include test results with their ads and catalog descriptions.
Great point! thanks Craig
I think so too
Last week i tested 2 sets of. 1.6 rockers from 2 different companys and one companys gave. O24 thou. More lift !! Got to check everything !
Good point, that was the inspiration for this video. AG
great info
Thanks for your kind words maldo72. Please keep watching my channel. AG
@@goldsgarage8236 will do keep it coming
Pretty sure the dark gold rocker arm is a Harland Sharp brand. Always known for quality!
At 10:03 you can see both are stamped CRANE. You are correct that Harland sharps are that Orange gold anodized color and a little more square shaped.
Thank you for the time and diligence to document these parts
Thanks Alley, GREEN is correct, they are CRANE. AG
Thanks GREEN, you are correct. AG
Thanks Woody. Thanks for watching and commenting. AG
I've gone with yella Terra 1.7 adjustable shaft roller rockers as I'm from Oz and will always buy local before anywhere else, so I know the quality is as good as it gets for my ls 427 cost 5 times more than the trunnion upgrade but I'm expecting to Rev my engine hard into 8k + zone
Thanks for your comment Chevy. AG
Our car owner sent our GM 604 crate engine to McGunegil in Muncie Indiana with 1.6 Chevy rockers and they checked out at 1.65. Which were illegal and we had to buy rockers that checked out a 1.6.
Very interesting, I have never checked out any that were more than advertised.
@@goldsgarage8236 do you use Chevie's jig to check them?
First I use a dial indicator to measure the lobe lift, then I use a dial indicator right on the valve. Then do the math. In Pro Late Model racing the tech guys use a go-no go gauge as per the GM circle track manual. I am working on a video where I measure the lift from off the seat to max lift at 10 degree increments of crankshaft rotation, then calculate the average ratio.
You do not mention the rocker stud size, but it looks like it is 3/8, if so you need to change to the 7/16 studs. It will change the valve lift and stabilize the valve train. Another common mistake I see all the time on stud mounted rocker systems is the length of the shank on the rocker stud. The rocker trunnion should NOT run on the threads of the studs. As you can see the threads have shinny spots where the rocker trunnion is slapping against the studs, that can change you valve lift also. Another note if you are looking for Max power, you need to adjust the push rod length so the contact patch favors the ex side of the valve. Great vids as always.
Thanks as always for your input and information Racer. AG
Why the exhaust side and not the middle where less valve guide wear (friction) happens?
Nice to see accurate numbers. Advertised ratings give me a headache.
Thanks for your comment Larry
Nice
Thanks for watching my channel and commenting John. AG
@@goldsgarage8236 Absolutely! I Love your Chanel. Maybe I can get you to build me a good street Engine one day? Or recommend someone to me.
I like PRW prices but there is a caveat, China. I have vowed not to purchase things for my engine that are made in China. I have been on the short end of the stick too often. Blue Scorpion is produced in Florida.
Thanks Stovebolt. Good to hear from you and sorry I missed this comment until now. Blue Scorpions are great. They need a lot of room under the valve cover. I agree about china but it is getting even harder to build anything without something from there. AG
Do you know the story of Jesel that launched that business? I think you would find it very interesting.
Also, that is a great idea with bolting the carb lift plate to the head for a surface to put the mag base to.
Thanks for your comment Gearhead. I will look into the Jessel story. AG
great vid whats the blue
tool called ?
Thanks for the question Punter, the blue tool is a Proform 66789 Push Rod length checker. You can buy it on Amazon for $23.96 $CAN or about $18 USD
@@goldsgarage8236 thanks very much
Is 110 octane unleaded race gas good enough for 13 to 1 in a SBC
Tough question Ben. IT depends on many other factors, ignition timing, cam timing, intake valve close ABDC, dynamic compression, cranking pressure PSI, aluminum vs. steel heads. If you have lots of compression, you need a cam with lots of duration and vice versa. Another factor is how the car is driven. Lugging the engine at low rpm with high volumetric efficiency is always dangerous. All that said, 13:1 is a lot, I think I would play it safe and use a higher octane to start. Read your spark plugs, they are a good indication of what is going on. Using a colder range spark plug and back off the timing advance to start. Hope this helps.
What do you consider to be the best rocker arms for marine/circle track where RPMs are high (6500) for long periods of time?
Thanks for the question amiable, and I am sorry that I missed it until now. I think they all are up to the task. From my experience in Pro Late Model Racing, the GM performance (the aluminum colored ones) are the standard in all CT400 race engines. The mandated max RPM is 6400 and we run on the chip every lap. I have never seen one fail. I also have them in my Z28 Camaro. Hope this helps. AG
Thank you for the reply
Hello, I would like to change the rocker ratio on my 92 Firebird from 1.5 (original rocker) to 1.6 (Comp Cams roller tip rocker). Would the engine control unit get this regulated because of the every 2 year exhaust gas test that we have to do here in Germany? My car is a 3.1 V6 but I like it a lot and want a little more power without making it complicated. Thanks in advance.
Good question NBS. In my opinion, I think you will be OK. If you were increasing the duration it might be a problem because it would make the engine less efficient at idle, however by changing rocker arm ratio from 1.5 to 1.6. you are only increasing lift just less than 7% with a negligible increase in duration. Hope this helps. AG
@@goldsgarage8236 Put a degree wheel on and prove that duration is 100% not affected
How old are those Crane rockers? They look nothing like my gold Crane rockers made in the late 90's.
Thanks James. Not sure how old they are. I inherited them from a previous video. AG
@@goldsgarage8236 Crane was the goto quality rocker but they say Crane went downhill and Scorpion is the good one now
Stock rockers are trash
I thought that was Nick's Garage guy. must be his brother
Thanks for the compliment.
Just use good name brand parts! Those PRW steel roller tip have never shown any performance, usually the opposite! Valve float much earlier! You also don’t want to use the smaller studs! (Unless it’s a low rpm pickup truck engine!) If you are building a performance engine & buying rockers, get the bigger studs! American made stuff! Overseas garbage makes more problems than they are worth! On lower power circle track spec type engines, the difference from the stamped steel, (stock stuff) & the Chevrolet roller rockers were very little! 1.5 to 1.5 it was only a few horsepower!
Thanks for your comments Brian. AG