The biggest misconception concerning cylinder heads that I hear too often is that bench flow CFM ratings somehow correlate to which heads are best and which are junk. I want to correct this by sharing some facts that will help gain an understanding of cylinder head flow and explore why that isn't the case. Cylinder heads are designed to increase velocity using the venturi effect. This is achieved by a restriction in the ports created by the port throat, which is absolutely essential by design. Meaning that if you were to remove the restriction and open the throat ratio too high, you will see increased flow, but the heads will make significantly less power. Lets say you take it to the extreme and maximize flow in your heads by making your ports totally open like a tube, they will flow without any restriction and look amazing on a flow bench, but when installed on the engine you will find the engine will barely run, if at all. This is because you have lost the critical throat ratio and lost velocity. For most Oldsmobile heads, a valve size percentage of 86-1/2% to 89% flows best with good velocity. On big displacement high flow V8 racing heads with valve sizes from 2.1 to 2.25 you can go as high as 91 to 92 percent. A well ported head should have a velocity gradient of less than 20%. Depending on the application, there are a lot of variables and caveats, but generally speaking a velocity of 350 feet per second at the short turn radius is good. So to sum up, high cylinder head CFM flow numbers don't correlate to high engine power, the balance of velocity and flow is what makes power. That balance is essential in matching the engine, placing race heads with 2.1" intake valves on a low compression 350 will make a lot less power below 3000 RPM and will feel very sluggish on the street. Considering valve sizes, throat diameter, velocity, engine application, and valve seat angles are all things that professional cylinder head and engine builders consider before flow numbers. Hopefully this will help increase understanding of why flow CFM ratings are a poor benchmark for cylinder head performance.
You are by far the best thing that happened to TH-cam in regards to Oldsmobile building and break downs👌🏽. Man keep up the great work this info is really helping me with my current 455 Olds project.
I am grateful to hear that, thank you. I was frustrated by internet misinformation concerning Oldsmobiles and wanted to give people a place with information they can count on. I hope your 455 build turns out great, thank you for watching my channel.
On any small block Oldsmobile engine, I only recommend performing advanced work, like cylinder head porting and valve size increases, after opening up the intake and exhaust systems. To feel all of the gains from cylinder head work, especially in a 307, Oldsmobile engines needs a better flowing intake manifold, a better camshaft, and 2-1/2" dual exhaust (no catalytic converters or high flow converters) with free flowing mufflers (something like dynomax mufflers). Prior to head work, it makes sense to start with the following upgrades in this order. ( Depending on your preference toward street torque or higher RPM.) 1) Better flowing Intake manifold: Like an Edelbrock Performer 7111 or Performer RPM 2711 2) Dual exhaust kit with 2-1/4" or 2-1/2" exhaust with something like dynomax mufflers 3) Camshaft: Mondello cam kits or Iskenderian cam kits, there are hundreds of other camshafts to consider, I only use Mondello or Isky. After these upgrades are completed, the cylinder heads should be the most restricting factor. If further performance is desired, head work is the next logical recommended step.
Haha, I know what you mean! I do have a set of 350 non smog heads I will be doing next. These 307 heads should be a pretty good set of heads when I'm finished. It's sad that I don't have a 307 to slap them on, but they needed a ton of work so it was a good set of heads to use for making videos.
@@jimmy_olds I live in Maine and I wouldn't ever say no to free Olds parts or engines. I will be performing the same upgrades to a set of 350 5a heads and will demonstrate the performance in my Cutlass on an upcoming video.
Though you might have shown more about where to grind ?...I see you did not block center exhaust balancing / heating system for cold weather and exhaust balance.. for APX. 50 h.p.. Like the W-30 "F" heads
Thank you for the feedback. I will be blocking the crossover ports in an upcoming video. The next heads I port I will try to get better footage so you can see more clearly where I am grinding.
@@chrismc.4437 that's a Joe Mondelo race head as well as the siammized center exhaust ports full the indent so all the exhaust ports are separate just by doing this I gained 65 hp. nevermind the extra with the porting remember to separate the two center exhaust ports because of the turbulence that is created...
That is a fair criticism. I have a set of 455 and 350 heads to port, I will make certain to do a more thorough narrative on the next video. Thank you for the feedback, I appreciate it!
I don't flow test, nor does flow testing heads result in meaningful data or HP correlations. Please see the pinned comment on this video where I explain why flow testing doesn't correlate to higher HP in cylinder heads. I know after porting in this manner, Oldsmobile heads have increased flow characteristics over stock heads for noticeable gains.
@@junkdump2720i think flow testing is meaningful but its just one part of the equation, just like parts of an engine need to be syncronized, aspects of the head do also. Flow testing can tell you a lot about a port, the sound, choke, stabilization, etc. Mostly though its just one part of a multitude of things that need to come together.
I don't have a set of heads on hand. If you get a set of 307 5A or 350 7A heads I can perform this work. Contact me at junkdump455@gmail.com for details on where to send the heads.
Oldsmobile small block head castings are all ported as demonstrated in this video. Flow characteristics of any small block Oldsmobile head can be dramatically improved with the modifications performed in this video series. Despite having been drilled for air injection, the 5A heads depicted here, are the best casting and sought out by owners of 307 engines. Feel free to drop off, or ship any of your scrap heads to my shop in New England, contact me at junkdump455@gmail.com.
I have also set of 5A heads under work for my Custom cruiser, just a question about that middle exhaust port. Is it helpful for better exhaust flow to weld plate separating those middle ports? I have set of 4A heads that came with my 350 engine and on those heads someone has welded plate between middle exhaust ports. My plan is to use 5A heads on 350 engine with high compression for RE85 fuel and smaller twin turbo setup. Main goal is to have very good cruising torque up to 4000rpm
With a turbo you will find a separator plate advantageous. Also back cutting your valves will help increase flow at low lift helping the turbo initial spool rate, at the cost of a small fraction of high lift flow.
Maybe you need to get a clue on your building of a motor needs a motor needs air flow people wholly shit people don't put them smog heads on the small block three fifty Olds motor if you are really serious about making real horse power numbers add the performer rpm intake and the performer rpm cam and the big block four fifty five head's duh people who don't have a clue
I just noticed that I didn't respond to your comment, so allow me to rectify that now. I highly recommend an Edelbrock 2711 intake manifold to replace the heavy egr intake. Get a set of 1972 or earlier 350 cylinder heads If you can find a pair in a junkyard or swap meet. If not than perform the mods in this video to your 307 heads. An Engle JM-18-20 or equivalent camshaft and new lifters is nice if you are planning on a cam swap. Those three upgrades will make the biggest difference on that engine. I also suggest a rebuilt quadrajet without the electronics, install an older alternator bracket that moves the alternator to the passenger side (opposite the power steering pulley), an HEI distributor if it doesn't have one, an MSD 6A box, and full 2-3/4 dual exhaust with mufflers and no catalytic converters, if legal in your state. Those upgrades will really wake up a 307 and create an enjoyable amount of power from a small displacement engine without any machine work.
@@junkdump2720 awesome thanks so much, ive pretty much been working on that list but i do have a roller 307 currently in the cae with 35k verified miles on the bottom end that i daily drive, what would be needed to throw the better 5a heads on it with the edelbrock intake, im assuming i just use the shorter pushrods from my 7a heads
Hahah, I feel like I'm never "done" with any of my projects! Smoothing the guides will help with velocity by smoothing flow, but it won't make a huge performance gain. When I port heads it's just one of the things I do because every little gain adds up. Thank you for the comment!
@@junkdump2720 in the end I got my hands on a proper grinder and went back in, cleaned the guides and touched up a few areas where I was lazy Thanks for the motivation!
Certainly, I charge $90 an hour for porting and it takes anywhere from 4-6 hours total to complete a basic porting on both heads, depending on the casting. Olds #8 heads should have 1.88 int and 1.625 exh valves, I can also check the throats, if they are below 88% it only takes an hour and a half to machine them to 88-92% depending on your application. Email me at junkdump455@gmail.com and we can discuss your wants and expectations. I also accept shipments if you prefer not to drive up to Maine.
@@junkdump2720 I have a 77 350 block bored to 355. I also have a cam and headers on it. It's mainly a street car that I'm trying to squeeze more power out of. I thought these 5A heads might be an easy way to up the compression, but I don't think they flow as good as the 4a heads.
@@MetalMania899 The 5A 307 heads in this video would definitely increase the compression ratio. With the porting, 2 inch intake valves, and 1.625 exhaust valves they should flow equal to or better than stock 403 4A heads. I think a set of 1972 7A heads would be best (port them like I did in this video) if you could find a set.
Do some research on the small block three fifty head's compared to the big block four fifty five head's by that time you might have finally have gotten a clue to what I'm saying 🙄 duh
Perhaps you misread the title and video description or had the audio muted. This video demonstrates techniques for porting small block heads for people who want better performance from their small block heads. The same porting technique will apply to big block heads. This is not a comparative video on flow and the depicted cylinder heads are not 350 heads.
I'm glad @rodneyhopper22 mentioned the head swap upgrade to big block heads. In my experience when swapping 455 heads (with 2"int and 1.6"exh valves and 80cc) onto a 350 (that had 2"int and 1.6"exh valves and 70cc) the HP gain is negligible and TQ gains tend to be very low, around 10-15. This is because the 455 heads typically have large 80cc+ combustion spaces which lower the compression ratio of the engine, in some cases from 8.5 down to 7.5. Also the swap requires a new intake and can cause issues with face and port matching. Conversely, mild porting of the 350 heads can net 30HP and 20TQ without changing your intake or lowering the compression ratio. If you are building a race engine small block then the big block heads are capable of being fitted with larger valves, and have better velocity and flow.
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The biggest misconception concerning cylinder heads that I hear too often is that bench flow CFM ratings somehow correlate to which heads are best and which are junk. I want to correct this by sharing some facts that will help gain an understanding of cylinder head flow and explore why that isn't the case. Cylinder heads are designed to increase velocity using the venturi effect. This is achieved by a restriction in the ports created by the port throat, which is absolutely essential by design. Meaning that if you were to remove the restriction and open the throat ratio too high, you will see increased flow, but the heads will make significantly less power. Lets say you take it to the extreme and maximize flow in your heads by making your ports totally open like a tube, they will flow without any restriction and look amazing on a flow bench, but when installed on the engine you will find the engine will barely run, if at all. This is because you have lost the critical throat ratio and lost velocity. For most Oldsmobile heads, a valve size percentage of 86-1/2% to 89% flows best with good velocity. On big displacement high flow V8 racing heads with valve sizes from 2.1 to 2.25 you can go as high as 91 to 92 percent. A well ported head should have a velocity gradient of less than 20%. Depending on the application, there are a lot of variables and caveats, but generally speaking a velocity of 350 feet per second at the short turn radius is good. So to sum up, high cylinder head CFM flow numbers don't correlate to high engine power, the balance of velocity and flow is what makes power. That balance is essential in matching the engine, placing race heads with 2.1" intake valves on a low compression 350 will make a lot less power below 3000 RPM and will feel very sluggish on the street. Considering valve sizes, throat diameter, velocity, engine application, and valve seat angles are all things that professional cylinder head and engine builders consider before flow numbers. Hopefully this will help increase understanding of why flow CFM ratings are a poor benchmark for cylinder head performance.
Nice job. Porting olds heads for maximum flow isn't that difficult, if you stay in the right areas, as you have explained. Good job!
Thank you!
Nice video,,thanks man!!!
great video
Thank you, glad you like it. It took many hours to put this one together.
The Oldsmobile 307 can go up to between 5000-6200 RPM and maybe 250 to 300 horsepower if it’s prepared properly
You are by far the best thing that happened to TH-cam in regards to Oldsmobile building and break downs👌🏽. Man keep up the great work this info is really helping me with my current 455 Olds project.
I am grateful to hear that, thank you. I was frustrated by internet misinformation concerning Oldsmobiles and wanted to give people a place with information they can count on. I hope your 455 build turns out great, thank you for watching my channel.
On any small block Oldsmobile engine, I only recommend performing advanced work, like cylinder head porting and valve size increases, after opening up the intake and exhaust systems. To feel all of the gains from cylinder head work, especially in a 307, Oldsmobile engines needs a better flowing intake manifold, a better camshaft, and 2-1/2" dual exhaust (no catalytic converters or high flow converters) with free flowing mufflers (something like dynomax mufflers). Prior to head work, it makes sense to start with the following upgrades in this order. ( Depending on your preference toward street torque or higher RPM.)
1) Better flowing Intake manifold: Like an Edelbrock Performer 7111 or Performer RPM 2711
2) Dual exhaust kit with 2-1/4" or 2-1/2" exhaust with something like dynomax mufflers
3) Camshaft: Mondello cam kits or Iskenderian cam kits, there are hundreds of other camshafts to consider, I only use Mondello or Isky.
After these upgrades are completed, the cylinder heads should be the most restricting factor. If further performance is desired, head work is the next logical recommended step.
I ported the k heads on my jet boat fixed the exhaust ports
How did it turn out, and were you satisfied with the difference after porting?
You gave those 307 heads much more love than they probably deserve!! It’ll be cool to see how they perform
Haha, I know what you mean! I do have a set of 350 non smog heads I will be doing next. These 307 heads should be a pretty good set of heads when I'm finished. It's sad that I don't have a 307 to slap them on, but they needed a ton of work so it was a good set of heads to use for making videos.
@@junkdump2720 where do you live? I have a 307 I’ll donate to the cause! Lol
@@jimmy_olds I live in Maine and I wouldn't ever say no to free Olds parts or engines. I will be performing the same upgrades to a set of 350 5a heads and will demonstrate the performance in my Cutlass on an upcoming video.
You wasted money on those small puny head's
Yo the idea is to increase air flow not the other way around duh dude
The Oldsmobile 307 was reinvented in 1980-90 versus the 1968-73 Chevrolet 307 small block V8 engine
Though you might have shown more about where to grind ?...I see you did not block center exhaust balancing / heating system for cold weather and exhaust balance.. for APX. 50 h.p..
Like the W-30 "F" heads
Thank you for the feedback. I will be blocking the crossover ports in an upcoming video. The next heads I port I will try to get better footage so you can see more clearly where I am grinding.
Oh Peter, you're misinformed.
@@chrismc.4437 that's a Joe Mondelo race head as well as the siammized center exhaust ports full the indent so all the exhaust ports are separate just by doing this I gained 65 hp. nevermind the extra with the porting remember to separate the two center exhaust ports because of the turbulence that is created...
great video, but disappointing in that you didn't describe in any detail what it was that you were trying to achieve. Oh well maybe next time........
That is a fair criticism. I have a set of 455 and 350 heads to port, I will make certain to do a more thorough narrative on the next video. Thank you for the feedback, I appreciate it!
What is the flow difference ????
I don't flow test, nor does flow testing heads result in meaningful data or HP correlations. Please see the pinned comment on this video where I explain why flow testing doesn't correlate to higher HP in cylinder heads. I know after porting in this manner, Oldsmobile heads have increased flow characteristics over stock heads for noticeable gains.
@@junkdump2720i think flow testing is meaningful but its just one part of the equation, just like parts of an engine need to be syncronized, aspects of the head do also. Flow testing can tell you a lot about a port, the sound, choke, stabilization, etc. Mostly though its just one part of a multitude of things that need to come together.
Do you have a set of those heads for sale?
I have an 1986 Oldsmobile Cutlass with the original 307 ci engine and would love to have this done.
I don't have a set of heads on hand. If you get a set of 307 5A or 350 7A heads I can perform this work. Contact me at junkdump455@gmail.com for details on where to send the heads.
I don't usually port scrap heads... but when I do..... 🤣
Oldsmobile small block head castings are all ported as demonstrated in this video. Flow characteristics of any small block Oldsmobile head can be dramatically improved with the modifications performed in this video series. Despite having been drilled for air injection, the 5A heads depicted here, are the best casting and sought out by owners of 307 engines. Feel free to drop off, or ship any of your scrap heads to my shop in New England, contact me at junkdump455@gmail.com.
Do you still have those 307 Olds Heads?
I still have them and plan to do some work on them for use in upcoming videos.
I have also set of 5A heads under work for my Custom cruiser, just a question about that middle exhaust port. Is it helpful for better exhaust flow to weld plate separating those middle ports? I have set of 4A heads that came with my 350 engine and on those heads someone has welded plate between middle exhaust ports. My plan is to use 5A heads on 350 engine with high compression for RE85 fuel and smaller twin turbo setup. Main goal is to have very good cruising torque up to 4000rpm
With a turbo you will find a separator plate advantageous. Also back cutting your valves will help increase flow at low lift helping the turbo initial spool rate, at the cost of a small fraction of high lift flow.
Maybe you need to get a clue on your building of a motor needs a motor needs air flow people wholly shit people don't put them smog heads on the small block three fifty Olds motor if you are really serious about making real horse power numbers add the performer rpm intake and the performer rpm cam and the big block four fifty five head's duh people who don't have a clue
When are you going to be running your motor at four thousand rpms
Just picked up a non roller 307 to build up a lil bit, do you have any reccomended mods?
I just noticed that I didn't respond to your comment, so allow me to rectify that now. I highly recommend an Edelbrock 2711 intake manifold to replace the heavy egr intake. Get a set of 1972 or earlier 350 cylinder heads If you can find a pair in a junkyard or swap meet. If not than perform the mods in this video to your 307 heads. An Engle JM-18-20 or equivalent camshaft and new lifters is nice if you are planning on a cam swap. Those three upgrades will make the biggest difference on that engine. I also suggest a rebuilt quadrajet without the electronics, install an older alternator bracket that moves the alternator to the passenger side (opposite the power steering pulley), an HEI distributor if it doesn't have one, an MSD 6A box, and full 2-3/4 dual exhaust with mufflers and no catalytic converters, if legal in your state. Those upgrades will really wake up a 307 and create an enjoyable amount of power from a small displacement engine without any machine work.
@@junkdump2720 awesome thanks so much, ive pretty much been working on that list but i do have a roller 307 currently in the cae with 35k verified miles on the bottom end that i daily drive, what would be needed to throw the better 5a heads on it with the edelbrock intake, im assuming i just use the shorter pushrods from my 7a heads
I thought I was finished Dremel ;) porting my SBO350 heads, you're making me think I need to smooth in the valve guides now
Hahah, I feel like I'm never "done" with any of my projects! Smoothing the guides will help with velocity by smoothing flow, but it won't make a huge performance gain. When I port heads it's just one of the things I do because every little gain adds up. Thank you for the comment!
@@junkdump2720 in the end I got my hands on a proper grinder and went back in, cleaned the guides and touched up a few areas where I was lazy
Thanks for the motivation!
@@DecibelCar excellent, glad to hear you finished them off.
i live in Dedham mass what would you charge to do that on my 1975 350 type 8 shitty heads? if i brought them to you
Certainly, I charge $90 an hour for porting and it takes anywhere from 4-6 hours total to complete a basic porting on both heads, depending on the casting. Olds #8 heads should have 1.88 int and 1.625 exh valves, I can also check the throats, if they are below 88% it only takes an hour and a half to machine them to 88-92% depending on your application. Email me at junkdump455@gmail.com and we can discuss your wants and expectations. I also accept shipments if you prefer not to drive up to Maine.
@@junkdump2720 4 to 6 hours on both heads not each head right? and what part of maine?
@@bobdimartino6738 You are correct, it takes 4-6 hours to complete the pair, and I am in Brunswick.
Good video. I have went port crazy and hit water on olds E heads.
That sucks, I love E heads.
@@junkdump2720 there all close to the same except J heads.
@@wildrosegarage4208 Don't forget about KA heads. True they are mostly similar but for shallow spring pocket heads I like those E's.
And there ain't no crazy like "port crazy"
Hay I will buy them if you have no use for them
I still have to cut valve seats, but when they're done I would sell them.
@@junkdump2720 ok let me know Thanks
@@coreyharris7090 so? Did you buy them?
Hey there, what head is that? It kind of looks like a #2a 260 head. Thanks
That's a 5A head from a 1982 307, though the techniques you see will work on any Oldsmobile head.
Hey thanks. Are these #5A heads a pretty good swap to use? I'm running the #4a 403 heads and I'm considering these to replace them.
@@MetalMania899 What is the year and displacement of the engine, is it a 403? And is it a daily driver, street/strip, or race engine?
@@junkdump2720 I have a 77 350 block bored to 355. I also have a cam and headers on it. It's mainly a street car that I'm trying to squeeze more power out of. I thought these 5A heads might be an easy way to up the compression, but I don't think they flow as good as the 4a heads.
@@MetalMania899 The 5A 307 heads in this video would definitely increase the compression ratio. With the porting, 2 inch intake valves, and 1.625 exhaust valves they should flow equal to or better than stock 403 4A heads. I think a set of 1972 7A heads would be best (port them like I did in this video) if you could find a set.
Well that's nice but Big block four fifty five head's flow more air that those small block three fifty head's ever will without porting them
Keep wasting time and money with those small block three fifty head's and get a clue people OMG people please use your imagination 😉😂😆🤔
Do some research on the small block three fifty head's compared to the big block four fifty five head's by that time you might have finally have gotten a clue to what I'm saying 🙄 duh
Perhaps you misread the title and video description or had the audio muted. This video demonstrates techniques for porting small block heads for people who want better performance from their small block heads. The same porting technique will apply to big block heads. This is not a comparative video on flow and the depicted cylinder heads are not 350 heads.
@@rodneyhopper22 You are mistaken, those aren't 350 cylinder heads in the video.
I'm glad @rodneyhopper22 mentioned the head swap upgrade to big block heads. In my experience when swapping 455 heads (with 2"int and 1.6"exh valves and 80cc) onto a 350 (that had 2"int and 1.6"exh valves and 70cc) the HP gain is negligible and TQ gains tend to be very low, around 10-15. This is because the 455 heads typically have large 80cc+ combustion spaces which lower the compression ratio of the engine, in some cases from 8.5 down to 7.5. Also the swap requires a new intake and can cause issues with face and port matching. Conversely, mild porting of the 350 heads can net 30HP and 20TQ without changing your intake or lowering the compression ratio. If you are building a race engine small block then the big block heads are capable of being fitted with larger valves, and have better velocity and flow.