Cylinder head flow

[Flat Screwd]

Head port flow. We all know what it means and how you get it but heres just something to chew on. If out of the box heads flow a given amount on the intake side lets say 300 cfm than if built corectly all 8 ports should flow the same. Right? And the same goes for the exhaust. Right? So heres my question. Assuming that you are running a single carb the four cornner cylinders are farther away from the carb. That means means unequal distribution of air fuel mixture from idle clear through wide open throttle. So assuming these conditions would'nt it make sence that the cornner cylinders should get a different flow value?

[mister460]

Sometimes. Port flow on an engine is VERY tricky. Most high-po manifolds are designed to equally ditribute the fuel/air charge so you want to keep head port flow equal. But on different engines with diferent combos the port flow may not be equal and will need to be adjusted somehow. But this is not usually done with head porting. Head flow is best kept consistent. Adjustments can be made by changing rocker ratios on the corners. It sometimes helps you pick up a few ponies if you run 1.5 rockers on the inside holes and 1.6's on the corners in a SB Chev. But that method might not work on other engines. This is one of those things where you ask 5 people and you'll get 7 answers. My answer:for most people, don't worry about it. Just use good components and don't "over modify" unless you know what you're doing and you'll always build a strong motor. Any other Q's, don't be afraid to ask.

[CrazyHippy]

I have been wrong before, but shouldn't the all flow equally. unless the cylinders are not all the same size, they should all get equal amounts of air. The fact that they are farther away doesn't matter, so the air/fuel they get is slightly "older" BFD
This 30 second rant was brought to you by the good folks at your mommas house.
BJH

[Flat Screwd]

Mister 460 your ideas and mine are quite the same. It would just seem lodgical that there is some differance between cylinder flow due to their relative distance to the carb. But like Crazy says whats the differance if each cylinder pulls gas from either the intake port or the plenum so what if the gas is as he says"older". The reason I ask is because you see guys working the flow bench and they have the intake bolted on. So if the heads already flow equal amounts , than why dont they flow the intake seperatly untill its equal?

[058]

Intakes are flowed seperately. The NASCAR engine builders put as much if not more work into their manifolds as they do the heads to try to minimize the differences in the runner lengths. They also make changes within the engine such as different compresson ratios from cylinder to cylinder and different timings for each cylinder individually to get maximum power from each cylinder. For example: a lean running or detonation prone cyl. will get a reduced c/r and slightly less timing to prevent that cyl from detonating. They see no sense in restricting all the other cylinders just because 1 or 2 can't run at a higher c/r. They tune these engines as 8 seperate one cylinder engines on a common block and crank rather than one 8 cyl. engine. The difference in runner length will cause the peak volumeteric effiency to occure at different rpms, shorter runners at a higher rpm and the longer runners at a lower rpm. Hope this helps.

[froggystyle]

God I love this place....

[ponponracing]

Every day I learn something new I feel I'm a better ponponracing. Unfortunatly, I didn't learn anything today, so please make my day and tell me how those nascar guys do to use different timings on cylinders in the same engine?
Do I like those forums.....

[superdave013]

Flat Screwd, Just like everything else in life it's a compromise. In a perfect world the runners would flow the same just like the heads. But with a cast intake you will not get that. Now if you drop over 2 grand on a custom one off sheet metal intake made just for your engine you can get much closer. Check out this web site. I wish I could afford one! http://www.hogansracingmanifolds.com/
http://www.hogansracingmanifolds.com/images/pic01.jpg

[058]

Very basic, Ponpon, they grind the point cam in the distributer for a conventional ignition and with electronic it can be programmed into the control box. For more info on this see Circle Track mag. Sept, 2001. "Compresson Balancing" So I just made your day 'cause you learned something new, are you happy now?

[Flat Screwd]

Man what a piece of work thoes Hogan people put out. As a experienced welder allum and sts. I have to say god thats a piece of art. And only sombody that has any experience can only appreciate the amount of work that whent to thoes manifolds. Man thats testomony to how far people are willing to go for that verry last HP.
How about that one that looks like a new small block LS1

[superdave013]

Originally posted by Flat Screwd:
Man what a piece of work thoes Hogan people put out. As a experienced welder allum and sts. I have to say god thats a piece of art. And only sombody that has any experience can only appreciate the amount of work that whent to thoes manifolds. Man thats testomony to how far people are willing to go for that verry last HP.
How about that one that looks like a new small block LS1
They look even better in person. I know a guy that is selling a Hogan tunnel ram for a big block chevy right now. He only wanted 1,800 I think! What's a new cast eldebrock tunnel ram cost? under 300 maybe.
Ask Racing Ray to post a pic of his engine when it was on the dyno. Wow, was that a high buck deal.
So your a good al welder? Where are you located? Anypalce in So Cal?

[Racing Ray]

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[This message has been edited by Racing Ray (edited March 12, 2002).]

[superdave013]

Ray, hell that's just a drop in the bucket compared to the rest of that engine! Like they say, speed cost money, how fast can you afford to go. Looks like you're going faster than most. That's not in your everyday lake boat though I bet.
This will be on my next blown engine.
http://www.hogansracingmanifolds.com/images/pic08.jpg

[spectras only]

Nice manifolds Superdave, I hope they're going to make some for the modular [4.6 L]Stangs someday.I had my composite intake replaced once due to cracking [7 year silent warranty program http://free.***boat.net/ubb/rolleyes.gif].Too bad that the Bullit intake isn't compatible with the older 4.6's.

[superdave013]

Originally posted by spectras only:
Nice manifolds Superdave, I hope they're going to make some for the modular [4.6 L]Stangs someday.I had my composite intake replaced once due to cracking [7 year silent warranty program http://free.***boat.net/ubb/rolleyes.gif].Too bad that the Bullit intake isn't compatible with the older 4.6's.
I bet they would make you what ever you want. Did you check out the site. All kinds of crazy late model stuff on there.