Thread: Porting Question.

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Originally Posted by BigTruckDriver

Is this pretty much with a street engine ,daily driver, or is it also with a race engine??

That's with any engine. Of course, the bigger the cam the worst reversion will become an issue. An 1/8" lip on the bottom of the intake runner has the most anti-reversion benefit. It's also beneficial if the headers are about an 1/8" below the bottom of the exhaust port.

Originally Posted by camaro_fever68

That's with any engine. Of course, the bigger the cam the worst reversion will become an issue. An 1/8" lip on the bottom of the intake runner has the most anti-reversion benefit. It's also beneficial if the headers are about an 1/8" below the bottom of the exhaust port.

I apologize I was reading your post wrong . Makes perfect since once I read it slow
So your saying you should have a small lip on the bottom of the intake and exhaust ports. Sides and top should be smooth???

Originally Posted by BigTruckDriver

So your saying you should have a small lip on the bottom of the intake and exhaust ports. Sides and top should be smooth???

Yes. You never want the bottom smooth if you can help it.

Denny That was an interesting article. They say that larger ports tend to lead to less top end power which does make sense, but the little I open mine up brought me better HP and higher RPM's. Why??

All I can tell you is the EPA bumps in the intake ports top corners have to be port matched to the intake . If not the air flow going threw the intake will hit it like a wall . Over the years I have ported Lots of cylinder heads . That is true about porting the roof of the intake port and not doing a Lot to the floor . The most HP on SB Chevy heads is in the bowl area . I make good money working on trucks but it's always gone when I need car parts ? That whey I just don't go out and buy a set . But if I did they would be a bare set that I would assemble . And I do not like aluminum heads . Every set of heads I have ported worked real well It's just the older SB Chevy heads need Less porting done to them . The 305 heads #416 # 601 need hours of porting . I am at 10 hours on the first head at 95% done . But Like I said these head will make my 355 Rage

Originally Posted by DennyW

Please explain why Ray ?

At low/mid rpm with a long duration cam, the intake valve is still open as the piston starts it's travel back up. The majority of air flow travels the top of the head port on it's way to the cylinder. When the pistons starts it's travel back up it can push some air back through the intake vavle into the port. That air will travel the bottom and the 1/8" lip exposed in the intake will create an air dam of sorts to block the air flow back into the intake tract.


Joe Mondello has a really good article on this from his head porting school.

Some real nice answers to porting guys. I learned more from some of you than I did reading up on it.