Intake manifold port matching, smoothing.

[enkeivette]

So I now have probably 5 hours into port matching and smoothing out my intake manifold. Lots of rough spots in there, I was surprised. And I had to take a bunch of material off the ports to get them to match up to my heads. Hope I gain more than 10hp for all that work!

[anthonydalrymple]

You probably will gain a good bit of some HP..... One way to find out...;)

[enkeivette]

I'll probably gain the most hp from no longer having a leaking intake manifold gasket.

[anthonydalrymple]

True.... Port matching is a tricky subject of which I've only barely communicated with a know "superb \ well known" porter. His theory involves two types of porting; one for the street & one for pure race track only. The street version involves making the port large at the opening, smoothly transitioning to a smaller dimension in "the middle", and then back to the same diameter as the opening at the "exit'. This is both for the intake and the heads individually by the way..... His theory for the race only version of course involves equal port dimensions of the largest matching dimension; enlarging from the intake through the head. Of course this involves taking the worst intake \head port, enlarging it and maximizing the flow of that given port, and working the other ports to match..... IMHO.... Yes, he's one of the guy's whom have built engines for the Car Craft Engine Builder's challenge and has consistently placed in the top three over the last 2 years....;)

[BRUTAL64]

True.... Port matching is a tricky subject of which I've only barely communicated with a know "superb \ well known" porter. His theory involves two types of porting; one for the street & one for pure race track only. The street version involves making the port large at the opening, smoothly transitioning to a smaller dimension in "the middle", and then back to the same diameter as the opening at the "exit'. This is both for the intake and the heads individually by the way..... His theory for the race only version of course involves equal port dimensions of the largest matching dimension; enlarging from the intake through the head. Of course this involves taking the worst intake \head port, enlarging it and maximizing the flow of that given port, and working the other ports to match..... IMHO.... Yes, he's one of the guy's whom have built engines for the Car Craft Engine Builder's challenge and has consistently placed in the top three over the last 2 years....;)

That's pretty much Basic Head Porting 101. :bigthumbsup:



I've been porting heads since 78. One thing to remember, "It is sometimes more important what you DON"T remove than what you do remove".:judge:

[Vettezuki]

That's pretty much Basic Head Porting 101. :bigthumbsup:



I've been porting heads since 78. One thing to remember, "It is sometimes more important what you DON"T remove than what you do remove".:judge:

What's the basis of the theory, particularly for the different dimensions in the street application?

[enkeivette]

Not sure but they do the same thing with headers. Maybe decreasing the diameter (so to speak) of the port in the center causes the velocity of the air to increase, and the widening of the port causes a sort of scavenging effect? I really have no idea though.

[anthonydalrymple]

What's the basis of the theory, particularly for the different dimensions in the street application?

From what I think I understand about this: It has to do with the "pulse waves" created by the valve opening \ closing timing events of the natural combustion process. Exhaust scavenging operates in a similar manor and the Thorley Tri-Y header claim to fame.

[SeanPlunk]

That's really interesting. It's amazing all the science and physics behind making big horsepower.

[Vettezuki]

From what I think I understand about this: It has to do with the "pulse waves" created by the valve opening \ closing timing events of the natural combustion process. Exhaust scavenging operates in a similar manor and the Thorley Tri-Y header claim to fame.


That would suggest the porting techniques are RPM related and the analogy of the Tri-Y to Long Tube is good.

Tri-Ys: great for low end torque (what is most needed in street applications).
Long Tubes: great for high rpm power (what is needed for race applications).

[anthonydalrymple]

....That would suggest the porting techniques are RPM related....

I very much believe so. It think it has much to do with the combination: volumetric efficiency, cubic inc displacement, flow capabilities of the heads and exhaust, intended rpm use, etcetera. I've played around with porting intakes based extensively on the advice of Tmoss (www.tmossporting.com.) and the info available on his website. I had an RPMII intake on my 302 that made good peak numbers (294rwhp & about the same in torque); but it really was a pain in slow driving and stop & go traffic. I decided to port an '96 Explorer intake since i felt it could nearly match the total flow numbers of the RPMII and still pick up the bottom end with the longer runner length. I ran the same engine combo with the exception of the intake only and on the same exact dyno in very similar atmospheric conditions. Imagine my surprise when both the torque & horsepower from 2G to 5G picked up 10-15. The peak was interesting; 280rwhp & 305rwtq. I also ran both combinations at LACR before it closed down; ran the same exact et's before & after. I chalked that up to the better acceleration in the mid-rpm range by the Explorer intake more than making up for the short high rpm advantage the former RPMII had IMHO....

[Vettezuki]

I very much believe so. It think it has much to do with the combination: volumetric efficiency, cubic inc displacement, flow capabilities of the heads and exhaust, intended rpm use, etcetera. I've played around with porting intakes based extensively on the advice of Tmoss (www.tmossporting.com.) and the info available on his website. I had an RPMII intake on my 302 that made good peak numbers (294rwhp & about the same in torque); but it really was a pain in slow driving and stop & go traffic. I decided to port an '96 Explorer intake since i felt it could nearly match the total flow numbers of the RPMII and still pick up the bottom end with the longer runner length. I ran the same engine combo with the exception of the intake only and on the same exact dyno in very similar atmospheric conditions. Imagine my surprise when both the torque & horsepower from 2G to 5G picked up 10-15. The peak was interesting; 280rwhp & 305rwtq. I also ran both combinations at LACR before it closed down; ran the same exact et's before & after. I chalked that up to the better acceleration in the mid-rpm range by the Explorer intake more than making up for the short high rpm advantage the former RPMII had IMHO....

Yeah Makes sense. It also implies pairing with exhaust headers is quite important because of the effects on back pressure and scavenging. It would be really interesting to do a study cominbining

Street Porting w/ stock headers, Tri-Ys, Mid Length, Long Tubes
Race Porting w/ stock headers, Tri-Ys, Mid Length, Long Tubes

My hypothesis would be that Street Porting with Tri-Ys would be the best option for most people and race porting with LTs reserved for people who are actually racing.


In my case, my Heads and Cam LS1 makes 391WHP with a mild tune and stock headers. However, the C5 Vette it came out of with a more agressive tune and headers made 432! (Some of that could be chalked up to different IRS, but not so much I don't think.)

Anyways, it do get complicated.

[BRUTAL64]

What's the basis of the theory, particularly for the different dimensions in the street application?


What I was talking about is the funnel effect that sets the flow to make the turn to the valve (intake) or the exit for the exhaust. Very important. ;)

[anthonydalrymple]

What I was talking about is the funnel effect that sets the flow to make the turn to the valve (intake) or the exit for the exhaust. Very important. ;)

I agree, but I'm not well enough versed in theory & dynamics to say anything more..... Engineering is a very interesting topic to me IMHO....