the flyin' scotsman

I know theres a difference between the intakes so if its believed the GT/GTS breathe better has anyone machined a S4 intake to GT/GTS spec?

Tom. M

I believe the GT is just port matched ..so you could do that to the S4 intake pretty easily. I also remember Mark A extrude honing an intake but it didn't gain that much for all that effort...

IcemanG17

The GT was port matched...I remember hearing early S4 intakes didn't have the ribs near the flappy and later ones had the standard 3 rib like in your photo...or maybe I have it backwards?

the flyin' scotsman

IIRC port matching needs the cylinder heads in hand with the intake?

I do have an extra S4 intake to play with.

FBIII

I have an R2 and an R4 intake and they both have the 3 ribs. One of the intakes came off my GT but I have forgotten which. Any idea which one it should be?

cfc928gt

I have the intake off my '90 GT right now and it's a 4R.

RyanPerrella

Malcolm,

What makes you so sure there is a difference between intakes from an S4 and from a GTS aside from different casting marks? ex: 2R and 4R?

I had read before that the GT engines were port matched. Thats a pretty simple thing to do on your own and that being the case takes out the idea of shopping for a magic limited intake that porsche made way back when. What did you think was different between the 2 or 3 examples?

cfc928gt

Was the port matching done on the intake or the head? I can see where my heads were ground and openned up, which I assume was to match the intake.

RyanPerrella

I think the heads were typically machined that way. The two GT engines i played with were modified post casting on the intake side. But I believe most of the later heads are the same.

The intake is not machined as obviously

I really think there is no difference in intakes whatsoever aside from the earlier ones not having the ribs where the flappy butterfly valve is located.

jon928se

My understanding is that the GT and later probably 90+ were port matched but the castings of the intake were improved so that less maching was required.

At the end of the day it's something that can be done at home with a dremel or die grinder and using the old gasskets as a template.

Vilhuer

Early '89 GT had modified intake as 4R casting wasn't around yet. Once 4R was in production less machining was needed. When 2R part stock was used also '90-91 S4 got 4R to simplify production. Engines using 4R intake but not yet later style heads had intake side opened up a little to match ports to intake.

FBIII

Were there then an R1 casting for 87 and 88 model years?

Vilhuer

R1 is early '87 without three ribs.

ptuomov

I think the standard operating procedure is to use the gasket as a template to match the intake manifold and the intake port separately to the gasket. I don't know if that is really the best thing to do, but I know it's the most common thing to do.

If you start messing with the intake manifold, my humble opinion is that you should send it to a head porter who's done these manifolds before, installs a spacer on the throttle-linkage side, and ports the manifold for balanced flow. With our ECU's, you don't necessarily want the most flow per individual runner, you want similar flow for all runners. One of Jim Morton's friends did my intake manifold.