Greg Phillips

We had an interesting discussion of mixing and matching 32V heads and pistons.
Now wondering about cams.
There has already been discussion of S3 vs GT vs S4 cams, but I was wondering what would happen if you were to use intake cams from one engine and exhaust cams from another, say S3 intakes and S4 exhaust

Is that possible?
Could it be worthwhile?

Greg Phillips

atb

I'm running GTS intakes with S4 exhaust. Good for about 10hp across the board.

Vilhuer

As long as S3 cams are modified to fit to '87+ heads or S4 cams are modified to fit '85-86 four valve heads they can be mixed in any combination one wants. Its even possible to have different style cams in each head. One S4 engine friend and I dismantled recently had one GT cam in it and other three cams were stock S4 parts. Luckily I had bought one cheap S4 cam earlier from Germany which just happened to be same part as missing S4 cam. So we now have full set of S4 cams and extra good condition GT cam for possible worn GT cam set. Best part of whole thing is that new GT cam had been installed by local authorised dealer few years before S4 engine lost its cambelt and was replaced with another S4 engine.

Dennis K

Is it possible? Sure. Is it worthwhile? Depends on what you start with, but I believe a complete set of GT or S3 cams is about as good a combo as you're going to get.

S4 cams have the lowest lift, S3/GT cams have the highest lift and GTS cams are exactly between.

S4 have the shortest intake & exhaust durations. S3/GT have the longest exhaust duration and GTS the longest intake duration. GTS cams are oddballs to me because the intake lobe center is heavily retarded.

GT's are rare and expensive. S3's are at least available, but you do have to modify one of the exhaust cams to fit an S4 head. You can also regrind, but that's another story.

Here's a chart w/ the first 4 columns showing stock specs and the next 4 showing some int/exh mix-n-matches.