Cheburator

Cutting the long story short - I have two perfect sets of GTS cams that came out of low mileage 5-spd cars. At the moment they are occupying valuable cabinet storage space. I also have a perfectly good set of S4 cams and a freshly built 1989 S4 engine.

I seem to remember that the intake GTS cams aren’t that bad in terms of lift and duration. It is the exhaust cams where Porsche really strangled the engine. That set me on the meandering path of combining a GTS intake and a S4 exhaust for a 1/2 house to GT cams.

Does it look promising or am I talking complete rubbish?

FredR

It might be rubbish but it is what I have fitted in my motor!

It seems OK but without a dyno it is difficult to say whether it is of any significant benefit on an otherwise stock S4 motor mechanically speaking. A faster exhaust and a bit of shark tuning thrown into the mix plus a pair of plenum spacers. The cam recommendation came from Louie and that was good enough for me.

Needless to say I have a pair of S4 inlet cams and a pair of GTS exhaust cams lying around somewhere.

SwayBar

I wish there were dyno charts to consult on the proposed combination in order to make an informed decision...

Cheburator

I have a shark tuner and will be fitting JDS PEMs to the ECUs, thus I will be able to optimise the set up. Wonder if I will see numbers beyond the stock 320... The engine was healthy before the teardown to the point of showing zero wear on most things...

SwayBar

Have you considered popping in S3 cams instead?

Essentially GT-cam performance, and should easy to track down a set and modify.

Cheburator

I have two pairs of S3 cams but modifying them in the UK isn’t easy and also I was thinking aloud. I already have these GTS cams, they are simultaneously worth a lot and also nothing, thus I wanted to see if there is a better use for them rather then being a doorstop. The S3 cams are destined for a spare GT motor that I have lying around. But it would be a while before I get around to installing them - have to find someone willing to weld the sleeve and cut them, as well as grind them to Elgin spec.

The GTS/S4 combo will go in a 89 S4 5-spd which is basically a GT in drag - LSD, sports seats, sports suspension, 2R heads, 10:1 comp pistons and also port matched manifolds. The plan with the S4 is to be stock. And the GT cams have been installed in my GTS 5-spd a long time ago.

SwayBar

Looks like a fun project!

Alright, so S3 cams are out for now...

It looks like you'll be the pioneer here using a GTS intake-cam and S4 exhaust-cam - with dyno results!

Timing the cams may take some guesswork, but I'd shoot for 180-185 psi on a compression test for a sanity check.

SwayBar

Just thinking this over...

It's the S3 intake-cam which needs the collar welded on, right?

If that's the case, why not use the GTS intake-cams with the S3 exhaust-cams instead?

Who knows, that combo may turn out to be more powerful than straight-up GT cams!

SwayBar

Did you ever make a decision on this?