Carpokes Porsche Forum

I have a porsche document somewhere that stated retarding the cam over 5500rpm in conjuction with the tuned intake gained them 3hp in that range due to the supercharging effect of the runner length and retarded intake valve closure. Since Im running very short runners with a large plenum and am basically in shovel air in at all costs mode at that point Im thinking there is at least some benefit to raising the deactivation point, but as MM says the dyno will tell.

The tuning Porsche put in place is certainly out the window

michaelmount123 wrote: Thu Jan 08, 2026 2:11 pm

944crazy wrote: Thu Jan 08, 2026 2:11 am I remember reading some old threads on rennlist where the variocam solenoid had been reversed on a boosted 968 so that the intake cam would be retarded 15 degrees in the upper rpm. The intended benefit was to reduce valve overlap in the higher rpms.

See my edits in last post.
For clarification:
The Variocam solenoid has the intake in its retarded position (increased overlap) under 1500rpm and over 5500rpm. A turbo engine often likes reduced overlap, but on a 968 with its relatively mild cams, only the dyno knows for sure.

I do think the 968NA cams are a fine choice with a turbo.

Would retarding the intake cam not decrease overlap? As the intake valve is opening later after the exhaust valve has closed more.

Very interested so see what your findings are with this @Bergerac as I will be building up a 968 turbo engine this year as well. I see you're in WA? I'm over in Qld, not too many turbo 3L's in Aus.

944crazy wrote: Fri Jan 09, 2026 2:45 am

Would retarding the intake cam not decrease overlap? As the intake valve is opening later after the exhaust valve has closed more.

Very interested so see what your findings are with this @Bergerac as I will be building up a 968 turbo engine this year as well. I see you're in WA? I'm over in Qld, not too many turbo 3L's in Aus.

Not many in Aus, only 5 or 6 that I know of;

- Sean Bs
- The light blue one that sold recently (I think that ended up in WA as well)
- The other White S2 that sold on Collecting Cars a few years ago
- Patricks time attack car
- I guess you can could RP968, though thats go a Thor engine now.

Im sure the Buchanans have built a few more for people who dont frequent the internet. There is another bloke in WA whos got some of the parts to build one but is finishing a 2.5 first.

Ill post results here once I sort out the source of this rattle, it will need to go on the dyno to do the tuning required to raise the boost past spring pressue, its simply too fast to do it on the road.

Replacing the tensioner and deleting it and going dual pulley pretty much cost the same, the only catch being clearance on the dual pulleys and the issues with front suspension geometry if you lower the crossmember.

Im installing a pressure sensor in the head this weekend and have a new J-tube and check valve to put in after. Fingers crossed that the issue is somewhere in the head and I havent managed to crack my new oil pickup somehow.

Let me know if you need any parts, Ive got all sorts of stuff I ended up with multiples or spares of, it might save you some shipping time/cost

Those are the only ones I know of as well, plus another recently turbocharged S2 here in Brisbane, Paul K's Time Attack car and a pretty serious track car with sequential box that was also on collecting cars some time ago and is now in Adelaide I believe.

Hopefully the rattle is an easy fix for you, keen to see some dyno results! What max boost will you be targeting?

Yep I will be needing quite a few parts no doubt, will send you a message when I start planning the build in earnest.

I've gapped the rings for above 18psi, was going to start there. Turbo would be happier in the low 20s from what I've been told.

Build thread is here if youre interested https://carpokes.com/viewtopic.php?t=2764