Porsche 3.0 performance cam???

[mschwien]

This may fall into the dumb question of the day category, but here goes. I've had my 83SC since feb (1st Porsche). The PO had the engine completely gone through while repairing a broken headstud. He also did some nice things to the car including BB stainless dual out headers, Carrera cooler etc. While the headers generate a nice sound, the engine at an 800 RPM idle has a rumble that slightly reminds me of the muscle cars days with a V8 and a high lift/duration cam. I've listened to some of the exhaust threads (with sound) and most don't seem to have that "rumble" to them. Not that familiar with performance cam options for the 3.0 and was wondering if there was even such a thing for a non-race street driven Porsche.

The car runs great with no low RPM hesitation at all which you might expect with a higher lift/duration cam either. I don't have all the specs as to what all was done to the engine.

Maybe its just the headers???

Any thoughts?

[javadog]

Mike,

I'd say the idle speed is too low, for a start. Check the sticker in the engine compartment to get the correct value. I seem to recall it is around 925-950 rpm. An incorrect CO setting, vacuum leaks, poor injector spray patterns and a host of other things can cause a rough idle. I'd start there first, as I doubt its a cam.

Some people do change the cams in these. There are several grinds that have been used.

JR

[bkreigsr]

have someone else familiar with the 3.0 take it for a ride and see if they can determine if the cars 'zones' (gets into the cam groove) in a different rpm range than their's.
I have had three pairs of cams in my 73 and each has a different feel when the car comes alive.
Bill K

[mschwien]

Thanks - I've seen some threads on checking for vacumm leaks - will give it a try this weekend. Whille it pulls strong through RPM's I've noticed there is some slight missing at no-load situations.

[flmont]

I have a 81' 3.0 with 964 cams...and it rumbels at any RPM......FM