cam upgrade on SC with 9.3 pistons?

Gogar · 03-20-2007, 11:20 AM

The stock rebuilt engine in my "new" SC is cool, just turned 3000 miles. I plan to do SSIs and an M&K or something sometime in the future, for a little more "ooomph."

My question is,

Should I consider a camshaft regrind, ie. 964 or 20/21 or something similar, even though I only have the stock 9.3 C/R pistons? Is it worth doing?

I searched and found a lot of threads about 964 grinds in SC's, but most of the time it's coupled with higher C/R pistons, which is not something I'm interested in doing at this time.

What do you think?
Thanks

Vin-barrett · Vin-barrett's Garage

I have 964 cams in my car but I also installed the 9.8 euro SC pistons at the same time. I wouldn't think 9.3 pistons would feel too different.
I would say where the car used to run out of breath somewhere above 5k , now it pulls all the way to redline, I like that so IMO it was worth it.

crashmy911 · 03-20-2007, 12:09 PM

I did the 964 cams with the 8 5 to 1 pistons. At first I thought I made a mistake becasue there was no power below 4000 rpms. but as the engine has a few more miles on it, it is alot better. It pulls from 3800 all the way to 7000 rpms. I'm afraid ro rev it higher then this. I did put 8000 rpm valve springs for insurance. I would do the 20 21 grind. Do you ssi's? I would also do ebs valve springs or jerry woods springs. Look for Noah's post on this engine upgrade. I think that is one of the upgrades in the list of things to do to sc's.

Superman · 03-20-2007, 12:11 PM

I have 9.3:1 pistons and 20/21 cams. I LOVE them. LOVE. I have applied for a marriage license, but the state won't let me marry more than one cam at a time, and I don't know whether I love the right cam more, or the left cam. I love them the same. I love them for their grunt below 3000 rpm. I love them for their turbine engine-like power above 5000 rpm. I know my stock cams will be much happier with someone else, but we don't keep in touch.

dd74 · 03-20-2007, 12:54 PM

Remembering fondly back to my 3.0/9.3 CR days, 20/21s were definitely part of my plan. But I stress only "part."

The rest of my plan entailed the heads and CIS from a 3.0 from 78-79. I already had the SSI-type h/es and free-flowing muffler.

All-in-all, I was quoted an estimated hp. of 230-240 with this combination. If you want CIS reliability but with a motor that will munch upwards of a 3.6, this would be the route to go, particularly since the heads aren't too far away from the cams.

sjf911 · sjf911's Garage

It seems to be conventional wisdom that the 964 cam works well in the 3.0. I have the 964 grind going in my rebuild right now. Camgrinder did not feel new springs were necessary but did suggest them with anything more aggressive such as the supercup grind which would have required new cams. Anything more aggressive than that would require carbs/throttle body FI.
I also plan SSI's but also have moved up to 3.2L heads/intake for an EFI conversion. This should result in a significant improvement in the old stock 3.0/CIS.