CIS with 964 grind cam
 

Apologies in advance if this is a rehash.

I've got an '83 SC with K&N filter, appropriate sized SSI and Dansk 2in/2out exhaust. Otherwise stock.

1. I have read various articles about using a 964 cam or matching reground cam with CIS as a performance boost. Additionally, I have read that this is the only cam (964) aside from stock SC cams that will work with CIS.

Are these claims true?

2. In these articles it was never specified if the SC motor was an early 44mm intake (Euro?) or a later 38mm intake.

Anyone know?

I assume I have the 38s, as my car was a U.S. car originally sold in So.Cal.

Feedback is much appreciated.

Can't speak for the 964 cams with the 38mm heads, but '80-'83 US spec cars came with the 38mm intake heads.

I had that combo in a 914/6....it screamed.

@Joe Bob. What motor?

83 3.0.....I did the upgrade and valves when I popped a few headstuds. BTW, new cams need work. They have an extra lobe for power steering.

@Joe Bob. Stock otherwise and 38mm as far as you know?

Dougherty and Webcam also have profiles that work on SCs... Webcam 20/21 comes to mind.

20/21 is also an option. The engine was otherwise stock with headers.......

My guess is the cam folk will know what intake size works with any given cam???

Gracias fellers'.

If you ever hear about some specific reference to the intake size on the CIS/964 cam combo, let me know.

@Joe Bob. I was planning to have my SC cams reground.

I have a set of 964 grind cams without the power steering drive.....they cam out of the engine that became my race motor. They are in good shape....

PM me if interested.

Scott

Pelican Article
 

Here's some good info:

Pelican Technical Article: Extracting Power from CIS 911s...

Hope it helps

Books have wrong Euro SC intake port size
 

Guys

The '78/79 US and ROW SCs had 39mm intake ports and 35mm exhaust ports. The intake runners were "large" to match the ports.

The 80-83 US SCs had 34 mm intake ports, and smaller runners to match the ports.

However, the 80-83 Euros continued to have the 39mm intake port heads.

Wayne's table in his book, as well as Anderson's, has this wrong - these tables would have you believe the Euros got the small port heads as well in 1980. But they didn't. Which is why the late Euro 3.0s had a factory horsepower rating which is a lot higher than just bumping up the CR by 0.5 points could produce.

If you doubt this, just look at the part numbers for heads and the #1 intake runner. The Euros have the same part number for all years of the SC. Which are the same as the part numbers for the '78/9 US cars. The 80-83 US part numbers are different for these parts.

Never was a 44mm intake. You must have meant 34. But your '83 US car has the 34mm intake ports.

@Walt. Thanks for the info. I was just going by the Pelican info on the intake sizes.

@Walt. So the Euro size was/is 39mm and the U.S. size was/is 34mm??

So have the articles I've been reading about 964 cam based on U.S. (34mm) intake or on the Euro (39mm) intake???

@winders. PM'd.

I believe that it is not CIS that limits your Cam choice but the shape of the SC piston.

I have a 1979 911SC and my intakes are 38mm. I had my stock SC cams reground to the 964 cam profile. You do not need 964 cams.

I also have Max Moritz 98mm P&C (short stroke 3.2) with 9.3 compression, aluminum flywheel, SSIs and M&K 2 in 2 out with the CIS. The car really Screams starting at 3,000 RPM.

80-83 us engines with their intake ports ported out to 39mm along with euro cis with the 4r runners is a hot setup. Over 200 hp.......