Simple Cam Question modified 3.0
 

My question is this:

To change to a "suitable" cam profile to make use of a high compression 3.0SC engine with EFI/ITB, is it better to

A) regrind a 4 bearing 3.0 SC camshaft set
B) buy a "suitable" 4 bearing camshaft set (i presume you can easily purchase modified 4 bearing camshafts?)
C) Switch to a 3 bearing camshaft and cam housing, such as an "early 911S" camshaft.

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In all honestly I am 2-3 years from building a 3.0 engine which would run single plug, high compression (less than 10:1), and EFI/ITB. In fact I have not yet fully decided the spec, as I am still learning the best route.

In the meantime, I have seen some "early 911S cams" in good condition, along with some 3 bearing cam housings, and I am wondering whether to buy them, or if sticking with the 4 bearing cams/housings is the only way to go....

stay with your 4 bearing camshaft.

You can get quality cams either reground, or from new billet, from John Dougherty or Webcamshafts etc...

If you are going EFI using a modern ECM, it would be a wasted opportunity not to go twin plug while you are at it.

Steve's comments may interest you: http://forums.pelicanparts.com/911-engine-rebuilding-forum/1033435-twin-plug-not.html

Ok brilliant, thanks for the advice. I will pass on the 3 bearing S cams/cam carriers, and stick with the 4 bearing stuff. I will also re-visit the idea of single plug in favour of a twin plug for high compression/EFI/ITB.

At the moment I am still figuring out the best route, the idea is to decide on that, then start buying parts. That way when I get to the actual build I have already accumulated alot of what I need.

Luke

Definitely stick with 4 bearing [49mm] cam housings. Increased base circle and lift available with 49mm housings is important.

The 3 journal cams are designed for a longer valve heads so dimension becomes an issue. Sell those factory "S" to finance your new purchase.

Cam selection is entirely based on person use parameters.
If you want to use your SC cams, regrinding them to 964 profile is pretty common. This is a conservative choice but very driveable.

My preference for street performance leans towards the 993 SS cams. Reasonable performance throughout the rpm range for a smaller motor.

DC-993SS I/E 248/234 242/228 .490".455" 114 1.6-1.8 mm
Maybe go with a closer lobe center [106/8] if you want to go a little more aggressive.

You might talk to Al Kosmal at X-Factory who builds engines and sells ITB EFI systems. He guided me on my 3L SC rebuild with 9.8:1 euro pistons. After discussing it with Al, we decided the stock SC cams suited what I wanted for the car (73 911T).

But the other comments here are certainly informative.

Hi runner4fun, thanks! Do you mind sharing your full spec? Were a bit off topic, but that dosent matter as the main thing i need to know was whether to buy 3 bearing cams and carriers while they were available....but thats sorted I will stick with the 4! And of course consider a twin plug.

• What 3.0 Sc engine did you start with? The 180, 188 or 204?
• "Just" the 9.8:1 euro pistons in place of your factory pistons and re-used your cylinders?
• Is it really just the pistons themselves that boost the 180 compression from 8.5 to 9.8 or do the heads needs work too?
• you stayed with the SC cams (same as 3.2 cams) but used a X-factory ITB/EFI system? Could you link to a system?

I can chat to them, but also nice to observe and record other specs. In fact any ideas on upgrading a 1979 180HP 3.0SC ROW euro engine and I am all ears! I am only looking for fun street use, and to gain a bit of MPG over the CIS design

SSI's of course, its more the P&C/ITB/EFI/and Cams/Cylinder Heads (valve sizes, etc) im not too sure on.