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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Sorry, basically it is not worth the expense to just change out the cams.

SC & C2 cams open the intake and exhaust valves higher and longer so they do breath better.

Because they are open longer they do not fully close the intake valve on the compression stroke as soon as the stock turbo cams do. This makes for a little less effective compression. Less compression means less pre-boost torque.

There have been a lot of guys that have been able to put out monster HP with the stock cams and stock ports so it is not a must have.

My opinion is first low back pressure muffler, then turbo, then intercooler as a best practices approach. Most go out and spend a pile on a header system.

With a 930 most of us are hooked on the big HP numbers as boost is addictive. Under boost the C2 cams and the SC cams will help make more total HP. They can help preboost but to work best some measured compression should be added back in.

I would not go to the expense of just changing the cams. If I had the motor apart anyway I would go with the C2 cams and shave the head to get back some of the effective compression and would port the heads at the same time.

Porsche did a couple of things with the 930 in the name of emissions. They put in a restrictive exhaust with thermal reactors or a cat; small ports to increase velocity to aid in air-fuel mixing; they put a low lift no over lap cam to keep exhaust gasses out of the intake tract and to speed up air flow for better air-fuel mixing; and, they left the cooling fins off the top of the cylinders so the motor would heat up and run hotter and to work with the cat. (Like the 5 blade cooling fan on the 75-77 911's).

I am not an expert so please take my comments with a grain of salt.
Old 07-31-2008, 03:17 PM
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