So is there a down side.

[autobonrun]

At least for a SC with SSI, is there a downside to 20/21's or 964 Cams as compared to the stock SC cam? Why didn't Porsche use these if the performance is much better?

Just trying to understand the total picture. Good discussion regardless.

[TRE Cup]

The ssi's are from the pre smog era. So the answer there is obvious. The cams (964) were developed to work with motronic controlled engines. I don't know of anyone that did a full environmental shed test of a SC equipped with these cams to see if they would pass smog specs too. I seriously doubt that they would; cis just isn't that "smart" to take care of cold start/ hot running in passing smog with a more radical camshaft design.
so in a word as to why Porsche did not do it? Smog

[autobonrun]

Originally posted by TRE Cup
The ssi's are from the pre smog era. So the answer there is obvious. The cams (964) were developed to work with motronic controlled engines. I don't know of anyone that did a full environmental shed test of a SC equipped with these cams to see if they would pass smog specs too. I seriously doubt that they would; cis just isn't that "smart" to take care of cold start/ hot running in passing smog with a more radical camshaft design.
so in a word as to why Porsche did not do it? Smog

Thanks TRE Cup. So I guess if I live in a state where there are no smog tests, I should consider one of these cams. I thought there may be some issues with rough idle, worse gas mileage, or something else like that.

[cgarr]

Thank God for the big three here in MI NO Smog Here!!