CIS power for an '83

[Porschedave]

Hi Folks
This is my first post - hope I do this correctly. I have a 1983 engine in my 1977 911S which I use for daily driving an every DE event I can manage. The car has been lowered, bigger bars etc. for the track and is a fantastic car to drive but .... I would like more power - don't we all. I recently drove a '78 SC at a DE event and his car had much more power than mine - I was very surprised. He had put in 95 mm pistons and the 964 cam grind which appeard to give him a peppier car. My '83 already has the stock 95 mm pistons and a CR of 9.3:1 (according to Dempsey's book). If I go with the 964 cam grind will I get a noticeable boost in power? Are there substantial differences in the stock SC pistons and the JE pistons (212435) that give a CR of 9.5:1? I have SSIs but a stock muffler. Do you have any sense of extra boost with a dual in/out muffler? Thanks for taking the time to read this and share your thoughts.

Dave
1977 911 3.0
1965 Notch
1972 SB
http://www3.telus.net/SUDAMA

[Eagledriver]

The 964 cam will give a small increase in power. His car has bigger ports and a bigger fuel injection manifold. That is why he has more power. The CIS is the big limitation on these engines. Your muffler is probably hurting you a little but to get big power increases you need to open up the ports and injection system or use carbs.

-Andy