Compression Change on 75 911S
 

I installed JE 9.5 compression pistons in my rebuild. Does anybody know what the HP and torque change should be?

If you didn't change anything else not much.

I read a post that said roughly 10 hp per CR point. Do a search.

Thanks for the information. I did put the pre 74 headers on too. It does run great and have enjoyed it.

At your altitude, its more of a power restoration more than an increase. :)

The '74-type HE's do help to the tune of about 10-12HP on those models.,...:)

For not much more you could find a pair of cams to work with the pistons you bought.

That'll give you some extra ponies. There is a technical article on the the 9.5Cr pistons and the 964 cams. This was my first idea. I went a little further.

You should definitely get a set of cams to bring it to life.

I have the 9.5:1 JE's, Weber's, 74 header back date, and a solex cam and I love the way the car feels. It pulls strong everywhere in the powerband.

I bought the car with a bad engine so I don't know what it was like before. I seems to have plenty of power from 2500 up to red line. I have the stock muffler now but thinking about changing it for more power and better sound. Any ideas? Also looking forward to taking it down to sea level to see how it feels. Thanks for the help.

Do what I wanted to do first on the same engine

High CR pistons(you have them)
964 Cams
SSi.

And the reliability ones
11 blade fan
carrera tensioner
Timesert/case saver

Missing something?

When I did the rebuild I did the Timeserts, enlarged oil pump, machined the block for new oil passage, new bearings and it had a 11 blade fan. Just trying to make a great daily driver. Any other ideas.