Changing the compression

ss_scuba

Registered User
I will be gutting my motor and rebuilding it with new everything (mostly). Since I'm going to have to bore out the cylinders and get some new pistons, I was wondering if it would be beneficial to bump the compression from 8.2:1 to about 8.5-8.7:1. I know the late model SC's had an 8.5:1 without anything different to the block. Can this be done safely on early style blocks?

I've already got a free flowing exhaust being put on the car, as well as minimum of 75mm intake size, an upgrade to 38lb/hr injectors with 255L/hr fuel pump. I will probably switch to MP blower and accessories when I get the cash.
 
I could be wrong ( wouldn't be the first time), but didn't they slow the SC down on late models and have less boost because of the increased compression and better efficiency of the new blower design? Plus the late model blocks had stud girdles didn't they?

To answer your question, I don't think there is an issue. Take it for what you will, but remember, at max boost your compression ratio is gonna be high, so build the bottom end accordingly.
 
Scott
I can't think of any reason you shouldn't be able to up your compression ratio to 8.5 or there abouts as long as you keep good gas in the tank.

Ripvanbl,
You are correct about the supercharger being slowed down via a bigger pulley on 94/5 SC's but they actually make/made more boost. Most believe the reason for more boost, even with the bigger supercharger pulley is because of the better efficiency of the second generation M90 blower that came on the 94/5. I believe the fact that the 94/5 cam has ten degree's less overlap then the earlier model cam's (28 degree's vs 38 degree's) also has a lot to do with the higher boost numbers.

Also, 94/5 SC's didn't come with a stud girdle but they did come with a windage tray.:)
 
Back
Top