So ive bought these 8.5-1 JEs.........
 

Right, Ive bought some 8.5-1 JEs. My 930 engine spec is as follows - 79 930 case, arp rod bolts, shot peened rods, 8.5-1 coated and dry filmed JE pistons, turbo studs, sc cams, K27, .9bar spring and the question is, what do I do- shim the barrels to bring the comp down to 7.5-1 or run it with 8.5-1? Im not going to be twin plugging, and ive got no idea how big my intercooler is going to be as my car is going to be a 73 SR replica with a duck tail. Yes i know, how the £uck am i going to get an intercooler in there. well, you tell me!

Im thinking that i should probably reduce the comp to 7.5, what does anyone else think? oh, and sorry if I keep posting stuff about pistons and comp ratios vs boost but im gettingf confused as to what way i should go!!!!


Andy

I personaly like the idea of slightly lower compression and more boost. You'll make more power that way than running higher compression and less boost.

The SC Cams will improve pre-boost drivability anyway, so why run 8.5:1 C/R?

I say go for 7.5:1 @ 0.9-1.0bar. Make sure you have good intercooling tho, that's important!

Also, you'll be limited in how thick you can go with gaskets and shims without upsetting Cam Chain geometry. Use 0.5mm C2Turbo Head Gaskets for a better cylinder->head seal with 0.5mm Base Cylinder shims. It won't take you to 7.5:1. Perhaps 8.0:1. Get your mechanic to do all the appropriate measurements to determine exact C/R using these gaskets/shims.

Good luck!