2 Questions: 964 cams how to increase comp ratio

[Rgroupie]

well I bought a set of 964 cams...for my SC...I know you have to grind off the power steering part of the cam...but I can't see where that is? I see the round bearings and the cam lobes...but I can't find where the powersteering part of the cam is...maybe it was already ground off in the previous application....

Also I have a great deal on 100mm Mahles with a ~9:1 CR...
2K...that is 1800 cheaper then anything I have seen...

but I am double plugging so I wanted to have an engine with about 10.3:1 CR....but andial wants 3800-4000 for 100mm 10:1 CR

I know you can machine the case or the cylinder or take out shims to raise the CR...can anyone educate me on this engine mod...also the pluses and minuses of raising the CR this way...

thanks...

MJ

[Bobboloo]

One problem with changing the deck height is the chains have the effect of being longer. The tensioners will make up for it but only to a certain extent. Then there is clearance issues you have to check for. When it's all said and done you might be close to spending what you would have for 10.1 Mahles and have chains that are long. (keep in mind I say this speculating)

An alternate might be to go with the 100mm cylinders and have JE Pistons make the compression ratio you want for those cylinders.

Bobby

[ChrisBennet]

"964 cams" usually refers to a 964 grind. Few people use actual 964 cams in earlier cars.

I went with JE pistons + bored out cylinders my own conversion (3.2->3.4). Raising compression by reducing the distance between the head and crank involves a lot of hassles that I personally would want to avoid (smaller chain idler sprockets, etc). I've been happy dealing with Engine Builder's Supply for my 98mm renic'd cylinders and JE pistons.
Chris

[marcesq]

MJ:

In addition to the above, which are all on point,
I'm not sure from your post which motor you have, but if you have a 3.2 the gasketless head to cylinder joint issue needs to be addressed when rebuilding. This means machine shop work.

My 1 cent

[Rgroupie]

answer to the 964's anyone????

MJ

[ChrisBennet]

Originally posted by Rgroupie

answer to the 964's anyone???? MJ

I'm not sure what you mean but here goes. If you're wondering about the 964 cam pump drive - there probably never was one on that cam. The cam was probably built up (with metal) and then ground to the same profile as the factory 964 cams.
I would recommend using some sort of racing valve spring with this cam. It's higher lift will wack those pistons even easier than normal if you overrev the motor. I did not notice a difference in performance when I went to them in my 3.2
-Chris

[Wayne 962]

The pump drive gear is on the back of the right (I think) cam. If the right and left look the same, then chances are it's just a 964 grind.

You said 964 cams, but then you said twin-plugging, and high compression. What fuel system are you thinking of using? People usually use the 964 grind with the CIS cars. However, if you really want the most performance out of your engine, I wouldn't keep the CIS around...

???

-Wayne

[Rgroupie]

yeah the monster engine is put on hold...flow of money is compromised!!!! crank, condrods and heads sitting around

So while at the garage sale I picked them up cuz they were so cheap...so one of these days I will pop them inot the SC to maximize what I can do with the engine for now

well I assume they are 964's since they say 964's...as a part number...

I lined them up...i am thinking it is the big cylindrical part sticking out on the upper cam (in my picture)

[Rgroupie]

anyone? I even provided visual aides!!!

thanks

[ChrisBennet]

The end of the cams should match when you are done. Rather than go to the trouble of chopping the end of the cam off (the longer cam in your picture) perhaps you can sell or trade them for SC cams with a 964 grind.
-Chris

[Jim Smolka]

Rgroupie,
You could sell the 964 cams and have Elgin cams modify your SC cams. Cost should be less than $300.