NEAL82 Stock SC

[Robert Neal]

I have been looking at options on the rebuild. Has anyone tried moving the center of the small end of the connecting rod closer to the head. I'm looking for a little more compression. How much does the center have to move to get from stock compression to 9.8. I talked to an engine builder and he wanted to cut the head. That changes the cam chain orientation. That doesn't seem like a good idea. If my pistons and cylinders are good I don't see a downside to this method.

[Aurel]

Did you mean using longer connecting rods?
I would not cut the heads to increase compression. Your machinist may remove 0.01" or a little more to renew the surface, but that is it. And if you reduce deck height, or increase stroke, you risk piston-valve interference. That is the downside. The best way is to use higher compression pistons with deeper valve pockets. How much more HP do you want? How much money do you have to spend to get where you want? Street or race motor? What octane gas will you use...

Aurel

[tctnd]

You can have the small ends rebushed and offset bored to make minor rod length changes but you must check valve/piston clearance.
regards,
Phil

[ChrisBennet]

Frankly, I wouldn't bother shaving the heads or changing the rod lengths.
There just isn't that much to gain IMO.

You don't mention what the motor is but I looked at a spreadsheet I had from a 3.2SS [3.2SS = 3.0L bored out to make a 3.2] I built a while back. Changing the deck height from 1.0mm to .9mm would have only increased the compression by .1 ("1 point") from 10.5 to 10.6.
(I wound up machining the pistons down to get 9.5:1 - about what a "9.8CR" 3.0 actually measures out to.)


-Chris