Printable View
I have a Chevy 402 with a compression ratio about 7.5, I would like to increase the torgue around 450 ft/lbs.
I looked at new pistons, but I could find pistons that was 17cc and the next size is 41cc. The 41 cc would increase the compression to 10.6. This would require the expensive gas. My goal is to increase the ratio to 9.5.
The heads casting# 6272292 are 113 cc, the block casting # 3969854.
We want to install this engine in a 73 K5 blazer.
Any suggestions on how to raise the compression?
buy the bigger CR pistons and have the domes fly cut. not a hard job any shop can do this if they have a mill and a piston vise i done the job .other then that you could look at more then one piston makers . the bigger bore o deck the block. mill the heads some. the L2240NF could get you close 9to1 or the KB 160
Thanks Pat for your reply.
I will find a set of l2240nf pistons.
I installed one head without a head gasket and had clay on the stock piston, it looks like there is about .170 clearance. I know there is a limit to amount I can mill off the head before we have trouble with the intake.
What is the max that I can remove from the heads? With the heads milled and using a thin head gasket, plus the L2240NF pistons, will this give me the compression ratio that I want?
One more question, do you have a recommendation for the cam?
you should check the intake fit but the bolt holes need to be sloted before you have to start milling the intake ports may or may not line up .this may not be a big deal as the intake can be milled or some port work or just leave it as is any more then 025off the heads you may want to see if the bolts will go in the intake i seen were more then 040 was off the heads and deck things still fit but you need to watch out for the intake rails will bottom out on the block use RTV here not the rubber rail gaskets. the steel shims i do not care to use. you need to find the cc of them i do not know. as for the heads i put them in the mill cc the heads to see were they are realy at. i make a 005 cut that.s per 1cc should be close but i cut then see were its at for cc.s in real life you need to know how big is the bore going to be as this can add to more CR. you not not want to get to nuts on milling the heads as you loose valve to piston room and on the intake side you do not have it to give up .what cam do you want a solid roller hyd roller or hyd /solid flat lifter cam ?