Change in compression ratio.

[Hemet8]

If you take a new engine, and mill the heads 020, how much would that bump the compression up? Stock i think is 9.5:1, i am shooting for 10.1:1 or 10.2:1. Any education on this is appreciated, thank you. the engine is a 3400.

[sharkey]

RE: Change in compression ratio.

you can shave the heads, however i think piston-valve clearance gets a bit close if you go to much. i know you can use gen 1 ironhead gaskets on it, they are .041" compaed to .060" for the 3400.

[v6h.o.]

RE: Change in compression ratio.

.020 will get you closer to 9.8-10:1 range.

Max amount that should be taken off 60v6 heads is around .018-.020.

NO do NOT use a gen1 .040 gasket!!!!! The piston to HEAD clearance is not there to provide space for that small of gasket the 3400 pistons stick proud by .020inch from the deck surface. Min requirements for Piston to Head clearance is over .030 inch. You have to stay with the stock 3400 head gasket.

[Guest]

Re: RE: Change in compression ratio.

.020 will get you closer to 9.8-10:1 range.

Max amount that should be taken off 60v6 heads is around .018-.020.

NO do NOT use a gen1 .040 gasket!!!!! The piston to HEAD clearance is not there to provide space for that small of gasket the 3400 pistons stick proud by .020inch from the deck surface. Min requirements for Piston to Head clearance is over .030 inch. You have to stay with the stock 3400 head gasket.

I was just about to say that.

I did the calcs at one time, since I'd like to run 10:1 with about 6 to 8 PSIG boost, it would take milling the pistons and using a thinner gasket to get to 10:1, basically zero deck the piston, to get the clearance. I haven't measured a 3400 piston yet to see if the ring and will become too short, which it very well may.

[Guest]

RE: Re: RE: Change in compression ratio.

Whast the difference of shaving off .020 off the head or going from a .060 head gasket to a .040 head gasket?

Either way, you are still moving the valve .020 closer to the piston.

I think some of you guys need to wake up and recognize.

[93camaro_zzz]

Correct me if Im wrong, but if you take 20 off the head, then you also need to take some off the lower intake manifold or off the head again where the IM meets the head.

[Guest]

Re: RE: Re: RE: Change in compression ratio.

Whast the difference of shaving off .020 off the head or going from a .060 head gasket to a .040 head gasket?

Either way, you are still moving the valve .020 closer to the piston.

I think some of you guys need to wake up and recognize.

I think you need to wake up and recognize something here...

The genIII pistons come proud of the block by .020", some, including myself have measured as much as .022", meaning that if you were to use the .040" head gasket you'd have less than .020" or even as little as .018", which is WAY too close.

What we are talking about have NOTHING to do with piston to valve clearance, we are simply talking about piston to head surface clearance.

[RacerX11]

RE: Re: RE: Re: RE: Change in compression ratio.

Hahahahahahahaha!