Thick vs thin head gasket

Coty Morrow

New member
With cc being the same between a .040 gasket and a .009 gasket is there any performance of the .009 gasket that anyone has proof backing up ? On track or on dyno ?
When I built my "house" engine, I had a valve float problem. In the process of fixing it, I swapped heads to one that had been milled too much to pass cc check. I put three thin gaskets to get it up to legal cc's, and it made the same power as the other one. I don't think the "quench" is as critical as a lot of people do. Now this is just my opinion...
Usually running a thicker head gasket is used after milling the head, for piston to valve clearance, or getting your cc's correct.
Not a performance enhancer unless you are tweaking for some extra compression or less cc's.
It would depend on how you equalized the cc's You have to deck it, mill the head or change the piston head shape. Example going from dished piston with small gasket to a flat top with a thick gasket changes chamber shape.
Mine has been thick for better seal and I had two motors. One I did and one by a top builder that the piston hot the head and caused rod to seize. Not break but seize from squeezing the oil out when piston would hit head.
Yea, I have seen that in v8 engines. Piston just touch enough to knock the clearance out. On my higher hp kart engines I leave .025 piston to head clearance. I like it safe..LOL
So yor bassically doing the same
Thing then. Just leaving piston on the hole .015 or more and thin gasket.

Mine have been .008 plus or
Minus .002 and .040 gasket with around .250 head depth. I set head depth to correct cc by checking it
Yes, but on a stocker I will leave the piston .010 in the hole with a thin gasket. I also copper coat the gasket, which may put a tenth or two on it. That's on a legal engine that shows around a max of 12 to 12.4hp and 6700rpm on my dyno. Above that I go at least .015 in the hole.
The 'thicker' gasket might be somewhat forgiving if the mating 'surfaces' are not flat. (This should only apply if doing a 'thrash' in the pit's on a saturday night!)
But what I am wondering is if anyone has seen results of thick vs thin when millin head for thick gasket

And then what the reasoning is behind it.
I use the thin gaskets even with my milled heads.I have also decked the blocks too.
but have stopped doing that and play with rods and pistons.even though I don't
deck them I still want to get the head as low as I can.My thinking is
with the thick gaskets why put back on what you tried to take off.
your only adding the thicker to make up the room lost for piston
to valve clearance.jmo and others may vary.
Does your theory show anything on dyno or on track or is it just a preference ? Not saying anyone is wrong I'm just tryin to do what's best of one way or the other is actually best.
I have been thinking a ton on this. There's more horsepower in this area due to alot of things that haven't been brought up. And with the new shim on the valve spring rule it makes me want to try a bunch of other things