Does it affect the fact that the bore size of a gasket is 4.100 vs 4.040?

given that you change the thickness to have the same volume on both, which one would you choose?

I want to run cometic head gaskets and they are either 4.040 or 4.100 on .027,.030,.036,040,043,045,051,054,057,067,078,120 thickness.

Any thoughts?

 

What is the bore size of the cylinder? Is this for your 4.030" bore, 383 motor?

You don't want the gasket bore so wide that charge is pushed between the
block deck and cylinder head.

On the other hand, you don't want the gasket covering any of the chamber,
or extending into the cylinder.

I don't know what the standard would be, but I'm guessing the gasket bore
should rest between 0.010" and 0.020" more than the cylinder bore after torquing.

 

Well... felpro's are 4.125 IIRC and .039 thickness... I just want to know what is the best thickness to make it hold on the lt1 block when pressures get a bit high...

 

i tend to agree on the .010-.020 larger gasket bore vs the cyl bore. as far as sealing goes. with the lt1 if you have your piston down in the hole a little bit and use one of the thinner gaskets available (assuming you have all surfaces meachined freshly and properly) what you're trying to shoot for with different gasket thicknesses is a .039-.050 distance between the piston top and the head. but my thinking is that the shorter gaskets with a few thou in the hole piston would be strongest. and get some high quality fasteners for the heads you want good even clamping force, it'd be a pain to remove the heads but i'd go with studs if i was that worried about it. and use the lube that the fastener manufacturer recommends for torqueing. hope that helps some.

 

English... you prefer the 4.040 over the 4.100? or choose the one that puts my piston to head clearance on the .039-.050 range? my block wasn't decked as my machinist said that it was pretty darn flush.... all surfaces are pretty new i would say as the heads are new.

I won't use studs.. will use ARP though... as a matter of fact.. ARP 100% on the engine.

 

1) really what bore i would use depends on the overbore the engine has. the last thing you want is the gasket to hang out into the cyl. if its like a .010 overbore or std i would probably go with the 4.040 if you get up to like a .030 overbore i'd probably step up to the 4.100's. also keep in mind changing the diameter of the bore in the gasket will affect your compression the same as changing the thickness of it will.

2) after you pick the bore then you need to find your piston to deck hieght and select a gasket with a compressed thickness that will put your total piston to head distance (quench) in the .039-.050 range pretty flush on the pistons doesnt cut it in engine building, most cheaper pistons are .020 in the hole and thats something that looking at i'd call "pretty flush" too.

the important thing is that you want to be in that range. it goes a long way to stop detonation. basicly it will squeeze most of the air/fuel mixture into the chamber and eliminate areas that the a/f mixture is poorly mixed. and supposedly it also creates a little extra movement of the mixture when its under compression. same idea with the head gasket bore size. minimixing small areas that it wont mix well in and trying to kill detonation.

on another note with your arp fasteners, i believe i read somewhere or was told by a marine engine builder that the 6 point bolts torque more accurately. but be good and sure your man uses the arp thread lube or sealer where applicable. you lose a lot of the force to friction when it should be stretching the bolt if you do it dry. hope i was clear this time if not ask and i'll take another stab. good luck on the buildup