Headgasket thickness (is bigger really better)

Hi all,

Im currently in the process of building a 2JZGE VVTI engine and i was having trouble getting the squish and compression i wanted without milling 0.030'' off the head as the 2JZGE engines have a 0.030" recess in the head, the only gasket that will work with what im doing seems to be the thin GE gasket.

my question is will the 0.010" single layer steel gasket that comes factory on the 2JZGE engine hold up to 9.5:1CR and 30psi of boost on E85 without any issues or will i need to go for something thicker and MLS.

Cometic do make a gasket that will work but im not sure if i want to go with that brand as i know alot of people who have had failures with them.

Have you considered removing some, or all, of the material from the block? Deck height has as much affect on squish/quench clearance as gasket thickness, and if both surfaces are getting a trueing up skim...

I don't recall using Cometic, but I understand they REALLY need smooth, flat surfaces to work properly, and most problems seem to arise from incorrect surface finish.

Hey Gord, thanks for rhe reply

I originally wanted to mill the whole recess out and run a GTE head gasket but was told by the machine shop that they won't do it, they said there is a hardened layer of alloy and if they remove too much the alloy will go back to a softer layer.

I also read that the cometic gaskets require a really smooth finish of 50RA but even with thay kind of finish bow reliable would they really be compared to a factory single layer steel gasket?

Forgot to note - I'm not a 2JZ chap, so these're generalisations.

Ah, I was a little confused, initially, as there're different versions of the heads - some with a relief in the quench areas and some without. I don't know about how they affect detonation control or how much compression is lost to the larger combustion chamber.

The machine shop may be spot on the money, if the head was hot quenched after casting it could have potentially a better surface structure which heavy machining could remove - same principle as chill cast cast iron, I would surmise. In which case, you may be best served with the lightest surface skim to ensure it's flat, with the required material - if any - removed from the block?

I can't comment on the relevant gaskets, but there are some very active sites specialising in these engines so perhaps they can assist?

30 pounds of boost on an n/a head gasket sounds like a bad idea to me, since you're in Aus I don't suppose you've heard of goleby's parts in qld? They're highly regarded when it comes to building and supplying parts for jz's, I'm sure they'd be happy to advise on what you're trying to achieve? I know they tend to stick with the oem mls gasket even with some big hp builds..

https://www.golebysparts.com.au/

Thanks for the information Gord

Anders, I have spoken to golebys, they recommend I just run a 0.050" gasket pushing my squish out to 0.080" and call it a day