EvoVIII Head gasket on 4G64

[Boostdgalant]

Just got Evo VIII Head Gasket from dealership and when I got it something came to mind. Is the piston holes in headgasket big enough to fit the stock piston on a 4G64 without causing problems to the rings? If I am correct the galant has a bigger piston then a stock evo, so where would I start or does any one have a solution they used for this project.

[mko]

evo's 4g63 bore is 85.0 mm and the galant's 4g64 bore is 86.5 mm which means the gasket wont work. your best bet is to sell this one and buy another one with the proper piston size

[Boostdgalant]

Wrong evo is 86.0 mine is 86.5 BUT thats the bore pistons seem just about right

[mko]

well if you have the 86.5 hen you should be good


edit: Looked in evom.net the evo piston bore is 85.0mm.

[Boostdgalant]

so your saying it wont matter as far as the .5mm off or should I use a whiz wheel really lightly....

[Cali]

the headgasket isn't the same diameter as the pistons...it's always slightly bigger.

you should be fine.

[Stewi]

I hate to go against you Noel but thats not correct.

There is a reason AMS sells stock EVO headgasket modified for the 4G64 block. That modification is enlarging the bores 1mm so it fits correctly. It does not fit correctly when the head is torqued down, the edges of the gasket overhang slightly inside the combustion chamber.

[Boostdgalant]

so basically its a NO GO...Right correct me if i am wrong what about a dremel could i shave it...

[Boostdgalant]

And so how would it work with a headgasket that is 86.mm when we have 86.5mm?

[Boostdgalant]

The Evo 8 hg works on my 2002 galant 15 lbs here we come....for every person trying to it worked on my engine..perfect bolt up..

[Stewi]

The Evo 8 hg works on my 2002 galant 15 lbs here we come....for every person trying to it worked on my engine..perfect bolt up..

Its not that it wont bolt up.

Its that when compressed (head torqued down) the headgasket will overhang into the combustion chamber causing hot spots and possibilty of pre-ignition (knock/detonation)

Just because something fits doesnt mean its right. Your using a headgasket that has a bore of 86.0mm on a motor that has a bore of 86.5 so the hole in the gasket is .5mm too small. Could you open it up with a dremel, im sure you could, would it still seal correctly, maybe, but for such an inexpensive part, I would just fork over the cash and buy the correct on rather than dremeling up a stock one wasting time, ruining a stock one and potentially damaging the engine or having to take the damn thing back apart after realizing you messed up and it leaks.

[Boostdgalant]

I thought about using the dremel but then it would be an uneven around each circle. My master tech said that i should be fine...HE says I am over stressing the situation. I dunno I could mic the the thing and see what it exactly is but even on most head gaskets for an earlier eclipse you can use the same head gasket +-1mm. Are you sure about the over hang and has anyone else you know had problems in the past with this modd??? Because if not then someone has to do it.

[Stewi]

I thought about using the dremel but then it would be an uneven around each circle. My master tech said that i should be fine...HE says I am over stressing the situation. I dunno I could mic the the thing and see what it exactly is but even on most head gaskets for an earlier eclipse you can use the same head gasket +-1mm. Are you sure about the over hang and has anyone else you know had problems in the past with this modd??? Because if not then someone has to do it.

Yes I am sure about the overhang. this is the same reason everyone I know who did the DOHC headswap is using a COMETIC headgasket specifically made for EVO head on a 4G64 block. Race engineering sells them for like $80. the website is raceeng.com

Even when I ordered my pistons from RRE 2 years ago, I tried to get an OEM headgasket from them and when I told them what motor it was going on, they steered me clear of it.

The only other company besides cometic who makes a gasket with a large enough bore is HKS and its $280. Thats why everyone went with cometic.

[PharmEcis]

You should NOT use an EVO headgasket on the 4G64. YOU SHOULD NOT USE IT!

The stock bore on an EVO is 85mm. The headgasket comes 1mm over which means it's 86mm. The stock 4G64 is 86.5mm. You need a headgasket that comes in at least at 87mm. If you have overbored your engine, you will need a gasket that is at least 87.5mm.

If you use an EVO headgasket on a 4G64, it will run for a while. If you are boosted, you will find that you start pushing coolant very soon. The headgasket will actually be in the combustion chamber and all the pressure from the mixture igniting will eventually push into the different layers of the gasket, expanding it, making it not seal and eventually blowing the headgasket out.