7mgte Metal headgasket 86mm on stock bore size. Okay? What about compression ratio?

[D51208]

Howdy, I am in the process of prepping my 7mgte for a metal headgasket. I bought a partially put together engine, it came with an HKS stopper style headgasket. New Pistons and rings, arp studs, etc. In the process of measuring stuff up though I came across the headgasket bore is 86mm. The headgasket thickness measure 2mm and change by the rivets.

The actual bore size of the engine measures in the upper 82mm region, so I'm guessing it has never been bored over. The block measures to be about about 198.5mm so I don't think it has ever been decked. I will have to remove some from the block to make it 32ra for the headgasket and I will need to remove the rest of the material needed to retain the best compression ratio from the head.




So my big questions are:

1. Can I use this 86mm bore headgasket on the engine?

2. If so will it affect compression at all?

3. Instead of subtracting 2mm from the total of both the block and the head for the compression to stay the same or in a better area, should more or less be taken off to account for an compression change from the larger bore size on the headgasket?

4. The headgakset thickness measures more the 2mm. Will this squish down to 2mm when installed and torqued on?

5. Is there a different compression ratio that is more ideal than stock compression?


Thanks for the help!

 

[D51208]

Well, looks like I answered my own question in regards to compression ratio. If the calculator is correct it will only change compression ratio by .04.... So I reckon that should be ok.

Further I have read that people have used 86mm bore headgaskets with stock bore size without any issues, so I'm gonna say it's good to go.

 

[gats]

I assume you have read this thread already? http://www.supramania.com/forums/showthread.php?97552-Head-Gasket-thickness-selection

Stock bore is 83mm.

Do don't need to subtract 2.0mm from the block & head to compensate for thicker gasket.
You need to subtract the delta between OEM gasket (1.37mm) and the HKS gasket (2.0mm) which is 0.63mm - or 0.025"

 

[D51208]

Yup, I have read that. And good catch that was what I was getting at. Been a long day.