86mm,86.5 or 87mm ?

[Dragon Humper]

On almost every eng I built I run a 87 Metal gasket on a 86.5 bore. Never had any pre det from that. Maybe on a old engine running crap gas, eventually that could be a possibility. I have also always ran with a 1.2 on 91/94 gas without problems with a light deck. Not big ass power on the builds tho so it was justified.

That's not bad at all .5mm equates to .25mm of space all the way around. I was more refering to someone that might be contemplating an 87 or an 87.5 on an 86 because that was all they could come up with. 1.2mm for the quench clearance is OK, I would run a little tighter quench though (1mm). A little more compression is never a bad thing and the tighter quench will give you more det. resistance. An 86.5mm HG on an 86.5 bore will also bump up the comp. a touch too.

8.5 to 1 is a little low in this day and age of tuning anyway, especially with a tiny bore like 86mm.




Jon.

[cobrAA]

I'm thinking about buying a tomei headgasket kit.. but with what was said, I don't think I will be able to use the 87mm 1.2mm on my oem rb26 bore.

Yes no? Should I sell the head gasket and get an apexi 86mm ( only brand I know who makes 86mm for rb26)

[cobrAA]

So me and my builder are wondering if I can use a 87mm HG on my standard bore or it can't be done ?

Thanks

[jdms13rhd]

Ive always had that gasket size with a 86.5. I kinda almost dont see the harm in doing it tho. Maybe someone with more experience will chime in.

[cobrAA]

Well Braden told me it's better to get 87mm instead of 86mm in my case. I dunno

[jdms13rhd]

well thats 2 for 0.

Another good thing.. if you do a rebuild and punch it out .5mm, you can re use the gasket