sharkycarlos

I was measuring the block bore yesterday and got:

Piston 1
X 3.327in (84.51mm)
Y 3.327in (84.51mm)

Piston 2
X 3.327in (84.51mm)
Y 3.326in (84.48mm)

Piston 3
X 3.327in (84.51mm)
Y 3.326in (84.48mm)

Piston 4
X 3.327in (84.51mm)
Y 3.327in (84.51mm)

Do you guys recommend that I should bore the block? If so, what size? If not, what size pistons should I use and what brand?

stefanst

iTrader: (1)

You're already 1.5mm over stock. AFAIK there isn't much more meat left to bore. Some people go to 85.0mm, but that's it.
If you get 84.5mm pistons you have .01mm (0.004") clearance that's not too bad. In fact that's what I asked my machine shop to do for me. So if the cylinder walls look good remove glazing, slap in new pistons and go.

But I'd definitely wait for one of the more experienced guys to weigh in too.

sharkycarlos

No one actually knows about this?

stefanst

iTrader: (1)

Sorry- made a mistake in my earlier post. I usually get the numbers right, but the order of magnitude wrong. 0.004" is 0.1mm, not 0.01mm!

You're sitting almost exactly at 84.50mm. You want your bore to be 0.05mm to 0.1mm larger than your piston- depending on your manufacturer's specs and your application.

If your bores look good, buy some 84.5mm pistons, measure them and then have the block machined to fit. If they need to remove less than 0.1mm, my guess would be that honing would be sufficient.

sharkycarlos

Thanks, will do that.

triple88a

iTrader: (2)

3.330"

sharkycarlos

3.330 what?

triple88a

iTrader: (2)

Cylinder size.

HHammerly

iTrader: (3)

Got a set of pistons and rings for sale if you are going with 9.5 comp ratio
https://www.miataturbo.net/showthrea...82#post1046782

triple88a

iTrader: (2)

Wait my bad i thought you were talking about those piston sizes being "piston size" and not the cylinder size of the block.

4 thao clearance is right at the upper limit.

stefanst

iTrader: (1)

Those 83.5mm pistons will be mighty lose in his 84.5mm bores!

triple88a

iTrader: (2)

LoL we're talking more than a 32th Would probably sound like an old school diesel.

HHammerly

iTrader: (3)

Brain fart, 1mm off
Sorry