Bore size questions
 

Ok, I have no experience with engine boring so I have a few noob questions. First, my pistons/cylinders are .030"/.76mm over (I assume that is .030 off around the entire cylinder), that means total cylinder bore is now about 1.5mm over, correct? So total bore would be 86.5mm?

Also, I have a 2.3 which means I have the 4g63 block, correct? So my bore size would be the same as someone with a 2.0 with .030" over?

Does mitsu make a headgasket in this size? If not can I get a quality composite gasket in that size from somewhere else, or should I just look at the PermaTorque or other MLS?

Re: Bore size questions
 

Andrew, your bore size is now 85.76mm, you don't add it twice. It's the difference in diameter across the top of the piston, not piston to wall clearance on each side. And the 2.3 block is just the standard 2.0 block with a 100mm crank and a little clearancing. Most of the headgasket manufacturers make them in larger bores, you could always use the 2.4 bore size of 87mm gasket.

Re: Bore size questions
 

You might be able to run stock Mitsu headgaskets, they usually have some room for overbore. The Permatorque can handle up to a stock bore 4G64 at 86.5mm. Or you can get Cometic HGs in all kinds of bore sizes.

Re: Bore size questions
 

I don't have to get the headgasket in exactly the right size?? Does the permatorque come in anything other than 86.5/87?

I need new rings too so the exact bore is pretty important for that. I ordered .030 over rings, but the engine builder was pretty sure it was 86.5mm bore, he said it was the original Magnus-designed Ross stroker pistons from 4 or so years back. Maybe I should call Magnus and see if they still have the order specs on file. Or if I could find the sheet that came with the pistons...

Re: Bore size questions
 

They only make the Permatorque in one size and it's too small for overbored 2.4l blocks. The HG doesn't have to be close to the perfect size. You don't want it hanging over or too close to the cylinder walls though.

Yea, you need exactly the right rings for your pistons.

Re: Bore size questions
 

Make sure that you grind the rings to spec and not just toss them in and also I would do the permatorque for a HG it rocks! I have a 2.3 and mine is 20 over and there was still room so you should be fine with the standard permatorque head gasket.

Re: Bore size questions
 

i have feeler gauges if you want to use them and some nice little files...if you are garage building it..

Re: Bore size questions
 

Ok the piston sheet says bore is 3.366 which turns out to be 85.5mm, and net diameter is 3.361 which is 85.37mm.

So is that saying the pistons are only .020 over, not .030? In that case I'm calling e-psi when they open at 8am and changing the order. Hopefully they didn't ship them out already, I called around 1:30pm eastern time today.

Re: Bore size questions
 

That makes more sense. Most pistons for our cars are .5mm or 1mm over, which is .020" and .040" respectively.