So here's the issue. I have a B20 block that I would like bore out to 84.25....maybe 84.5 if need be.

In most cases, when you take your block to get bored out - they ask for the pistons that you plan to use so that they can exactly match the cylinder with the piston.

My problem is that I really dont want to buy the pistons first, just to have the shop tell me that those pistons wont work. For example, say I go ahead and pick up 84.25 pistons, but the shop says sorry we need to bore out you cylinders to at least 84.5 to get a clean hone. Then I'll be stuck with pistons that I can't use.

I plan to visit a few engine shops and get their suggestion. But I'd figure I'll check here first and see what you guys have to say.

 

The machine shop should be able to tell you how much overbore you need.

 

You need the pistons before boring IMO because not all pistons are created equal. You need to run the correct piston to wall clearance and the only way you can determine that is comparing the piston diameter to the cylinder diameter.

 

Go with the 84.5mm bore so that your safe. Easy question if you ask me...

 

you can bore the block w/o getting pistons if your that worried about them not working later.You just have to get them before he hones the cyl to final size.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LSvtecMike &raquo;</TD></TR><TR><TD CLASS="quote">Go with the 84.5mm bore so that your safe. Easy question if you ask me...
</TD></TR></TABLE>

Quite possible that even 84.5 wont be large enough for a clean hone. I'm hoping hoping that I wont need more than 85mm. Even that is pushing it without sleeves.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Fkned &raquo;</TD></TR><TR><TD CLASS="quote">you can bore the block w/o getting pistons if your that worried about them not working later.You just have to get them before he hones the cyl to final size.</TD></TR></TABLE>

Good advice