Question about 81.5mm overbore pistons
 

Hi,
When I had my B18b block machined, I had the machinist bore my block to accept 81.5mm pistons (Topline brand Oem replacement .020 over pistons). If I want to upgrade to 81.5mm forged pistons (I was thinking SRP), is the bore needed the same as what is in there now, or will it differ slightly from manufacturer to manufacturer?

Re: Question about 81.5mm overbore pistons
 

call srp and ask them. i think its .004-.006 over bore on the pistons

Re: Question about 81.5mm overbore pistons
 

Yeah, thats what I'll probably do. I hope that the Topline pistons I have in there now didn't call for a bore larger than that of an SRP 81.5mm piston. I would have to get a new block and spend the extra cash to get it re-machined. :7

Re: Question about 81.5mm overbore pistons
 

It's called the piston to wall clearance. Depending on the material of the pistons and the heat expansion and all that, the manufacturer of the piston will have a recommended piston to wall clearance. I wouldn't bore/hone a block until I had the pistons to match each hole.

Re: Question about 81.5mm overbore pistons
 

Wise words from a man who knows how to bore a hole O0

Re: Question about 81.5mm overbore pistons
 

Yeah, I should've manned up and went for the forged internals when I got the machine work done but I cheaped out. I just hope that there is still enough meat left to fit some forged pieces in there.

Re: Question about 81.5mm overbore pistons
 

http://www.youngmoviethumbs.com/ct/thumbs/tn1918.jpg

Re: Question about 81.5mm overbore pistons
 

That ---- needs a hone ASAP!

Re: Question about 81.5mm overbore pistons
 

Dude, the crosshatch is perfect. I run tight clearances too. >:D

Re: Question about 81.5mm overbore pistons
 

my thread is ruined! :'( :'( :'(