I have a 84.5mm Darton sleeved B16 block. I'm wanting to bump up the piston compression from 8.5 pistons to 9.7

My question is when I have the block honed will it take off so much that I will need to go up to 85mm pistons or can i stay with 84.5mm?

Thanks ahead of time.

 

Honing without boring is always a half-assed way to do things. A good machinist will bore cylinders to a very, very slightly smaller diameter then the pistons will fit properly in. Then, after the hone and break-in, the cylinders will finally reach the ideal size. Unless the rings are in really bad shape, honing by itself will probably lower compression because the larger diameter cylinders will create a larger ring gap. Also, the more perfect the cylinder size is, the less room there is for the piston to tilt, which wears down cylinder walls and causes other problems.

 

The only reason I was asking is because I was planning on a rebuild, and I really didn't want to have to buy new pistons if I didn't have to.

 

I truely believe that just honing is a waste of your time and money and that you'd agree after performing the work and seeing how it affects performance. Obviously I don't know your monetary situation or the prices in your area, but I've twice gotten a cylinder bore & hone performed on bare blocks by a machine shop (most regular automotive shops outsource boring and mark up the price) and oversized OEM pistons for under 300$ total. I'm pretty sure it came out to about 270$ without any other parts at 30$/cyl boring, 10$/cyl hone and about 110$ for the pistons shipped. I don't know if you can find OEM pistons in the size you want or a credilble and nearby machinist, but IMO you should have a look around. If you go this route, buy the pistons first and give them to the machinist with the block. He then should bore and hone based on the pistons' actual measurements.

 

you're going to have to measure the wall, and decide your ptw clearance.