Bore to Piston clearance

[Spraynlog]

OK, I melted #4 piston at the drags. I've torn the motor down and taken the pistons & rods out. I need to replace 2 pistons that were melted, so I ordered 2 used ones from Cindy at FWD-P.

The bores were all within .005 on taper, but my pistons (the 2 that I will use) are a bit undersize. My piston to bore clearance is looking to be
.005- .006. the book (Haynes) says the clearance should be .001- .003.

Is the book quoting factory specs or acceptable wear? I can't tell. Has anyone put one of these together with .006 piston to bore clearance without a problem? Should I bother to put this together?

[glhs875]

OK, I melted #4 piston at the drags. I've torn the motor down and taken the pistons & rods out. I need to replace 2 pistons that were melted, so I ordered 2 used ones from Cindy at FWD-P.

The bores were all within .005 on taper, but my pistons (the 2 that I will use) are a bit undersize. My piston to bore clearance is looking to be
.005- .006. the book (Haynes) says the clearance should be .001- .003.

Is the book quoting factory specs or acceptable wear? I can't tell. Has anyone put one of these together with .006 piston to bore clearance without a problem? Should I bother to put this together?

I don't think you will have any problem. A motor a little on the loose side seems to work better for racing alot of the time. Providing the ring gaps aren't too wide. I've ran and built many engines with that much clearance, and they ran hard and did great. It might be a little noisy is all. Some people purposely run alot of clearance as much as maybe .008 on the piston to bore.

[2.216VTurbo]

It would be helpful if you told us if you were running 2.2 or 2.5, forged or cast Specs are perfect for forged, a little loose for cast though...

[Spraynlog]

It would be helpful if you told us if you were running 2.2 or 2.5, forged or cast Specs are perfect for forged, a little loose for cast though...

Sorry about that! I had been doing some measuring with an outside micrometer, and in my concentration on it I forgot the big picture.

The motor is a 2.2 T1 log intake with cast pistons (stock). The bores measured from 3.441 out to 3.445. The pistons measured 3.439.
I was planning on putting it back together with standard rings after a hone job.