K321 Rebuild Questions
 

I am in the process of rebuilding a K321. This engine had a knock. The balance gears did have a substancial amount of wobble. I plan on leaving them out. I had the crankshaft turned .020. Since I noticed a little oil on both sides of the headgasket I had the head milled. I also had the cylinder bored .010. Now for my problem. The new piston feels sloppy in the cylinder without the rings installed. Now I am not an expert with a set of mic's and I do not have a bore gauge but I do have a set of inside mic's. I measure .009 cylinder to piston clearance. The shop that bored it says that measurement is .006 and since the piston is totally aluminum it will expand as it gets hot. Therefore it needs that much clearance. Any comments? Would you guys recommend I go with it?

Not the expert here. You should get lots of good feed back.
My two cents would be to check the end clearance (gap) of the new rings inside the cylinder bore with out the piston. Usually this is dimension is marked on the ring package. This should tell you if the bore size, to ring fit, is going to be correct.
Regards,
Chris

Thanks Chris. I did that. The company that I purchased the rings from recommended that the gap be at least .012 or more. If less they recommended the rings be filed to obtain it. They measured a loose .012. Thanks Gary

If I take the upper 'new bore' limit and subtract the smallest 'new piston' diameter shown in the manual, I get 0.008". The 0.006" the shop got is less than that, and I'd be more inclined to trust that since their mics have likely been calibrated more recently than yours unless you are also using them daily and getting them recalibrated.

I've had some worn-out, but still running engines with close to 0.060" of slop between the piston and bore. Yours will be fine. And yes, the piston will expand more than the block, so that clearance will tighten up somewhat with the engine running.