I took my LS block to the local machine shop to be machined. I will be running over sized CTR pistons. The machinist recommended the piston to wall clearance to be around 10 thousandths? I thought it would be better to run something tighter like .003-.004? He wanted to even run loser then that but he said we could meet in the "middle of the road" The engine is going to be running some hot cams along with the supporting mods, it will be driven around quite a bit but am not building it expecting it to last 200,000 miles. It will be beat on. What do you think? It just seems pretty loose especially when it comes to gap the rings? Wouldn't they be on the loose side also.

Any suggestions would be appriciated.

 

Those are cast pistons and should be run at .0010" - .0015". At .003"-.004" they will knock like mad.

 

The specs for cast pistons in a stock sleeve or 0.25mm OS bore are 0.010mm - 0.040mm (0.0004" - 0.0016") and the service limit is 0.05mm (0.002")