Mopar Performance short blocks, any good??

I can tell you what I did to mine though before it ever ran.

I bolted one of my heads on it with my cam and determined the amount of non existent piston to valve clearance. I pulled all the pistons, obtained a spare and cut it up to see how deep I could cut valve reliefs. Ended up with about .030" between the top ring groove and the intake valve relief. On the exhaust side the top of the piston is about .090" thick at its thinnest point. This allows me very minimal valve to piston clearance though. Like .058" intake and .080" exhaust, with the lash set, and I had to move the cam timing around to get that.

I never pulled the crank out but I did install main studs, head studs and weight matched the big end of the rods. I cleaned the cylinder bores with lacquer thinner three times and installed ARP rod bolts. I never touched the rings or even checked their clearance.

I used the cam that came in the shortblock in my sons Scamp.

I don't know what happened to John's motor but I do know proper camshaft break in is important. 2500 rpm's for 20 minutes. If you have double or triple springs take the inner springs out and just use the outers to break the cam in with, then reinstall the inners.

Too much valve spring pressure will also wipe a cam lobe so know what you got or use the cam manufacturers suggested spring.