Pieces of steel in cylinder??

FWIW... another cam suggestion:
Lunati Voodoo Camshafts 10200701

Torquier right off idle, and will be a stronger right off idle than a stock 318 and will just get better from there. Needs some better valve springs than what comes on those reman heads.

The summit 6900 is an old slower ramp design; engine performance will be a bit weaker off-idle up to maybe 2500 RPM or thereabouts. The nice thing about it is that you can run it with easier valve springs. Easy to just put in and have few worries.

Either one, check P-V clearance once you get the short block together and a head temporarily set in place, using proper techniques. Both cams are lower lift so neither should be any issue, but no reason to take any chances.

OP, do you know what the rear gear is in that Scamp?