69mach1377

The failure was due to a dropped valve and includes damage as follows; #3 piston badly dimpled but not broken, 2 bent push rods, probably both valves and lifters, #3 rod now suspect but usable, #3 cylinder scored, one rocker dinged (how?), #3 combustion chamber damaged/cracked (? Magnaflux/leak check req’d) Other pistons, rods and bearings okay, crank is clean, chain is tight. The cam has some wear on 2 lobes (?), valve to piston clearance measured as .100” min on intake and more on exhaust.

Option 1 is to fix this engine and option 2 is a 1986 351HO warmed up a bit.

Need to figure out why this keeps happening and if it is worth rebuilding? If a piston cannot be found or the head is damaged, the Clevor option is dead. We suspect that too much heat is the cause with several contributing factors at this point. The duty cycle is only 5-10% ‘abusive’ loading, so maybe highway cruising conditions are worse? Contributing factors are; coolant holes drilled in the block may not be large enough, headers may be too small, valve geometry not optimized, exhaust valves not the highest quality, cam too small or cruising rpm is too high? The original stainless steel, one piece, undercut and swirl polished valves cost $175/set in 1997, so were of decent quality, much better than stock 351C valves.

So does anyone have the following piston? TRW Forged piston #L2414F-30 (400M). It will need to be machined to match the other 7.

Any thoughts or suggestions are welcome.