(I think you have been).....but I would be looking for a different motor. Why? Because good running, low milage 6 cyl engines can be bought pretty cheap.
I'm with the others on preignition and/or detonation. You can also count on at least replacing the bearings on the crank and possible crank journal damage from that condition. What forces are applied to the top of the piston are applied to the rod bearing as well. The newer engines like to spit out rods under those conditions. and for what it's worth, you usually don't have sustantial audible warning with pre-ignition, it just melts metal and results in incredible load on the crank/rod assembly(basically combustion is fighting the upstroke). With detonation, you can actually hear the colliding flame fronts. If you think back to what led up to this before, you might be able to diagnose the root cause to a degree. Good luck
Thanks guys......I remember it backfired through the carb a couple of times and white smoke came pouring came out the back...the exhaust gasket in the middle(#3 and 4 cylinder)it was burn't away. Jason
I just bought a 250 out of a 1980 Ford Granada...it's a rotating assembly...I made sure of that before I bought the engine. Jason
Don't let go of any of the old stuff till it's all transfered. I have mixmatched stuff and it's not fun. 75 Comet with a 79 Granada motor is what I was told I have. Pulleys and brackets nightmare.
"rotating assembly" is the crank, rods and pistons, not what you thought it was. It can be such even though it's frozen tight. You bought a running engine and you were right in verifying that it did before you forked over the cash.
I'm gonna put all the blame on whomever uses that sippy cup just chillin' on the engine bay. Detonation sound like the culprit though.
...That would be my 3yr old son...He is going to turn out to be a speed demon...just like his father....