[antique69lemans]

Originally Posted by gearbanger

Were the upper rod bearings cupped to the point they wouldn't stay in the rod. If so, I would say definitely detonation. I went through several engines back before I knew about detonation. Engines all ran good and you could not hear any pinging or rattling. But after a few thousand miles the oil pressure would go away and eventually would start knocking.

Pull it apart and all the bearing would be down to the copper. That was back when I was trying to run 670s on a 406 with pump gas. Not gonna work.

Bearing inserts being loose AFTER meltdown is common. They are deformed under the extreme heat and lose their shape. The rod big end is suspect from the heat. Even if they were perfect before, the rods will probably be "egged" and cause improper clearances with new inserts. I have seen oil starvation cause rods and blocks to blacken from the heat and burnt oil. I would personally consider another set of rods in the next build.

[Ken K]

If the crank was standard and you just had it polished then there should not be any problems with clearence. I had a machine shop check a set of those rods, I was told the big end was right where they liked it.

[Ken K]

Riffle brush the oil passages. 1500 miles should not be enough time to get them dirty. If they were cleaned then you should not pull any gunk out of them. Dirty ones can be just like tar.

[Ken K]

Now you are starting to scare me. I have a set of those rods and they checked out and the engine is still running. The reason I am scared, that is the second engine I have seen pictures of using those rods that had bearing problems. The other was a 400.

[Ken K]

This is the bottom end on a 400.

[rod cole]

The discolored one indicates it was to tight[most likely cause] or starved for oil. Poor clearance checking as a fyi I receive a new set of FM bearings and they were half .010 and .020 right out of the box.