408 thrust bearing wear

Hey guys had built a 360 mag based 408, had the block line honed ect. good clearance numbers ect. Broke engine in on dyno, made pulls and it was good.Put 10 runs on engine chewed up thrust and a few rod bearings. 60 psi oil pressure when I pulled off trailer Redid engine, sent converter in to get check(nothing wrong). Trans was rebuilt last year and I ran it with no problems last year. So I redid engine after one day racing same issue.caught it In time to not get rod bearings this last time. Where else do I need to look to fix problem. Thanks for any suggestions.

Look for restriction in the transmission cooler or cooler lines. The fluid comes out of the converter and into the cooler. When there's a restriction, or simply not enough flow for the volume of fluid, it creates pressure against the snout of the converter and drives the converter into the engine creating excessive thrust wear.

A misaligned block hone can create an issue also, although it's unlikely.

The 727 torqueflite uses 5/16 cooler lines. The 518 uses 3/8 cooler lines. Upgrade the cooler lines and fittings to 3/8.

Make sure the converter hub floats freely into the back of the crank. I had one that wouldn't and took out the thrust

I put 4 thrust bearings in my sb, had the converter checked by the place that built it, new flexplate, converter spacing, line pressure. All that and it would still eat thrusts. New converter from another manufacturer, no problems.

Thanks for the responses I'm running a 904, is there anything I can check on it?, Front pump or something?, Hashing it out in my brain I might have a bit to much trans fluid in trans,i need to check that although no fluid is coming out anywhere.I have -6 an fittings for trans lines, checked for kinks and don't see any. the converter does float freely on crank, weird situation volare I hate to buy another converter,what amount of spacing do you have?. what I don't get is I was running trans with stock 360 and never had a issue. Thanks again guys.

Take the converter bolts, converter should spin freely in the crank. Push the converter back into the pump, u should have around 1/8" gap between bolt lugs & flex plate .