Are bearing clearances the same for alum connecting rods as with steel rods? I have a set of BME rods and Cleveite bearings that are tight by my standards (2.2" with .0015"-.0018" clearance, used bearings , less than 20 1/8 mile passes). The bearings and crank look good but I normally want to see around .0025" on that sized journal with steel rods. This is a large CI drag race only engine.

Thanks, Brian

Aluminum rods get smaller with every heat cycle. Did you measure the rod bore? I'd bet it's under where you started.

Knock the pins out. Home the rods to size and go.

Brian, the Installation instructions for BME forged Aluminum rods calls for minimal bearing clearance of .003. That is what mine are.
Mike

All aluminum rods require more clearance because they get smaller with heat. Blown alky motors run .004 plus... On smaller engines you should use .003 as an absolute mininum.

Mine were tight like that. Sent them back to BME and they opened them up. Ran with .004" clearance (crank is .001" under) with no issues. Bearings went 300 passes in a 15-1 572 with 15-1 compression. Looked like new when inspected.
Doug

.0035-.0040" is where I would aim, with an edge to the larger end of the scale.

Thanks for the replys. That is pretty much what I was expecting to hear. Except the part about alum rods getting tighter the longer they are run. I would have thought they would get looser. I checked the rod with no bearing, the results were that they are round, but approx. .0004" tight.
I will try a set of X bearings this week, but even they might not be enough.

Thanks, Brian