Thread: Insert bearings
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Old 01-31-2017, 04:02 PM   #3
Dave in MN
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Join Date: May 2010
Location: Jordan, MN
Posts: 1,290
Default Re: Insert bearings

Yes, it has happened to me. The correction to this is that additional oil clearance needs to be achieved.

You say the bearing spun and cut the oil flow...I disagree. The bearing to shaft clearance was likely too little and it was the lack of oil that heated up the surfaces to the point of rubbing and melted the bearing material to the crankshaft The spinning of the insert in the block housing bore was the last thing that occurred as the engine locked up.

The manufacturer of the bearings I use stated .00175" as the correct clearance for the main bearings. That clearance did not work well for me when he switched the final surface of his insert shells from Babbitt to bearing grade aluminum. I find that the aluminum lined rear main insert should have .002" to .0022" to be reliable, (means no lock-up) and leak free. The front and center mains can finish at .00175" and not be an issue with running tight. JMO: The best clearance for all three journals is .002".

I have a Sunnen precision honing machine with the proper sized mandrels to hone the aluminum insert bearing shells for the proper clearance. The Sunnen rep. advised me as to the correct stones and hone oil to use for the aluminum. I built a fixture to clamp and hold the bearing shells at the same tension (crush) they are installed from two rear main caps. The final fitting of the mains requires about 10-30 minutes depending on how many need to be adjusted but the precise clearance is worth the time.

The description you give about the insert shells welding themselves to the crankshaft is a very real occurrence. The inserts, I use with an aluminum bearing surface, are prone to this happening if there is inadequate clearance. I discovered the lock up issue when breaking the engines in on a dyno at full operating loads and high rpm after an extended session of operation.

How to save your crankshaft if this happens: I discovered that the aluminum bearing material can be removed from the crankshaft journal by careful use of muriatic acid. Be careful when using this stuff, it is nasty. Goggles, gloves and a well ventilated area (best outside and stand upwind of the acid bath). Carefully knock the shell from the journal by using a chisel at a low angle on the seams. They will pop off. Next, submerge the end of the crank in muriatic acid for 5 minutes, remove and scrub with a bronze wire brush. Repeat until it is all removed and rinse well with water. Do not leave the end of the crank submerged for an extended period of time or it will ruin the surface of the journal (believe me...don't ask!) Some may suggest you neutralize the acid with baking soda, I did not bit washing it with a slurry of baking soda and water would do so.
After all the aluminum is removed, polish the journal and you are ready to fit the new bearing.

I am sorry for your is frustrating. Inserts have been a good product for me when they are installed with the correct oil clearance. I have over 150 of them operating very well with insert bearings.

PM me if you need more info or help.
Good Day!

Last edited by Dave in MN; 02-03-2017 at 09:33 AM.
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