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HD tri metal main bearings?

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They certainly can't hurt. My belief is that it's worth the extra money.

I'm a big fan of Vandervell, but they're not made, at least not under that brand name, any longer.
They can be found NOS at shows, eBay, etc.
 
The King bearings are a Tri-Metal type and work very well in your application. Rod bearings part no. CR4403AM, and your mains MB341AM.
 
All the bearing I know of have at least tri-metal design. The top layers should be soft. The soft metal tends to absorb small hard debris like bits of sand or metal to keep it from scratching the crank. The second is there to support the first and is a bit harder The next layer is a bit harder still (usually a sort of copper which is stronger to support the previous layers and is mainly there to absorb the hammering. Then there is the final part that is there to hold the bearing in place and transfer heat from the oil to the block or rods. The three process' are called embedability, load strength and conformability.
that said, for a street engine with normal compression let's say less than 11 to 1, a lesser expensive bearing fine. In fact I prefer these because they don't eat up the surface of the crank. A michigan 77 type bearing while very strong and good for those almost diesel like 14 to 1 racing engines tends to be harder on the journals.
I have used the so called cheap bearings for years in my mild prepped racers and have never had a moment where I said "danged I wish I would have used one of those big buck bearings". I have pulled engines down after 5 or more seasons and found that the bearings were in great shape and so were the journals. But the cheaper bearings check the clearance during final assembly and don't worry about it.
 
Listen to Alan, (AKA bluemax), the factory built your engine with tri metal bearings, so why should you use anything less to save a few bucks is way beyond me. King is the best bang for a buck in a tri metal bearing, and BPNW is good place to get them.
 
I heard elsewhere that these bearings surfaces are harder and would cause problems if contamination gets lodged into it which could eat of the crankshaft bearing surface?
 
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