I'm struggling with a dilemma. Building my 53 Merc with 1/8th offset grind crank. I've got a set of NOS 21A rods and a set of NOS FoMoCo rod bearings. They are "A6" bearings. "Sil-Alloy" on the Ford chart. My concern is that they aren't a desirable bearing. There were 6 different full float factory bearings. I've read certain ones eat the crank. Cad-Silver being the best. Is A6 Cad-Silver? Unfortunately my Dad, Rich Willim, was my flathead guru, he passed away in 2014 so I'm a bit lost on this. Been contemplating selling this stuff and buying Eagle rods with 2 inch bores and using insert bearings. Anyone know right from wrong? Thanks.
Can’t really answer your question but these are the bearings from my’34 Had a rebuild sometime back in the day crank ground.010” under mains and rods Everything still measures within spec but recently found out that the rods could also be honed oversized so will have to go back and measure rods
Thanks Oldmtech, but that's a different application, so bearings are different. I'm looking at 175hp and spinning it 5500. So I don't want to take chances. I may sell the rods, bearings and a spare Merc crank as a 4 1/8 stroker kit and get aftermarket rods with insert bearings.
It looks like we have the same parts and looking to have the same application. I have the 4 1/8 offset Merc crank along with two sets of original NOS 21A rods and two sets of original NOS 81A-6211-A6 Std. connecting rod bearings. One set of bearings look to be the same as yours, namely the Ford Tri-alloy connecting rod bearings. The other set I have are are in Ford boxes as well but are marked "Silvaloy" on the box. The box is blue and white with the blue Ford oval all over the box and by the Silvaloy name on the box one has to assume that these connecting rod bearings are a silver alloy. I have opened up both boxes and both sets of bearings look to be identical. I have a an excellent 100% crack free 59L block and fully intend to use the crank, rods and bearings in the rebuild of this engine. No China made parts for me. I'm wondering if the bearing failure or the crank eating up the bearings was due to lack of bearing lube or improper assembly to begin with. I can't see original Ford bearings such as these prone to failure. These NOS sets of bearings in original Ford boxes are next to impossible to find.
I can't nail down which bearings were having issues. I believe aftermarket and they were delaminating. I know in the 50s 21A rods with offset grinding was the rage. I also know of one currently that turns 6500 with the SilvAlloy bearings and 21A rods. I really appreciate that feedback on what was in the boxes and what they looked like. If thats the case I can move forward as is.
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