I am toying with the idea of running full floating rod bearings on my 4" Merc crank for my 4 9 F1. After doing some quick measurements, it looks like the big end of the rod has to be machined to fit those style bearings. Would like to use 8BA rods, but will they be weakened too much after being resized ? Any help appreciated. Thanks !
And why would you want to do this ? If that was a superior way to run the rods,,,,wouldn’t they still be that way ? I’m not saying the floaters are bad,,,,,,but why spend the money and effort to do it ? Tommy
These bearings came with the crank, no extra charge, but I must be missing something. Were they meant to run a special rod ? The theory behind them makes sense, but my 8BA rods will not work unmodified. Any of you out there still buildi g Flatheads. My last build was a long time ago, and I used traditional insert bearings. Anyone posting non heipful opinions need not reply. Does'nt help me, and just clogs up The HAMB. Thank you !
Well I'm not super sure on this, you'll have to do some research. Some guys take a Merc 4" crank and offset grind it so they get 4-1/8" stroke. When you offset grind the crank it makes the rod journals smaller, the 21A rods work on the smaller journal offset ground Merc crank and full floating bearings.
I guess we need to know which floating bearings you have? What year flathead are they for? The 29A rods are circus 1942-48, right? The 21A rods are smaller journal and are from 1939-40 ish.
Been doing some research. I have 4 inch stroke Merc crank fro 49 to 53. I have to use 8ba rods cuz the crank is goinng in uncut, unstroked etc. Also read up on floating Rod Bearings. Lots of work to fit them. Why doesn't Federal Mogul just make the dam things to fit ?!? I'm just going to run insert type bearings. Thank you all for your input.
Just to add a little fuel to the fire, there was an article on "full floaters" in another engine (I think it was an Olds or an early hemi) in Hot Rod magazine in the late fifties or early sixties. It was an all out racing engine and it was a special setup. Whoever wrote the article was very impressed with the build an how easy it was to turn over when assembled. I guess it was a top of the line update back in the day. That being said, if the bearings you got are new in the box, you'll be money ahead to sell them to someone with an earlier engine and get s set of proper inserts.
use full floaters on an 8ba but not inserts on a 59a--oil holes. the full floaters are thought to be better, but are somewhat tedious to fit.
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