[35fordtn]

Originally Posted by Bored&Stroked

For Info: These are bearings designed to be used with what were originally Ford 221 cubic inch engines - from about 1939 to 1942. These 221 cubic inch engines used a smaller rod journal size than the Mercury or most industrial WWII engines of that era (which were 239 cubic inches and used 29A rods and 2.138 full-floating bearings).

All connecting rods in those years used "full floating" bearings - where the bearings rotated/floated in BOTH the rod and the crank journal - in other words they were not "tanged" to hold the rod-bearings stationary in the rod. So, this meant that the inside of the big-end of the rod was a floating bearing surface - just like the crankshaft journal. It was critical that the bearing was setup to easily "float/spin" on both the rod big-end bore and on the crank . . . hence the name "full floater" bearings.

Where these 81A bearings became popular was NOT in racing applications for the 221 Ford, but when the late 49-53 Mercury engines came out with a 4.00" stroke crankshaft (with the larger 2.138 journal size). The old flathead hotrodders came up with an easy way to create a "stroker" motor - without having to weld-up a crankshaft or have a custom billet one made.

The "hot ticket" back in the day was to take a 49-53 4.00" stroke Mercury crank and have it "offset ground" to increase the stroke to 4.125" - and you did this by reducing the size of the journal to approximately 2.00 inches - but also moving the journal centerline further OUT in the stroke. You now took a 4.00" stroke crank and made it into a 4.125" stroke crankshaft.

Then, you used the old 221 cubic inch Ford 91A/21A rods and the 81A bearings for the smaller journal. For the original full-floater bearings to correctly "float/spin", one has to hand-fit them to the specific rods and crankshaft . . . not many folks know how to do this these days. But, back in the day, this combination of the early rods, the smaller journals, the stroked crankshaft and the full-floater bearings were what dang near ALL the serious race engine builders ran . . .

Today, it doesn't make a whole lot of sense to invest in 91A/21A rods, rebuild them and then run full-floater bearings . . . as the end combination will probably cost just as much as running a new set of SCAT/EAGLE H-Beam rods and modern Buick insert bearings.

So, sadly for old goats like me . . . you won't see many full-floater stroker motors being built . . . except by a few of us that still love to build stuff like it was . . . "back in the day".

So there yah go . . . a little babble about the ole days of flathead lore . . .

Dale what were guys doing back them for pistons on a 4.125 stroke. I know nowadays a simple phone call to Egge or such resolves that issue, but what about back then?