[Bored&Stroked]

1) Easy 1/8" Stroker (Traditional): You take a 3 3/4" stroke crankshaft with 2.138 journals and offset grind the rod journals to fit the 39-42 91A or 21A 2.00" rods. Given that these rods used the full-floating bearings, the crankshaft can be any 3 3/4" stroke crankshaft (39 - 53) with 2.138 rod journals.

Oiling Holes: The 39 - 48 crankshafts only had one oil-hole per journal, so you have to use the full-floater bearings. If you use a 49 - 53 Ford crankshaft, it will have 2 oil holes per journal, so you could use a set of H-Beam rods with insert bearings.

Oil-Slinger vs Rope Real-Main Seal: The 39-42 engines used crankshafts without a rear-main seal - they had an oil slinger setup. If I was going to build an engine like this, I'd use a 45 - 53 crankshaft that supports the later rear-main rope seal. You then use the later 59 AB pot-metal rear-main seal plates and install them in the 39 - 42 block (they fit right in). This gives you a rope rear-main seal (which is a lot better than a slinger setup - especially if you're running larger bearing clearances and a later oil pump).

2) Welded Stroker: There were some high-end racing engines that had their crankshafts welded up (by hand) to add enough material to increase the stroke beyond 3 7/8". They would regrind the rod journals to use the 2.00" 91A or 21A rods and full-floater bearings.

Given the different material types between the cast iron crankshaft and the steel weld material, it was common to initially grind the journals to a bit undersize and then have them hard chromed and finish ground. The hard chrome gave a consistent journal surface for the full-floater bearings to run on.

In later years, one could use a submerged arc machine to weld up the journals for the initial material adding process. I've seen many of these machines in action . . . they work well, but the process is expensive (to do all the journals).

3) Full-Floater Bearings: The standard Ford/Mercury full-floater rod bearings from 39 - 48 used a hard copper alloy. While these will run just fine, they are harder on the journals (wear). In most of my early stroker engines, I'd always look for Ford bearings marked "Heavy Duty Truck and Bus" - these used a much softer cadmium-silver alloy.

Most of the major bearing manufacturers had cad-silver rod journal bearings as an option. In Federal-Mogul full-floater rod bearings, they had a part number suffix of "CS"

Given the longer stroke and higher HP of our race engines, having cad-silver bearings was a blessing as far as crankshaft wear. The cad-silver bearings are a lot harder to find these days, so "squirrels" like me tend to have a bunch stored up for the future.

4) Full-Floater Bearing Fitment: In order for full-floater bearings to work as designed, they must be hand fitted to the rod journals . . . such that they easily float in both the big-end of the rod and on the journal. You can't just buy a set of bearings and throw them in the engine and expect them to float and not score the crank or rods . . . tuning them is key!

Some of the bearing shells will not be perfectly round, so a rubber mallet comes into play. Also, the bearings should be polished with fine Scotch-Brite and lacquer thinner. Also, it isn't a bad idea to increase the diameter of the big end of the 91A or 21A rods about .001 (to help the bearings float). This is all stuff that was/is done for high-performance stroker engines where we always wanted increased bearing clearances and "loose" fitting crankshafts!

Always remember the ole' saying "Loose is fast, tight is death" when considering bearing clearances! LOL