Thread: High Power Flathead

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Maxb49, Bob can tell you the exact year the flathead went to insert bearings, 1939? I know the 21 stud blocks had babbit bearings so maybe any 24 stud block will accept the later Merc 4" crank. As far as I know the '49-'52 Merc crank will fit in the 59A, 59AB and 8BA blocks. Bring a truck, I also have a rebuilt 59A with a bad crack but other good internal parts and an 8BA block with a scored cylinder and a broken water pump ear. A good machine shop might be able to make a good engine out of this but it is beyond my financial capability. The obvious answer is to buy one of those french NOS blocks if you have the funds. You are probably going to chop the flywheel anyway so my Merc flywheel should do. I pulled the crank, flywheel, rods and pistons out of a '50 Merc block in a junkyard but you will probably need new pistons after a clean up bore. By the way I looked at quite a few flathead blocks before I gave up and went to a SBC 350 and the overwhelming problem is that folks have bored the flathead blocks more than once or too much and then the thin walls run hot and crack between the cylinder and valve pockets right where you want to relieve the ports. Recall that the basic 59A block only had 3 1/16" bore so if that is the main mold for the later blocks the sleeves will be mighty thin with a 3 3/8" bore! On the other hand the 59A block I have has a 2" long crack along the bottom edge of the head surface over the exhaust ports. That said it would seem that if you find a good useable block any boring should be the least that you can find pistons for. For what it is worth there are main cap girdle kits which would seem to be essential with only three main caps. Gee I fretted over having only a two bolt SBC block but there are at least five main caps so thinking back to the flathead situation with only three mains reminds me of pictures in Hot Rod Magazine covering the Bonneville events in the 1950s where it was evidently common to see ruined bottom ends on the sand, how common I don't know but I do recall seeing several pictures of folks looking sadly at broken cranks and twisted rods, so that three cap crank is a limit. If I would have found a good block my intention was to build a mild flathead with a 4" crank and just 3 5/16" bore with an Isky Jr. cam and take what I got in the way of performance, but while I think a 400 H.P. flathead can be built, it might not last very long? Just for the sake of chitchat, I recall reading a Model T article which described a machine shop project that milled two T blocks at a 45 degree angle on the bottom end and made a V8 from two T blocks which was claimed to be a mighty powerful engine but since the siamesed rods had to be shaved to half thickness to share a common space on the T crank the rod bearing surface was way too small and the rods did not last very long. Maybe that is where Henry got the idea for a V8? At the moment it is interesting to me that even the SBC 350 is getting close to an antique engine so maybe it is a good idea to buy up a few 350s for future value?

Don Shillady
Retired Scientist/teen rodder