I've got 2 good flathead blocks. One is a 1940 in perfect shape with one exception, it is already bored to 60 thou and it would need to be honed to 80. I have had some people make 2 comments about this: not much meat left between cylinders, and that I may have heating problems with the motor. I'm not making a racing engine, it would be a street motor, although hot rodding it a bit is sorta the idea. Is this motor worth rebuilding? I already have a lot of the parts to do it. The other block I am not sure of the year, I have to double check as I just inspected a large number of various flathead blocks to find another good one. No cracks, but would need to be honed to +30 to be rebuilt. What else should I have done while this bare block is at the machine shop? Again this would be a street motor. I'd like to improve performace a bit though. I have a 4" crank and would probably go that route with this engine. Suggestions and comments would be appreciated. (No the engines are not for sale.)
A 1940 3 1/16 221 will easily go 1/8 to 239 with room for a rebuild or two; Almost all 239's are entirely safe 1/8 out, and a majority will survive happily at 3 3/8. OPrewar 239's were oft raced at 3 7/16. This is an entirely different planet than 289 and 427 Fords that disintegrate beyond 030...
I don't think ANYONE would be scared of 080 on a flathead. They are thick, except some like 99 blocks that are thicker...and usually the upper area of the bore subjected to the actual stress is even thicker than the lower part. For the 3 3/8, the hotrod pistons are made in the usual small oversizes, 3 5/16, and 3 3/8. 3 7/16 is generally a racer-risktaker only size, the others are pretty safe. Big bore racing engines were usually based on '39-42 (and wartime) blocks that were often perfectly happy on nitro at 3 7/16. This huge bore capacity is actually pretty typical of pre-1960 engines of many brands and types...even SBC's in early form were capable of racing at 1/8 overbore.
If you can post a pic of one the decks on the 2nd block you're unsure of it might yield the generation of it.
Thanks for the input guys. I could identify the block if I could see it. (I think) I took a bunch of flatheads to a shop for inspection, and they called me back and said "block 2 and block 6" are good. I just don't remember which ones were actually numbered what. What should I do to the bare blocks while they are at the machine shop? Obviously hone the cylinders. I'm thinking of making the oil filtering mod, to change both to 100% oil filtering. Any other must do's?
If they are not familiar with flatheads they will want to deck the block. Tell them no unless there is a reason. I know this from experience. Neal
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