Hi all, I have a question for the Pontiac flathead guys; Do any of you have knowledge of how much a 249" can be bored without risking damage? I have an engine that got some marks from the piston pins, but otherwise it's in fine condition. Since the stroke is the same as on the 268" I was thinking that might work. The difference between the 249" and the 268" is 0.125 inches. One reason for not just put in a 268" is that the water pump will not be centered in the radiator on my '47 Streamliner and since I must do this job anyway... Thanks, JC
In the old days people used to bore engines 1/8 inch all the time. So it "should" be OK. What have you got to lose?
Having the block checked for thickness can't hurt and make sure you can find some pistons that will work.
RichFox is right. Before the early sixties, it was expected that an engine would be rebored once or twice during its service life and they were made to be bored .125 or more. Some Olds V8s could be bored .250. Using stock size pistons from a bigger bore engine was common because they were cheaper than oversize pistons. Many Chrysler 331s were bored .125 over to take stock 354 pistons for example. If you are concerned about possible core shift or rust damage you can have the cylinders sonic tested. I know a Chrysler mechanic who has rebuilt many 426 hemi and 440 engines. A few years ago he did a 1941 Plymouth flathead six for a customer. He told me it had the thickest cylinder walls he ever saw. This was typical of older engines. He sonic tests as a matter of routine.
@RichFox, you got a valid point. @Rusty, if I can't get modern-styled 268" Pistons, I got two donator engines. I think I go for it, "no one remembers a coward", right?
@jnr49, I will report when I get to it. It might take some time though, since I have more things to look at (rust, interior, suspension) and also need to raise money as I must import everything needed from the US. Sadly, no one have things for more exotic engines on the shelf over here. Sent from my iPhone using The H.A.M.B. mobile app
Never heard of them, will check it out. Thanks @sunbeam! Sent from my iPhone using The H.A.M.B. mobile app
Hows your build going, im about to start my straight rebuild, wondering howd your boring went Sent from my SM-G900I using The H.A.M.B. mobile app
Well @jnr49 , the question about re-sizing a 249 to 268 is still to be answered as I all of a sudden was offered to buy a .030 oversized 268 with a crankshaft in better condition than what I got, so I went the easy way. I fired it up some weeks ago and it seems to work well without a shroud for the fan. Now my main concern is to find a crossmember from a '48 streamliner for my next project, putting in a hydra-matic tranny in the '47. Oh well... Sent from my iPhone using The H.A.M.B. mobile app
Nice well done...then ill let you know how the boring goes as ill be doing that when it gets a full engine rebuilt with new camshaft, piston, shaved head and a few other goodies. Ill keep a eye open for a trans cross member for u Sent from my SM-G900I using The H.A.M.B. mobile app
Thanks, it is still an interesting question. For me it was more convenient at the time, I got a good price and I also had to bail out the restored hydra from the shop Sent from my iPhone using The H.A.M.B. mobile app
Now I have broke in the engine over around 1000 km and it runs like a dream! It runs best around 100 km/hour. The only caveat is that it runs a bit lean, I think it's because the increased volume. I will try to adjust the needles and see what's happen. Skickat från min iPhone med H.A.M.B.
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