Ok, quick question here: I've searched, and it looks like 304 CID is the upper limits of Ford flatheads. Is this correct? Is there a way to get 325 CID from a Ford, without going with the 337? Just curious.
Money is always a factor! What I want to know is, what do the physical constraints of the engine allow?
You can prety much make them as big as your wallet. But the bigger you go the bigger the bang will be when it all lets go.
Back in the early 50's we used to run 59AB's bored to 3-7/16"X4-1/8 (306 cu.in.) Although not a Ford block Motor City is getting 330+cu.in.with 3-1/2" bore and stroked crank.
What do you plan to do with it? For a big inch flathead you will need a French block. 304 is a really good street motor. -Danny Sent from the best app on the web.
you can spend 10-15 grand on a flatty and get power and torque but nothing amazing that you can run on the street. my old buddy gave me advice on building flatheads many years ago. keep it simple, get the bore and the stroke and carburetion and dress it up nice but don't sell the farm. the enjoyment in this motor isn't racing it but showing it off IMHO. enjoy.
3 3/8 x 4 1/8 will get you 296-pretty common. 3 3/8 X 4 1/4 will get you 304-that's a lotta stroke if you're using stock parts. 3 7/16 X 4 1/8 will = 306. That's stretching the bore to practical limits. 3 7/16 X 4 1/4 = 315.6-everything is at the point of eminent disaster. (And that's the end of my chart). However, as has been said, given enough $ anything can be made to work. Sleeves, SCAT cranks------.
I don't think I'm going to try anything. At Bonneville, XXF is a Ford flathead class, that requires 325+ CID, or a specialty head with at least one set of valves i it. I just wondered if the guys were building 325+CID engines, or going with specialty heads.
Guys, after the FlatCad, I know big flatheads cost money. This is only theoretical, to see if it can be done. I have a lot on my plate, with the FlatCad, and the mods I want to follow this engine with! Having said that, I was thinking 3.405" bore, 4.5" stroke, for a 327. I just didn't know, if it could be done.
Pete1 was telling me about a few 325ci flatheads he has done. My Bonneville motor is a 304ci but Ive got a 59L that was 3 7/16 bore with 4.25" inch stroke. The rod journals from that motor failed and were loose... you could actually detect a slight wiggle. I haven't done the math to figure displacement....314ci or so... A French block isnt needed to go big... but Merc, truck and 59L blocks are preferred. I don't know of current XXF cars running anything other than Ardun heads (original and repops)..... whether or not they are 325ci is unknown but the contemporary mindset seems to be less cubes, with an emphasis on breathing.
Back in 1960 I had a late flat head Mercury over-bored .125, I think that made it 3.3125" with a 4" stroke. After driving it a few weeks I noticed that the oil was climbing up the dipstick. Then it turned brownish gray. It turned out that a .125 over-bore was too much for that engine, not enough cylinder wall.
I ran a 301 (3 3/8+.030 x 4 1/8) back in the mid'60s. Cracked very quickly. Walls very thin. Problem with Fords is getting the air in and exhaust out to feed a big flathead.
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