I have an extra 265 I will be installing in the 52 and was thinking of doing some extras to it. Other than boring it out is there a way of changing rods to increase the cubes? Would there be any pitfalls in doing this? Has anyone done this already? Any thoughts??

I suppose you'd have to weld the crank...but your going to be getting off the center pretty good....I heard once that George in PA figured out how to make a 280....although I don't know how to get in contact with him...it's in previous posts.

I talked to George Asche about this earlier, he said something about boring it out 60 and making it a 277? I'm still torn about getting a 265 or keeping my 230.

George Asche's number is 814-354-2621

Great guy and he knows his old flathead MOPARs

I have talked to George also, we talked about the 60 over on the bore and 60-70 thou off the head and 380 re-grind on the cam. I thought I would see if anyone has tried to stroke these to pick up more cubes------there was talk by Hudson and Carlos about this awhile back---some ideas but no positive on if it could be done. Still food for thought----still open to ideas.....52er

Really if a person was to get serious..there are companies that can make you a new billet crank... $$$!!! but if you want to go there..
personaly I don't just because of the piston speeds involved....I'm going with 237" just because of the avaliblity (the only engine I've access to) and I like the idea of a 4.25 stroke and finding an 8.5" rod....I'll just have to get some custom pistons....

The 4 3/4 crank used in the 265 is pretty well the limit. They even had to use special rod bolts with "no heads" to get them to clear the block.

The flatheads were made to be rebuilt several times during their service life so a 1/8 overbore is not out of the question on a good block.

Personally I think boring and stroking this engine for more displacement is futile.

I agree you can have a lot of fun pepping one up with a cam, carbs, split exhaust etc and not spend too much money.

But if you want any serious horsepower, forget the flathead and get a bigger OHV engine.

If it was my engine I would do a straight rebuild of a 251 or a 265 if I could find one. Possibly add a cam, dual exhaust, twin carbs, and electronic ignition, mill the head and let it go at that.

O ya shave the flywheel, this is an old time hot rod trick now forgotten, that adds a lot of snap.

These mods should give you around 160 or 170 HP and a good performing car.

If you really want substantially more than that, forget the flathead.

I should also point out, for those who are not familiar with the old long stroke flathead engines, that pure horsepower does not tell the whole story.

Their broad powerband and ample low speed torque make driving sooo easy especially in the low to medium speed ranges. And the old Mopars are surprisingly light in weight.

A good flathead is a lot of fun to drive and does its work a lot easier than you would think.

Most engines made before the mid sixties had cylinder walls thick enough to stand a 1/8 overbore.

I haven't checked the Chrysler 6 specifically but believe they can be bored this much.

A 265 bored 1/8 over would have a bore and stroke of 3 9/16 X 4 3/4 and a displacement of 284 Cu In.

This would be the largest practical Chrysler flathead 6.

"changing rods to increase the cubes"

Rod length does not affect stroke or displacement.
The purpose of changing the rod is to use another rod journal diameter by grinding the crank undersize, but not concentric.
For example, if the rod journal were 2.25" now, reducing the diameter down to 2.0" which increases the stroke by the offset difference, a maximum of .25" in this case, then finding a suitable rod with that smaller journal size, length, width and pin size.
Alternatively, the rod journal size can be increased by welding but again not concentrically. You get the size increase as the stroke increase.
Whether this will fit in the engine or cause other problems is another matter, of course.