I keep hearing guys flap about how putting an early Plymouth head on a later engine makes more compression and more power. This always struck me as foolish due to the low compression of the early motors. Today I got around to CCing three heads. The right hand one is a 54 head, center is a 37 P4 head and the left is a 36 P1 head. The P4 and the 54 head are EXACTLY the same 85cc(note the updated combustion chamber shape on the 54 head.) The P1 head is larger at 88cc's. So switching on an early stock head seems to be a large waste of time. Mill you late head.
Also of note is the larger transfer area and the shape of the late head. It has less room behind the exhaust valve for more flow where it counts.
Pretty easy. Put the spark plug in. Cover the combustion chamber with a piece of lexan with a small hole in it. Push in a fluid out of a graduated syringe. See how much fluid fits in the chamber.
since we are talking flat head sixes: a 40 dodge coupe gets towed into my shop, i diagnose a leaking head gasket, i pull the head and find it is warped and the last guy used two head gaskets to seal it. i had the head milled [a lot] to get it straight and put it back on with one new head gasket. i go to crank the motor and it is seized. i drained the fluids and took all the head nuts off and the motor would spin, lifting the head up and down as it went around. i took the head off and noticed the pistons stuck up above the block 1/8". i guess the guy before me used two gaskets to clear the pistons and that is what warped the head. i took the pistons out and they were from a chrysler 6. [same bore, different wrist pin location] we turned them down 1/8" and put them back in the motor. with the flat pistons at the top of the bore and a cut head this motor made some impressive power, you would almost think it had a v8.............only problem it wouldn't start when it was hot.......
Not too mention the later heads have internal water pump by-p*** holes to mate with the more modern blocks...
Any fool with a drill bit can make the late head fit an early motor. And going the other way just requires a pipe plug in the head.
Yup, not a huge deal, but as you mentioned on another thread, it has to be done to work, without leaking. 54 Plymouth engine, is that a 228 Canadian version? Or are you talkin a US 230? Why not go with a 250 or 265 , no replacement for displacement, if you are using a Canadian Plymouth engine.
Short engine. American 230. Not enough room for a long engine and there are way to few speed parts for them. I have a 251. Pretty slow to rev, that crank is way to heavy for what I want to do.
I always understood the best head was the 57 up 8:1 compression job. Highest compression and best shape.
Yes and there were the 2 bbl intakes and carbs for a few more HP on some. Oh, so how much weight difference in the 250 crank and the 230 crank? What RPM range are you intending to go to with this long stroke engine? And how do you intend to attain it? There certainly are more speed parts for the US 218/230 if that's what you are getting at.
Here you go. 57 up have the highest compression and most HP. This was the last revision by Chrysler engineers as the engine was dropped after 1959. http://www.carnut.com/specs/gen/ply50.html
That is just more internet dribble. How about some actual cc numbers and a picture of a 57 head combustion chamber?
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