The X heads are 894 number.
They do flow a bit better stock and
chambers are bit better aligned to block.
However, on a stock low compression 340
you will never feel the difference in performance.
I have done extensive research and testing on these
different heads for 50 years. If you gained 10 HP that
would be a lot. The headers would probably add much
more for less trouble and expensive. The intake and carb
if properly tuned and adjusted work quite well and aftermarket
parts would only add a small amount as well = although save some
weight.
OK, time for my enemies on this site to flame away and throw
rocks at me!!
As long as there is no positive deck height, and a stockish cam, would a set of thinner gaskets help get a little bump in compression, like a set of .027 metal gaskets? I recall that the 440's came stock with those.
I like how the poor guy said he was happy with the stock bottom end and exhaust manifolds, and just asked if the heads would make a difference.
Now everybody wants him to port heads, add headers and intakes...
:BangHead:
Not every thread is looking for a max power build.
He did mention “Possibly look at headers in the future.”
That always leads to….. LOL! Exactly what you said.
I do like collecting parts to swap at once though. That’s where you really feel the gain.
To the thread starter (OP) A, FWIW stock head flow video set. Both heads are mine and start with stock cylinder head flow. Being. Charlie ports heads, results are also seen. The J heads are a 1.88/1.60 valve set.
“Should you change a camshaft, in the street, not looking for a drag win, I’d lift the valve until the cam starts to fall off and not really anything ore than that. Someone mentioned stock head flow to .500 was accurate in this case and most every other head I’ve personally come across. You can get a lot of performance out of a stock head.
He S heads were previously ported by someone else and not in a fashion I’d suggest. Enjoy!
