Y-Block Interchange? 239C.I. crank swaps?

I'm looking into Racing a 54' 239c.i. Y-block.
Is this as bad of an idea as I allready think it is.(Bad Oiling, sodium valves, etc...) Is there any-way or any good reason to soup up a 239 block?

What other cranks will drop into a 239?
Will any other later heads swap onto 239 block?
What year did the intake runner size change for y-blocks?
On average how much can you punch out a 239?

Did some searches, and was all over Mummerts Page but still looking for these answers...

Thanks,
-Torr

 

Occasionally, a 239/256 crank was dropped into another Y block to DE-stroke it for class racing. It is possible to use a different crank in the 239...but there's not much reason to do it.

You may or may not be aware of it, but there are two different versions of the 239. The Dearborn version was used in all 1954 cars & early '54 trucks. It has a 13-tooth distributor gear & larger camshaft journals. These cam blanks are no longer available & NOS ones are very difficult to find, as well as the cam bearings.

The Cleveland version was used in later '54 trucks and all (early) '55 trucks, replaced by the 272 in mid-'55 trucks. It has the 14-tooth dizzy gear, & the same cam journal dimensions as all '55-'64 Y blocks.

To directly answer your questions...a 256 crank will directly drop in (since it's the same crank ); a 272/292 crank will drop in; the 312 may or may not hit things. It shouldn't but I have not personally tried it. Of course the 312 crank will need its mains turned down to the smaller journal size.

Later heads will interchange onto Cleveland 239s...... but not onto Dearborn ones, supposedly.

As a rough guide, the ports were smallest in 1954-early '55; increased once in mid-'55 for certain larger/higher hp engines; & increased again in 1957. Basically, three different port opening sizes. The runners vary in design between casting numbers (in some cases), for the same size port opening. After '59 they were downsized.

It is generally considered that a Cleveland 239 can be bored as much as .125 to the 256 bore of 3.625 as they use the same block patterns. To put it bluntly, if you want to try this, get it sonic tested.

Whether it's a good idea or not is another story. If you bore it to 3.62 & use the 3.30 crank....you get a 272. You definitely want to junk the dumbass 239 front cover with the inverted fuel pump & use a later cover, car or truck, whatever suits. You also want better heads than anything that ever originally came on a 239....and a different intake, carb, distributor, pushrods, rockers....

It might be easier to start with a 292.

BTW, the oiling problems can be easily fixed....and a 239 should not have sodium valves, unless different heads were swapped on, which is quite possible.