mixing of silverdome 4 cylinder u and pa

[29dodgetruck]

hey does anybody know why crank rod and pistons out of a 1931 silverdome 4 cylinder motor could not be crossed into a 1929-30 silverdome u engine? is there any difference in stroke or bore size. interesting hmmmm!

[29dodgetruck]

has anybody even tried this. the info I found was the bore and stroke were the some for these engine from 29-32.

[cahartley]

I think you would have to compare heads.........it the later engine has a little higher compression, it may or may not, there could be valve clearance trouble.

TOTALLY guessing here....... :confused:

[29dodgetruck]

thanks for your reply. what I am going to attempt to do is swap pistons rods and crank from a 1931 pa 4 cylinder to a 29-30 Plymouth u motor. the heads are different like you stated. I do have some specs on the 29-30 u motor. example pistons; length 41/8", fitting clearance .001" to .0015" at the bottom skirt, .003" to .0035" at the top of skirt. lower ring grooved drilled with twelve 3/32" oil return holes. I do not have this info on the 31 pa. I have only found general info on the bores and strokes. another example is the cam shaft mounted on 3 bearings, front bearing 11/4" da, 1 9/16 long, center bearing 2" da 1" long. rear bearing 11/4" da by 1 3/8" long. center and rear bearings machined in crankcase. also connecting rods 8 13/16" between centers. crank bearings are Babbitt cast in rod 2" da x 1 3/8" wide. this is kinda where I am going with this. has any body got similar specs for the 31 pa? just to see if any differences or not. thanks

[cahartley]

ASSuming everything else interchanges I think your best bet is put in ONE of the other rod assemblies, lay the head on the block and turn it over.

If the head stays put I think you'd be good to go.......

[ply33]

. . .has any body got similar specs for the 31 pa? just to see if any differences or not. thanks

Will this help? 1931 Plymouth Model PA Detailed Specifications