M38A1 front pulley?

Jack Innes · #1 22-03-12, 23:43

M38A1 question; I have discovered the nut that holds the crankshaft pulley in place is missing from my newly acquired M38A1 & the pulley is loose on the shaft. This appears to have been like this for some time. It has about 1/4" movement radially which indicates to me a worn keyway & key. I can deal with that but I do not know if the nut is an odd size or if the shaft has some distortion. A 1" NF nut will start but becomes alarmingly tight after about one turn. Does anyone know the thread size? The pulley may need to be replaced. I am sure I read that the pulley & nut are are the same parts on both the flat head & the F head engines,; is this correct?

Secondly could this allow the timing gear to work loose on the shaft as well? The distributor cap shows evidence of the timing being off but perhaps this was a previously corrected situation.

Thank you for any input.

SteveJ · #2 23-03-12, 00:45

most of the vendors, P debella, Midwest Military, Ron at the G503 should have the nut you seek.

rob love · #3 23-03-12, 01:16

When the nut works loose, you must remove the pulley to inspect for wear. Occasionally the damage would require replacement of the crankshaft and/or the pulley, usually do to a buggered keyway slot.

The nut is 1-16 thread. As Steve mentioned, they are available from a variety of sources.

I have seen loose pulleys, but never seen it effect the timing/cam gear. Perhaps because that gear has a steady pressure against it, as opposed to the belt pulley which gets tugged back and forth with the changing of the RPMs. A slop of anything appreciable on the timing gear would also effect the valve train timing, and the engine really would sound like a bag of hammers.

Frank v R · #4 23-03-12, 02:16

Jack ,please note that the cdn2 & cdn3 have the 3 groove pulley, all U.S. M38A1's had a 2 groove pulley system ,just in case you need to get a pulley
Frank

Jack Innes · #5 24-03-12, 04:20

I was able to locate a good pulley & the nut today, I had the key in stock. Fortunately the crankshaft seems to be harder than the pulley so the wear was primarily in the bore & the key. New parts are now installed & all is tight. I did use Locktite on the nut .
Thank you all for the information & help.