Ditto on the Hex Head timing gear oiler hole
diameter. I said .040 down to .015. WRONG!
"OldJeeps@aol.com" points out: was originally .070
and the replacement was .040.
I remembered it wrong. My notes were right.
Thank you sir. .070 down to .040!!! Don't want to starve
them gears.
And there is only ONE (1) hole, pointed right at the
junction of the two sprockets.
*****FROM:OldJeeps@aol.com
Wow, this is a very timely thread. I was just discusing these differences
with someone today. Perhaps someone with a disassmbled MB/GPW block can
help...
According to the manual (civilian) the nose of the crankshaft on those
engines equipped with a chain and sprocket (not gear..) are oiled thru 4
holes in the sprocket itself. There is an annular groove on the bore of the
sprocket, and the nose of the crankshaft has a thru hole drilled at 90
degrees to the keyway (which is at the 3:00 position when at #1 TDC). This
cross hole is fed by the front main.
(Ted):On my wifes GPW, Serial Number:21244 (Same as motor),
Date Of Delivery: 4-22-42,
her crank sprocket has (2) .090" holes
drilled 180 degrees apart, not quite perpendicular to the key slot.
The crank has a grove cut into it, all the way around the shaft, so both
holes are fed, where the sprocket holes would
lineup with it. There is a drilled passage which goes from this groove back
to the 1st main journal. Its similar to the one that feeds #1 rod journal but
closer to the front of the motor.
Ever wonder why there are two grooves in the bearing inserts?
One is from the pressure feed from the pump for the 1st Main and the 1st Rod,
the other groove is for the excess oil to the front sprocket. The sprocket
doesn't see full pump pressure, just what bleeds through between
the two main bearing grooves.
DOES THIS MAKE ANY SENSE? Hard to describe, but real easy to see.
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Can anyone confirm if there is in fact a plug at the 11:00 position where a
'gear' equipped engine would have this hex shaped nozzle? Is there a hole in
the engine mounting plate around it?
(Ted): Her GPW doesn't have it. Too early or has never seen a refit.
But I'm betting that later overhauls, probably did drill and tap
for the Hex Head oiler. I'll need to check and see if the pressure
feed does go that far, I don't know right now.
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Secondly, since the chain means that the Camshaft and crankshaft turn in the
SAME direction, but with a gear the camshaft and crankshaft turn in the
OPPOSITE direction, I assume this means a totally different cam so exhaust
doesn't open before intake? And since the camshaft drives the oil pump, I
assume the pump is set up for reverse rotation?
(Ted): The cam, oil pump drive gear, and the oil pump gear itself is
reversed between
the two drive schemes. Pumps themselves are different as well.
I don't know if the actual pump driven grear can be swapped or not.
I have a unique opportunity here; we are putting together her GPW
which was disasembled many years ago before we got it, and
I'm starting an M-38 motor. A little luck and patience, we
should be able to compare both
motors side by side.
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Did they use the same cam and reverse the rotation of the engine and firing
order? I assume NOT!
Would this mean that the flat bottom pump comes on gear equipped engines and
the pump with the bump on the bottom is for the sprocket and chain. Or was it
a bump on the left vs a bump on the right?
I seem to recall that the oil pump bore in the block was slightly larger on
MB so the MB pump couldn't mistakenly be inserted in the wrong block?
(Ted): I can only speak to the GPW block, I'll find out soon. Then there
is the issue of WHEN these things were made.
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Am I imagining all this?
The chain and sprocket was MB and CJ2A thru Serial number CJ-2A 44417 (engine
number) motors after this started with a "J" prefix
The much later manuals state that a new timing gear oil jet entered
production with engine serial number 3J-166871 The earlier jet has a .070
diameter aperature, the later has .040 inch. It goes on to tell you if ther
is evidence on older engines of oil starvation to #1 rod, retro fit the
smallet jet.
(Ted):I still need to find out what the diameter of the restrictor is
in my M-38 and GPW oil filter assemblies. I prefer the oiling
system in my 38. I had very good oil pressure and wear patterns on all
the parts. Thinking of updating the GPW but then IT will
not be original.
Thanks all! (Did I get my MV content in?)
Best of the season to you all!
Ted H.
This archive was generated by hypermail 2b29 : Tue Jan 02 2001 - 23:13:23 PST