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· Registered
round one , square one
1,587 Posts
Discussion Starter · #1 · (Edited)
I have been having a tough time trying to find TDC to do the timing on my Mog(om352)
The timing adjustment is simple but finding the TDC is not.
My vibration dampner has only one mark so I,m not sure if that is FB or OT, I adjusted it of the line and something sounded way of on the valves.
I sighted down the timing gear case but could not see an arrow, I could see the marked teeth on the IP gears but the only thing resembling an arrow is a small stub off the back(inside) of the hour meter. So I adjusted off that, I have lots of low end power/ no rattle of valves but my exhaust temp zips up to the red way to fast for my taste (on the flats/6th gear/punch it and within a few seconds I'm at 1250).
I had the IP out when the cab was tilted before and I do remember that I lined it up with a very distinctive mark when removing and putting back! Only now I cannot see/find it.
My IP is not advanced at this time!
If anyone can give me some pointers It would make my week.
G Vavra

· Registered
1970 406 Unimog with 9'2" Boss V-Plow....... 1974 404 Unimog Rock Crawler
876 Posts
The following articles are from the Mog archives, perhaps these will help you:

"There is a large reference notch on the crank pully at about the 1:00 position...get that lined up, again I had a ratchet on the my air compressor pully to turn the motor over. Once you are there, check the rocker arms on both cylinder #1 and cylinder #6 just to see where you are. You will find both rockers of only one cylinder will be loose. Cylinder #1 is at the front of the truck. Sooooo, if you feel that both intake and exhaust rockers are loose at cylinder #1 then you can do the first set of adjustment...valves #1, 2, 3, 5, 7, 9. Just to restate the obvious, valves are numbers 1-12...two per cylinder.

Now that you have checked those for the proper spacing (0.2mm intakes and 0.3mm exhaust) and made any necessary adjustments, then you can move onto the other half. Rotate the motor 360 degees until the reference notch lines up again. Now you are ready to for the last set of valves #4, 6, 8, 10, 11, 12."

"Turn the crankshaft right until number 1 cylinder is at compression TDC. This point is obtained when the rocker arms of number 6 cylinder overlap.

Check and adjust play of intake valves 2, 3, 7 and of exhaust valves 1,5,9.

Now turn the crankshaft one revolution until number 6 cylinder is again at compression TDC. This point is obtained when rocker arms of number 1 cylinder overlap.

Check and adjust clearance of intake valves 6, 10, 11 and exhaust valves 4, 8, 12"

Valve clearances on cold engines
intake .20
exhaust .30

· Outstanding Contributor - Always Remembered, RIP
Zotye Auto 1.5T T600 2016
52,890 Posts
Give me your vin # and I will try to find pics in WIS for you.

· Registered
85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
5,842 Posts
The above procedure is good for findin TDC.
Your IP gear and it's drive gear should have very distinctive marks on them that are visible from the round hole onto of the gears.

· Registered
Sold .....1987 U1250 Unimog
1,011 Posts
So… I adjusted my valves, I think I did it correct looking for opinions and advice.

I pulled the valve cover off and turned the harmonic balancer to the FB mark and the big notch. Valves 1&2 on piston 1 were both loose and valves 11&12 on piston 6 had one open and one closed. I proceeded to set the intake to .20mm and exhaust to .30mm after setting the valves listed in the book I rotated 360 degrees and did the second half of the motor, again noting that piston 1 and 6 swapped positions as expected….

So here are my concerns and Q

I had to adjust every single valve…
I didn’t think to check the before setting until after I started to do the last half of the motor but I could easily slip both my .20 and .30 feeler gauges under one of the intake valves, I didn’t’ think about getting the exact amount but I would say easily .60 valve to rocker and honestly all of them seem to be about the same amount out of adjustment.
So … Is it normal to be this far out of adjustment?
Engine HR meter is around 1250 HRs, and I don’t know who last touched the valves be it Mercedes elves or last owner. Ben? Did you?

I don’t have tabs on my Unimog as they just expired so I didn’t’ go for a drive yet “trust me I want to go for a drive I just turned up my injection pump while doing a valve adjustment” I did start it up though and I’m not sure if it’s a Placebo affect or the modification of IP, or just the hot weather but the motor started right up, first revolution quick and sounded really health.

So opinions on the valve adjustment?
Did I do it correct?
Is FB = TDC?
WHY no TDC or OT mark?
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