Timing pointer M.I.A.

[K9keeper]

Hi,
I'm new here so I hope this post is in the right place. We're in the process of getting a 1982 5 Ton Military truck back on the road. It is powered with the Cummins NHC250. In preparation for performing the overhead adjustments, we have noted the absence of a pointer anywhere on the front cover used for indexing the 1-6, 5-2
and 3-4 marks on the accessory drive pulley. Although this truck is a 1982 model the I.D. plate on the engine shows a build date of "10-71". Could this earlier engine of had a bolt-on type pointer that has been omitted? There is a flat machined pad with a threaded hole located where the pointer should be. The pad faces the front of the engine. I've cleaned the area quite well but have found nothing resembling a pointer. I believe the pulley is marked with a #1TC position that I could use as a reference point and fabricate a pointer to install. We are pulling the injectors out for testing anyway so a dial indicator on #1 piston will find TDC.
Has anyone run into this before? The accessory drive pulley appears to have the necessary markings on it but no pointer to be found.
Thanks for your consideration in this matter.

 

[doghead]

https://www.steelsoldiers.com/showt...head-adjusting&p=909780&viewfull=1#post909780

 

[K9keeper]

Thanks for the link Doghead, however, my issue isn't how to perform the tune-up but rather why I can't find a pointer on the front cover to line up the marks on the pulley. I have read this link previously and it does
give useful information.
Thanks again

 

[WillWagner]

Unless it has been shaved off, it is there....

 

[74M35A2]

You can find TDC of a diesel easily without much work. Pull the valve cover, remove the rocker of an intake or exhaust valve on #1 cyl, and by hand push down a valve in different crank positions until you feel the valve hit the piston top (by hand or with spring compressed by a screw type spring compressor). Keep going on crank rotation until you can hand push the valve down only the smallest amount and it hits the piston top. At this point, remove the spring keepers, retainer, and spring, leaving just the valve stem. Place a dial indicator on the tip of the valve stem. Slightly rotate the crank in each direction of TDC, for example, let's say 0.200" of downward valve tip travel. When you reach one side, mark the crank damper in reference to any block mark you desire. Then, rotate the crank past back up toward and past TDC to 0.200" down on the other side, and mark the damper at the same block reference point. Now, the point exactly between these two marks on your vibration damper is #1 TDC.

Because of the higher compression diesel combustion chamber, the piston is very near the valves at TDC, so you are typically able to remove the valve springs with the piston is at or near TDC. Be careful to move the crank slow and slight, otherwise you will drop a valve into the combustion chamber and have to pull the head to retrieve it.

 

[K9keeper]

Will Wagner,
If it's there, it's buried out of view or shaved off. Thanks.
74W35A2,
Thanks. I find it easier to go down through the injector hole with an extended dial indicator to find TDC.

 

[WillWagner]

The only thing that pointer is used for is the overhead set. It is normally located almost directly dead center of the two outer most bolt holes in the top accessory mount pad and just a shade outward toward the accessory mount hole that runs thru the cover.......leme see if I can find a picture....

You don't need to be on the mark perfectly to set the overhead, you can be around a 1/2 inch either way.

 

[WillWagner]

Here's a good pic...

And, you can set the overhead w/o looking at the pointer. Put a socket with a 6-10 inch extension on it on the #1 injector lever. Bar the engine until you see the extension start moving toward the exhaust side, keep barring until it stops moving, then just a tad more...on the end of a 24 inch ratchet, that "tad" equates to about 2-3 inches...You should be at the point to set the #1 cylinder using the torque or OBC method.

Just for S&G, look at the pulley to see where the marks are, this is also how you verify the accessory drive is in time, the engine will run fine with it out of time, the timing here ONLY has to do with overhead adjustment. If someone has R&I'd the accessory drive without timing it, you will know now, if you DON't check it, you engine will run like crap, you might bent push tubes.

If the marks are close, 1/2 to 1" either way, you are GTG, if not, the drive is out, but no biggie, make a mark on the pulley and somewhere fixed, label it "A", move on to the next cylinder, #5. Do the same thing to check yourself, mark it "B", go on to the next one in firing order, mark it "C" and finish off the last 3.

 

[K9keeper]

Thanks for the responses guys. Great photo Will. Nothing like that pointer is in view on our front cover. Could have been sheared off at some point in time. The marks on the pulley and the pointer are just for convenience anyway and, as you pointed out the overhead can be performed without them. As a fleet mechanic on Detroit's, overheads were done by observing intake valve position then making adjustments on companion cylinders.

K9keeper