I know this a strange request but if some one has an IP sitting around can I get the measurement from the center of the shaft to the where the zero mark is stamped in. This is to roughly figure out distance turned of the IP to degrees advanced/retarded. Either radius or diameter will be fine and within an 1/8 of an in. will be close enough. That's unless someone has got this already figured out.

Hmmm. I know what you mean, that would be interesting to figure out. I have an IP laying around I can measure in the morning if I remember.

Ya kinda simple circumference/360 = ? thou per degree

I am going back to the shop to work for an hour or two. I can measure a 6.5 mech pump, it should be the same.

If the difference in timing is one degree when you turn the pump one degree, you already know how much difference you get ...

The distance (radius) from the centerline to the Timing Mark on the housing which has the bolt slots for rotating the IP is 2.324" or a diameter of 4.648 inches. Pi times the diameter = the circumference, or

Circumference = 3.1416 X 4.648" = 14.602 inches

Circumference / 360 degrees = 14.602 / 360 = 0.041 inches per degree turned.

To advance or retard timing, turn the ip 0.041 inches to change one degree.

Turn 13/64th of an inch (0.205") for a 5 degree change.

And jmay2174 get the gold star! Thank you very much you even did the math for me. Some things I hack at, others I can be fanatical about.

Great info! So 1mm is 1 degree --- I wonder if that is coincidence or a design decision ...

Unfortunately, it doesn't say anything about the actual timing but only how much difference the turning makes. Do dealers usually have timing tools?

diameter of 4.648 inches

Exact the same as what I just measured on the 6.5 mech pump.

Unfortunately, it doesn't say anything about the actual timing but only how much difference the turning makes. Do dealers usually have timing tools?

Dealers and/or diesel shops that have been around since the mass production of the 6.2 and mech 6.5 should have the tools to time the injection pump properly.

We used to have an adapter that clamped to the #1 injector line (anywhere, not on the GM special nut) and it converted the vibration from the injector line into a conversion box. You could then attach a regular timing light to a bar on the convertor box and use the timing light as you would on a gasser. It was simple and worked very well. I am pretty sure it was made by either Snap On or Mac. It also worked on the 5.7 and 4.3 GM engines as well as the IDI Navistar/Ford engines. I guess it is probably still there at the shop, just not the corner where I work.

For the guys that do not realize it, there is actually a timing tab and a mark on the harmonic balancer to allow the timing of these engines.

Shouldn't that be about .020 for 1 degree as the camshaft rotates at 1/2 the crank speed ?

Dealers and/or diesel shops that have been around since the mass production of the 6.2 and mech 6.5 should have the tools to time the injection pump properly.


Hmmm, that's a good idea to look for one that has been around since then. I'll have to try that ...

Shouldn't that be about .020 for 1 degree as the camshaft rotates at 1/2 the crank speed ?


You are correct, but, the equivalent we calculated applies to the physical movement of the IP at the timing marks. As an example, if you wanted to advance the injector timing ten degrees (crankshaft rotation), you would move the timing mark on the IP five degrees clockwise which is 13/64th of an inch (0.205"). Normally you would want to move the IP no more than 1 or 2 crankshaft degrees at a time which would require moving the timing mark 0.020 or 0.040 inches at a time.