How Much Difference Pump Timing makes?

[MBBOB]

When I installed the new engine, I aligned the pump to the same reference mark as the old engine. It started and has run great for 1600 miles now. I finally got it to a GM Tech ( who does side work) that knows diesels and has access to the GM Scan Tech. I asked him to get it as close to -1.50 as possible. He said my initial setting was -2.20 and he was only able to get it to -1.15 because every minor adjustment he tried to make took it way out. I will pick it up tonight and see if it runs better or even different.

My question is, how much difference ( feel / sound) is there from:
(-.50 to - 1.0 ) factory
-1.50 best economy
and -1.94 best performance

IIRC a 1mm movement changes the timimg 1 degree, so how do you get it dead nuts?

Should I attempt to get it to exactly -1.50? will the effort make that much of a difference?

I will be adding a Heath GL4 chip in the near future.

 

[Brooklyn Tow]

From what I heard Heath strongly recommends the TDCO set at -1.94 or as close as you can get it.

 

[Acesneights1]

-1.15 tdco is within acceptable limits. When moving the pump a c hair means alot . Best to use or make ip turning tool. You can use a small prybar with two 3/8 bolts. -1.94 is optimal. Average drivers probably won't notice the difference. I didn't.

 

[nvmtnlion]

I run my pump set at -1.51 because I got it there first time I turned the pump. Dumb luck I guess. So, I just had to scribe a line and fool with it. Acesneights1 is right, you even nudge it and it appears not to move, it will change your timing quite a bit. I got -1.94 but when it gets cold, it scares me to hear it run with the timing set there so I nudged back to -1.51

 

[chrisk1500]

I had to unbolt my pump and yell at it to rotate it enough to go from -1.6ish to -1.94.

It is a very fine adjustment.

I don't mind the rattle in the cold so I leave it where it is....and we get REALLY cold here...

 

[MBBOB]

We were able to get it to -1.41 by snugging the nuts tight and bumping the turning tool.

I notice no difference in starting or driving from the -2.20 it was set at.
( only drove it home)

I totally respect Bill Heath's recommendation of -1.94 but I wonder if you need a dyno to see the actual difference. IIRC one of the dyno runs I saw showed a 3hp gain when going from -1.50 to -1.94.

I will keep it there until I get the chip.

 

[radrick]

I don't mean to hijack your post but what is there anyone in the Minnesota area that has a scan tool and would be interested in helping me set my timeing? I have access to several scan tools that buddies own but they are all snap-on. If not where should I go, the gm dealer that I use for parts when I need them thought it was foolish for me to buy my truck and clearly isn't exited about working on any 6.5.

 

[preachermic]

Aces,
How do you use a pry bar with 3/8 inch bolts to turn the pump?

 

[preachermic]

I found the holes!

 

[gmctd]

2.5mm = 5*, either direction -

radrick, see if any of the Snap-On scanners will read your timing to get a reference, post the results here radrick (just move the right lever on the steering column to adj the timing\tdco on that truck in your avatar)

MBBOB, main difference you'll notice is in the rattle, particularly on a cold morn when the timing goes full advance at START and it sounds like the valves are gonna shred outta the head - scary, very scary - the most noticeable sop result is after increase from oem -0.5* TDCO +3.5* timing to -1.5*\-1.94* +8.5* timing - add one of Bill's chips for simply astonishing results.........................