How muchis too much?

[rlyons]

I saw it written somewhere a while back that when you advance the timing too much your cummins will sound like an old Mercedes diesel. What does an old Mercedes diesel sound like? I have advanced mine about a 1/16 to 1/4" above what it was when I bought it. It runs good and has good power but I do have a rattle at about 2000 to 2100 RPM that seems to come through the accelerator pedal, maybe normal pump noise I don't know as I haven't driven another truck to see. My EGT's are good and I have about 29 to30 lbs max boost. So how do I know if it is advanced too far?

 

[Greenleaf]

Advance

Do you have a scribe mark on your pump? If not, it's a replacement. There fore you have no idea where it is. Even if you do have this scribe, you really don't know 100% for sure where it's at. I set mine up a good bit past the 1/8" which is normally accepted because I have changed injectors and notice no change in sound. I will be advancing further when I modify my gov. settings.



If you have noticed a change in sound at full advance, you are at the limit of "safe"



When I adjust farm tractors, I use only my ear. Advancing to the point the engine does not sound quite right, then back a small amount. Not scientific, but it works well if you have an ear for it.



Scott

 

[cerberusiam]

All other things being equal and in good shape, if you advance the pump you should be able to hear the change in the normal diesel rattle. At an idle it will be more distinct and as you tip into the throttle it will be very noticeable, a definite sharp crack on ignition. As the rpms come up the sharp crack should dissipate as the advance is absorbed. If you have ever advanced the timing too far on a gasser and heard the knock on acceleration thats about what it is like only louder.



Too much is a relative term and has a lot to do with your injectors, pump, and fueling. What is too much on one is not enough on another. The best way is to set the pump timing with the correct tools as the pumps can be off with relation to timing marks.



The hazards of too much timing, among other things, is that sharp crack a pressure spike and too much too long will cause head gasket problems. Hope this helps.

 

[dpuckett]

I wouldnt go much past the 1/8" on the marks. But like cerberusiam said, it would be best to get it done right. I am in the process of setting up an old dial indicator of JLEONARD's to time out trucks. Might keep it for a "timing kit," speceific to the first gen trucks, kind of like the KDP jigs some guys keep. I can see the point of some guys not wanting to pay $150+ to get the timing set, esp when the shop may not know about tming pin inaccuracies. I know mine and Mom's are dead on, but only because I've checked and double checked. THe rattle you'll hear at too much advance is noticeable. When it is cold, with the KSB on, it will sound like an old 6. 9/6. 2 with the Stanadyne pumps when you step on it lightly. If you hammer it, you wont notice it as much; it either gets drowned out or disappears.

Daniel

 

[rlyons]

Well I don't seem to get the rattle you guys are talking about just off idle but I do get a clatter at about 2000 to 2100 rpm when going up through the gears and it seems to resonate through the gas pedal. I assume it is the pump causing it. If I run it up with no load I don't hear it at any speed. If I really romp on it I don't seem to get it either so it may be just the nature of the truck. It was there when I bought the truck and the timing changes and injector and pump setting changes seem to have had no effect on it. Maybe just normal pump/line noise? I don't mind I guess if it don't cause a real truck is supposed to rattle. I have never driven a 1st Gen with an automatic, are they any quieter? I know a gas truck with a standard seems to be a little noiser due to the shifter coming through the floor I guess. Maybe I will convert mine to automatic some day when my Getrag dies, who knows.