Hey guys,
Ive been battling with really bad fuel economy and Im not having much luck finding the source. The truck is going in the shop this week for an injector pump rebuild since it also runs with a knock / rhythm and I know the valve lash is ok and the cyls are making the same compression.
I called zack hamilton a couple weeks ago to see if he had any ideas from working with so many other folks' setups, and he suggested lowering the timing to 16, setting the valve lash to .015 and returning to stock thickness injector shims.
Anyone know what the effects from changing shim height might be? Id imagine you lose a little compression since less of the tip is in the squish area. But the height of the injector and the timing might do some things with power and economy, Im just not sure what.
Im also running .005 extra gasket thickness for valve float and boost, but I dont think thats helping things. It would cost too much to return it to stock so Im not touching that till the HG pops again.

 

Shim thickness has a major effect, the only thickness to use what the injector manufacturer recommends.
Too thick and the fuel spray pattern hits the cylinder walls, too thin and the pattern hits the top of the piston.
It's a delicate balance. Both problems result is unburnt fuel.
Head gasket thickness will also play into the shim thickness but that's above my pay grade.

 

The thinner the shim, the deeper it will spray into the bowl. If you have 155 degree injectors, you'll want to run the thin (0.020") copper. Same if you are running elevated timing. If you're running a a thicker headgasket, you'll want to run the thin shim. You want to keep your tip in the same position relative to the piston. Since you decked your head .005" and put in a .010" thicker headgasket, you're still .005" higher than you were when stock.

 

Infidel has a point too, I just fired off an email to dynamite diesel to see what they recommend with my setup. Chances are the thin shims are ok to use
Im getting poor economy and oil that gets like black paint after half a tank, so its certainly worth looking at.

 

my truck has a rythem to it also, sounds like bad bearings, i would be interested to know what shop tells you about your truck.

 

It didnt used to have it. The last time it was like this I did the valve lash and one cylinder was a little off, so that fixed it.
This time I had the valves checked when it went in for other work and everything was ok. So something fishy is going on in there. It used to run really smooth.
Ill post back here if I learn anything. Maybe its not the pump after all... Im stumped.

edit:
DDP says they use .5mm washers with their injectors. Pretty sure thats what I have now.