Hey guys,
First off, I've been reading on here for a long time, and I'd like to say thanks for all of the great information. I finally bought a truck, that was already built about exactly as I was planning to do it anyway.

The truck's been great, but last night on the way home from work it after a very brief run up to 55psi I noticed it start running funny. It felt great when the revs were up and boosting a little, ~10psi. But it felt like it was chugging at low revs and definitely does not run right starting from a stop. It honestly feels like a gasser that's got a bad plug or 2.

I don't have any oil/water mixing, but it seems to make sense that a hg might blow being relatively cold and at all that boost. My engine temp was just above 140 like it runs most of the time in this cold. It's o-ringed, but I have not torqued the head since I've owned it (1.5 months) and was planning to adjust the valves and torque the head this weekend.

The miss I suppose could be attributed to the leak at low rpm/boost pressures not making enough heat to fire a cylinder. Then at higer boost it's not bleeding pressure fast enough and the cylinder is still firing . . . does that make sense.

Otherwise I was thinking (hoping not) that I cooked a cylinder, but I don't thnk so, as I have not had that much heat in there. I can get the pyro to about 1500 but not for a very long time, as I'm already at 80mph at that point anyway. I didn't notice any blowby either.

Is there anything else I should check before I tear the head off? I've heard about a stuck plunger in the IP, but I doubt that, it seems to run fine higher in rpm.

Seeing how I didn't build it, and don't know specifics, where should I get a new gasket? And is is standard practice to replace the o-rings with every gasket change? I know with a fire ring you do, but I'm not sure about the o-rings.

Thanks,
Phill

 

does the engine sound like its missing? Maybe try cracking the injectors one at a time and listen for a change in tempo? Youre looking for the one that doesnt cause that to happen.
If you do have a HG leak there are tests for combustion gases in coolant that might help you if there are no other symptoms like missing oil and coolant.
But if you suspect it, keep a close eye on the coolant level in the overflow as well as your oil level and quality. Dont let it run on oil that looks like chocolate milk (contaminated with coolant)
Otherwise the only things I can think of that would cause poor running at the low end and ok running up top are a boost leak (sounds pretty likely after that 55psi. Maybe a popped intercooler boot?) or a AFC problem. Dont know what year you have, you might want to post your truck's specs in your sig.
To check for boost leaks, get a PVC pipe cap from home depot about the same diameter as the inlet from the air filter and screw an air chuck through it and compress the air in the system to about 15psi and listen for air escaping.

 

Thanks for the reply . . . is my sig not showing up? It shows when I view the thread.

I'll try cracking the injector lines first. It does feel and sound like it's missing. I kind of doubt a boost leak because it's that way when there is no boost at all. Idle, 2nd-3rd gear etc. I'll check it out though. I'm almost positive it's the HG because the PO said he had some issues when he initially did the work. I'm thinking that I just pushed it out between 2 cylinders, because I can't see any oil in the coolant, and there is no coolant in the oil. I've seen that on other stuff plenty of times, hehe. (the ATF I got out of my Jeep after I sunk it was just like a strawberry shake for about 3 changes)

I'll see what I can uncover this weekend. I have 2 other truck to fix first . . .

I'll post pics when it's all said and done.

Thanks,
Phill

 

your truck has a factory cummins marine headgasket on it.

Travis