Onemore, I'm not sure I know what you mean when you say air flow problem or blow by. I know when diesel engines have eccessive blow by, it can mean worn rings; I don't think that's what's going on with mine as it never smokes and seems to be in good condition otherwise. A third party SAE-certified mechanic who knew the engine intimately told me it was in good shape when I bought it. I must say I'm starting to think he might have missed a thing or two though. If you mean blow by as in loss of compression, I hope that's not it, but ugh, yes, you may be right - particularly around cylinders 7 and 8.

 

What I am referring to is oil blowing by the rings or maybe from whatever is leaking on your rig. I have oil blowby coming out the breather into the air cleaner. It had me thinking my plenum kit failed for a bit.

 

Well, I'm in the process of replacing the plenum pan, as it may be the cause of some of the issues I'm having. I'm pretty sure the plenum gasket is blown out because there is oil on the pan. I have a new aluminum plate for the plenum, and a set of Fel-Pro gaskets ready to go.

I 've also found the 2 bolts holding the EGR valve to the manifold were never tightened - my fault. That's the kind of thing that happens when you're forced to work on something sporadically - things get missed.

So, while I've got the manifold off I figured now would be the time to see if there's something going on with the head (s), like a leaking gasket or a crack.

 

I'm keeping this thread alive in case the symptoms I'm seeing, including the way my plugs look, end up being important clues to a particular malfunction. These might just be indicative of several smaller problems, I don't yet know, but I hope to find out before too long. Appreciate the ideas you all have shared.

 

Id be more worried about #5 and 7.

 

Why? Is that side more prone to fail, or are you talking about how those 2 plugs look? If It turns out I've got a blown gasket I'll probably only repair that side. But, if its something like a crack and the head needs replacing, I will replace both heads.

I took a few minutes this morning to put cylinder 4 at TDC and connect the leak down tester. I had a feeling the test wouldn't work because the engine hasn't been run in months and the cylinder walls are likely pretty dry. As expected, the air leaked down quickly thru the rings. Hopefully I'll get another chance soon, at which time I'll fog the cylinders, hook up the battery, disconnect the fuel pump relay, and spin it over a few times to get an oil film on the rings.

 

going by how they look especially #5... crusty, fouling.... dont jump to conclusions that you need new heads....

 

The black carboned plugs are more in line with what I expected to see, given the extremely rich running. Its the clean plugs that don't make sense to me. I won't be jumping to conclusions regarding the heads, that's why I'm doing the leak down test. That being said though, doing the plenum makes now an opportune time to rule out a head-related issue.

 

Finally got to the leak-down compression test today. All 8 cylinders held pressure, well within the upper half of the "good" range on the scale. Glad that checked out OK, but I forgot about the valve covers being off when I spun the engine over a few times before starting; ended up with a nice puddle of oil on the garage floor

Gotta leave town for a few days, so probably won't have time to finish the plenum repair before I leave.

 

Finished putting it all back together yesterday, then took it out for a test drive. Wow, what a difference! It now runs like it should, very responsive and plenty of "throw-back". I was having so much fun going through the gears I had to remind myself that I'm supposed to be a responsible grand dad. This thing is really fun to drive now.<br /><br />So what was the problem? Well, because I made several changes, I can't say for sure, but here's what I found and what I did:
...Plenum kit installed (but once in it, I didn't find a blow out in the gasket. Oil came from PCV valve which I replaced)
...New intake manifold bolts
...Repaired RTV gasket blow out on the rear manifold seal (this fixed a bad oil leak. There was no gasket, only RTV, which failed)
...Cleaned injectors by running 50/50 lacquer thinner and fuel thru them (3 of them were very dirty but pattern improved considerably after cleaning)
...Cleaned up intake manifold ports to remove rough casting edges, etc. Not a kegger mod, just lots of smoothing (this obviously had no bearing on fixing the original issues)
...Repaired the EGR tube. The sealing flare was damaged, preventing a good seal. Also, I had never fully tightened the EGR valve previously, so I made sure to do it this time
...Cleaned throttle body thoroughly, also the IAC
...Along with new Fel Pro gaskets for everything I took apart, I also replaced the PCV valve and crankcase breather cap
...Installed new vacuum hoses (the PCV hose had a crack in it that I hadn't seen before)
...Installed new thermostat (180 for now)
...Cleaned plugs

The likely suspects for power loss and apparent rich running? Off hand, I think at least 2 injectors were dribbling, possibly stuck or not closing fully (before I cleaned them), allowing unburned fuel to pass thru. Another contributing factor was the vacuum leaks from the EGR and the PCV hose. Although the intake manifold seal was leaking at the rear mating surface, I doubt that caused anything more than an oil leak.<br />