Slant 6 boost sages,
Well, I got the '68 Dart bolted back together after my head gasket blow at Bristol, and I have some unsettling results - major oil smoke and rough running at low RPM. I am looking for ideas/advice on this problem before I do something rash like sending the turbo back or pulling the head again.
Here are symptoms and observations:
1) With head off, there was no evidence of piston or cyl wall damage. I drove this car 130 mi home from Bristol with #4 and #5 injectors disconnected and valves slightly open all the time, and on disassembly the plugs and piston tops were a bit wet with oil (I assume) since any residue was not being burned up on the way.
2) When cranking, sometimes it kicks back hard against the starter, quite violently. Tomorrow, I'll reinstall plugs in an alternating sequence and crank it to see if I can tell which cylinder(s) might be causing this kickback.
3) It still sounds like it's missing on 1-2 cylinders, but is smooth above 2000 RPM.
4) It burns a bunch of oil when under load, and even a little at idle
5) AF ratio is leaner at idle than I feel it should be given the tuneup. Could be oil is screwing up WB O2 reading?
6) Compression test showed pretty good numbers on all cylinders, although the range was broad - 130-165 psi. Medium warm engine (160 F?). The range of psi across the cylinders could be valve adjustment variation? I only did a rough (cold) valve adjustment, thinking I'd warm it up and reset them.
7) All plug tips were dry of oil when pulled, but a bit sooty, likely from the rich cold weather tuneup.
8 ) There was a crackling sound (boiling oil) and oil smoke coming out where the downpipe hooks to the turbine housing, after a drive around the block. I pulled the exhaust downpipe and there is oil just visible down behind the turbine blades, and on the bottom edge/floor of the pipe and turbine housing. This could come from oil exiting the cyilnders, or from the turbo shaft seal.
9) I pulled oil drain line and cranked motor to see flow out of the turbo. It looked higher than when I did this in MN on first startup. Out-the-drain flow was something like 1/2 qt in 10-20 seconds after the oil pressure came up. Drain flow liquid column was just over 1/4" in diameter.
10) I had made and installed a new oil drainback line. I just blew into the disconnected drain line and confirmed no restriction.
11) Upon reinstall, I twisted the oil input nipple on the turbo, which seemed to be epoxied in place. I will pull that tomorrow to check inside. Increased the flow somehow??
12) I pulled the intake tube from the turbo to throttle body and no oil inside the compressor housing or tubing.
13) The head gasket was blown (about 3/8" section) between #4 and #5 cylinders, and a bit heat spotted in a few other fire ring spots, but was otherwise not damaged. I found no debris in any cylinder.
Thoughts:
1) Blown rings on 1-2 cylinders? It's hard to see how there could be 1-2 cylinders with horrible rings if the comp reads 130+ psi across the board. If somehow just the oil rings got stomped but comp rings are OK, why would this cause kickback against the starter??
2) Blown turbo shaft seal? That would have shown up as smoke clouds on the way back from Bristol, and there were none. This would not cause rough running, but would cause smoke. Given that the oil smoke started with a pretty cold engine and before loading the turbo, it seems doubtful it is the turbo shaft seal, since that oil would not burn inside the turbo housing when cold.
3) Valve adjustments are off causing rough running at idle? Wouldn't make oil smoke, but would cause rough idle.
4) Did I leave something in a cylinder and then it is in the chamber and poked a hole in a piston? I can't recall that could have happened. Also, then one plug at least would be oily, and that cyl would have ~ 0 psi pressure. #1 cylinder was the only one with even a little oil on it, and that seems to have come from the aluminum drool tube and futzing when I pulled it. Also, #1 had 165 psi cyl pressure (the highest). This could explain starter kickback, though there are no crunching or pinging sounds with engine running for >20 min.
5) This kickback against the starter is really creeping me out.
So, there's the data. Anyone have ideas about WTF is going on?
Thanks so much for reading, if you made it this far...
Lou
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