Strange Slant 6

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Chuckman

Chuckman

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The last day of school last year my sons slant 6 went from running great to running awful. Had to first gear every hill, would not idle, and went through four quarts of oil in 15 miles, with hardly any smoke at all.

Anyway we now have a crate motor to put in it and I have a question. The other day I unbolted the tailpipe from the manifold, and the front end of the tail pipe is as white as cotton inside. Does it mean anything?
 
So the white stuff was in the pipe at the motor end by the manifold? Well thats no good at all.That should be brown to black. White could be a contaminant. Sometimes coolant. Sounds like the engine went lean and the high exhaust temperature burned off all the carbon that usually accumulates there.And the excessive throttle used will build a lot of crankcase pressure, which I imagine pushed the oil out somewhere.Would you associate the power loss with a recent fill-up? Also note, that a plugged exhaust system will suck up power in a hurry.Similar symptoms, but doesnt usually come on like a switch.Its more of a gradual thing.Take a look at the exhaust pipe all the way back to the muffler. It might show a hot-spot,But the muffler is the usual culprit.
 
AJ/FormS said:
So the white stuff was in the pipe at the motor end by the manifold? Well thats no good at all.That should be brown to black. White could be a contaminant. Sometimes coolant. Sounds like the engine went lean and the high exhaust temperature burned off all the carbon that usually accumulates there.And the excessive throttle used will build a lot of crankcase pressure, which I imagine pushed the oil out somewhere.Would you associate the power loss with a recent fill-up? Also note, that a plugged exhaust system will suck up power in a hurry.Similar symptoms, but doesnt usually come on like a switch.Its more of a gradual thing.Take a look at the exhaust pipe all the way back to the muffler. It might show a hot-spot,But the muffler is the usual culprit.
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The entire exhaust system starting at the muffler is brand new. If you are saying it went lean, is it a carb issue?
 
i was thinking a lean condition too. it only takes something the size of a single coffee ground to really mess things up. i would look at the carb. the oil missing is odd though. when was the last time it was checked before noticing it was that low? what does the coolant look like?
 
RustyPlymouth said:
i was thinking a lean condition too. it only takes something the size of a single coffee ground to really mess things up. i would look at the carb. the oil missing is odd though. when was the last time it was checked before noticing it was that low? what does the coolant look like?
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Coolant is still bright green, except for a little bit of rust in it. Oil was checked 15 miles before it started running terrible, and was full, then after 15 miles it would barely touch the end of the stick. If its the carb, I certainly do not want to put it on this new crate motor and mess it up too.
 
have you checked the oil again after letting it sit for a while? a valve cover will hold quite a bit of oil if the returns are blocked. its not very common but it does happen. what kind of carb?
 
A gallon of oil in 15 miles could not have gone out the tail-pipe without smoking the whole neighborhood. Since you didn't see it leak out, it must still be in the engine. If not in the oil pan, it must be in the top. Another guy had a similar issue and found clogged drain holes (beside lifters). Seems an engine must be extremely gunky to do that, and even stranger in a slant where you need to remove the valve cover every few years to adjust the valves. Of course, yours could be a later hydraulic cam since we don't know what car or year.
 
BillGrissom said:
A gallon of oil in 15 miles could not have gone out the tail-pipe without smoking the whole neighborhood. Since you didn't see it leak out, it must still be in the engine. If not in the oil pan, it must be in the top. Another guy had a similar issue and found clogged drain holes (beside lifters). Seems an engine must be extremely gunky to do that, and even stranger in a slant where you need to remove the valve cover every few years to adjust the valves. Of course, yours could be a later hydraulic cam since we don't know what car or year.
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Its in a 66 Valiant, old style with drool tubes. In installing the crate motor we have removed the valve cover, the valves etc. were rather clean. Certainly not a blocked return issue. Some of the springs had a little bit of a green look to them. The oil is NOT in the motor. We did find a curious spring or what is left of one, in the head behind the thermostat. The others helping me seem to think it is an old thermostat that came apart in there quite a while back. If it is, it had a lot heavier spring on it than the current one.
 
Its not in a spiral spring shape, it is bent out and is about the same gauge wire as a ring on a three ring binder. It is stuck back in the head and will not budge.
 
Wait-up. From oil is full, to barely on the stick, is not a gallon. Its only 2ish quarts. Right? Any way , if youve not got a PCV system but rather a "road draft tube", then thats where the oil likely went. Check the underside of the floorpan. If the engine lost power to the point that a ton of throttle needed to be used, then the engine may have been creating a lot of crankcase pressure. Well that pressure had to go somewhere. The "drool-tube" is the easiest place for it to go, and it takes oil with it, in the form of blowby that the rings couldnt control. It should have been leaving a visible trail of smoke behind it, to lose that much oil in just 15 miles, unless its all stuck on the floorpan.
-So lets think about the power loss.To lose that much power in so short a time, without reporting backfires, missfires, or serious engine noises, but reporting white deposits in the headpipe.....leads me to...contaminated fuel, wrong fuel,slipped timing, or serious compression loss. So the first question should be; How does it idle? If the idle is ok; Then timing is at least close, and compression hasnt changed, and at least the low speed circuit in the carb is working, and the fuel is ok.So then I would look to an overheat. But you say the engine doesnt idle or doesnt idle well. So then you will have some homework to do. The easiest check for me, is the wrong fuel test. I just pop the filler cap and take a little sniff; smells like fresh gas,good to go.Next, if the engine runs at all is the timing check.Next is a toss up between a compression test, and contaminated fuel test. I would do the fuel test first. I would pop the top of the carb off and see whats in the bowl. If the fuel is CLEAR, smells like gas, and has no water or sediments in it, put the top back on. Lastly, is the compression test. I would have first guessed a jumped timing chain except IIRC those old slants dont have chains, but rather,gears. So; good hunting.
-As an aside; I usually just do the compression test first. I know I have to do it sooner or later. Then if I find the problem there, then I dont have to charge the customer for the other tests.For you though Im really interested in seeing whats in the floatbowl, and if you do the compression test first, then the engine is likely to ingest whatever is in there before you get to inspect it.Just FYI.
-I know you didnt report an overheat condition, but the symptoms you did report, also do sound like an overheat.I think its at least something to think about.That would also help to explain the white stuff in the headpipe, and the power loss.I would just have expected it to puke coolant though at the level of power loss you experienced.At least check your lower radhose to make sure the expansion spring is still in there. You should be able to feel it through the hose without taking it off. If its gone missing, then the hose may collapse under higher rpms and lead to an overheat.
-One other thing, that will produce similar symptoms, is burned valves. But that will show up on the compression test, and the engine wont idle. Burned valves also put the white stuff in the headpipe.They dont usually come on like a switch though.
-Its also possible that you have all these events occurring in a string.Heres how I IMAGINE that;Engine went a little lean at cruise speed.You didnt really notice it yet, just increased the throttle a bit to maintain speed.But the engine is building heat, and continuing to lose power. Perhaps a valve is beginning to self-destruct and the engine is losing compression. Now you are noticing it.You probably look down to your gauges,but cant really see anything. Well maybe the temp is gone up a bit, youre not sure.You are using more and more throttle as the car loses speed.Finally you have to downshift to keep moving.Now the rpm goes up, and so does the water pump speed and the engine is working harder and harder.Its lost one cylinder for sure maybe a second one is starting to burn an exhaust valve.But the 4 remaining cylinders are still pulling.The engine has been creating a lot of crankcase pressure.Its pushing oil out the drool tube.The increased waterpump speed is pulling hard on the lower radhose which is starting to collapse due to the old rusty failing expansion spring leading to increasing water temps. You are well on the way to CATASTROPHIC failure.The temp is rising. The oil level is falling. the compression is going away.The high exhaust temp is burning all the soot out of the headpipe and leaving traces of the burned exhaust valves in its stead.You downshift one more time to keep the engine running. You are seriously worried about making it home. But, you do finally make it home.You take your foot off the gas, and the engine quits. And wont restart....... Relax. Its just a scenario, invented by a creative mind...I do hope its just a scenario.

-Again, good hunting
 
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