D.O.A. (almost)

[kc8sfq]

My truck has been running a bit poorly this past few days. Dropping one cylinder. My hope was a bad plug.... No such luck. I started out by pulling one plug wire at a time. That narrowed it down to hole #5 then I switched plugs with hole #2 The problem stayed in #5 (BTW Lots of spark). The telling moment was when I found compression to be about 10 Lbs in that hole.

The engine is quiet so I don't expect a broken rod or ring. My suspision is a broken valve spring or stuck valve. Whatever the problem is, it is inside and will require at least a partial teardown. This is an engine I bought and dropped in, unknown. I needed an engine a few years ago and a fellow MVer had it on a trailer. It had 90PSI in all 6 holes so I bought it. I guess I can't kevetch much, I got about 30K out of it. For a pig-in-a-poke engine, I suppose I did OK. At this point, it doesn't make much sense to do less that a major overhaul. And here I was hoping to not have to do much to it this winter.

[Lifer]

That's not so bad, time-wise. IF you have all the necessary parts on hand and IF you have all the necessary tools and IF you have a ton of mechanical experience, the job would go something like this:

Day 1: disconnect and remove the engine.

Day 2: disassemble and inspect the engine. Buy any needed parts not already on hand.

Day 3: replace parts and reassemble the engine. Then paint it so that it's pretty when it goes back in the truck.

Day 4: reinstall engine and hook up all peripherals.

Day 5: cuss up a storm because you just noticed an essential part still lying on the bench where you put it to make sure it wouldn't get lost.

Day 6: nurse hangover resulting from previous day's discovery and begin repeating steps 1 through 4.

NOTE: This process may have to be repeated several times, depending on your experience level. Note also that your experience level will increase substantially with each repetition of steps 1 through 4, as will your consumption of that "soda pop" that comes in brown or green bottles.

FEAR NOT, however, for surely thy truck shall run on all 6 cylinders again (someday).

[SOTVEN]

Hahahaha...Lifer is right on the money. IMHO, what you descride points out to a valve like you said. Maybe you are in luck and it is only stuck open, not shatered, not bent. I would take a long shot and try to remove the rear valve cover in order to inspect. If you are even more lucky, it may be possible to free it. This will be at best one day's work and perhaps the result will sent the engine overhaul towards the summer. Just my two cents. Good luck.

[Paul in Kempner, TX]

By the time you are 70 years old, you'll begin to apply the "K.I.S.S." principle to all the situations you encounter. I suggest that you and the others who responded consider this option.

The most common and most SIMPLE cause of the compression loss you describe is a bad head gasket. You don't have to remove and repaint the engine to fix that.

And if it is a stuck valve, there's a good chance that you can fix it also by removing the head. Turn the engine over by hand (certainly you do have a hand crank) and simply tap the valve down each second revolution after applying a penetrating lubricant to the stem. We did this fix to a M-37 about 8 years ago. That truck now belongs to an avid hunter who lives less than 20 miles from here. It's still chugging right along.

If this does not solve the stuck valve, a bent valve is possible and you can remove the valve covers and remove the offending valve.

Remember that these engines were designed when maintenance and repair procedures were much more SIMPLE.

I had a rod bearing surface reground to make it round and use a undersized bearing with the crankshaft still in the engine. The mechanic came to my house, removed the head, oil pan, and flywheel dust cover. Next, he removed the piston and rod. Then he hung the bearing surface grinder on the damaged throw and had a small motor rotate the crankshaft until the grinder had the throw perfectly round. Once it was round, he ground it to a standard diameter that used the undersized bearing. He reinstalled the piston and rod with the new bearing, put everything back together. After three trouble-free years, we sold that car to a neighbor who had another four trouble-free years before he sold it.

Again, we went the SIMPLE route and removing and repainting the engine was not involved.

[MSeriesRebuild]

My truck has been running a bit poorly this past few days. Dropping one cylinder. My hope was a bad plug.... No such luck. I started out by pulling one plug wire at a time. That narrowed it down to hole #5 then I switched plugs with hole #2 The problem stayed in #5 (BTW Lots of spark). The telling moment was when I found compression to be about 10 Lbs in that hole.

The engine is quiet so I don't expect a broken rod or ring. My suspision is a broken valve spring or stuck valve. Whatever the problem is, it is inside and will require at least a partial teardown. This is an engine I bought and dropped in, unknown. I needed an engine a few years ago and a fellow MVer had it on a trailer. It had 90PSI in all 6 holes so I bought it. I guess I can't kevetch much, I got about 30K out of it. For a pig-in-a-poke engine, I suppose I did OK. At this point, it doesn't make much sense to do less that a major overhaul. And here I was hoping to not have to do much to it this winter.

Well, you have already been a lucky man with no room at all for complaint. I base that on the fact that 90 PSI compression readings aren't good AT ALL, it needed a rebuild when you bought it, yet you got 30,000 miles running out of it anyway. 100 PSI is the borderline reading, 90 PSI readings generally come from engines that have already established skips on 1 or more cylinders as a result of low compression. Readings of 110 PSI & above with no more than 5 PSI variation from 1 cylinder to the other would be considered good. Extremely lucky with this one, indeed you were.

To address your current issue, most likely a valve problem (certainly a stuck open valve) would have produced a ZERO reading instead of 10 PSI. If it were a head gasket failure that will most often produce a ZERO reading on 2 cylinders that are side by side unless it's an external blow to the outside which would be very obvious or an internal blow into a water port which will cause coolant to flow out the radiator over flow tube like a faucet. If it's a valve problem at all, it's most likely a slightly burned valve or seat surface, however a broken spring is also a possibility, but not nearly as likely. To double check, add a tablespoon full of engine oil through the spark plug hole & immediately re-test compression. If a valve problem is the cause for the low reading, adding the oil will make no significant difference at all, however if the low reading is a result of ring/cylinder wall wear, the addition of the oil will temporarily seal the rings & the reading will rise significantly. This will let you know right up front if you are facing a valve job or a full rebuild. I will add this, in my opinion you are correct in your thinking that it is absolutely obvious a total rebuild is at hand. If you had not so good (90 PSI readings) 30,000 miles ago, it certainly hasn't improved since that time.

[SOTVEN]

I have put my head to a "vise" and yet I can not come up with a decent answer of what K.I.S.S. stands for. Keep it simple- solution perhaps??? How is it related to 70 years of age??? Just wondering...

[Lifer]

K.I.S.S. means "Keep it simple, stupid!"

[SOTVEN]

Ahaaa.... got three out of four right Lifer. Thanks for the clarification. Another thing, is your signature written in German? What does it mean?

[Lifer]

Yes, SOTVEN. It's German, and it means "All skill is in vain when an angel pees in the touch-hole of your musket."