Gas in oil equals rebuild

[STSCSS]

Well folks sad news
Fuel pump failed in the worst way and now I have an engine to rebuild and would like to know the short list of the parts Ill need.

Also someone offered me a M37 Short block engine and need to know the details on that one.

Any help would be greatly accepted

 

[poppop]

If you want to rebuild it correckly you won.t know what you need until the engine machine shop mearsures the bores and the crank and checks the rods. Everything needs to be inspected and mearsured for tolerances first. If you want to put it back like it was you may can get by with just bearings if none seized and turned in the rod. this would also damage the crankshaft.

 

[STSCSS]

Will still turn over and she did not seize up. Bought the manual for the overhaul and we have a good machine shop here. On the plus side I will be able to redo the wiring now and have a reason to put the winch on

 

[armytruck63]

Are you sure you need a rebuild? I would put on a new fuel pump, change the oil and filter, and do a test drive before condemming the engine. Try the easy path first and you might get lucky.

 

[m35a2cowner]

I agree with Armytruck63, I would add check the type of oil that is suppose to go in that type of engine straight weight vs multi-weight (stick an oil pressure gauge on it too) start her and if the pressure is within specs driver her around a bit. If its OK then change the oil again as the gas might have loosened some varnish in the motor. I had a tractor that the fuel pump failed on it while in winter storage and the crankcase filled up with gas. Just happened to check the oil before using it. Drained it, changed the pump and 5 years later still using it. What you got to loose?

 

[6x6guy]

Ditto, I also believe that the problem, in the fuel pump when working -the only thing that prevents
the fuel from going into the oil system is a rubber orifice- that after a lot of use dries out and cracks
allowing fuel to enter the engine block cavity and contaminate the oil.

 

[clinto]

I've had plenty of engines where fuel pumps failed and allowed fuel contamination of the oiling system and none required a rebuild.

As the others said, fix the pump, change the oil, run it and see if it either knocks, smokes or has insufficient oil pressure.

 

[poppop]

I assumed you had run it enough to damage the bearings is why you wanted to rebuild it. i agree with the others, just fix the pump. If you have any concerns drop the pan and pull a couple caps and inspect the bearings.

 

[STSCSS]

The worst part is the compression checks came out as a flat 70psi for all the cylinders. Even with hot shot I could not get her to turn over. I have a spare fuel pump so that will not be a problem. Going to do the wet test tonight to see if I can get the PSI up.
Still if I overbore by .020 do I need to buy new pistons and rings or just rings?

 

[clinto]

The worst part is the compression checks came out as a flat 70psi for all the cylinders. Even with hot shot I could not get her to turn over. I have a spare fuel pump so that will not be a problem. Going to do the wet test tonight to see if I can get the PSI up.
Still if I overbore by .020 do I need to buy new pistons and rings or just rings?

A .020 overbore would require pistons. I wouldn't reuse pistons at much more than a mild hone job (.005+).

I think you need to do a leakdown test and see if the compression is escaping past the rings or valves.

What's the TM say one of these should have? They are low compression anyhoo, so the cylinder pressure should be reasonably low.

 

[m35a2cowner]

You know an even 70 psi is not really that horrible on an old truck. Especially since the battery, starter motor, poor connections may not be turning the engine over that fast. I would be much more concerned if it was really uneven. If it doesn't try to start on ether, I would suspect the ignition system is weak or malfunctioning. If it fires, but doesn't seem to pick up check the timing. Check to see that the positive side of the coil (not the side that goes to the points) is getting near (within a volt or two) battery voltage when cranking. If the battery voltage drops off pretty quickly when you begin cranking try cleaning the connections (battery, starter motor, ground) and if this does not do it swap out the battery. It just might be a good idea to make sure ignition is up to snuff before you try to start it. I have seen a bad condenser keep the ignition from working. Check to see if points pitted. Check to see that the plugs are not fouled, (if so will not fire at all) exhaust/fresh air system not restricted, engine turning over at a decent speed. According to the laws of physics, if you have fuel, ignition spark (at the right time), air, and some amount of compression its gotta run. One of these things is missing, and that is why its not running.
Good luck.

 

[vtdeucedriver]

A fresh M-37 should be about 110psi. I would change the pump and the oil and run it a bit more. Attempt the leak check, if you are even across the board like mine is right now at just above 80. You may just need a valve adjustment. I have not done a full diagnostic but thats where I am headed next.

 

[STSCSS]

Pulled the fuel pump and oil today and put the new pump in. Looking at some 5w oil to see if that helps in this endeavor. If that doesn't work the spare engine is going to be pulled out of mothballs I just hope that one has good compression

 

[vtdeucedriver]

What have you been running in the past?

 

[STSCSS]

New fuel pump in and changed the oil, had to use the 28 volt MEP to get her going but she ran yesterday. Going to fire her up this morning and see.

 

[rizzo]

put some Lucas engine oil stabilizer in it. Helps compression a lot.

I would think thicker oil will help in this situation, not thinner oil(5w).

 

[STSCSS]

Put some oil stabilizer in and it seems to be running fine. Just in case took the dust cover off the spare engine I had and started to do the pre checks on it. Alas the compression was in the 30s on this one so fresh oil in each of the cylinders and compression goes up to 70-90 range. Still something did not seem right so I did an air check and as the 125 psi air blew past the values it dislodge the stockpile of dog food that a small critter had deposited. So with that off came the exhaust manifold and value covers. Inside the valve covers found chunks of blue RTV. After that did a vacuum and pressure check on the ports and found that thier was leakby in the valves. So any tips on cleaning up the valves???

 

[rosco]

You can do a valve job, in-frame, but its a pain to work on it that way. Its ment to be pulled. If you do the valve job/re-build thing. Absolutely be sure to change the valve guides. Put new ones in. They are easy to do, not too expensive, and have a lot to do with compression. Don't just kurl them - that won't hold. Also be sure to check the head for "flat", that its not warped. That is common.

Lots of Folks like that fuel pump, but its a pain too. The vaccuum part routinly fails. I run a 24V Facet

 

[m35a2cowner]

5w seems a little thin for a motor that probably was designed to run on a straight weight oil. I would consult with someone very knowledgeable on engine oils (1-800 customer service on oil can?) Also, I would check the valve to tappet clearance to make sure its not to tight and making the valve leak. Also, make sure your on the compression cycle (check manual to see at what crank angle--timing marks-- both valves should be shut) when you do your leakage test. Its possible you might not be on it. Also remember, steel on steel is not the ultimate seal, there is going to be a small amount of blow by on an engine that is cold and hasn't been running in a while. Chances are if it runs well and there is no popping back through the carb (valves adjusted properly) its going to run decently for a while to come. You can always do a valve job in the future when there is a problem. Do the required maintenance and enjoy driving that very fine looking truck. I really like the looks of those trucks.

 

[STSCSS]

With the spare engine it looks like pulling the header is the next step. The block has to be stripped for the machine shop to do the valves the right way it's always amazing how fast a simple swap can go into a full overhaul