Zero compression #3 Cylinder

Baypac

Baypac

Member
Just had a 1930 pickup delivered today. It was supposedly rebuild about 1,000 miles ago.

Tried to start it, no luck. Changed out the Tillotson with rebuilt Zenith...starts, runs rough. Checked compression, 1,2,4 were 56. #3 was zero.


Added oil to #3 still no compression. What's the best guess on the problem. Stuck valve, burned valve or ??
 
Dry reading zero/wet reading zero? direct loss of compression,usually means a stuck/ burned valve.You can do a leak down test to determine exactly whats leaking,you remove the spark plug and pressurize the cylinder with shop air..Failing a wet/dry is enough evidence for me to pull the head.
 
If rebuilt only 1,000 miles ago, it's 99.9% sure to be just a stuck valve. Try spraying something like PB Blaster at the valve stems through the spark plug hole (don't waste time with WD40) and let soak a few days. Or, pull the manifolds and side cover and pry down a little on the valve.
 
I would add a can of Sea Foam to the gas, and another can to the oil. I'd also add 4 ounces of Marvel Mystery Oil to each 10 gallons of gas. I know you guys are stuck with crap gas.
 
I would suggest removing that sparkler and trying to spray some penetrant, such as deep Creep [ spray SeaFoam] thru the hole and over near the valves. See if that helps. If it doesn't then removing the side cover will allow you to spray and work the valve up and down in the guide. My thoughts too are a stuck valve, kinda common.
 
Thanks to all for the advice. I started the process of spraying penetrating oil through the spark plug holes on the valves. Good advice on the manifolds and valve cover. Easier than pulling the head.
 
There is one or two other potential causes.

Is there obvious leakage of head gasket to the outside of motor or into the cooling system? swishing sound while cranking? not always obvious.
Is the piston moving up and down? this may seem basic, but have seen it before.

Sorry to be pessimistic, I found if I search this way any other diagnosis is a blessing.

John
 
Model A engines are expensive to rebuild,when diagnosing an issue its important to find the root cause,to put your finger on the issue and address it and any potential damage.If you tear it down a bit and find a stuck valve you can clean it and reassemble,with the knowledge the repair is done correctly. Easy? not as easy as shooting chemicals and praying,nope,but if your into peace of mind its worth it.
 
I have often had a valve stick on a rebuilt engines. Usually new valve guides and new valves take a hundred miles or so on them before they slide freely. Turn the engine over until both valves are open. Use penetrating oil down the spark plug hole and then with a small brass driver reaching through the spark plug hole, lightly tap the stuck valve closed again. The valve needs to cycle up and down this way a few times before it will cycle freely on its own with the engine turning over. Marvel Mystery Oil is your friend. Use it both ways: Put it down your stuck valve's open spark plug's hole, and also into your gas tank.
 
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The best suggestion is SSsssteamer's Suggestion. When done with getting valve moving again, run some kind of oil in with the gasoline, lotta suggestions on this. MMO should do the deed!
 
Thanks again for all the suggestions. More information...Water in Oil probably about 1.5 quarts based on the the amount of emulsion that drained out of the engine. I don't know how long it has been there. Once I saw the emulsion, it was obvious that the problem was not a sticky valve after the rebuild.

I will pull the head, but still changed the oil and drained the radiator. Put stop leak in the radiator. It won't fix the problem, but may slow down the water into the oil. Hopefully the bearings will still be in good shape when I get the top of the engine done.
 
My answer to the problem, 94psi in all but #2, was to add a healthy shot of Marvels Mystery Oil, replace that plug, spin the engine over with the starter and key off. Next morning I placed the other three plug in their holes and drove off to coffee with the lads. Came home and did another compression check, 94 in all holes. Did smoke a bit on start up until the oil burns off. Still driving it three years later.
 
The alcohol blended gasoline we have now will really gum up the valve stems if the car sits and the fuel goes stale. I have seen this happen many times, MMO and Seafoam will be very helpful.
 
Baypac said:
Thanks again for all the suggestions. More information...Water in Oil probably about 1.5 quarts based on the the amount of emulsion that drained out of the engine. I don't know how long it has been there. Once I saw the emulsion, it was obvious that the problem was not a sticky valve after the rebuild.

I will pull the head, but still changed the oil and drained the radiator. Put stop leak in the radiator. It won't fix the problem, but may slow down the water into the oil. Hopefully the bearings will still be in good shape when I get the top of the engine done.
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It is my hope for your sake, it is a top engine issue with the head or head gasket!
 
Huh...odds are its a head gasket,but now you will find the root cause of the issue,and make the repair accordingly. Avoid using radiator sealer like 'stop leak',once again,its best to cure the cause.
 
Railcarmover said:
Huh...odds are its a head gasket,but now you will find the root cause of the issue,and make the repair accordingly. Avoid using radiator sealer like 'stop leak',once again,its best to cure the cause.
Click to expand...

Agree..but some of you may remember Mike Flanagan from the old Ahooga board. He had a lot of pithy comments, but he always said about the engines he rebuilt that he always finished them with stop leak in the radiator just to fill the small leaks that he might have left. :)

Afterwards it should not be necessary as long as the engine is correctly rebuilt.
 
Well I got the head off after a lot of work and moving my cherry picker around. Starting the engine to pop the head worked perfectly, however there was a lot of rust on the studs through the water outlet. Finally had to put wedges between the block and the head and a hydraulic jack under the water pump.

Found a major water leak that looked like a warped head problem between #2 and #3 cylinders. Engine restoration job was good. Hardened valve seats, adjustable lifters, and thread release on all the studs. The water ran down the exhaust valve for #2 cylinder and caused some rust on the spring. I am not certain if I need to be concerned about it. Any thoughts?
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