29 Model A Running Bad

L

leatherback1929

Junior Member
My Model A was running well but I kept losing coolant so, I replaced the head gasket and all was well. But, after maybe 40 miles it started running bad, back firing through the exhaust. I remove the plugs and noticed that when looking through the spark plug holes all cylinder areas looked wet. So I removed the head again and saw no sign of gasket leaks or cracks in block or head. But when removing the intake and exhaust manifold the two intake ports in the block were wet with something. After setting for a day the area is still wet, since I use antifreeze in my cooling system it could be wet from it or are the clearance between my valves and guides be excessive and the wetness is oil? Because of the back firing I did check my timing and it is correct, any suggestions. :( Thanks!
 
leatherback1929 said:
My Model A was running well but I kept losing coolant so, I replaced the head gasket and all was well. But, after maybe 40 miles it started running bad, back firing through the exhaust. I remove the plugs and noticed that when looking through the spark plug holes all cylinder areas looked wet. So I removed the head again and saw no sign of gasket leaks or cracks in block or head. But when removing the intake and exhaust manifold the two intake ports in the block were wet with something. After setting for a day the area is still wet, since I use antifreeze in my cooling system it could be wet from it or are the clearance between my valves and guides be excessive and the wetness is oil? Because of the back firing I did check my timing and it is correct, any suggestions. :( Thanks!
Click to expand...

How does the oil look? Like milk??? If so, antifreeze may be getting in oil from somewhere.
 
Did you retighten the head and manifold bolts until they quit loosening up?
You need some heat cycles to compress the gaskets. So check the nuts with the engine cold. Drive it, let it cool and recheck.
Seems like there are several that take a while to get tight enough after the head , or the manifolds are removed and new gaskets installed.
This has been discussed, and there should be some threads here to cover this.
 
Maybe try a simple wet test?

1. Pass fingers in wet area:

a. Fuel has fuel smell.
b. Water/antifreeze should slightly smell antifreeze.
c. Pure water, no smell.
d. Oil, not much smell, but will be slippery between rubbed fingers.
e. Water in one or two combustion chambers will turn to steam & steam clean spark plugs & tops of cylinders &have less black carbon than others.

B. If the wet on your finger has a strong fishy smell, could be you had sardines for lunch; or, ........... ?????.

C. The wet test usually helps.

Letting us know what you find may help to find the problem.
 
It must be oil or antifreeze because gasoline would have evaporated by now. Plus that would be a lot of gas from an updraft carb system. I'll check it again tomorrow but hard to believe the head gasket isn't sealing plus I looked for cracks and didn't see anything. Are there certain areas in the A block to look for cracks and thus coolant leaks. Plus I don't understand why it back fires through the exhaust if I rev the engine?
 
"Your plugs may be weak causing an over rich condition, that would cause the backfire."

Not so much. A lean mixture causes backfire. Plugs are typically not weak but the spark can be, but what he describes does not fit this
 
If a water leak, water could get down in valves & either rust valve stems & valve guides or even form a sticky goo-like material in same.

If this is the case. then valves begin to move up & down so slowly that valves open & close at the wrong delayed time.

Next, unburned or partially burned fuel/air mixture is pumped into your exhaust manifold & exhaust, & the heat or burning embers in same ignites the partially burned fuel.

Very common occurrence with engines that did not operate in a long while & sticky varnish appears to create this dilemma .... overnight soaking with kerosene works great to clean valve stem varnish.
 
You say that you are losing water. Is it vanishing with out a trace? Or is it being pushed out of the radiator and onto the ground?
If not leaving a puddle it is either being burnt in the cylinders while running and should produce some white exhaust smoke. If going into the oil pan drain the oil and you should see the water come out first followed by engine oil.
If leaving a puddle or splashing out while running it may just be simply over filled and seeking level. The water only needs to just cover the radiator tubes.
Another way water can be pushed out of a radiator is if there is a lot of rust / crud on top of the radiator tubes partially blocking them and not allowing the water entering the radiator to flow down through the radiator fast enough to keep up with the water pump.
If water comes out of the radiator only under heavier acceleration I would lean towards a head gasket not torqued well enough or a warped head or block surface allowing exhaust gases to enter the cooling system.
Some of the things that can cause back firing are an intake / exhaust manifold leak, carburator gasket leak or possibly the rubbing block on your points has worn some closing the point gap too much.
 
I would say that If you are using motor craft TT10 or maybe Champion W16Y spark plugs and they have fouled they will pop and backfire. I run and recommend Champion W 18 spark plugs, they are hotter and run clean.
 
Cory,

When I bought my A it had Autolite 3076 plugs which had carbon covered insulator after a short period of time so I rebuilt the Zenith Carb. Even though the passage in the new compensation jet appeared to be smaller than the standard number 19 jet, it didn’t eliminate the carbon on the plugs insulators so I cleaned them often. But based on your advise I’ve ordered the Champion W18 plugs and will give them a try. I've filed the points and now get a better spark for the coil wire. So maybe weak plug sparks and carbon on the plugs insulators caused the back firing and a wet condition in the cylinder areas. But if the wetness was un-ignited gasoline it should have evaporated.? Thanks
 
Sorry, the following note was intended for Purdy Swoft and not Cory,

When I bought my A it had Autolite 3076 plugs which had carbon covered insulator after a short period of time so I rebuilt the Zenith Carb. Even though the passage in the new compensation jet appeared to be smaller than the standard number 19 jet, it didn’t eliminate the carbon on the plugs insulators so I cleaned them often. But based on your advise I’ve ordered the Champion W18 plugs and will give them a try. I've filed the points and now get a better spark for the coil wire. So maybe weak plug sparks and carbon on the plugs insulators caused the back firing and a wet condition in the cylinder areas. But if the wetness was un-ignited gasoline it should have evaporated.? Thanks
 
leatherback1929, I've never used Autolite spark plugs in the model A but had similar problems with Motorcraft and other spark plugs that were too cold or fouling. With Motorcraft TT10 plugs , sometimes I could clean them once and after that they wouldn't spark and would remain wet and sometimes backfire. I feel that the Champion W18 plugs will help . Good luck .
 
You must log in or register to reply here.
Back
Top