Originally Posted by glennj3cub
Finally I replaced my spark plugs and wires yesterday. What a job, very difficult to reach some of them !
Anyhow, I should have done this a long time ago as I was instructed to do by several of you guys. I was surprised it even ran, much less was running smoothly! Bad gas mileage though.
Of course you are interested in what condition I found them in?
The first wire I pulled broke off leaving the plug cap on the plug, the plug cap crumbled in my fingers as I squeezed on it. Another one had a white spot on it (like it was burned through).
Now the plugs, oh the plugs...the gap was about .050, one looked moist like gas, not oil. None were burned or had bad color. The outside was very rusted and the metal tips were very rusted.
I replaced that little pipe from the manifold to the air breather, the old one was hard and did not fit well.
Of interest, while underneath the RV I saw on the driver side at the exhaust connection a heat sensitive valve I believe it opens when warmed up. Looks like it pushes heat up a small metal tube to ward maybe the carburetor ? Anyhow that metal tube was rusted with open areas to the air. The rest of the tube is strong and looks good.
Thought I might wrap the open area with some sort of exhaust tape ??
Still looking for the fuel filter!
She cranked up and ran fine, now I need to test drive her. Hope she gets better mileage too!
Go back and read my post #22 for fuel filter location.
The exhaust valve you saw is known as a heat riser valve. Later they became known as EFE valves. (Early Fuel Evaporation) The early valves had a thermal spring mounted on the valve shaft which wound the valve closed when cold. There was also a weight attacked to the end of the valve shaft. As the engine warmed up the spring tension lessened and the weight forced the shaft to turn allowing the butterfly inside the valve to open and allow full exhaust flow out of the manifold. Later designs used a vacuum diaphragm mounted on a bracket attached to the manifold and a rod going from the diaphragm to the valve. The vacuum was routed through a thermal switch usually located near the thermostat housing on the intake manifold. The vacuum would pull the diaphragm closing the valve when the engine was cold and as the engine warmed up vacuum would drop off allowing the valve to open.
The reason for these valves was to prevent carburetor icing in colder weather. Especially cold high humidity days. I have seen cars and trucks stall to a stop because the carbs froze up. Let the vehicle sit a couple minutes and the engine heat would warm the carb enough to thaw it out and the engine would restart and run fine. When the valve is shut the exhaust would be forced up through the port in the cylinder head through a passage in the intake manifold directly under the carburetor and warm the carburetor to prevent the icing.
It is important that the heat riser valve is free and will be open when the engine is hot. If it is stuck shut the exhaust valves on the two center cylinders will be exposed to tremendous heat all the while the engine is running eventually resulting in burnt valves and possible valve seat burning. The high heat under the carb after engine warm up can also result in vapor lock as the high heat can actually boil gas in the float bowl introducing air bubbles into the gas.
Be sure the valve is free and operating correctly. Do not just grab the shaft and force it if the valve shaft is rusted in place. More than likely you will snap the shaft off and you will need to buy a new valve and have it installed. Sometimes the shafts can be freed with a good dousing of penetrating fluid and being patient when trying to wiggle the valve free. Just don't force it.