Acceration stumble when warm

[51Deluxe]

Took my '51 for the maiden voyage this evening and she drove quite well. Once warmed up, the temp gauge went to the warm end, a bit outside of the "normal" zone with ambient temp of only 80 or so. At that point I accelerated into traffic and it stumbled as if to stall, but kept running and eventually took off. I don't think it's the accelerator pump as I wasn't moving the pedal  when it happened. Happened again later, twice in a 30 minute drive. The engine was just rebuilt and pretty much everything looks new, such as fuel pump, carb, etc. Gas tank has been cleaned and coated. Even though the gauge read near "Hot", when I got home I could actually place my hand on the radiator, so it wasn't all that hot. Any ideas?

[boatingbill]

If the thermostat is sticking in the partial open position, the engine may be overheating and
boiling the gas in the carb, causing the engine to run lean and bog down. The radiator would
not be hot because the water is in the radiator longer and therefore more time to cool off.

[boatingbill]

If the thermostat is replaced and the engine bog is still there, the heat riser in the exhaust
manifold may be sticking partial open position (likely) causing the carb to overheat. This was
a problem on the '51 Kaiser. Look at the bottom of the manifold and see if you can move a
weight connected to a shaft and a spring to see if it is free. Use PB Blaster on the shaft where
it goes into the manifold to and let soak for a hour or so. If this does not work, unbolt the
exhaust pipe from the manifold and use a pliers and PB Blaster to wiggle the flap inside the
manifold and free the shaft. This is a common overheating problem on the 51 Kaiser.

[51Deluxe]

The heat riser seems to be working perfectly, appeared to be wide open when warmed up. Guess I'll pull the thermostat tomorrow, but wish there was a was to avoid that. The car is supposed to have a new radiator, hoses, etc and they do appear new. Any way to accurately  test the temp of the warmed up engine?

[dpledger]

Could also be the engine isn't as hot as it thinks it is. Might check the temp sensor- put it in a kettle of water with a thermometer and heat it up, while measuring the resistance across it with a VOM. At ambient should be 70-100 ohm and at the top temp of the gauge about 10 ohm. This will tell you if the sensor is behaving properly. The other possibility here is that the instrument voltage regulator is outputting high. In this case the fuel level and oil pressure would also be reading correspondingly over.

Another possibility for the stumble is ignition- advance might be off, or vacuum advance. Both could produce that effect. Conceivable the mix could be too lean as well, so that under sudden load it starves.

[retired wrench]

n.
 Get your wifes candy thermometer and stick it in the rad. to see whats going on.

[51Deluxe]

Will do. Call it intuition, but I'm pretty sure this is fuel and /or heat related rather than ignition.

[JoeKeys2010]

What about gas lines? My 49 gave me a fit. I dropped the tank and had it lined, replaced the fuel pump but it wasn't until I replaced the gas liens from the tank to the fuel pump that my problem went away.

[51Deluxe]

That's a possibility since according to the seller, the gas lines are the only part of the fuel system that has not been repaired or replaced. Funny thing is, today the car ran perfectly. Same outside temp, same kind of driving. The ONLY difference is the tank was nearly empty and I filled up with ETHANOL FREE gas. Not only did it never hesitate or try to stall, it ran much cooler. Temp gauge before approached hottest area, this time it barely got over half way. I took retired wrench's advice and checked the coolant temp with a candy thermometer when I got home. It was a balmy 185 degrees,

Not sure if the new gas really had anything to do with the change, but still pleased to have a good driving car, at least for today.

[brian.b]

where did you find ethanol free gas :)every station around my area has the ethanol,,,i hate running it in my car and my saws.

[51Deluxe]

List of all ethanol free stations in the US (some entries may be out of date)


http://pure-gas.org