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heat riser


bluefoxamazone

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Bluefoxamazone,

   It all depends on just how the heat-riser is defective. If it’s stuck open, it’ll cause the fuel in the manifold to vaporize less, causing the car to take longer to warm up, and run rougher during this heat-up phase. If it’s stuck closed, it’ll cause the fuel in the manifold to vaporize more, which could cause the car to vapor-lock.

   To test the heat-riser with the engine cool, push the counterweight down as far as it’ll go, then release it. The counterweight, shaft, and valve, should spring back to the closed position. Next, start the engine, and allow it to warm up as you observe the action of the heat-riser. With the engine operating at idle, the counterweight should move slowly downward as the engine warms up. Continue to observe the counter weight until the engine reaches normal operating temperature. At this point, the heat-riser should be fully open. If it isn’t open completely at normal operating temperature, rust is the usual cause.

   If the heat-riser shaft doesn’t rotate completely each direction, or if it sticks anywhere during rotation in its base in the riser casting, try spraying some carburetor cleaner on the ends of the exposed shaft. After a few minutes, gently try to rotate the shaft with the counterweight, or the shaft lever itself. Continue repeating this until it rotates freely, and completely. If this doesn’t work, the heat-riser may be too far gone, and will require replacement.

   Good luck. Regards . . . .

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Bluefoxamazone,

   I had a Pontiac with a supercharged big-block engine that had the heat-riser removed. I had to run an electric fuel pump, because the supercharger over-powered the mechanical fuel pump, and pushed the fuel back into the fuel tank – not good. I also had to run a manual choke. I couldn’t run dual exhausts, since the fuel pump resided when one of the exhaust pipes passed, so I ran a single 2½” exhaust system vs the original twin 2” system. The point of this is that without the heat-riser, that car was one cold-blooded SOB. In the summer, it’d take a good 15 minutes to get it to the point where it’d move under its own power. And, in the winter – plan on a ½ hour!!! During warm-up, it ran like crap. Warmed up, it ran great. As a young guy – the supercharger was worth it, but now as an old guy – well, that’s why I sent it went down the road . . . So, the moral of this story is – functioning heat-risers are definitely a good idea!!!

   Lastly, I went to Belgium during post-WWII with my parents (we lived in the American Zone of Germany for almost 5 years) – the country was lovely, and the people were very gracious. And, the pastries – incredible!!! Best regards to you . . . .

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