Re: Rusted open/closed heat riser valve

Posted by Phil Randolph On 2010/2/11 14:35:13

I just took a look at my NOS and yet uninstalled exhaust manifold. When the weight is down the flapper plate blocks most of the hot exhaust gas from hitting the bottom of the intake manifold. In operation when the engine is cold exhaust gas warms up the intake gas charge, as the engine warms up the flapper diverts the hot exhaust away from the bottom of the intake. My old exhaust manifold was missing the flapper and it made hot starts a real pain as it would boil the gas in the carb and dump it into the intake. I wouldn't remove the flapper Just run it with the weight in the down position.