When do you close the heat riser valve?
When do you close the heat riser valve?
Every time an engine cools down, the heat riser valve closes. Every time the engine warms up, the valve opens. Heat risers have no earthy value on very cold or very hot days, but only in damp, humid temperatures in the thirties range.
What happens when an exhaust heat riser is closed?
Should this happen, the engine will be forced to burn fuel that has been overheated by the exhaust manifold for a steady, full-time diet. Since a closed heat riser flap directs hot exhaust gasses toward the base of the carburetor, fuel bowl temperatures now rise and fuel will boil, especially on hot shut-down.
When do you need a heat riser in your car?
Heat risers have no earthy value on very cold or very hot days, but only in damp, humid temperatures in the thirties range. When they are needed, it is only for two or three minutes, until the engine warms the carburetor sufficiently to overcome this icing issue.
Why do I need to remove the heat riser valve?
I have no compelling reason to remove the heat riser valve, except that it does rattle. And when I said it’s functional, it does really work as it should, but one side, opposite the spring, has lost its bushing, so the little tiny axle just rattles around inside the shaft. At idle, it sounds like a very loud rattling coming from the engine.
Should this happen, the engine will be forced to burn fuel that has been overheated by the exhaust manifold for a steady, full-time diet. Since a closed heat riser flap directs hot exhaust gasses toward the base of the carburetor, fuel bowl temperatures now rise and fuel will boil, especially on hot shut-down.
When does a heat riser make a difference?
In the very benign climate I live in I do find that having a working heat riser makes a difference in cold start drivability especially during our “winter” when the morning temperatures are in the 40F range. That first mile or so takes a bit more futzing with the choke and hand throttle if the heat riser is not functioning properly.
Why do you need a heat riser in a car?
As Rusty says, the drivability of any vehicle will improve dramatically with a properly functioning heat riser and a clear exhaust crossover. At best, it will run poorly until it warms up. At worst it will stall repeatedly when it is put in gear with a cold engine. More sharing options…
