Heat riser: Do i need it?
#1
#2
#4
#6
The heat riser just warms the air going into the carb. This means that the air is less rich in oxygen. Cold air makes more power and efficiency. I really can't see how it could have burned your valves as it really is just a route for the heat to rise into. There is no actual airflow from the exhaust there.
#7
Trending Topics
#9
Yes, it's a thermostatic controlled flapper valve that bolts on the exhaust manifold exit flange and forces those hot gasses to backup thru the crossover in the intake and finally exit out the other side. It puts a lot of pressure on the intake crossover and intake gaskets sometimes blowing them out. When you romp on it the exhaust pressure will open the spring valve a little but it's still a lot of back pressure. When it sticks partly closed it's a valve burner.
Last edited by BB; 02-19-2004 at 01:54 PM.
#10
It closes off one side of the exhaust so the exhaust gases flow thru the crossover in the intake and exit via exhaust on other side of engine. Usually pass side to drivers side. It heated the intake in order to prevent fuel puddling or dropping out of the airflow when the engine was cold. They opened as the engine warmed up and the preheat wasn't needed.
#12
#13
#14
Now that's where the problem is. Exhaust manifolds that use the heat riser have a flat face on the exit flange. A flat gasket goes between the manifold and the heat riser. The outlet of the heat riser is carved for the donut gasket.
Manifolds that don't use the heat riser have the exit flange already carved for the donut gasket.
There was a special spacer that replaced the heat riser that was flat on the manifold side and carved on the outlet side for the donut. I doubt if you could find one now, maybe eBay? Here's what it looked like (that dark ugly thing):
Other option is to replace your exhaust manifold with one that doesn't use the heat riser (takes the donut instead).
Or maybe you could weld your heat riser so it's permanently open.
Manifolds that don't use the heat riser have the exit flange already carved for the donut gasket.
There was a special spacer that replaced the heat riser that was flat on the manifold side and carved on the outlet side for the donut. I doubt if you could find one now, maybe eBay? Here's what it looked like (that dark ugly thing):
Other option is to replace your exhaust manifold with one that doesn't use the heat riser (takes the donut instead).
Or maybe you could weld your heat riser so it's permanently open.
Last edited by BB; 02-19-2004 at 03:18 PM.
#15