Heat riser: Do i need it?
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From: Jackassville
Heat riser: Do i need it?
im hooking up my tailpipes and i was just wondering if i need to put that thing back on. also where can i get a spring to make it work? mines gone and it burned up my exhaust valves.
Post Fiend
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From: Missouri
Welcome to FTE!
I'm not sure how your heat riser burned up your exhaust valves. You do not need it. I don't know where you can get the spring. I'm sure Obsolete Ford has it but they are going to want a truckload of money for it.
I'm not sure how your heat riser burned up your exhaust valves. You do not need it. I don't know where you can get the spring. I'm sure Obsolete Ford has it but they are going to want a truckload of money for it.
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Posting Guru
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From: Jackassville
it burned them because it was stuck closed, at least i think thats why almost all by exhaust valves were burned up on that side. are you sure i dont need it even in really cold weather?
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Glad to be here on FTE!!!
Post Fiend
Joined: Feb 2001
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From: Missouri
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.
Post Fiend
Joined: Feb 2000
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From: Brea CA
He's talking about this heat riser:
It's a thermostatic cork for one side of the exhaust, forces the gasses to go thru the crossover. You don't need it and Ford phased them out by '68.
Barry
It's a thermostatic cork for one side of the exhaust, forces the gasses to go thru the crossover. You don't need it and Ford phased them out by '68.
Barry
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Post Fiend
Joined: Feb 2001
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From: Missouri
Whoa! I've never seen one of those. Which crossover are you referring to Barry? The crossover inside the intake? Are the gasses pushed right out of the exhaust?
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Post Fiend
Joined: Feb 2000
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From: Brea CA
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; Feb 19, 2004 at 01:54 PM.
Posting Guru
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From: Colville, Washington
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.
Post Fiend
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From: Brea CA
Just a clarification, they were phased out in '68 on the cars, some trucks still got them up to '74 I believe.
Hey you're welcome! Thank Putt too he knows more than I do.
Hey you're welcome! Thank Putt too he knows more than I do.
Last edited by BB; Feb 19, 2004 at 02:21 PM.
Post Fiend
Joined: Feb 2000
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From: Brea CA
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; Feb 19, 2004 at 03:18 PM.