Exhaust manifold heat riser/flapper

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takehikes
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Exhaust manifold heat riser/flapper

Post #1 by takehikes » Tue Jul 11, 2017 3:30 pm

I took my exhaust manifold off this weekend (1968 F100 with 240-6) and found the flapper in the manifold works fine BUT the spring is broken.
Any idea how to get one, repair it? Diagrams? Anything? Or should I forget about it and whack it shut? Or wide open (heat to intake)?
My sheet metal heat riser is intact to the air cleaner.



Haywood
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Re: Exhaust manifold heat riser/flapper

Post #2 by Haywood » Tue Jul 11, 2017 10:52 pm

Depends on where you live, here in Texas I'd just wire it open. We get some cold weather, but if you keep your foot in it for a couple of blocks / miles, what it would have done becomes redundant. I even used to do that in the northern climates, but you notice it a bit more. I looked on the net to see if they still sold the whole heat riser, doesn't look promising. I'd wire it open and see how it does, likely you really won't mind. Better than having it flopping around.



takehikes
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Re: Exhaust manifold heat riser/flapper

Post #3 by takehikes » Wed Jul 12, 2017 1:45 pm

Wire it open? As in heat going to bottom of intake all the time.

Or wire it shut to stop it going to it all the time?



takehikes
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Re: Exhaust manifold heat riser/flapper

Post #4 by takehikes » Wed Jul 12, 2017 2:33 pm

Anyone know where to get one of the bimetal springs for the heat riser?



takehikes
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Re: Exhaust manifold heat riser/flapper

Post #5 by takehikes » Wed Jul 12, 2017 2:45 pm

Also looking at the drawings of the exhaust manifold it shows a spring going in to a round tube cast in to the manifold. Appears to ahve a square cap on it. What is that all about? My manifold has the cast in round tube area but nothing i it. Whats supposed to be there?



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bubba22349
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Re: Exhaust manifold heat riser/flapper

Post #6 by bubba22349 » Wed Jul 12, 2017 3:41 pm

You are probally going to have a tuff time finding a new spring but it maybe possible if you can find the OEM part number for it, maybe you can ask the "Number Dummy" over on the Ford Truck.com site. You might also look for a used one at your local wrecking / junk yard and the springs used on V8's may also work.

X2 in the past I also used to just tie them open if they were flapping around or knock the butterfly valve out of them when they were frozen shut. :shock: They will need to be open for best all around engine performance you wouldn't ever want them to be wired closed all the time, this would cause a big exhaust flow restriction. Under normal operation they are only closed when the engine is cold at first start up then as the engine warms up they open fairly quickly so they have very little effect on carb heat. The Carb heat is separate and is mostly full time as it normally comes from the top of the stock exhaust manafold being bolted directly to the bottom of the stock intake manifold (radiated and transferred heat)

Most of my life I lived in warm areas of California so if I was installing a new exhaust system or head pipe I just removed the whole non working valve, :hmmm: :rolflmao: now that I am living in a much colder place, so might need to rethink the need of that part some or maybe not. Good luck :nod:


A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

66 E100 Pickup
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Re: Exhaust manifold heat riser/flapper

Post #7 by 66 E100 Pickup » Wed Jul 12, 2017 10:17 pm

I had a 66 exhaust 240 with that spring. When I took the pile of parts in for cleaning to the engine builder, he recommend cutting it out and plugging the shaft. He said that with modern unleaded, burnt fuel exhaust is 400 degrees hotter than the old regular leaded that this system was designed for. Checking my 66 shop manual, the valve flap is supposed to be mostly horizontal when hot (eg, does nothing), and vertical when cold (exhaust goes up into the intake and then back down into the exhaust).

I think the small pipe hole you are talking about is actually for a tube heat riser for the hot air choke carbs. Carter has a version of this, and I remember my 289 mustang having one also on an old autolite. Hot air chokes were common back in the day...careful of that material that covered the tube, it's asbestos.

I may have one of those old flap manifolds still around. I won't use them again, but let me know if I can check for you.

John/Fresno



Eff1 Shifty
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Re: Exhaust manifold heat riser/flapper

Post #8 by Eff1 Shifty » Sun Jul 16, 2017 10:57 pm

On a slightly related topic, is it possible to use the old 1 barrel carb in. manifold with efi exhaust manifolds? and by "possible" I mean at all practical or worth the effort if modifications are involved.



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