1974 fj40
- Thread starter marcusd
- Start date
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Visible external portion of exhaust divert flap in the manifold.
While the spring on the backside is cold the flap is pointing the hot exhaust gas up onto the bottom side of the intake.
After the manifold/spring heats up, it rotates the flapper to shield the bottom of the aluminum intake and divert the hot gasses more directly out of the manifold.
Problem is they sieze in the cold position and roast the intake.
While the spring on the backside is cold the flap is pointing the hot exhaust gas up onto the bottom side of the intake.
After the manifold/spring heats up, it rotates the flapper to shield the bottom of the aluminum intake and divert the hot gasses more directly out of the manifold.
Problem is they sieze in the cold position and roast the intake.
That flap inside your exhaust manifold opens and closes with the coil spring and temperature. I believe they all rust. If they rust closed the heat can crack the intake manifold. It's used to warm the carb for optimum operation.
- Thread starter
- #4
If I can not manually move it i assume I will have to take off manifold and replace?? Is their something out there that can take its place or an aftermarket or oem manifold without one? Thank you for the information
Many people just cut them out; cut the shaft on each side inside the manifold, or if not completely rusted in, drive the shaft out and put JB weld or similar in the holes. It may be possible to make them work again, but I have never done it (most of those I have done are on old american cars, my landcruiser has a header.)
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- #6
So i can move the flapper. Hit it with a hammer to unstick it. Lubed it and it moves freely now. Ran the motor for a while. The spring got really hot and the flapper did not move. I can move it manually but not sure if the weight should be straight up and down with the motor hot or at the slant. If I knew which was the position it should be in once hot I could tack weld it open. Some clicking and puffs of smoke that come out of the carb once turned off. Also some exhaust that seems like it is coming from the manifold / exhaust pipe connection which is really tight. Pain in the ass but would it be better to just take apart and replace the gaskets and remove the flapper?
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- #7
I suppose I could just take the exhaust pipe off below it, cut off the external pieces and remove the flapper from below and then close the holes??
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- #9
I think the simplest way to do this is to take off the exhaust pipe directly below it and put my finger up there to see how the flapper is aligned. Know if I want it straight up or at a slant to prevent the cracking people are talking about?
@JohnnyC is correct. If frozen , keep it from heat constantly hitting the manifold. I have one exhaust manifold I removed the entire flap assembly and drilled the holes, tapped , and plugged so nothing is there. Another one I had a shop fab new parts that are still holding up. Material used in these parts originally were pretty much used in gasoline exhaust before unleaded. Exhaust gasses were different pre mid 1970s when all went unleaded . Each have different chemistry on materials.
Mine (69 fj40) was seized up as well. I broke the studs off trying to take it apart. Ended of finding a non USA version without the heat riser and used the block off plate. New manifold gaskets, New studs all around and I was back in business.
If you have winter - modify the block off plate with 2 fittings and a gasket to make a fluid heat riser. Carburetor Ice B Gone
Check paragraph 4 in section 15 intake and exhaust manifold. Your tension on the bi-metal coil spring may need adjustment. Also your counter weight stopper, item I, is stamped with a C and H as a guide. See attached.
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- #16
Thank you all. I think I will try to buy a new coil spring piece and see if that works. Otherwise I will get the block off plate. We do have cold spells in Baltimore area so would be nice to have a working version of this mechanism
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- #18
What manual is this? My dad said there was a manual in the truck but the mice ate it.
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- #20
Thank you!