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Heat Riser Seized


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Hey all, started a similar thread on the car side a week ago. On my 55 Fargo 251, the heatriser flapper is seized in the cold warm up position. the weight is off the shaft, the shaft is broken off too. i could not move it to allow exhaust gas to flow out freely.

Here is my ?, is it safe to use this engine with this problem in summer? i will not have time until fall to remove the manifolds, and install the donor manifolds.

The carb will heat up, but will i do head or exhaust valve damage if I run this engine in summer.

I would of course avoid the heat of the day, and not drive it too hard or long. I do not want to do engine damage though Perhaps I could install a heat spacer under the carb for now.....thanx 

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Try a penetrating oil.  If that doesn't work, MoPar dealers used to have a heat riser lubricant that they used that actually loosened up a stuck flapper in my Dad's 40 Plymouth.  Performance may suffer, and she may run a little warm.  I think you'll need to be concerned with gas boiling in the carb after a run so it may be hard starting when hot.

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I have tried heat,penetrating oil, trust me, it ain't gonna budge, at least not for Me.

The hot starts are not too bad, as I am 12 volt, which makes a huge difference. I just came back from a few miles drive, it is a warm night, nothing got overly warm, but was just puttin around and it's evening. I just do not want to do damage to exhaust valves head etc. I do plan to not drive in the heat of the day, until I have fixed this problem....thanx

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Here's a nice article dealing with heat risers.  If anything you want it open.

 

http://dodgepilothouseclub.org/know/riser/riser.htm

Thanx Bob, read it a long time ago. I do know the reasons for the heatriser. i would simply turn mine open if I could but I cannot, so unfortunately have to pull it off the engine, but will try again beforehand. 

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Yea, eventually you're going to have to pull and split the manifolds to get to the problem and properly fix it.  I leave the one on the 230 in my 1 ton open.  Years ago the one on my 36 Plymouth was stuck closed, and she ran hot and wouldn't start when hot with the 6 volt system.  It was also kinda sluggish.  Luckily the manifold came off and apart very easily.  I did the proper repair on that one.  She still won't smoke the tires, but she's better than she was.  I gotta look at the one on the 251 in the old firetruck once I get where I can lay over the fender again.  The military used a manually adjustable baffle that you put in one posistion for cold weather driving, and at the other end for warm weather.   Mike

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Yea, eventually you're going to have to pull and split the manifolds to get to the problem and properly fix it.  I leave the one on the 230 in my 1 ton open.  Years ago the one on my 36 Plymouth was stuck closed, and she ran hot and wouldn't start when hot with the 6 volt system.  It was also kinda sluggish.  Luckily the manifold came off and apart very easily.  I did the proper repair on that one.  She still won't smoke the tires, but she's better than she was.  I gotta look at the one on the 251 in the old firetruck once I get where I can lay over the fender again.  The military used a manually adjustable baffle that you put in one posistion for cold weather driving, and at the other end for warm weather.   Mike

Actually I don't have to split this manifold, as I have a donor waiting that has the flapper working well. I see no reason to have it anyway. I do not need it to drive in mostly warmer type weather. In cold weather it can warm up a little longer.

If I can get the flapper to move, I will not even take it off.

I have done 2 of these before, and it ain't fun if a manifold stud breaks in the block....thanx

Edited by 55Fargo
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I just read Erb's article on the heat riser which was a good learning experience fo rme. My riser was rusted shut so I just removed the flap, case closed, but then I'm in a warm climate and and grew up in a cold climate where I was accustomed to letting a horse walk a bit before mounting and an engine run a bit before pulling. Yet it is good to know that a heat riser has little value if one lets the engine warm up which includes the oil, etc.

Now I will have to learn to know how the automatic choke works on my 53 Plymouth. Question: Can I elimate the automatic choke and have the same carb that is on my 52 Pilot-house?

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I just read Erb's article on the heat riser which was a good learning experience fo rme. My riser was rusted shut so I just removed the flap, case closed, but then I'm in a warm climate and and grew up in a cold climate where I was accustomed to letting a horse walk a bit before mounting and an engine run a bit before pulling. Yet it is good to know that a heat riser has little value if one lets the engine warm up which includes the oil, etc.

Now I will have to learn to know how the automatic choke works on my 53 Plymouth. Question: Can I elimate the automatic choke and have the same carb that is on my 52 Pilot-house?

Paul, did you weld in some plate to allow exhaust gases to exit out ? if not you may have a full time heatriser going on in there.

1 thing I can tell you is this, years ago had a 1979 Ford Fairmont 6cyl, heat riser was not working. I was driving down a highway, engine fully warmed up to temp, outside ambient temp around 30, very wet, carb started icing, had to pull over several times to allow the carb to thaw. On the return trip, no problem going with the wind, musta helped keep things warm underhood. So in some case a heatriser is necessary beyond warm-up...

Edited by 55Fargo
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Now you have me curious.

Wouldn't removing the plate altogether eliminate the heat riser effect? Mine functions but I have been wondering if removing it would result in a cooler carb. I live in a warm climate and stop and go traffic is the norm. I have never seen anything conclusive on this subject but it would seem to me that removing the restriction might result in slightly better warm weather performance. Anybody have a take on this?

 

Jeff

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Now you have me curious.

Wouldn't removing the plate altogether eliminate the heat riser effect? Mine functions but I have been wondering if removing it would result in a cooler carb. I live in a warm climate and stop and go traffic is the norm. I have never seen anything conclusive on this subject but it would seem to me that removing the restriction might result in slightly better warm weather performance. Anybody have a take on this?

 

Jeff

If the flap inside the manifold is taken out, exhaust gas from the front 3 cyls can flow through, but some of the hot gas will rise up under the carb intake area.

If your taking this flap out, you should weld a plate to stop hot exhaust gases from entering the area driectly under the carb.

If you do not, then possibly the carb will continue to get hotter in warm weather driving conditions.

If your not going to repairthe heatriser to function, then seal off the are, and allow xhaust to exit freely through the exhaust manifold, not doing so will allow gas to rise up into the area...

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The heat riser valve on my p15 stuck in the horizontal position. I don't know how long ago this happened but it was that way when I got the car. The car never accelerated right although it seemed to Idle OK. I was checking it out one day and I found a hairline crack in the intake manifold under the carb. I bought a new set of manifolds with a working heat riser and installed them. Now it runs much better. When I removed the intake manifold I found more cracks on the engine side and a fragment of the intake manifold was about to fall out. I blame the heat riser which had been stuck in a horizontal position. If you can free one and get it working correctly, you're a better man than I Gunga Din.  If you do check carefully for cracks in the manifolds.

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The heat riser valve on my p15 stuck in the horizontal position. I don't know how long ago this happened but it was that way when I got the car. The car never accelerated right although it seemed to Idle OK. I was checking it out one day and I found a hairline crack in the intake manifold under the carb. I bought a new set of manifolds with a working heat riser and installed them. Now it runs much better. When I removed the intake manifold I found more cracks on the engine side and a fragment of the intake manifold was about to fall out. I blame the heat riser which had been stuck in a horizontal position. If you can free one and get it working correctly, you're a better man than I Gunga Din.  If you do check carefully for cracks in the manifolds.

I have repaired these before, but obviously the manifolds were in good condition. I think what you stated is correct though, drive with this in the wrong position=highheat=possibly cracks.

I do have a donor in good shape, or maybe I will buy and intake and headers from Moose and go 251 super stock, watch out Coatney.....LOL ps for you Guys south of the 49th parallel, 1956 Dodge and Fargo pickups in Canada are 120 hp long block 251s

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oh no Don..you being called out again...by a truck no less...sure hope there has been lots of final gearing chances made by the challenge let alone engine mods.....or you will be using your car to tow home the dead beast..but..being a truck, there is room in the bed for the pieces you pick up off the road... :)

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Hey Dilla killer, quit hi-jacking my threads go out and shot a squirrel.

 

 

Sorry Paul...but this thread is the only thing of value you have worth hi-jacking....(someone give me a rimshot here...)

 

hey..at least I was basy painting a panel when you called.....

Edited by Plymouthy Adams
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BACK ON TRACK: After an explanation of the heat riser question with Plymouthy , he explained that the exhaust flow in the manifiold is from the front of the engine back to the exhaust port. On the way, the heat riser baffle in a vertical position : (a) deflects the fumes from the front three cylinders up to the carb to warm it or (2) the baffle in an horizontal position closes off the route to the carb and the exhaust goes straight to the exhaust port.

If the baffle is removed, which is what I did, then the bottom of the carb always gets SOME of the non-diverted fumes which may be problematic it a warm climate. However, as Tim explained, those problems may only occur under high load condiditions. Accordinly I'm not going to change my setup until I discover problems.

Edited by pflaming
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  • 2 weeks later...

all this talk of heat risers had me thinking this AM.  I had to run FEF for 15 minutes to cure my latest attempt to stop the water jacket crack from weeping and I checked the heat riser.  It was sitting in the 12 o'clock position after running and idling for 15 minutes....it moves freely with a push and springs back...granted it's not all THAT hot out, but it's not THAT cold out...I wonder if this is what causes me some power issues once in a while?  I reread the article and kinda concerned at this point (potential dmamge).  When should it go to being closed?  Is 15 minutes NOT enough?  I know the engine compartment was plenty warm.

Edited by ggdad1951
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The default position of the riser is with the flap vertical.  The job of the bimetallic spring is to move it to horizontal as the manifold heats up. When at operating temp, the spring and the exhaust flow both work to keep it in the horizontal position.  So If you can turn the flap pivot clockwise to the stop this is the horizontal position.  Since the flap does not completely close the flow, there will always be some circulation of exhaust gasses to the underside of the intake manifold.  Again I will state that mine is welded in the horizontal position, and I have no known or notable drive-ability issues with this over the 12 years I have driving since it was modified.  I do operate the car in the early spring and late fall early winter weather permitting and have had no issues even with ambient temps in the 20/30 degree range. 

 

As Don mentioned the bimetallic spring reacts to exhaust manifold temps not air temp, although it stands to reason that ambient temps will have a small effect on how quickly the manifold itself gains or looses heat.

 

As far as how hot, I can attest to the fact that when the exhaust manifold riser is in the horizontal position. the manifold will easily and quickly raise a blister on exposed skin brought into contact with it.................

Edited by greg g
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I'd think running for 15 minutes would get the manifold hot enough?  Maybe I just have to take a joy ride this weekend and see if it moves after driving around,  Idling in the garage/slight rev might not be enough to kick the spring?  I know when I rebuilt the manifold, a tease with the propane torch defintely moved the flap and counterweight.

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