Exhaust Manifold Heat Control Valve

[avgwarhawk]

Looking at the 60's 401 it appears the passenger side exhaust manifold heat valve is stuck in the partially open position. Rusty as it were.  Has anyone been able to get the valve free again?  Currently I hit the exposed shaft ends coil and counter weight with PB Blaster. Also soaked the nuts that secure the exhaust pipe to the manifold in case it requires removal. 

Edited November 22, 2017 by avgwarhawk (see edit history)

[KAD36]

Recall warming the area around it with a torch, either propane or mapp, then hitting the ends of the shaft with a piece of ice and just kept working it.  Mine was frozen from sitting in the shed for 20 years- I mistakenly ran it for about a year before I knew what the counterweight and valve was.  Once I had it loose I used that kerosene/graphite slurry on it every time I greased the chassis and that helped keep it free.

 

On the manifolds on the rebuilt engine now I cut the valve right out of the manifold and welded shaft in place.

[Beemon]

Don't try to strong arm it, you'll spin the counterweight off the end of the shaft. Also when you free it up, make sure the spring is retained otherwise during motion it may vibrate off the end of the shaft as I had on my working exhaust manifold.

[NTX5467]

In the heat riser valve repair kit for another brand of car, the hole in the exhaust manifold had brass bushings the shaft was inserted into.  They were knocked out and the new ones installed.  Then, when the new shaft was installed, it was tight in the bushings.  Suspecting that another "freeze-up" would occur, the tech used a "cutter" in the drill to clearance the bushings for a looser fit AND ease of movement of the valve against the spring.  It stayed operable MUCH longer after that, with no maintenance.

 

The valves usually stick in the part-open mode, I suspect.  Key thing is to make sure the shaft moves freely in the bushings, which will require disassembly and re-fitment after the shaft is de-burred and polished and the bushings are clearance.

 

Just my experiences,

NTX5467

[Bloo]

Chrysler still makes real heat riser solvent, they just don't call it that anymore.

 

https://www.amazon.com/Genuine-Chrysler-Accessories-4318039AC-Penetrant/dp/B00BV4DBAU

 

Amazing penetrating oil for other uses too. If you can heat cycle it a time or two by driving the car, and spraying more on between cycles, things are almost sure to come loose fairly easy.

 

As Beemon says, don't strongarm it.

 

NTX5467: What kind of car had brass? I tried to replace the steel bushings in a mopar with brass once, and they melted and fell out. The heat riser worked after that, but it rattled.

Edited November 23, 2017 by Bloo (see edit history)

[avgwarhawk]

I have found the exhaust pipe to manifold flange collar is loose when cold.  I detected what sounded like an exhaust leak passenger side when cold.  Dissipates as it warms and swells. I'll drop the pipe and see if the valve is open or partially open. Install a new gasket upon reassembly.

[NTX5467]

Perhaps the bushings were steel rather than brass, but they did need to be reamed-to-clearance for the shaft to move smoothly in them.  To me, that was the reason the valves usually stick/freeze in place.  Not enough shaft clearance.  Add a little carbon, some heat, some moisture, no natural lube = stuck valve.

 

NTX5467

[Bloo]

3 hours ago, NTX5467 said:

Perhaps the bushings were steel rather than brass, but they did need to be reamed-to-clearance for the shaft to move smoothly in them.  To me, that was the reason the valves usually stick/freeze in place.  Not enough shaft clearance.  Add a little carbon, some heat, some moisture, no natural lube = stuck valve.

 

NTX5467

 

Exactly. But if you increase the clearance too much, they tick like an exhaust leak. They are also prone to rattling.

[avgwarhawk]

I found the valve to be stuck open. Logically this makes sense as the power is evident. However, the flange to exhaust manifold was found loose.  Tightened and cold running exhaust noise is gone. 

[Guest]

On 11/22/2017 at 5:51 PM, avgwarhawk said:

Looking at the 60's 401 it appears the passenger side exhaust manifold heat valve is stuck in the partially open position. Rusty as it were.  Has anyone been able to get the valve free again?  Currently I hit the exposed shaft ends coil and counter weight with PB Blaster. Also soaked the nuts that secure the exhaust pipe to the manifold in case it requires removal. 

S

Edited December 11, 2017 by Guest (see edit history)

[Bloo]

9 hours ago, 2carb40 said:

Fighting with the heat riser to get it "working" is causing yourself an ongoing maintenance issue. In my opinion using a "workaround" makes the most sense from a cost/benefit perspective. Just my opinion.

 

Do you by any chance live in a warm state?

 

If enough nailhead enthusiasts think this wont be an issue, I wont argue, but it has been my experience that most vehicles that are built with heat risers need them. It really can make the difference between a car that is an enormous pain in the ass, and one that is a joy to drive. Where I live, last winter it was no warmer than 19F for 3 straight weeks. --20F is not unheard of here. Summertime temps over 100 degrees are relatively common as well. How would your car do here?

 

Heat risers are only a maintenance nightmare when people neglect them and let them rust up for 40 years, and they need the shaft and bushings replaced. Spray a little solvent on when you change the points or plugs. Flip the lever back and forth a couple of times. It really isn't a big deal.

 

Thats also just my opinion. All the best!

[fraso]

Intake manifolds need to have a hot spot underneath the carburetor to vaporize any fuel that falls out of the air stream.  Vaporizing gasoline also causes the intake manifold to cool and, if that heat isn't replaced, condensation or frost can can appear downstream of the carburetor.

 

See Intake Manifold Heat and Engine Wear.

[Guest]

On 11/24/2017 at 5:19 AM, Bloo said:

 

Do you by any chance live in a warm state?

 

If enough nailhead enthusiasts think this wont be an issue, I wont argue, but it has been my experience that most vehicles that are built with heat risers need them. It really can make the difference between a car that is an enormous pain in the ass, and one that is a joy to drive. Where I live, last winter it was no warmer than 19F for 3 straight weeks. --20F is not unheard of here. Summertime temps over 100 degrees are relatively common as well. How would your car do here?

 

Heat risers are only a maintenance nightmare when people neglect them and let them rust up for 40 years, and they need the shaft and bushings replaced. Spray a little solvent on when you change the points or plugs. Flip the lever back and forth a couple of times. It really isn't a big deal.

 

Thats also just my opinion. All the best!

N

Edited December 11, 2017 by Guest (see edit history)

[Beemon]

I can't say that I've ever driven below 20 degrees, but for what its worth I drive my car year round and it has both the heat track at the base of the carb plugged and the heat riser torn out. In 30 degree weather, I've never noticed any difference other than the carb being on fast idle and higher oil pressure at start up. 

[NTX5467]

Before we get into an engineering discussion of the purpose of the heat riser valves, we need to realize that the world these cars now reside in is much different than it was when they were designed initially.  That means much more aromatics in the modern gasolines than were probably known about in the earlier 1950s or so.  Main thing, I suspect, back then was getting enough octane to support the  then-higher compression ratio motors, using TEL as the main anti-knock compound.  

 

Earlier carburetors probably did not do as good of a job of atomizing fuel as later versions did.  Intake manifolding was more about getting the fuel/air mixture from the carb to the combustion chamber, rather than in one smooth flow with gentle bends in the castings to accomplish this.  Therefore, at those "direction changes/turns" the fuel needed to be vaporized (which would normally happen in a low-pressure "vacuum" inside of the intake manifold).  As some fuel droplets might be larger than others, the "hot spot" in the manifold plenum added heat to help vaporize these larger droplets.  BUT as the fast-moving mixture, in a variable vacuum venue, would cool the mixture to below ambient temperature, the plenum heating the heat riser valve provided could be helpful.  Depending, of course, on the ambient winter temps.  Port mis-matches can also help get these larger droplets back into the air stream to the cylinders, as the rough-cast finish can also assist in this, too.

 

By the time we got to the earlier 1980s, typical USA gasolines had improved greatly from what they were three decades prior.  Vaporization characteristics were greatly improved.  Most fuel formulations were not predicted, I suspect, thirty years prior.  End result was that, in one case I know of, a '70 Road Runner 440+6 car could pass 1975 emissions specs, without any catalytic converters.  

 

The heat tracks in the carb mounting flange/pad area were to help decrease carburetor icing in cold and humid weather conditions.  I suspect that by the time the exhaust gases got up there, the various cold engine heat sinks the hot gas had to pass though all took heat out of the gases.  Then, by the time the gases had heated the carb baseplate area, they were probably not very hot.

 

The heat passages in the intake manifold will put some additional heat into the mixture, via the "hot spot" in the center bottom of the plenum.  But for best results, the  whole intake manifold should be heated, too, by that time.  Considering that this "hot spot" will be continually cooled by the fast-moving air/fuel mixture, until the cast iron components get enough engine heat into them, the heat riser valve's opening can be important.  I suspect that by the time the vehicle had driven 10 miles in city traffic, the engine would be approaching operating temperature, which would heat the intake and related manifolds.

 

The heat riser's purpose is to selectively restrict exhaust gas flow from the y-pipe, to force it thorough the small port in the intake manifold and go out the other side with that side's exhaust flow . . . when the engine temp needed that to be done.  On a dual exhaust car, there would probably be enough negative pressure pulses in the exhaust flow to send some of it into the bottom of the intake manifold by itself.  No real need for a heat riser valve, except in extreme cold conditions, I suspect.

 

Therefore, I suspect that many advances in gasoline design technology allows older vehicles to get along, usually, with the heat riser valve and intake manifold 'heat tracks"not being fully functional.

 

Whatever works with your vehicle!

 

NTX5467

 

[60FlatTop]

If the heat was passing through the intake manifold from one of those being stuck some old guy standing around the cracker barrel would hook his thumbs in his overall suspenders and say "Yep, you got a problem with that vapor lock."

Bernie

[avgwarhawk]

Me thinks people back in the day simply let their cars warm up. 

[old-tank]

3 hours ago, avgwarhawk said:

Me thinks people back in the day simply let their cars warm up. 

Yes, a lot of that.  As soon as the thermostat opened and warm air was available for the intake, performance was normal.

[avgwarhawk]

No further questions your honor. 

 

[fraso]

On 11/26/2017 at 1:01 AM, NTX5467 said:

The heat riser's purpose is to selectively restrict exhaust gas flow from the y-pipe, to force it thorough the small port in the intake manifold and go out the other side with that side's exhaust flow . . . when the engine temp needed that to be done.  On a dual exhaust car, there would probably be enough negative pressure pulses in the exhaust flow to send some of it into the bottom of the intake manifold by itself.  No real need for a heat riser valve, except in extreme cold conditions, I suspect.

 

Therefore, I suspect that many advances in gasoline design technology allows older vehicles to get along, usually, with the heat riser valve and intake manifold 'heat tracks"not being fully functional.

 

That sounds like a lot of wishful thinking.  Atomized fuel still falls out of the airstream and chokes are still needed to enrich the fuel mixture. Vaporizing gasoline continuously cools the intake manifold regardless of ambient temperature.

 

 

21 hours ago, avgwarhawk said:

Me thinks people back in the day simply let their cars warm up. 

 

it is the intake manifold that needs to warm for the engine to be warmed up.

[Beemon]

On 11/26/2017 at 11:23 AM, avgwarhawk said:

Me thinks people back in the day simply let their cars warm up. 

 

I'm guilty of this occasionally. Always get weird looks at my girlfriend's apartment. She lives in the ghetto so I would never leave the car alone and it usually dies two or three times as I try to finesse the throttle while backing out this fall. At my place, I usually give it three to five minutes and the car is always happier for it. 

 

With fuel injected cars it's not really a necessity because the computer does all that work for you and in a world of ever growing impatience, auto makers are making their cars to go at the turn of the key. Everyone says majority of wear is at startup but modern cars last much longer than their predecessors, to some degree. 

[Bloo]

Actually that is nothing new. My daily driver for more than a decade was a mid 60s Plymouth Fury. You stomp the gas once to give it a squirt of gas and set the choke, (two squirts if really cold, like 0F or something). Wait a couple of seconds (5 whole real seconds if it is really cold out). Tap the key. It starts on high fast idle. Hit the gas again (after waiting 5 seconds if really cold, otherwise just do it). It drops to a slower fast idle. Throw it in gear and drive away. Can you stomp it all the way to the floor? No, but you sure didn't need to feather the gas. After a little while the idle would come the rest of the way down.

 

Just about any stock American car from the mid 50s on (except homologation specials and such) that has an automatic choke can do this if things are working like they should. There was some variation between makes in how the starting procedure went, but what I have outlined above worked on most cars.

 

Back in the day, we drove these cars. Those of us with a bit of mechanical sympathy babied them, out of respect for the old tired mechanicals, but we used them, every single day. My Plymouth was not a restored car, it was a tired oil-burning old rat that had shot rings when I got it and still did a decade later. It was well-tuned. It started and ran pretty good, even at -20F, which it had plenty of opportunities to do in the winter of 1983/84. If it was warming up in a parking lot, it was because I was out scraping the windows. It never had to be towed.

 

I thought nothing of driving it hundreds of miles in the snow. I was much more worried about the cost of fuel (and oil) than car trouble. One time several friends piled in and we drove from Chelan, WA over Stevens Pass to Sultan, WA (and back) in a blizzard for sub sandwiches. I think about that trip every time I see some car with a $10,000 paint job struggling to get out of the parking lot at Cars and Coffee.

 

Edited November 28, 2017 by Bloo (see edit history)

[NTX5467]

 

The KEY to reducing that initial wear period is the 5W and 0W oils we now have, especially the syn oils with such low pour point temperatures.  When the first 0W oils were announced, it was mentioned that the oil would get to the far points in the engine about 40% faster than the then-popular 10W oils.

 

To me, the "wishful thinking" is that one hot area of the intake manifold plenum can really vaporize fuel droplets, in a cool/cold environment, as they momentarily pass over that hot spot (at a speed of how many feet/second?).  Remember, too, that this hot spot would be in the boundary layer of the air stream, not in the middle of it.  If the base of the carb is too close to the base of the plenum, the air comes down, hits the floor, and then scatters.  In that case, the hot spot will be more exposed to the full air flow.  But such a short dimension can diminish engine WOT performance, too, by observation.  It's more there to help heat the rest of the manifold quicker than if the heat radiated into the manifold, after it passes through the OTHER heat sinks in the top of the motor.

 

On an engine at "full operating temperature", it was mentioned years ago that when the engine was under mostly full power, the additional fuel might puddle in the plenum.  When the throttle was suddenly closed, the "fuel would boil", which could cause a momentary rich mixture situation.  Of course, going from a 5" Hg pressure to a 18+" Hg environment, would cause the fuel droplets to expand and vaporize with the negative pressure increase.  Just as evacuating the a/'c system causes any moisture to expand so it can be removed from the system.

 

In our more temperate N TX environment, I could tell no difference in the cold-fire-off on our main vehicle when the heat riser was fully functioning and when it was stuck 1/2 open.  Colder climates might make it more important to have it fully functioning?

 

EFI does help cold drivability as few of those intake manifolds have any provisions for exhaust heat to the manifold.  

 

NTX5467

Edited November 28, 2017 by NTX5467 (see edit history)

[Bloo]

On Mopars like the one I described above the automatic choke wont even work unless the heat riser does. Some other choke designs will work without it. I have yet to encounter a car that didn't run better after repairing the heat riser. I repaired the one on my 1936 Pontiac a few months ago and the difference was pretty astounding. Most fuel here is 10% ethanol. Your mileage may vary......

[Beemon]

22 minutes ago, Bloo said:

Actually that is nothing new. My daily driver for more than a decade was a mid 60s Plymouth Fury. You stomp the gas once to give it a squirt of gas and set the choke, (two squirts if really cold, like 0F or something). Wait a couple of seconds (5 whole real seconds if it is really cold out). Tap the key. It starts on high fast idle. Hit the gas again (after waiting 5 seconds if really cold, otherwise just do it). It drops to a slower fast idle. Throw it in gear and drive away. Can you stomp it all the way to the floor? No, but you sure didn't need to feather the gas. After a little while the idle would come the rest of the way down.

 

This is exactly what I do, but sometimes if I put too much foot into the pedal, it bogs and dies. So I just lightly feather it under load. Once moving, it's no issue, just that first drop into gear.

 

13 minutes ago, NTX5467 said:

EFI does help cold drivability as few of those intake manifolds have any provisions for exhaust heat to the manifold. 

 

What I meant is that the computer gives throttle enrichment at idle for cold start up until warmed to temp, there isn't a choke to obstruct flow into the plenum so throttle response is more forgiving - in my limited experience between the two systems.

 

2 minutes ago, Bloo said:

On Mopars like the one I described above the automatic choke wont even work unless the heat riser does. Some other choke designs will work without it. I have yet to encounter a car that didn't run better after repairing the heat riser. I repaired the one on my 1936 Pontiac a few months ago and the difference was pretty astounding. Most fuel here is 10% ethanol. Your mileage may vary......

 

I noticed this, too. My thermostatic choke, the original one, would not function properly without a postive heat source I assumed. Under normal conditions, it would take a very long time to unwind, and even then the choke was still unloaded. And this is with the choke lightly shut at 75 degrees F. My issue was fixed with an electric choke from an Edelbrock.

Edited November 28, 2017 by Beemon (see edit history)

[avgwarhawk]

Let get to the crux of the matter. EFE: early fuel evaporation.   Gasoline will only burn as a vapor/atomized form.  The carburetor does a good job at mixing fuel with oxygen. 14:1 is optimal.  However, the most efficient burn is warm atomized air/fuel getting sucked into hot cylinders.  When cold, vapor/atomized fuel/air will puddle or become droplets once again and will not burn well if at all.     NTX5467 touched on the puddles created from cold intakes and cold air.  The engine stalls, stumbles and begrudgingly sputters down the road. The engine can not burn these droplets.     The engineers designed many features to remedy cold drivability issues.  

 

1. manual/automatic choke

2. warming antifreeze plumbed through the intake

3. exhaust manifold valves

4. hot air tube from exhaust manifold to the snorkel on the air filter assembly

5.  Electrical heating grids under carb and throttle bodies

6. hot exhaust gases plumbed under the carburetor

 

I still have in my toolbox the Thexton choke angle tool I used many moons ago to set check pull off.  

 

Then the advent of computerized fuel delivery via injectors solved many cold drivability problems.   It is a tailored fit with the use of coolant temp sensor, MAP sensor, TPS, MAF sensor and fine tuned via the O2 sensor once in closed loop.  

 

All of this equates to one thing.  Efficiency of the burn.  More so today with the advent of strict emissions.   

Edited November 28, 2017 by avgwarhawk (see edit history)

[old-tank]

14 hours ago, Bloo said:

On Mopars like the one I described above the automatic choke wont even work unless the heat riser does. Some other choke designs will work without it. I have yet to encounter a car that didn't run better after repairing the heat riser. I repaired the one on my 1936 Pontiac a few months ago and the difference was pretty astounding. Most fuel here is 10% ethanol. Your mileage may vary......

I can see how the heat riser is needed on the mid 60's mopar where the heat source for the thermostatic choke is the intake manifold crossover.  Mid 50's Buicks use the passenger side exhaust manifold via a pipe to the thermostatic choke on the carb as a heat source; the heat riser on the driver side manifold would have no effect on this.

[KongaMan]

On 11/27/2017 at 5:08 PM, Bloo said:

 If it was warming up in a parking lot, it was because I was out scraping the windows.

 

Bingo.  Start the car, turn on the defroster, clean the windows, get back in and drive away.

[Guest]

W

Edited December 11, 2017 by Guest (see edit history)