What's the black thing that spins on the side of the exhaust manifold? Something to do with the egr valve or hot air chimney? Emissions?

It is kind of like a disc that is spring loaded or something...

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madam im adam

That is the spring loaded intake manifold heater flapper. I can't recall the specific name of the part, but its purpose is to provide varying amounts of hot exhaust gasses to heat the floor of the intake manifold. This is actually a very useful and important part, especially in colder climates. Opinions vary about whether or not to leave it in. Personally, I am in favor of leaving it there and making sure it works and is adjusted correctly, especially on a daily driver street vehicle.

I always wondered what that thingie did!

Cool that you knew what I was talking about.

It is adjustable? How can it be setup right/wrong?

Thanks

It isn't "adjustable" per se, but the shafts, especially on the older version with the triangle shaped counterweight, can become stuck. Once the shaft becomes stuck, people can actually force the flapper out of proper alignment by pushing on it to try and get the shaft freed up. If yours is present and moves freely, all you should really do is get some of the correct Mopar lubricant and apply it according to the instructions.

Some people remove these under the theory that it is an unnecessary exhaust restriction. Other people believe that the restriction caused is minimal, if at all, and argue that leaving it in place is beneficial to a street motor due to the carb heating it provides. So, removing it could be considered to be "wrong" depending on what camp you find yourself in. Me? I think Mopar wouldn't have wasted the material and machining costs to install that part unless there was a good reason.

The heat riser or manifold heat control valve has servicing info in the exhaust system section of the FSM...in my case group 11.

FSM highlights:
The Servicing consists of a few drops of Manifold Heat Control Valve (MHCV) Solvent every six months to both ends of the MHCV shaft. The solvent is applied when the engine is cool and the solvent is allowed to soak a few minutes. Then work the valve back and forth until it turns freely.

To check it's opertaion:
With the engine idling, accelerate momentarily. The counterweight should respond by moving approximately 1/2 inch and return to it's original position. If no movement is observed the shaft is binding excessively or the thermostat spring is weak or broken.

The FSM gives detailed steps in replacing the spring & properly preloading the assembly by twisting the spring the correct amount.

The Mopar solvent that I use has part number MS-3613 & 04318039AB and it has kept my 65 Dart SL-6 working per the above FSM test. Although the ingredients do not list graphite in the emulsion, it sure has the look of something like graphite when applied.

I tried PB Blaster & WD-40 in past years will little success...they loosen it up only briefly and then it got sticky....it needed servicing in weeks instead of months.

It's doubtful that the part number in my 65 FSM is available today so I didn't provide it.

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

There is no exhaust restriction created by the manifold heat control (or "heat riser") valve on a slant-6; the debate is whether it's necessary to apply heat to the intake manifold. There are opinions "yes" and "no", and there are varying levels of understanding of how the system works and why it's there, and the right answer also depends on the engine configuration and vehicle purpose. I don't mind saying I have a very complete and accurate understanding of how and why the system is there, and my opinion is that on a street-driven vehicle in any climate with a non-race engine, the heat riser should be in place and working correctly for best driveability and fuel economy.

The valve is pretty simple in its function: when its thermostatic coil spring is cold, the valve is rotated to the "heat on" position so that some of the exhaust is circulated past the underside of the intake manifold. This vapourises liquid fuel that would otherwise condense on the inside of the intake manifold. This need continues long after it would seem from outside that the engine is warmed up, because the fuel flowing through the carburetor and manifold exerts a cooling effect. Once things are well and truly heated up hot, the thermostatic coil spring relaxes and allows exhaust flow to push the valve into the "heat off" position, which deflects the exhaust away from the underside of the intake to keep from overheating it and causing hot driveability problems. The heat riser used through 1969 has a rectangular counterweight rather than the round disk you see on '70-up manifolds. The rectangular counterweight on the earlier system is eccentric; when the valve swings over to "heat off", the weight goes overcentre and keeps the valve in that position until the thermostatic spring cools down enough to swing it back to "heat on". The later round-disk type valve just uses exhaust flow to keep the valve in "heat off" until it's cold enough to rotate back to "heat on". The later valve tends to apply heat to the intake up to a higher underhood temperature than the early valve; this was done to improve driveability and reduce exhaust emissions and engine oil contamination from unburned gasoline. The later round-disk setup also has better bushings that seem less prone to seizing up.

The valve is not adjustable, but it requires periodic inspection and maintenance -- with the engine cold, grab the disc and give it a counterclockwise twist. It should rotate easily and spring back clockwise smartly. To keep it working smoothly (or to free it up if it's sticky), get a can of part number 4318 039AC from your Chrysler dealer -- it is not Liquid Wrench or anything of the sort -- shake it well and apply some to each end of the shaft, then rotate the shaft back and forth.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Actually, that is the Chrysler Materials Specification number. The part number (under which you order it from the parts counter) is 4318 039AC. It's certainly a strange brew; nothing else looks or smells (or, presumably, tastes) like it. The main sticking agent isn't rust, but exhaust deposits and carbon, and this stuff is specially formulated to dissolve those.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I agree with Dan unless I free one up,and it rattles,then I wire it open and forget about it.It does get down to low 40s in Cal.Dont know why it matters but if I lived in alot colder climents I would want it working correctly.Ask Kevin Johonson and I am sure he will explain the importance and workings better.Wilfred

In 1933 the Chrysler flatheads had heat risers and on most engines for more than 50 years.

Several generation of engine designers must have challenged it's function over that time as the Chrysler organization changed.

Add to that the number of cost cutting measures that must have been enacted as Chrysler went in an out of hard times.

Yet the heat riser concept survived. Might that be a hint at how important a funtion it serves while getting an engine up to operating temperature?

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

Label and price...it's possible "AC" is the Canadian version (w/bilingual labelling) and "AB" is still used in the States. The important part of the number is 4318 039, which has been the P/N for this stuff since the late '70s or so.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

This 1935 Jam Handy cartoon, "Down the Gasoline Trail", would be a real trip to watch even if it didn't contain a sequence at 5:37 specifically answering this question (and confirming Donpal's point) about the manifold heat.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

For several days my 1933 Plymouth Flathead six was stumbling & idling irratically during the warm up phase.

Finally one day I got a glimpse of the outside lower part of the carb with ice on it....on a hot summer day!

I checked the heat riser & it was stuck in the closed position.

After loosening it up the stumbling was eliminated during each successive warm up period.

I was convinced this was not a coincidence.

Expanding fluids suck heat from the surroundings and locally cool objects which might be part of the process described in the Jam Dandy 1935 cartoon as the gas/air mixture changes speed thru the venturi section of the carb?

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

I like Dan's technical explanation of the importance of a properly functioning heat riser in our beloved slants. Donpal's point is well taken also.
I liked that Jim Handy cartoon, cool stuff!

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"Ja, Ich fahre ein altes auto."
'78 Volare 225
'67 Charger 318

hi sages- i remember the part being called the heat riser butterfly in the 60s. they frequently got stuck and needed solvent and working to free them up. when they got stuck some would cock them half way so the butterfly would be in like a half choke position. both sl6s and 318s had them. they were a real pain in the keester in the 318s because if they got stuck or were weak and ran too cold. the crossover in the intake manifold would get clogged up with carbon deposits and prevent carberator heat from properly vaporizing the fuel. engine would hesitate badly especially when weather was cooler until the the running engine radiated enough heat through the steel, a very slow process. you had to take the 318 intake manifold off and rod out that passageway or boil it in solvent. dont remember having much problem with the sl6 though as long as the butterfly was properly maintained. sometimes the bimetal thermostat spring would break or come off and the riser would be noisy and non functional. led to occassional use of bad words. bf