VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 manifold heat valve

we have a question about the manifold heat valve, which is stuck...

can anyone tell us, by the orientation of the slot for the anti-rattle spring, whether it's stuck in the open or closed position?..

thanks,


epi

Its best described by the position of the "weight" at the front of the manifold.If the flat portion of the D is horizontal the heat riser is in the cold position.OK for warm-up but NG for extended driving.After thermostatic spring warms up the exhaust pressure will tilt the weight to the tilted position.The large clock type spring is not an anti-rattle spring but it is incorrectly described that way in the parts book.Its a heat controlled thermostatic device

Gene,

Thanks. I've been meaning to ask that question and the shop manual is not clear on the orientation. Apparently mine was frozen in the "cold" position (why not. it spent most of it's life in Minnesota and Iowa). With the aid of profuse amounts of PB Blaster and much 'horizontal' hammering, I've managed to get it to about a 45 degree angle from horizontal. So could you tell me what the upper limit position is before I go too far? We don't need no "steenking cold setting" down here and I have despaired of ever freeing it up entirely.

Doc

Doc, don't give up on freeing the heat rizer valve, once you get it moveing you are half way home, tapping on the shaft on both sides and also working it up and down usually work wonders even with those that appear hopeless!

...been there done that.... it is nice when the manifold is off the engine...then you can see how far the flapper should move!

As MrMack says keep trying--but 45 Degrees is about as far as it goes to the hot position.

gene & mrmack,

thanks...doc beat me to the next question...

how much lateral movement along the shaft is normal, or, how far/hard can I pound on the shaft before doing damage to the internal flapper?..


epi

Hey Chev Nut: What is the heat control valve "thermostat"? The parts books lists that and also the anti-rattle spring. Isn't the "thermostat" the coiled spring that opens and closes the heat control valve? :confused: :confused:

The flapper inside moves approx. 90 degrees.

There is a mechanical stop built into the weight. It comes to rest (bidirectional) against a stainless steel pin externally pertruding on the heat riser.

GM has an excellent lubricant which I highly recommend to restore the effectiveness of that valve.

The spring is made of a bi-metal construction. Since the different metals expand and contract at different temperatures, the coils will relax and tighten as the temperature changes. This action opens and closes the flapper. The spring in the open position also keeps the flapper from rattling. This is the same type of action as an automatic choke spring found on later made cars.

The thermostatic spring-part number 838573 group 3.640 is just that.It covers 1937-62 6 cyl. engines.The anti-rattle spring part # 602799 is smaller and slides on after the thermo. spring.It is described in the 1941 parts book as "to prevent rattle of exhaust manifold therm."..It keeps a little tension on the weight..I don't recall them as being installed from the factory.It probably was a factory fix that could be purchased if the heat riser rattled.By the part number I would guess that it came out in 1938 after they were recieving complaints of rattling.I do remember of having them in stock but the heat risers were usually "stuck" so they were silent.Has any one ever seen on on their '37-'62???....It would appear as a little helper spring.

I don't have either of my 6's home right now to check the angle.Will be going over to Michigan on Monday to pick up my '50.It has been there since my disastrous trip to N.J. in the beginning of Sept.

I disagree also that the heat riser turns 90 degrees on a 6...don't force it that far or the valve will break loose from the shaft.

Hey Chev Nut: Thanks for the reply. That's about what I thought since I have both the new old stock thermostat springs and the anti-rattle springs in stock. The parts book was a little vague on these two springs, so thanks for the confirmation.

By the way, the heat riser on my '51 Chevy only goes to the 45 degree position also........just like it should.

:cool2:

And remember old parts books never lie--only old parts men do

And so does the one on my 53 (45*)and also the one on a spare manifold that I freed up the hear rizer on a couple of years ago. I worked on that one for a half hour a day for several days, thank God for PB Blaster and a brass hammer and vise grips.

Hey, thanks all you guys. I guess that if a 45 degree angle is the max, I've already opened the sucker and I am well leaving it there until I can find a 54 or so 235 engine. My original 216 already has 76,000 on it and I am hearing some pretty heavy babbit sounds.

Doc

gene,

thanks for the info...it's all a lot clearer in my mind, now...

the '40 shop manual shows two excellent sectional views of the heat valve open & closed...as already confirmed here, the valve moves about 45 degrees to function correctly...

and ours is stuck in the cold position...we now have a better idea as to what to hammer to free ours up...

obviously (per another thread), we still have a problem with the carburetor, but this can't be helping...still, until last week, the truck ran pretty good...

thanks again,


epi

With the manifolds off, some dudes have also had success in freeing up the heat control valve by gently heating the shaft with an acetylene torch and letting it cool.

it's pretty stuck...something tells us we shouldn't grab the counterweight & twist to try to free the shaft, huh?..


epi

No! Don't just twist the counterweight. Mine was so rusted that even after heating it red hot and cooling, etc. it wouldn't budge. Trying to free it, I twisted it, and broke the weld to the inside plate.

You also need to be careful not to mushroom the spring end. I've found after a couple of these now, that its best to remove it so you can get the torch heat to the inside and see what you're doing. Then it can be painted too - so it'll look pretty *and* work. :cool2:

jim,

thanks for the warning...guess we'll pull the manifold off when we have some time...


epi

You can also go to a Chrysler dealer (incl.Jeep) and buy a can of Mopar rust penetrant - part number # 04318039. It has graphite in it and seems to work good for the riser.

When using a penetrant you are applying it to only one side of the casting when the manifold is on the car.To reach the "inside" dump a good amount of Marvel Mystery oil or ATF thru the carb. with the engine running.Do when engine is cold so it dosen't burn off the cast iron.This will lube the inner part of the shaft.Let it stand over night and soak.

Gene,

Thanks. I'm going to try your suggestion one more time. The ATF Fluid trick worked on the wipers, etc., so why not try it here.

For all you other guys, ATF fluid has additives for almost every purpose - seal swelling, friction modifiers, etc,. etc,.

Doc

gene,

we're a little confused about pouring the oil in the carb, as we thought that the frozen heat valve shaft is in a different chamber below the intake manifold...we were thinking that the exhaust flow, when diverted to heat the intake, was directed around the intake "tube" below the carburetor and that the exhaust gases & intake would never mix...if so, how does the oil get from inside the carburetor to the inside of the exhaust manifold where the heat valve & shaft are?..


epi

gene,

oh!..do you mean we pour enough into the cold engine that a certain amount gets pumped out through the exhaust valve into the exhaust manifold, thus lubricating the shaft?..


epi

The anti-rattle spring was 1st mentioned and pictured in a service bulletin dated December 1937. I found this out after being deducted points for not having one on my 1937. The "judge" assumed it should be the same as his 1939. He was wrong.

The bulletin also mentions what the Heat On or Off position is and how much play or adustment is required when the anti-rattle spring is installed.