VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 Heat Control Valve

Seems like with good modern gasoline, one might not need the heat control valve on the manifold.
Does everybody keep them working, or block them off?

Wilson,
On the 35 std I've been working on the heat control valve was locked up tighter than a drum. The spring and heat coil were bad and in removing the exhaust manifold we broke a couple bolts (thats another story). In trying to loosen up the damper all we accomplished was to loosen up the rivets holding it to the shaft it pivots with. Now that it was loose on the shaft we had to get the shaft to move (and retighten the rivets) or remove the damper. The shaft had become like one with the housing and it didn't seem like it was going to free up. Thought we would try to run the engine without the damper in place so I drilled out the rivets and removed the damper plate and so far we haven't noticed a problem. My understanding is that the purpose of it is so that your exhaust gases will warm up your fuel mixture sooner for cold weather running. Once everything is warm the damper pivots to give it a straighter shot to the exhaust pipe and once everything is warm I'm not sure if it is actually necessary anyways. Maybe some of the other guys can respond to this and give their input......Bill

You may find that the intake maniold will get a little too hot and may have some problems with loss of power. It's not that hard to make a new shaft after drilling out the exhaust manifold.

35,
That's a good observation and one I didn't figure on when removing the plate in mine. If the intake gets too hot you might have problems but so far we haven't. We even had the car in the 4th of July parade here on a hot KY day, just creeping along, stop and go, and standing still for probably 1 and 1/2 hours. While the temperature gage ran slightly hotter, we had no problems with the car. Maybe we are very fortunate considering the damper plate is removed. Advise to Wilson is: if at all possible restore or fix it the way it was meant to be. Those Chevy engineers had a reason for it, we should try, if possible, to make it correct.....Bill

Well, I'm sure I can fix it, but am considering blocking the opening with a piece of metal. I'd start a little cold, but temps here are moderate and this ain't a snow truck anyway! Some heat might breal the shaft loose, or of course it can be drilled out.

This is an interesting thread. I had 3 or 4 manifolds and all of them had the heat control valve rusted and seized. I was unsuccessful in getting any of the freed up, so I used it "as is". Upon first starting the engine runs a little rough for a minute or two, then as things warm up she smooths out. I do have a bit of an overheating issue, but I think that's more a function of radiator blockage or crud in the block than from a warm intake manifold. If my soon to be installed NOS radiator doesn't cure the issue then I may look at rebuilding the control flapper.
I'd like to hear in more detail how to make repairs to this item!

Coach

I would not leave it open (hot), which will limit power and efficiency. If it's stuck closed, I'd sure consider leaving it alone. I'm thinking some sheet metal and an extra gasket could be used to make a permanent block.

Wilson:
I honestly don't remember what position the valve is stuck in! I went back to my old reference book and read up on the operation of the manifold heater. I suspect that since my engine runs a little rough when cold, but fine when warm, that the valve is frozen in the closed position. The purpose of the valve is to assist in fuel vaporization when the engine is cold.

Part of my planned Spring updating is to sandblast and paint the exhaust manifold, so I'll check the heater valve then.

Coach

My flap was rusted to nothing. Shaft yielded to WD-40 and hammer impacts, but came out in two pieces. I had a new shaft and plate made from stainless steel. Bimetal was ok. Had to tack weld washer on end of shaft to maintain location so plate would not rub on inside of manifold.

All engines run better with a well operating heat riser valve. When they are stuck closed is when the intake can get too warm. When they are stuck open, the engine runs cooler longer and wastes gas. When they work well, they pass some heat to the carb even when the engine is at operating temp. Some heat is needed as the carb can get too cool when running at highway speeds and waste fuel. It won't show on the temp guage so much, but will still waste fuel....

Hi Guys,
Is anyone still reading this thread?
I just saw Bill B's great picture collection. It shows '31-32s with the heat valve on a pushpull cable from the dash! Good idea. One could experiment with the setting and choose what's best for the season. I may do this to my truck.

In 1932 the cable for the manifold heat control valve was used, not 1931. 1931 had an updraft carburetor (1932 was the first year for a downdraft carburetor) therefore, no manifold heat control valve was used.

Yep, I imagined the '31 part.
Here's the definitive shot:
http://1932chevrolet.com/photogallery/roadster/32chevy12.jpg

I've been looking through this old thread to get some hints about repairing the exhaust manifold heat riser in my 36 Master. I know most people either leave them seized in the open position, or remove them completely. But I'm going to attempt to restore it to working condition. Mine is seized, and I managed to pop off the plate from the rivets. I'll have to redo that part. Also, I have a NORS thermostatic spring.

My question is this: How is the shaft mounted in the exhaust manifold? Are there bushings that it turns on? I've seen some repair kits from that era for Packard that include a new shaft and spring, but have replacement bushings. Did the original have bushings? If so, wouldn't there be an exhaust leak through the space between the shaft and the bushings?

I'm hoping I can drill out the old shaft, and use one of the repair kits from other models with the bushings. I've got a spare exhaust manifold, just in case I mess this one up. Any advice would be appreciated.

Hi Randy,

On my 33 OD truck there were no bushings in the manifold for the heat riser valve. I had to drill out the remnants of the original shaft, then made an oversize stainless steel shaft to the size of the new hole, So far has worked just fine. There was evidence of slight leaking around the shaft at first, but it seems to have sealed itself off with use.

Once the valves are repaired, and kept away from moisture they should never seize up again, but I am wondering if anyone has used any preventative maintenance once repaired. A drop of oil perhaps? Or some other lubricant that can withstand exhaust temps?

jozeppi I can make you a new stainless steel shaft for a small fee; e-mail me. The shaft did not have any bushings but there is a washer on both sides of the manifold on the thermostatic spring side and a single washer on on the inside of the housing casting on the weight side. You can use stainless steel pop rivet to re-attach the valve plate to the shaft.

A new stainless steel shaft would be great. The bushings that they use in the Packard repair kit are brass, and I just can't imagine that brass would respond well to the huge fluctuations in temperature. Send me an email to: nudor@aol.com with specifics.
Randy

Randy,

I just went through the same process with the heat riser shaft on my 33. I sent you an email with photo's.

Mark

Mark--Could you send me those photos also, as I am restoring a 33 Master and mine is froze up also.

hoppy
rhop1@sbcglobal.net

Mark,
Thanks for the offer to send the pictures. I haven't received them yet, but I'll keep an eye out for them.

Sorry, I haven't been online in awhile. I just re-sent the pictures and included n2chev's email address. Let me know if you do/don't receive them.

Mark--I really want to thank you for sending all the pictures and explaining in detail about how this was done.

hoppy

A mate of mine had a 1938 Business Coupe that came from New Zealand,and it had a pronounced exhaust leak from between the heat control valve shaft and the exhaust manifold.
After taking off the manifold,we found the valve plate itself
was in real good order,we just had to figure out how to eliminate
the leak.
After marking the position of the plate in relation to the pin that retains the bi-metallic spring,I drilled out the spot welds holding the plate to the shaft.The shaft & the manifold were both badly worn,so I set the manifold up on the milling machine table,and put a cutter through that was 7/16" in diameter.
I then made 2 cast iron bushes as it would expand and contract at the same rate as the manifold.A new shaft was made out of high tensile high temperature stainless steel.The shaft &
valve plate were then "timed" to the pin for the bi-metallic spring,and a couple of spots with the mig had the valve plate fixed to the shaft securely.
I then hooked up the bi-metallic spring and checked to make sure it hold the plate in the "on" position when the engine was cold,and used a hot air gun to heat the spring up,and watched to make sure it gradually opened up as it heated up,which it did.
Then I liberally applied a chain & wire rope spray lube that contained a lot of graphite & moly-disulphide anti seize compounds,and problem solved.
No more exhaust leak,and a working heat control valve.

:)