Packard Forum Index » Post-War (1946-54)

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I would agree except for extra insurance I would still make sure it stays down.

Heat riser valves usually get stuck because of rust or corrosion around the shaft. If enough of a jarring action or even centrifugal force overcame gravity and caused the weight to bounce or move upward enough to close the valve, if the shaft is partially sticking and another jolt does not come along soon enough to help it move, the weight alone might not be heavy enough for gravity to bring it far enough down again to fully open the valve.

A partially closed heat riser valve can still result in overheating and burned exhaust valves so a piece of wire is cheap insurance that even an unlikely scenario of a jolt closing the valve won't happen.

How readily available are the springs for the heat riser valve? The inside tip of mine broke off, but I can bend it and it will still work. I can get another without too much trouble I'll replace it. I'm guessing most any heat riser valve spring will work, is that true?

Merritt has them new.

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You can just leave it broken if you don't care about the car taking a little longer to warm up.

I might have a spare spring lying around.

I do know there is a specific tension involved in order to make the valve open or close properly.because some of the SM instructions have you shorten or lengthen where the fixed end point to the spring is fastened to change tension or else they tell you to position the center of the spring so when the fixed end is fastened the number of coils it uses is tighter or looser .

The Packard item is probably based on an inexpensive universal spring stock where you could pick up something from multiple make vendors it you can match thickness and width but while there is no mention of NOS or repro, Max Merritt lists having the correct spring for almost all models

Having the heat valve working is more important on inline engines since the intake manifolds get less engine heat than a typical V-type engine. The Packard will run better and the automatic choke can function correctly if the manifold heat system is working correctly. A lack of manifold heat or insufficient heat can lead to delayed choke opening, idle circuit freeze-up, poor drive-ability, hesitation on opening the throttle, and poor fuel mileage. Adverse effects will be more severe in cool, damp weather and cold weather, but it's best to have the system working as it should all year long.

"A partially closed heat riser valve can still result in overheating and burned exhaust valves..."

True... and I'd add cracked manifolds, burned out manifold gaskets, carburetor flooding, and poor performance. If you have to choose between open or shut, wire it OPEN, but it best to have it working as it should.

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100%

I would never run without a functioning heat riser valve. The spring on my heat riser valve had come unhooked once, and start up was terrible. Not to mention, who wants to start up their car, especially in public, and listen to it struggling until it warms up. There will be no balancing a coin on that engine! :LOL:

I've seen white frost form on the outside of the carburetor throttle plate area in cool damp weather. It can form on the inside, too, and cause poor idle and hesitation on accelerating.
This can happen at ambient temperatures far above freezing. At light throttle operation, the carburetor can act like an air conditioner due to evaporating fuel and due to air expanding into the low manifold pressure. The carburetor throttle plate area can get surprisingly cold.

I have a spring from a broken exhaust heat riser valve. You can have for the cost of shipping, unless you’re going to up in this neck of the woods? Tariff free
It’s off my 56

I'll let you know! I might just grab one from Pete's.