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My heat riser is stuck in a position where the split for the spring is horizontal. Is this open or closed? What is the effect of this being stuck in this position? How can I free this up? Do I have to remove both manifolds, separate them and then access the valve?

I started squirting the ends of the shaft with PB Blaster tonight. I'll tap and twist tomorrow, then re-apply PB Blaster and repeat twice daily.

The weight should be hanging down when the valve is open. In addition to the PB Blaster you might also do a few GENTLE taps on the ends of the shaft to give a bit of shock along with the chemical. Just don't get carried away and break something. Sometimes you can free up the valve externally with these methods but if it has rusted so tightly those methods do not work then tearing the manifolds apart is probably what will be necessary.

Having the heat riser stay closed will result in overheating and probably burned valves. Having it stay open causes nothing problematic except maybe a slightly longer warm up if you live where it gets extremely cold. In more moderate climes you won't notice any difference and some have even wired theirs to stay open when springs or other parts were broken.

Take two small ball peens, one in each hand, and alternate blows left/right on the shaft till it begins to walk back and forth. After a while you will be able to rotate it. Do not tap the counterweight in an attempt to rotate the shaft. It will break almost immediately.

I think the weight is pointed toward the engine. Do you know the relative position of the valve to the split in the shaft?

If I take off the manifolds will either of them need to be machined? Will I have to replace the gaskets between the manifolds and the block, between the manifolds themselves, between the exhaust manifold and the exhaust pipe, elsewhere?

Be sure not to tap or or turn it by the weight because it is fragile and will break.

My heat riser now operates freely. The split in the end of the shaft is at about 1 o'clock when I lift the counter weight. When I release it, it travels to about 3 o'clock and bounces slightly. There is no spring. In the absence of a spring, is the heat riser not in the warm position? This would correspond to the spring being extended due to being at operating temperature. Why would this need to be wired in place?

As long as gravity can be counted on to keep the weight down it probably would not need wiring. The issue is since it has already stuck once, when -- and it will -- the carbon starts sticking the shaft and motion again something like a large bump or maybe even inertia from a turn could bounce or move the weight. If the shaft is sticking gravity might not pull it completely open again. Since without a spring it is not going to be functional anyway, the bit of wire to ensure it stays open is just insurance.

If you did want to restore function Kantor or Max should have the spring. The instructions for adjusting the tension are in the fuel and exhaust section of the 51-4 SM. The SM cautions against using oil as a lube for the shaft so I would work some dry graphite powder commonly used for lock cylinders into the area between the shaft and casting. Move the weight up and down as you squeeze the tube and blow the graphite into the space around the shaft.

HH56. I will restore the spring. I believe the shaft was stuck in the open position since there was no spring.

I have the "Packard Serviceman's Training Book". What other service manuals are available and from where?

BTW, where can I get a tach? Also, I assume the flash I'm getting from my 12V inductive timing light should be true.

The inductive timing light works fine on a 6v car IF you connect its power leads to a 12v battery. If you connect it to the 6v battery, the light may be damaged. Probably not but it's not worth the risk.

All the service manuals are available here as PDFs in the Literature and Manuals section.

When using my 12-volt timing light on a 6-volt car, I just power it from my 12-volt trickle charger, works perfectly.