Packard Forum Index » V-8 (1955-56)

So on the V8's there's a valve on the driver side exhaust manifold that's supposed to open when the car is warm. Before it opens, the driver side exhaust is directed thru the center manifold passage. Went for about a 10 min drive yesterday and there was still about 2-3x the amount of exhaust coming from the right tailpipe as the left.

Was peeking around and it's hard to see where this valve is. What's a good way to work it to make sure it's not sticking?

Also the center manifold passage looks like it's had some heat in the past, so I definitely want to fix this issue.

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The valve is a small inline assembly located at the bottom of the left manifold between the manifold outlet and flange connected to the left exhaust pipe (or crossover pipe if a single exhaust). It is held in place by the bolts fastening the exhaust pipe to the manifold. There is a weight on the assembly that when cold is held in the up position by the thermostatic spring. When warm and the spring relaxes, the weight will drop down opening the flapper that would have been blocking the exhaust exit to the pipe thus letting the exhaust move thru the pipe rather than the intake manifold passage.

You should be able to move the weight freely by hand with minimal resistance other than maybe light spring tension. Any sticking or roughness should be freed and is what coud be causing it to stick. If you need to free the valve do so but do not use any oil to lubricate. the shaft. There is a procedure in the service manuals and suggested lubrication. If freeing is not possible the only option is replacement or if in a moderate winter climate, wire it open or leave it out entirely. In moderate climates warm up time will be slightly affected with it open but there will be no driveability issues. Heavy winter climate and you might want to fix it.

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Thanks Howard. Now that I think of it, this car seems to have been undercoated in the past so much of the original parts under the car are coated in black goo. For example, this was quite an annoyance when trying to repair the power antenna. So if that thing doesn't have a cover on it I bet some of that goo is jamming it up at the very least.

It's a typical manifold heat valve. As said, it's sandwiched between the exhaust manifold and the pipe at the flange on the driver's side.

The weight on the crank arm pulls the valve open by gravity when the valve heats up enough for the bi-metallic spring to loose tension. The spring pulls the valve shut when it's cold. It needs to move freely.

NEVER USE OIL! It will carbonize on the shaft and stick the valve. Use graphite lock lubricant, which is nothing more than powdered graphite suspended in solvent. Spray the shaft and work the valve back and forth. This is normal maintenance every few thousand miles.

If it's rusted trying to force it without a penetrant might break it. I had an old Ford and freed the thing up using penetrating oil and no problems afterward.

When the car has dual exhaust and a stuck open or missing riser, I used to stick a rag in one side and let the car warm up that way. Drive a few miles and take the rag out.