First Gen Maniforld Valve Shaft

[Guest dwhiteside64]

Hi all,

I was looking at the general maintenance section of the 1964 service manual, and on page 1-4 there was mention of a "manifold valve shaft" lubrication. First off, what was this used for, and secondly, where is it located? Book says on the "right exhaust manifold".

Thanks

[Jim Cannon]

Yes.

It is now commonly called the "heat riser valve". It closes when the engine is cold. This puts back-pressure on the passenger side exhaust manifold, which forces hot exhaust gases from that side to cross over through the intake manifold to heat it up. This improves cold weather driveability by helping the fuel to vaporize better on the inside of the intake manifold and distribute more uniformly to all the cylinders. It opens as the exhaust manifold warms up.

It is a butterfly valve with a thermostatic coil spring and a weight in the passenger side exhaust manifold. Look up at it from below and you will see it. You can see it from above but I think it is easier to see from below.

They want you to lubricate the shaft ends with a graphite lube that can handle the heat.

If this valve rusts up and the shaft seizes, it will stick closed. This is bad. It forces all the exhaust through your intake manifold, even when the engine has warmed up. This cooks your carb, boils your fuel, makes your engine ping, and kills your performance. If you find this valve stuck shut, you want to open it or go in and cut the flapper out. (Warning: If you do, you will have poor cold weather driveability.)

Hope this helps.

[Guest dwhiteside64]

Thanks Jim for the great info. I will see if I can find it. Is there a way to test it without the engine running, or can you watch it open as the car warms up?

[Guest dwhiteside64]

By the way, can you recommend a lubricant for this device? Not sure what would work the best, as I don't want to make things worse by adding the wrong stuff!

[Jim Cannon]

To lubricate, spray shaft ends with a spray graphite lube. They sell one in a spray can where a liquid carrier evaporates and leaves the graphite behind.

You don't really need to do much more than confirm the weight swings freely and lubricate the shaft.

When the engine is cold, the spring should close the valve. You can turn the end against the spring on a cold engine and let go. It should spring back closed again. When the coil spring warms up it relaxes and the weight built into the end of the shaft pulls the valve open. So after confirming that it is working the way it should be when cold, go drive it for 20 minutes and come back and check it again. It should now be open. You can turn the weight on the end of the shaft and the weight should drop it open again.

Often you find the coil spring missing. They rust away and fall off, or a previous owner removed the spring. Then you have no problem, as the valve is open all the time. You might notice poor driveability in very cold weather, then. Lots of people drive them this way. It is better than driving it with the valve stuck shut.

[Guest dwhiteside64]

Thanks Jim for the added advice. I will check it and see what happens.