Looking at the riser control control from the front of the engine, is it open when turned clockwise and closed when turned counter-clockwise? Mine seems a little balky, and there is no spring tension in either direction.

Clockwise: Heat on.
Counterclockwise: Heat off.

When cold, should be spring loaded into the "heat on" position. Give it a few shots of Mopar manifold heat control valve solvent p/n 4318039 (renamed "rust penetrant" and probably now superseded to a new P/N). This stuff is not the same as liquid wrench or any other regular penetrant.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks Dan. It was too stuck to figure out which way was open.

How much is it supposed to move?????????


Mine's not stuck, but seems to float somewhere in between (this was after about 15 minutes city driving/idling with outside temp about 65)

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

A little over 90°.

!!!!!!!!!!!!!!!
Possible broken thermo spring

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

It does move 90 degrees (did try with my fingers when it was hot)


Spring isn't broken, and is currently holding the valve fully clockwise.

When valve was floating, the spring was also away from the stop.

When revving the engine, the valve did move more counter-clockwise.


Looks like the valve opens with exhaust flow and the counterweight. The spring then closes it when the spring is cold. I previously thought the spring would open it up too.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

The spring never forces the valve into the heat-off position; that's the counterweight's job. The early (pre-'71, rectangular) counterweights will hold the valve in heat-off once it's warmed up. The later ('71-up, round) counterweights will float, tending towards heat-on at idle even when the engine is hot.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Hmmmmmmmm..... mine's definitely square, but it floats.....

I did just find this in the manual:

"With the engine idling, accelerate momentarily to wide open throttle. The counterweight should respond by moving counterclockwise approximately 1/2-inch and return to its original position."

Which makes me believe they should all float.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

That applies when the thermo spring is cold and still loading the counterweight into "heat on". Once the thermo spring is hot, the counterweight should be in "heat off" and stay there—not float—on the pre-'71 manifolds.

Note that over time, the thermo spring can lose its thermal sensitivity so it fails to uncoil/relax with heat.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

The spring was relaxed and the end was about 1 inch from the the stop. I could move the valve open more until the spring touched the stop, then keep pushing until valve movement stopped altogether.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I have this stuff:
http://pacbrake.chargedmultimedia.com/c ... 2a02aa147c

Do you think it would be a good idea for the heat riser thing?

I would think they are for somewhat similar conditions

Never heard of it, never used it...I like the Mopar 4318039 stuff.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Ok with engine really warmed up, valve is fully counterclockwise.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Anybody tried grinding the round counterweight to hold it heat-off when hot? Once the engine is warmed up, I don't see the point of idling heat-on.

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1970 four-door Dart, 225/A-904/2.45 gears. 0-60 in twenty three minutes!

I've thought of that very idea, taking a chunk out of the round counterweight to make it work like the old rectangular one. It'd take either cutting apart some round counterweights, testing the spring tension of the thermo spring, and making weight calculations to figure out how much to grind away so it'd work in both directions. If you get this wrong, either the valve won't stay in heat-off when hot, or it won't return to heat-on when cold.

The point of heat-on-at-idle was to pass Federal emission certification tests.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.