WHAT IS THIS FOR
 

I just found some sort of thermostatic valve that passes thru the passenger side exh. manifold just above the flange. It has some type of heat actuated coil and a lever on the other side. There is no spring tension so I dont think it is connected properly
Thanks

I think it is for faster warm-up of the engine. Remember there is a exhaust crossover under the carb on the intake manifold. This valve restricts the flow of exhaust out that side and forces it to go through the crossover. The spring relaxs like the cookstove spring for the choke when it get hot and opens up the valve plate. High exhaust pressure is also able to overcome the spring when driving.
Mike

This one seems to be shot. Are there replacements available? Or is there some sort of retainer for the spring ?
Thanks for the quick reply Dawg

Most guys just pull it out and either weld up the holes, or tap them out and plug them. These things are notorious for freezing up. That's probably why they dropped them in '69 (if I remember correctly).

It is to divert hot exhaust to open the choke more quickly. if removed the choke will stay closed longer and may cause the car to load up. It does make the hot exhaust go through the intake manifold.

Anyone have a detailed pic or digram of how the coil mounts? Looks like a slit in the end where the coil mounts near a small stud that it may hook on. Does the coil need to be preloaded and, if so, how many turns ? Also found a small retainer.
Thanks

the flapper valves were used much longer than up to 69.

The 77 engine I just got has one.

67 was the last year. 68-74 didn't use them, must have brought it back by 77. The spring was tensioned against a pressed in pin on the side of the manifold that rusts off. I think they're making repro pins if you don't want to use a nail.

must have, since it is there and is original and has a vacuum actuator.

The ones they are talking about from the '60s had no vacuum actuators. It was strictly a bi-metal or similar spring with a counterweight. When the spring got hot enough, it expanded to open the valve and allow the gasses to pass out of the exhaust rather than up through the intake crossover.
They were kind of bothersome and everybody just hoped when it froze, it would be in the open position.

Isn't that thing called a heat riser valve? They are notorious for rusting shut, at the station I worked at in the 70's the mechanic would weld them open or take them off and put in hand operated choke kits.

My 70 Lemans has the one without the vacuum actuator and it's all stock.

That's what I've always called them. I've had to replace a few over the years, usually the muffler shop has them in stock.