Whatsis Thingamajig Called Manifold Heat Control Valve?

[71_bronze_gtx]

Set about trying to change the spark plugs in my 71 440 the other day. What a PIA. Took me 2-1/2 hours. The last hour and a half on the plug just behind the manifold heat control valve, which blocks any reasonable approach to starting a new plug in. The thing seems to be disabled.

What is this device for? Part of the engine warmup system to channel exhaust gasses to the choke thermostat via backpressure?

It feels like the butterfly has been removed, and it rotates back and forth so easily that I'd bet the shaft seals are leaking and that's part of why I get asphyxiated in the car while it's running.

[JimT1971RR]

You are correct. It is supposed to be closed, or mostly closed, during warm up to send heated exhaust gases across the intake to aid it the warm up process. Personally, I have never had one that actually worked by the time I owned the car. One was stuck in the open position and the other didn't have the termostatic coil to open or close it.

That's why I run headers!

[Uppy]

The valve is supposed to have a clock spring on it, unfortunately they are usually broken or missing all together. The car is probably not your daily driver, I would remove the valve flapper and either put the shaft back in so it looks legit or remove all and have holes welded shut.

[71_bronze_gtx]

Hey JimT - what's it like changing plugs with headers? What headers are you using?

[71bird]

You know Chrysler had a solvent that you sprayed on the shaft to deep those things from freezing up.But after they already have its to late.

[JimT1971RR]

Hey JimT - what's it like changing plugs with headers? What headers are you using?

I am running Summit Racing branded headers on a 440. Changin the plugs themselves is not bad but getting the #s 5 & 6 boots on was a bit difficult. I have also experienced a problem with excessive heat against those two plug wire boots and have needed to frabricate a couple of heat shields. They weren't the easiest fitting headers in the world but very reasonable on price. I am also running a Summit 2 1/2" dual exhaust system as well.

[71_bronze_gtx]

You know Chrysler had a solvent that you sprayed on the shaft to deep those things from freezing up.But after they already have its to late.

Mine's not frozen - it's flappin' in the breeze. The hardware to anchor the outer end of the thermostat spring is MIA, or maybe the end of the spring is MIA - didn't really look it over. The valve itself might have been removed.

My buddies told me they have just removed the whole assembly and then drill / tap for 1/8" pipe plugs. If I ever take that manifold off..................