I reported earlier about my Dart warming up, and then losing idle. It really happens after I stop at a store, and then come out and start it. And only in 90 degree plus weather. So as suggested, I did the fuel line swap, to a rubber hose. I like that much better. Now, since that didn't help, step two. Checking out the heat riser valve, I see something with cloth that stops at a stop. And it moves back and forth easily. My question is, which way is open, and which way is closed? As well as what makes it open and close? The reason for asking that is, warmed up or cold it typically sits on the stop, and doesn't move. I think with this, I found the reason for the idle problem. But need some advice on this valve. Thanks.

As you stand at the front of the engine bay and look at the valve, full-clockwise is "heat on", and full-counterclockwise is "heat off". If it's staying against the stop when the engine's warm, your thermostatic spring has lost its thermostaticity.

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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 is staying on Heat On. So now I know what is causing the problem. The Spring you are talking about, I am not sure about. I put my finger back there, and feel something round and flat, kind of like a spring. So how would I fix this? Is it easy? Or do I just move it over to Heat Off, since this is now getting hotter here in the Sacramento area?

Oh yeah, when I tried to look at this, I noticed sometimes when I put it to the Heat Off spot, it would spring back to Heat On. Other times, it will get stuck. So for sure, I know this is a problem. I am getting a super six carb put on this later this summer. I am thinking at that time, might be the best time to fix this. I don't drive it enough to worry about it. And just driving in the morning, no problems.

That's two different problems. Getting stuck usually means it's time to apply some Mopar solvent P/N 4318039AB to both ends of the shaft, and check that the guide spring is in place (runs from a fixed pin to the end of the shaft on the rear wall of the exhaust manifold's collector area). "Returns to heat-on by itself" means somebody screwed up the assembly and has somehow got the spring backwards!

There are detailed diagrams of how to put this together in the factory service manual...

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

As somebody suggested when I had a similar question, try this; When the engine is hot, put the car in park, open up the hood and check the position of the valve. Then, with the engine running, pull the throttle cable and see if it rotates to the "heat-off" position. It seems some of these are designed to return to "heat-on" while at idle.

Nat

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

That is only true of some of the '71-up units with the round counterweight.

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

Okay, so tonight I turn the thing counterclock all the way, and it sticks. I drove it a couple miles, parked it, and after 5 minutes, started it up, and even with that with Heat Off, the problem stayed there. Ah, you know what I think now. The valve is messed up inside there. Okay, so I have a buddy who just bought a Demon and told me I can have his Slant Six, as he is putting in a V8. Thus, he told me when we install that super six, he will replace that at the same time. What we are waiting on for the super six, is getting it setup on his Demon, to make sure it works fine, before putting in on my Dart. So thanks for you help. And I think I can live with this until we get that super six stuff in there. I could probably lift the carb, and see what is going on down there. But I think waiting for my buddy who knows what he is doing better than I, is the best idea. If that for some reason doesn't stop it, you will hear back from me.

Careful, Demons were only sold '71-'72, and all the '70-'72 slant-6s have a special exhaust manifold with respect to the choke. The arrangement is different (open stove w/stainless steel cup and impossible-to-find gasket instead of a simple well cast into the #5 runner) and the '70-'72 style is not compatible with the 2bbl choke. You can get the electric choke package, but you'll still face the gasket problem. Is this Demon engine a 198 or a 225? What's the VIN of the Demon?

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