I recently re-did my manifolds and discovered my heat riser valve plate had seized. I freed it up and lubed it before re-assembly and made sure it was moving after the install. I checked the other day and discovered it in the on position (diverting exhaust to the hot spot) even though the engine was hot. I checked again several times and always found it in this position. The plate is still free, so I know it hasn't seized again. I suspect the bi-metal spring is toast. I have had problems locating a replacement. Is there a source for this part I am unaware of, or could my problem be something else? The car runs well otherwise, but I'd like to address this problem ASAP. Any help would be appreciated.

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

That's odd. If the shaft is loose, the exhaust flow should tend to blow the valve in the "closed", "no heat" position, even if the bimetal spring is broken or missing. How about the "stops"? Are they still present or has one or both rusted and fallen off? It is possible for the exhaust to blow the valve upside-down if they are missing or bent.

D/W

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If it ain't broke, fix it!

Interesting. Are you working with an early (rectangular counterweight) or late (round counterweight) exhaust manifold?

It's a later manifold (Round counterweight) It still has the stpos present and I checked to make sure they were set properly before re-installing the manifold. I wonder if the spring may have been installed backwards by the last owner/ previous mechanic? I'll admit I don't know how to tell if this is the case. On an unrelated topic, I think I have a coolant leak into the exhaust manifold. I'm getting spray out of the tail-pipe when I first start it up and noticed a low level in my rad. I guess I didn't get a good enough seal when I replaced the bolts on my manifold. Can I remove and replace the bolts without re-doing the manifold? Or would I have to re-do and re-gasket the whole thing. I used metallic anti-seize on all the threads, but I don't know if that's sufficient to stop the flow of coolant into my manifold. Can you suggest another reason I'd be getting water out of my exhaust? The car was sitting for about 4 hours after a 50 mile jaunt when I re-started it to check my idle. I noticed a wet spray pattern on the driveway and promptly checked my rad only to find a slightly low level of coolant. Anyone ever had this problem before?

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

Some of the round-counterweight heat risers remain spring-loaded (albeit lightly) into the "heat on" position until they get well and truly HOT, much hotter than the older rectangular-counterweight valves needed to get. It seems possible that some of them might be set up to provide "heat on" and "less heat on" modes at idle for emission control reasons, rather than the expected "heat on" and "heat off".

Though I've never tried it, I've played with the idea of cutting a chunk out of the round counterweight to make it into more of a counterweight which, like the older rectangular items, would actually go overcenter and use gravity to hold the valve in the "heat off" position once the bimetal spring's tension relaxed enough not to yank it back to "heat on".

Also, check the article section on manifold mounting

http://www.slantsix.org/articles/manifo ... unting.htm

If you use a 70 or older manifold you should trim the center out of the metal gasket so the "flapper" doesn't hang up on it

Should have read 70 or newer?

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Oldsarge

1964 Dart 170, Some work done, lots more to come!

Nope, the article reads correctly. The later heat riser shaft (and therefore valve) is positioned slightly lower within the manifold casting, so the valve plate's edge doesn't have a tendency to hang up on the center bar of the late-type manifold-to-manifold gasket.

NewSlanter, sorry, I forgot to comment on your coolant-loss/spray issue.

The manifold-to-head studs do seal a coolant passage, so they need to be sealed into the head. Anti-seize is perfect on the external threads (where the washers and nuts go) but on the internal threads into the head, you need thread sealant. See Here.

Spraying out the tailpipe (steam and dripping water) is normal when the ambient temperature is below about 65°F and you first start up. if the steam has a sweet "burned antifreeze" smell to it, though, then that's not normal. It would be very difficult for coolant to leak past the manifold stud threads *and into the exhaust manifold*; it would take an extremely poor manifold-to-head gasket seal, and you'd have a very noisy exhaust leak up front and probably some severe vacuum leaks from poor seals on the intake side.

The valves are counterweighted to hold them lightly closed at idle speed or engine off. If you blip the throttle open with engine running you should see the valve go to the other position and then return as engine comes back to idle speed. The newer round counterweight style seems to take a bit more exhaust flow to push it open.

I know my manifold re-seal was successful as I don't have any leaks in that regard, but nevertheless, I'm losing coolant (no drips on the driveway -save a minor oil leak) and saw spray from the tailpipe. I also don't see any tracks from a coolant leak on the side of my block (my engine is dirty. So sue me). I have noticed a bit of a rough idle and a tendency to want to stall when idling in gear when hot. I attributed this to the fact I cracked my carb base during the re-installation, but I'm starting to have doubts. I know I had a *major* vacuum leak before and didn't notice this effect and now I have a relatively small vacuum leak and am having this problem.

P.S. Thank you all for your incredibly prompt responses. I'm so glad I found this site!


Oh, and Dan; 65 degF? Aren't we both Canadian? What's that in degC?

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

Well, yeah, a cracked carb base will spoil things. What kind of setup are you working on? Model, year, engine, stock or modified, carb type?
Ummmm....hang on, I know this one...*scratching pencil sounds* Ah. Here we go. 65°F is 42 litres.

I drive a 1970 Dart four door. Engine is stock 225, Holley 1920 carb, points-type ignition. It's no show-piece, but it gets me there.

42 litres? what's that in cubits?

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

Cool, the '70 4-door is one of my favourite Darts. I wish we lived in BC rather than salty, car-hostile ON, but my other half is a lifelong Ontarian and very reluctant to change that. Me, I've lived in the pacific Northwest, so I know what I'm missing. Perhaps we need to visit, maybe that'll help me make my point...

Well, there's no salt, but man does it rain. Now that it's spring I can tackle that wiper leak I found during one of our classic mid-winter downpours.

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

Rain? Man, I *love* rain. They don't throw salt on the roads when it rains. Rain constantly washes things like old cars so they don't rust near as fast as they do where lack of rain causes dirt and crud to build up. Rain keeps everything green even through the winter. And best of all, you don't have to shovel rain.

(Besides, y'all got effective antidotes to rain. Strong local coffee, strong local beer, and stuff.)