Choke Thermostat

Tech Question


Bill Secules, Philadelphia PA, 1971 Plymouth Satellite Sebring Plus 383

Hi Rick, I’m a first time writer, long time reader! I havesome questions about choke thermostats. I’ve never really seen theirfunction explained, unless you’ve done it already when I was napping.

My ’71 Satellite Sebring Plus came equipped with a 383 2 barrel, and I want to swap a more or less factory 4 barrel (Holley) on. I have the carb, manifold,gaskets, what I think will work for linkage, etc.- all gotten on the cheap,and I want to keep it that way, since I now have Triplets! I want to use aregular choke thermostat rather than go to an electric choke. They are nolonger available as service replacements anywhere, and NOS pieces for theapplication (69-72 383-440 with Holley 4 bbl) have gotten very expensive.I’m not concerned about strict originality, I just want it to work the wayit did when it was new.

If I got a less expensive 2 barrel, 6 barrel orCarter piece and modified the linkage to fit, would it function the way Ineed it to, or are all of these different applications really that specificin function (different springs, rates, etc.)? The Holley set-up seems likeit has a shorter link than the Carter set-up, so it looks easy enough to dothis on the surface (cut it & bend it to mate up to the Holley). I can’timagine that they differ so much except for the way that the link fits thecarb, but I really just don’t know for sure.

The car will be a 3-seasonoccasional driver – no winter driving for the forseeable future. What do youthink?

BTW- whatever happened to your ’72 Road Runner project car?



This could be expanded to at least 50 pages. So, brief facts will have tosuffice. Here goes…

First: Quite a few of the thermostats are being re-pop’d, look around.

The basic principle: As the engine warms, and vaporization is easier / morecomplete, the choke opens, leaning the mixture. In warm weather, coldengine, the choke should just barely close fully, then adjust the diaphragmto immediately open the max that the engine can “take” as soon as it starts.Over-rich is really a major problem – fuel wash, carboning up, etc.

All thermostats from that era are very similar. Later ones used athermal-switch activated electric assist, which assured that the choke wouldopen quicker in warmer ambients; some were even 2-step. (Requires differentmanifold). Also the stainless cup style reacted more quickly.

Some had an adjustment which basically adjusted the spring tension. In the’50s / early ’60s, you were even supposed to disassemble and change thesetting summer/winter.

Electric-only chokes are lousy. Hand chokes, w/skilled driver — the best.

You didn’t ask, but, if it were mine, I’d sure use a late-’60s Carter AVSsetup.

The ’72 ‘Runner is complete and sees occasional street and show use. Stillice cold air, too (R12, nuke the gay unborn whales with CO2 and Freon).


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