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Veteran
Posts: 170
 
| Hi.
My heat riser thermostatic spring works with a heat gun, but not during normal operation. I think it's still the original one installed, which is why it's stopped working after all these years. Andy Bernbaum is the only source I've found. He only has the L-442, supposedly for cars only from 1961 onwards. Is that true? Does it not fit pre-'61 cars? I can't imagine that.
Does anyone know for sure? Are there any other shops that sell this coil?
https://www.oldmoparts.com/engine/heat-riser-thermostatic-spring-273... |
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Exner Expert 10K+
Posts: 11182
 
Location: Lower Mainland BC | .
That thermostatic bimetal spring for the heat riser should be Mopar PN 960 003. It shows up in the 1955-58, 59 and 60 parts books.
All the same PN (for the V8s)
Bernbaum (and others) has them for decent money:
https://www.ebay.ca/itm/176720531540
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Veteran
Posts: 170
| Yes you're right. But on his website, Bernbaum only lists two different springs: one for 6-cylinder engines and the one I linked above.
Honestly, I think he's selling the same spring for supposedly different model years and models.
For example, the 960003 is also listed for 1960 Dodge models according to the OE specs. But those aren't even listed in the eBay offer.
What do you mean by "and others"? Are there other shops that offer them? I haven't found any...
Edited by Todd 2026-03-09 2:44 PM
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Exner Expert 10K+
Posts: 11182
Location: Lower Mainland BC | .
I really have no idea why there are two different thermostatic springs, one for the 6 cyls and another for the 8 cyl engines in 1959 and 1960.
*BUT* there must have been good reasons (When did the flat head 6 go away and the slant 6 come into play, for example. Did they change the weight of
the counter weight? Did they change the direction of the coil movement?)
The 960 003s for the 55-58 6s and V8s, but in 1959 the 6 cyl spring was PN 1752 418 and 1960 it was 2121 554. There must be good reasons. (But they might
not be critical)
There are other suppliers beside Bernbaum, e.g. Mopar Mall, AMS Obsolete, etc to check out.
And these:
https://picclick.com/1933-1969-Plymouth-Dodge-Desoto-Chrysler-Exhaus...
Have a look at this thread for even more numbers:
https://www.allpar.com/threads/1955-dodge-custom-royal-heat-riser-sp...
Good luck.
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Extreme Veteran
Posts: 488
| Depending on where you live and/or you drive in cold temperatures, do you really need a Heat Riser?
The purpose of the H/R is to warm the cold air for better vaporization, etc. when I worked on the bench we were always loosening the darn things up with a hammer and Heat Riser Solvent. They always sized up closed and that created other problems. Even with a functioning H/R there is a restriction out the right side that pushes some exhaust gas across to the left side. If you have dual exhaust it is easy to notice the difference, single exhaust, not so easy. I took mine out and don’t really notice any difference in the warm up period. I think my old 56 single rocker 315 runs better and sounds like a big old V8 should sound.
Del |
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Board Moderator & Exner Expert 10K+
Posts: 13210
Location: Southern Sweden - Sturkö island | You could use a bimetallic spring for whatever mark, this is not rocket science. Just check a local junk yard and see if you can get one for a V8 engine.
I bougt a new one from aftermarket suppliers years ago and it works flawlessly. Just be sure that the shaft isn't rusted and seized.
The butterfly valve are important as for quick warm-up and better fuel economi. A car manufactorer rarly installed anything that were not needed. |
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Veteran
Posts: 170
| Hello. I recently installed a new coil spring and I'm wondering why the heat riser opens after about 8 mls, then closes again while driving, even with the engine warm. I should mention that I can monitor the heat riser with a small camera while driving. I don't understand why this is happening. My coil spring is about half an inch away from the manifold; could that be the reason? Shouldn't the coil be a maximum of 1-2 mm away from the manifold? Perhaps I should cut the slot in the shaft a little deeper so the coil spring sits closer to the manifold?
Edited by Todd 2026-03-22 9:30 AM
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Board Moderator & Exner Expert 10K+
Posts: 13210
Location: Southern Sweden - Sturkö island | Do you have the couterweight mounted? The counterweight shall pull the butterfly valve open and the spring (when cold) will lift the weight to closed position. |
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Veteran
Posts: 170
| Yes Swen, everything is installed as it should be. When I saw that the counterweight had moved upwards again (towards the closed position), I stopped and opened the hood. With a little push, the counterweight dropped back down (open position). Then, when I started driving again, it went back up (closed).
What surprises me so far is that the lock is not aligned with the shaft end. It protrudes a few millimeters. I can't push it any further into the slot because the spring is already at the very end (half an inch from the manifold, it can't go any further).
Edited by Todd 2026-03-22 12:02 PM
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Veteran
Posts: 170
| I've now filed the slot in the shaft deeper. Everything looks perfect now; the coil spring is flush with the manifold. However, it still closes while driving, even though it was fully open just moments before. I'm sure the cooling airflow is the cause, because when I park the car with a warm engine, it opens again.
If I didn't have a camera in the engine compartment, I wouldn't notice any of this.
Was there a small wind deflector, a small metal plate, installed at the factory to protect against the wind? Has anyone ever seen or heard of such a thing? |
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Veteran
Posts: 170
| I know this topic only interests a few people, and I'd like to wrap it up with this post:
I've found the solution to the problem where the counterweight kept rising (flap closed) despite the hot engine while driving. I suspected that the bimetallic coil was constantly cooling down due to the airflow, which is why 1. the flap opened too late, and 2. it cooled down again after opening (due to the airflow). So, I simply made a small metal plate and attached it in front of the heat riser to protect it from the wind while driving. IT WORKS! The flap now opens after just 2 miles and STAYS OPEN! The bimetallic coil can no longer cool down due to the airflow. I just wanted to share this with you.
If I hadn't installed a camera in the engine compartment for monitoring, I wouldn't have noticed the problem.
Here is's a pic...:
[img]https://thumbs.picr.de/50730826xv.jpg[/img]
Edited by Todd 2026-03-31 12:09 PM
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Heat riser thermostatic spring
![[img]https://thumbs.picr.de/50730826xv.jpg[/img]](https://show.picr.de/50730826xv.jpg.html){kind=link}