I am working on a historic hot rod powered by a 1933 Chrysler CT straight-8. It has a semi-modern radiator with a 13psi cap. I am not sure that this should be a thing, or at least not that pressure. I just rebuilt the water pump, because it was pushing water past my the packing. Before I put it back together, I want to make sure I am not repeating an error. No cap that I have seen for cars with this engine appear to be pressure caps
The open type (non-pressurised) radiators had the over flow below the level of the cap seal (Straight atmospheric vent). It may have a 13 PSI cap, but if the vent is below the seal, the rating means nothing,
I am aware. I am trying to figure out if this engine, and more specifically this water pump, is supposed to be paired with an unpressurized radiator.
A quick search shows a lot of that era Mopars used a Stant R-2 cap 1934-1936 MoPar Stant Everseal R-2 Radiator Cap - NOS - Vintage MoParts No pressure rating but I am thinking somewhere between slim an none.
That is what I assume. I am not convinced that a water pump of this ancient design is going to be all that happy with that 13psi cap. I had to rework the whole inside. The packing tube, which is a separate steel piece, fell out during cleaning. I bonded it back in with Loctite 660. I have no idea what was supposed to be in there, but there was nothing for the packing to be snugged-up against. It could not seal. I suspect some stuff was left on the bench. It was fitted with shielded (not sealed) bearings that I identified to be from the 1980's. It already had a stainless steel impeller. I cannot imagine that it was stock. I loaded it up with sealed bearings, and high-tech carbon graphite packing. I left the packing nut a little loose. I will sneak up on it until the drip stops, if it drips. Fingers crossed. These are pretty rare.
The first pressurized caps that I have ever seen were 7 LBS. And that was in the 40's. Nothing in the 30's had a 13 LB cap.
Remember, all cars can run fine with a no pressure cap. All pressurizing does is raise the boiling point of the coolant. If the coolant temp never exceeds 212 degrees, everything is fine without pressure. I'd run a no pressure cap and watch the temp gauge. If you use a thermostat, use a 160. Probably be ok with no stat, as long as you don't need a heater. Hope this helps.
A 50% antifreeze mix will give you about 14 more degrees. A Google search pointed to @Blues4U old post: https://www.jalopyjournal.com/forum/threads/radiator-cap-size-pressure-update-resolved.1152017/ Scroll down to post #8. Russ
The original rad on my '47 Plymouth was vented so I would imagine that a Chrysler much older would be also.
First Chrysler products with pressure cap was 1951 and it was 4 pounds. 1933 was not pressurized. Not to say you couldn't use a pressure cap on one if the water pump had the right seal, and the radiator and heater were rated to stand the pressure. I have used a 4 pound cap on cars that were not pressurized but wouldn't go higher than that.
Our 56 had a 7 psi cap, no recovery, and you keep the coolant 1” low in the upper tank for expansion. The chart shows a lot of boil over protection. If you have a heater; the core might be a weak point. Since it’s not sealed contamination does occur. I change the 50-50 mix every 4 years.
Just curious, does that Chrysler have a 3 slot/tang radiator for the cap? I’d like to run the Honey Comb radiator I have, but has a radiator fill for a 3 tang cap, and haven’t been able to find one. Hate to try and have someone put something “modern” on it. Any chance you can post a pic of the cap if it has 3 tangs?
Straying a bit from the post, I always run a coolant recovery tank on the non-pressure systems. Just run a hose from the overflow tube to the bottom of the tank, fill the radiator completely and add half a pint to the recovery tank. It keeps the radiator completely full of coolant, and the expanded hot coolant flows out the tube to the tank. The radiator cap isn't a pressure cap, but does seal against the radiator filler tube so as the system cools off it draws coolant from the tank back into the radiator.
It has a modern radiator. I am sourcing a cap that fits, but does not hold pressure. The owner is sourcing a period-appropriate vessel for overflow. It is a hot rod. It does not have the Chrysler radiator.
Wow is that way out there...it looks to possibly predate the bloody red Baron...is it a new build or survivor...sorry Stogys Nosy...
It is the Von Zipper. It is a tribute. It was built after. The oldest parts are from 1919. It has been in a whole mess of photo shoots, to a zillion shows, and has appeared on numerous album covers.
Thanks for Sharing that Gimpy...truly a tribute in Showrod/Hotrod and all in between...love those exotic engines of the Yesteryear just seeing all the linkage working those carbs and the sound... probably like an old airplane...
It appears to be a late 30's GM radiator. The top with the angled filler tube and center outlet looks like 37/38 Chevy or Buick.
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