Pressurized Radiator cap for `30 Model A?
- Thread starter macbubba
- Start date
Charlie Stephens
Well-known member
Remember the seals in the original water pump are not designed for a pressurized system and your pump will leak. I am not sure how "leak-less" pumps would handle the situation. Also note you should have posted this in the section that deals with the Model A as you will have a better audience.
Charlie Stephens
Charlie Stephens
Lawson Cox
Well-known member
Saw this thread, and it caught my attention. Sort of a hijack, but as I’m getting closer to firing up my C59A I’m wondering the same thing. It’s a custom “pre-war” speedster build, and is using a late model radiator from Dodge Dakota. The stk radiator cap is about 16 psi. The folks on the HAMB mentioned stk Ford systems are 5-7 psi, with some even running open systems. The plan to alter the cap to get it to work between 5-7 psi. I have new water pumps from Denis Carpenter IIRC. Will those be ok with a pressurized system of 5-7 psi?
tubman
Well-known member
Not being into newer stuff, I'm not real sure, but don't the different pressure rated caps have a special latching pattern so they don't get mismatched?
No, my modern Toyota cap will fit my Brassworks radiator just fine, and vice versa.
You can walk into an auto parts store and buy a cap off the shelf that will fit a Brassworks radiator.
tubman
Well-known member
Good to hear. Every once in a while, they do get something right.
I couldn’t find any caps with a 5-7 psi rating that will fit the Dakota rad.
I'd quit looking for a Dodge Dakota radiator cap, and figure out what cap size your radiator uses, and search based on the radiator cap/opening size needed.
The cap doesn't know what the make and model of the radiator is, and the radiator doesn't know what the make and model of the car it's sitting in is.
Radiator caps are pretty standard, there are different sizes and styles, but not many.
I did do that, but didn’t look for a long time. The issue is that almost all of those low pressure caps are from the 30s -50s from what I found from my digging. I’ll have to keep looking I guess. I might just drop by a local rad shop next week and see what they can come up with.
I don’t know, but my 4lbs cap that fits a Toyota and a Brassworks radiator is brand new (2024), by standt.
Sounds like you need to spend some time problem solving.
tubman
Well-known member
Hmmm. Looks like there still may be some incompatibility between caps and necks. The only example cited so far is a 4 lb cap and a Brassworks radiator. That doesn't surprise me, as the radiator is probably for an older car. There are other limiting factors (water pump seals for one) that may indeed cause the Brassworks unit to have been made for a 4 lb cap.
The Brassworks
Member
Caps are standard sizes for standard necks. For Model A blocks using pressure, 4psi is recommends. The shallow brass cup and fiber board design of a bayonet style cap in a non pressure will hold ~3.5psi and a threaded cap like the 28-29 can hold >20psi.
Conventional pressure caps have the spit-suck feature that reclaims the fluid. Radiators are tested in excess of 20psi but the greater concern is the rest of the system and people utilizing excess pressure in an attempt to find another tool of cooling.
We do occassionally utilize smaller caps for hiding pressure in a non pressure systems. These are commonly referred to as import caps and we provide them in 7psi for flatheads and 13 psi for modern engines.