VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc AC Delco Parts Book Help

Does anyone have an AC Delco catalog/parts book? I need to know what an AC RC2 4# radiator cap fits. Thanks

RC-2 fits many vehicles GM, Ford and others. Most Chevrolet from 48-55, Buicks 48-49. Too many to list. I could look something specific up for if needed.

Dave

Dave, thanks for the info. I purchased one for a 1950 with 216 engine. BUT I later found out that the correct cap was a no pressure one. This cap is a 4-pound pressure cap most likely for a 235 with power glide. I just need to know which Chevrolets it would fit so I can find it a new home. Thanks for the help.

The 1948 Chevrolet was the first to have a 4 pound pressure cap FROM THE Factory AND THE FILLER NECK IN THE RADIATOR MODIFYED FOR A PRESSURE CAP.

iN 1949 NO PRESSURE CAP WAS USED.

In 1950 the PowerGlide came with a 4 pound cap and Chevrolet said the standard transmission models could use a pressure cap for heavy duty cooling.

Same for 1951.

In 1952 all had a pressure cap from the factory due to the reduced cooling radiator used in 1952 due to the Korean war copper shortage.

All 1953 models used a 4 pound cap.

1954-1957 came with a 7 pound cap and a 170 thermostat and a 180 thermostat was not to be used because the bellows type 180 thermostat did ot work correctly with a 7 pound cap.

For 1958 and up a 13 pound cap was used with the new pellet type thermostat.

I understand, here are the catalog pages , 1969 AC catalog;

Gene’s notes are great info as always. He also introduced another key point.

You need to look at the configuration of your radiator to determine if a pressure cap makes a difference.

If the overflow outlet is in the top tank or very low in the filler neck (below where the cap seats) the radiator will not build any pressure.

The other day we were working on the cooling system on a ‘49 3100. The owner thought there was something wrong because he never had to worry about relieving pressure in the cooling system when checking the coolant level. The system had a 4 psi cap. The overflow tube is connected to the filler neck.

When I removed the cap I immediately saw the “problem”. There is no seat in the filler neck for the lower seal on the cap to seal against. So it is a non-pressurized system in its current configuration. I also have confirmed that for 1949 only the 5000 series truck had a pressurized cooling system. As Gene noted, that year cars were non-pressurized.

You can use a pressure cap to seal the top of the radiator. It just won’t build pressure.

Here are some photos of my original radiator #3122692.







I don't think there will be any pressure in this one looking at where the over-flow tube in located.

THANKS Gene, Dave & Rusty for your help.

That is were it is supposed to be located for a pressure cap or not. Sameradiators were used for Power Glide or sticks.
Thst is a late 1950 radiator.
1949 radiaors were designed for pressure cap use, Chevrolet just did mention it because of the wider core used in 1949, guess they thought it was not necessary.
No seal is necessary for a pressure cap but is necessary for a pressue cap AND an over flow tank.

Neat! You have the original Harrison tanks!

Your picture looking down the filler neck shows exactly what I saw on the '49 3100. The bottom of the radiator cap did not extend down far enough to seal against that inner lip. So the overflow tube is always open to the radiator.

If you could find a cap with a lower seal that extends far enough to fit that seat you would have a pressurized system.

In my limited collection of parts I have a 1939 radiator that was converted for pressure use. In that radiator the overflow was originally soldered to the top of the upper tank. The previous owner had it converted by having the overflow moved to the filler neck and the neck modified so the lower seal would fit against the seat. The overflow tube is only open to the radiator when the pressure has pushed the cap open.

The Chevrolet information says all 1949 3000 trucks had a pressure cap.