Radiator Cap 58-59 w/F.I.

[David L.]

Which AC radiator cap is correct for the 1958-1959 Corvettes w/F.I.?
I found 3 versions as shown below in the photos. Based on my research the 850800 AC cap (RC-6) was also used on 1958-1964 Chevrolet passenger cars (Assembly Manual part number 850559). GM # 850800 was replaced with GM # 3852236 in May 1964.

Dave

[Ian G.]

Re: Radiator Cap 58-59 w/F.I.

Hey David, I've been looking at some of the other threads in the past on your research and I was wondering if you have any info on why the FI would need the 13 lb cap vs the 7 lb RC-1 cap? While my 59 parts manual does list the 850800 13 lb RC-6 cap as applicable, my assembly guide doesn't list it as one of the options as referenced in the blue prints by Noland Adams in his book. I know the Judging Guide is not perfect, but again it doesn't list the 13 lb cap as correct for FI. If anything, I'm wondering if GM offered this cap after the sale, for those drivers experiencing overheating problems in which the radiator overfilled that the higher pressure would resolve? I own a 59 Fuelie so this controversy is very interesting to me.

[David L.]

Re: Radiator Cap 58-59 w/F.I.

Ian,

I am not an authority on straight axle Corvettes by any means but over the years I have collected straight axle parts as I once wandered thru the swap meets back in the 1980's and 1990's. I sold my 1955, 1956, 1958, 1959, 1960, 1961, and 1962 Chevrolet parts catalogs several years ago but I still have a few of my notes.

My 1960 Chevrolet parts catalog (Mar. 1960) did list the following about Corvette radiator caps in Gr. 1.203:
850795, 7lb., RC-1 for 55-60 (exc. F.I.)
850800, 13 lb., RC-6 for 58-59 w/F.I.
861422, RC-20, for 60 w/H.L. Cam

I only have the Corvette assembly manuals from 1962 to 1970. What are the radiator cap part numbers listed for the 59 Corvette with and without F.I.?

Page 252 in N. Adam's 53-62 restoration book lists 850549, 3708173, and 3708174 as the part numbers for 58-60 Corvette radiators and all are 7 psi caps. There is nothing about radiator caps for models with F.I.

My 1963 Chevrolet passenger car Assembly Manual (Sect. 11-13, sheet 14.00) lists the following radiator caps: 850559. 3748424, and 3748425. My 1963 Chevrolet Parts Catalog (Oct. 1962) lists GM # 850800 (13 lb., RC-6) for 58-63 PASS. & 58-59 CORVETTE w/FI.

You may be correct about possible over heating problems with FI engines. Maybe there was a change made concerning the FI radiator caps that was not noted in the 1959 Corvette assembly manual. The assembly manuals show a lot but not every thing.

BTW, I do remember some about increasing pressure to lower the temperature in a required Thermodynamics class that I took back in my college days in the late 1960's.

ALSO, I just found another vintage AC radiator in my collection stamped "AC", "549/7#", and a patent number so small that I will need a magnifying glass to read it. I will post a photo when I get a chance.

Dave

[David L.]

Re: Radiator Cap 58-59 w/F.I.

Enclosed is a photo of my "549" 7# AC radiator cap. The 1955 Chevrolet Parts Catalog (July 1955) and 1953-1955 Corvette Parts Catalog (July 1955) list the 850549 cap for 1955 Corvettes.

Dave

[Ian G.]

Re: Radiator Cap 58-59 w/F.I.

That cap looks like an NOS example I have of an RC-1 part #850509. I have a pic of another similar part RC-7 cap #850801 that says "MADE IN USA PATD" instead of the patent numbers. The part numbers you see in Noland Adams book are the same as in the assembly manual.I've not heard of any specific oveheating problems in fuelies, aside from the well referenced "fuel percolation" issue in the spider lines, but still it seems like it could be related. My feeling is the RC-6 13 lb cap was just used in SERVICE vs at the factory...