1963 Radiator Overflow Tank Cap

[Hugh P.]

In reviewing the overflow tank caps for a 1963 from sources such as Long Island and Corvette Central, some options look like the AC-307 and RC-26.
I am looking for a 1963 with air conditioning cap and it looks like the AC-307 is recommended for both air or non air cars, but the RC-26 is for 64-65 air cars only. Other than one being a 13 pound cap and one being a 15 pound cap what is the OPERATIONAL difference? Is something specific such as the proper rivet/diode material? I realize either cap is not the best for judging, but I am interested in something close if either of these would provide proper operation and not need to worry about possible galvanic corrosion.

Anyone recently have experience with either AC-307 or RC-26 for a 1963 air car?

[Edward J.]

Re: 1963 Radiator Overflow Tank Cap

Hugh, I would say that either LI OR Corvette Central cap would be the same. a lot of the venders purchase from LI . I can tell there is no perfect reproduction cap for judging, the 307 as far as I know is correct for 63/64.i did test my repro cap that I use to drive with and its tests right on the money.

[Patrick H.]

Re: 1963 Radiator Overflow Tank Cap

As noted in my email I'd go with a brand new ACDelco RC-26. Note that 15# became the standard for AC (and later non-AC) cars, which means that there had to be some benefit. The RC-26 is compatible with both copper and aluminum radiators, and in fact it now replaces the RC-15 in service.

For judging purposes an original 307 should be easier to find than an RC-26. However, the cap from LICS is better than the one sold by the majority of other vendors with regard to external configuration. LICS has the caps that they sell made specifically for them, and as far as I know do not sell them to anyone else.

Does the 63 JG say which cap is correct with AC?

[Harry S.]

Re: 1963 Radiator Overflow Tank Cap

Patrick, the 63/64 indicates a change for 64 to 15#. My 63 non-A/C car and my 63 A/C both have 13# caps.

[Patrick H.]

Re: 1963 Radiator Overflow Tank Cap

Thanks Harry. I suspect as noted above that there was an engineering reason for this. For a "driving" cap I think that the 15# would work quite well for him.

[Hugh P.]

Re: 1963 Radiator Overflow Tank Cap

Patrick/Harry....Thanks for the information. As noted above, the change from 13 to 15 pounds was probably driven by an engineering change based on Desert Proving Ground hot weather testing and other cooling performance evaluations as well as a reduction of p/n's in the system. I just wanted to make sure the RC-26 listed for 64-65 air conditioned cars was backward compatible with the AC-307.

[Patrick H.]

Re: 1963 Radiator Overflow Tank Cap

Patrick/Harry....Thanks for the information. As noted above, the change from 13 to 15 pounds was probably driven by an engineering change based on Desert Proving Ground hot weather testing and other cooling performance evaluations as well as a reduction of p/n's in the system. I just wanted to make sure the RC-26 listed for 64-65 air conditioned cars was backward compatible with the AC-307.

Yes, that's the beauty of the RC-26. Still made, and backward compatible too.

[Alan D.]

Re: 1963 Radiator Overflow Tank Cap

And here is one from a Mar64 (original !!!) yet another point lost for an original car
Note the start of the circle around the number, I suspect that the circle often looked for is the
manufactures dye starting to get old. It seems from other samples that the older (mfg wise so newer)
cars have a easily seen circle.

[Joe L.]

Re: 1963 Radiator Overflow Tank Cap

As noted in my email I'd go with a brand new ACDelco RC-26. Note that 15# became the standard for AC (and later non-AC) cars, which means that there had to be some benefit. The RC-26 is compatible with both copper and aluminum radiators, and in fact it now replaces the RC-15 in service.

For judging purposes an original 307 should be easier to find than an RC-26. However, the cap from LICS is better than the one sold by the majority of other vendors with regard to external configuration. LICS has the caps that they sell made specifically for them, and as far as I know do not sell them to anyone else.

Does the 63 JG say which cap is correct with AC?

Patrick------


One caveat regarding the current AC RC26. The shell configuration is completely different than original. It has no "ears" and, instead, features an "octagonal" shape. Script on the cap is printed or silk-screened and not embossed. Also, it's rated at 16 PSI rather than the original 15 PSI. I believe these caps may be made in India.

Nevertheless, from a functional perspective the AC cap is the way to go.

[Patrick H.]

Re: 1963 Radiator Overflow Tank Cap

Patrick------


One caveat regarding the current AC RC26. The shell configuration is completely different than original. It has no "ears" and, instead, features an "octagonal" shape. Script on the cap is printed or silk-screened and not embossed. Also, it's rated at 16 PSI rather than the original 15 PSI. I believe these caps may be made in India.

Nevertheless, from a functional perspective the AC cap is the way to go.

Yes, I relayed that to Hugh in an email that it appears completely different. However, I have FAR more faith in the current ACDelco with regard to function than any of the reproductions.

One of the largest radiator cap companies is in India, and I believe you are correct that they are manufactured there at present.

[Peter L.]

Re: 1963 Radiator Overflow Tank Cap

Alan - As far as I know the faint "circle" (if there is supposed to be one because you don't see it on some 307 radiator pressure caps) around the 307/13# stamping is not a design feature as it is on some of the newer AC caps where there is a specific circle around the AC & the other stampings. We tend to see interesting features after 50 plus years from when an item was manufactured. Pete