307 Radiator Cap

[Joe C.]

Can anyone point out the difference(s) between an original 307 cap, and the reproductions. I understand that the config of the inner seal surface is very different. Also, are there any differences in the lettering, font, etc on the upper surface.
Pictures would be helpful.
Thanks in advance,
Joe

[Patrick H.]

Re: 307 Radiator Cap

Can anyone point out the difference(s) between an original 307 cap, and the reproductions. I understand that the config of the inner seal surface is very different. Also, are there any differences in the lettering, font, etc on the upper surface.
Pictures would be helpful.
Thanks in advance,
Joe

"Which" of the repro 307 do you mean?
There are at least two sources - just like the RC-15.
One is moderately noticeable, the other is much closer to correct.

Patrick

[Alan D.]

Re: 307 Radiator Cap

To compare different caps here is an original 64 cap. Note there is some of a circle left just above the 307. Do not have picture of other side.
Now it seems to me that some discussion on the circle has been kicked around, but you will need to do a search since I can not recall what conclusion was or if reached.
Think Peter Lindahl knows the minor details on this subject.
Hope this helps a little.

[Joe C.]

Re: 307 Radiator Cap

"Which" of the repro 307 do you mean?
There are at least two sources - just like the RC-15.
One is moderately noticeable, the other is much closer to correct.

Patrick

Thanks for the responses, Patrick and Alan.

The photo tells it all.

About 3 hours ago, I spoke to a noted expert within the "hobby" on rad caps. He informed me of a couple of things to look for, in the lettering, and appearance of the visible parts while the cap is installed.

I looked at some of the vendors' offerings, and it's obvious that the LICS version is closer to the original than the "other" offering I saw, from C******* C****** and P****on. As a result, I now realize that the repop cap I bought years ago, which is exactly like the P****** piece, is very different from the original one.

As far as the underside is concerned, I have some old AC-Delco caps in my "radiator cap locker", and I see the construction of the AC caps are all the same. The repop piece that I bought, some years ago, in addition to being totally inaccurate in the visible portion, appears to have valving which is common to that used in some old Mopar caps that I have.

[Dan H.]

Re: 307 Radiator Cap

Joe, Alan, have recently come accross two original '307' caps which are like Alan's. There was NO trace of the 'circle' on either. Peter Lindalh is repairing one for me, the bottom gasket rubber is old and cracked which will be repaired, the rest of the 'underside' will be as originally manufactured etc. The obvious differences are that the 'AC' is slightly cocked and the arrows are closer to the center than on repros.
Dan

[Patrick H.]

Re: 307 Radiator Cap

Thanks for the responses, Patrick and Alan.

The photo tells it all.

About 3 hours ago, I spoke to a noted expert within the "hobby" on rad caps. He informed me of a couple of things to look for, in the lettering, and appearance of the visible parts while the cap is installed.

I looked at some of the vendors' offerings, and it's obvious that the LICS version is closer to the original than the "other" offering I saw, from C******* C****** and P****on. As a result, I now realize that the repop cap I bought years ago, which is exactly like the P****** piece, is very different from the original one.

As far as the underside is concerned, I have some old AC-Delco caps in my "radiator cap locker", and I see the construction of the AC caps are all the same. The repop piece that I bought, some years ago, in addition to being totally inaccurate in the visible portion, appears to have valving which is common to that used in some old Mopar caps that I have.

Joe,

You figured it out yourself.

The LICS one is better than the "other" one marketed by most of the catalogs. Not entirely perfect, but much better.

Patrick

[Joe L.]

Re: 307 Radiator Cap

One other thing to keep in mind: some may have the notion that all original "307" caps (or, for that matter, any other caps) were exactly and precisely the same with respect to every nuance of detail. I HIGHLY doubt that was the case.

[Joe R.]

Re: 307 Radiator Cap

One other thing to keep in mind: some may have the notion that all original "307" caps (or, for that matter, any other caps) were exactly and precisely the same with respect to every nuance of detail. I HIGHLY doubt that was the case.

Joe L.

I highly concur with your assessment! GM wrote a set of specifications that were basic and received parts from several sources.

Owners and judges have to realize that there were variations from vendor to vendor and throughout the model year.

This microscopic mentality that seems to be spreading thru the hobby can do a lot of damage.

Lighten up folks! This is a hobby and does not need to be evaluated thru the microscope or magnifying glass.

JR

[John D.]

Re: 307 Radiator Cap

Many years ago I ruined a perfectly good 307 cap by having it cad plated. You know the big aluminum washer under the cap? Well when I got the cap back from the platers it was eaten away. Something to remember. JD

[Joe L.]

Re: 307 Radiator Cap

Many years ago I ruined a perfectly good 307 cap by having it cad plated. You know the big aluminum washer under the cap? Well when I got the cap back from the platers it was eaten away. Something to remember. JD

John-----


I'm not surprised, at all, if you had the cap plated as an assembly. I don't think these caps, especially the '307' or RC-26, can be properly re-plated without disassembly. Of course, this destroys the rivet.

[William C.]

Re: 307 Radiator Cap

Actually on an issue like Rad caps that are all sourced inhouse at AC-Flint, I believe you will find the differences are due to the multiple sets of tooling built over time to meet he increasing demand as GM increased it's sales throughout the 50's and 60's. Minor details on each new tool, unless explicitly defined on the part print would have been left to the discretion of the tool shop, easily resulting in slight variations between tools.

[Dan H.]

Re: 307 Radiator Cap

Joe, Alan, have recently come accross two original '307' caps which are like Alan's. There was NO trace of the 'circle' on either. Peter Lindalh is repairing one for me, the bottom gasket rubber is old and cracked which will be repaired, the rest of the 'underside' will be as originally manufactured etc. The obvious differences are that the 'AC' is slightly cocked and the arrows are closer to the center than on repros.
Dan

Gentlemen, I meant to say only on the 2 '307' caps I had just found as far as the partial or full circle around 307 etc. is concerned. All shades of grey are and should be acceptable on these caps. They were not very uniform.
Dan

[Jack H.]

Re: 307 Radiator Cap

Now, that's an explanation I can BUY, Culp! So many times, I hear people saying this/that about tiny differences in component construction and what these differences mean, that I almost want to SCREAM!

It's obvious to me that a given part spit out in the millions of units per annum HAD to have had multiple assy sources, And, it's probably a good bet there were subtle tooling differences between these producing source sites...

But, we seem to try to tie down what's 'factory correct/orignal' to the smallest details ABSENT primary research. Our yardstick seems to be based on what we've seen from admittedly small sample statistical observations on various 'untouched' and/or Bowtie cars brought to the judging field...

Take the neck band emboss on temp senders. Lay the current NCRS JG books from '57 to '67 side by side and read the descriptive text.

Some want the emboss to be upright on the neck while others say it's inverted. Some call for the emboss to read '12V' while others say '12 Volt'. Is it possible there was only ONE feeder line at AC serving the St. Louis final assy plant using these parts making it possible to determine what's 'correct' for each model year?

Heck, I've pulled maybe 300 temp senders off various scrap yard cars over the years and I've seen ALL FOUR variations with apparently no rhyme/reason as to the date/source of the donor car...

Yep, hearing one who was there admit there were tooling differences that could/did lead to minor visual differences in the same part produced in a given time period is VERY refreshing!

[William C.]

Re: 307 Radiator Cap

Sometimes those who have not been in the business lose sight of just how many tools, built at different times were needed to supply some of the more common parts to GM car builds. During 1974, the year of the "seat belt interlock" government mandate, One of my responsibilities was running a test area that tested every module before they were sent to the GM assembly plants. I still remember the pressure involved in starting an operation from NOTHING to test an electronic widget that was literally being designed at the same time as the test equipment. I also remember the daily target, 24,400 units every day to cover 5 day straight time production requirements for GM cars. There were not only four suppliers of the part, but four totally different designs, with the only thing common being the case and the logic that had to be executed in the module! (and they were all interchangable in any car)