This is the radiator cap that has been on my 67 RT for years. I do not have a coolant recovery bottle and only have a overflow hose that allows the system to if it ever needs to. It doesn't ever do it, but it could!! I am wanting to get a new cap but most everything I find at Summit or local parts stores say they are vented caps for closed systems with a bottle. Where can I find a cap used for no bottle? Also, this cap shown is a Stant SP-17 cap but i cant find any info about whether it is vented or non vented. I guess I need someone to explain the visual differences in non vented vs vented caps to edgimicate me

A recovery cap will have the thin brass disc on the bottom of the rubber seal & it's loose. To use it you'd fill the system up to the neck flange where the neoprene seal seats & run a hose to the bottom of a recovery bottle. It reportedly helps prevent rust as it eliminates the 1&1/2" or so air pocket below the neck which makes sense & when it came out in the 70's it also reportedly dropped temps up to 10 degF from more uniform/better cooling. Even if you dont have a hose to the bottom of the bottle just fill the rad all the way up to the neck & let it puke & find it's own level but for the minor effort of adding a longer hose I would suggest it if the cap has a loose brass disc which tells you it's a recovery cap. A vented cap will vent to the hose nipple on the side of the rad cap flange to the ground or to a bottle using the lever & it's a safety feature to protect an uninformed motorist from scalding himself & sueing Stant. Not sure if the lever caps are available in a recovery cap (which have the loose brass disc)(or not)but I think they are since with a recovery system they want you to check fluid at the bottle and not at the cap & to let the system work the bottle needs to be kept partly filled so it dont suck air back in & defeat the recovery purpose & with a homemade bottle you want the cap on top on tight to stop evaporation

I run the cap with the thermometer in it from Summit.Mines a 16 pound on the 65.I think Mr.Gasket makes them.Looks good and no problems after 3 years.Plus you have another way to check the rad temp.No recovery bottle on mine.Rocky

I run the MRG-2471-r cap.Thats a 16 pound red cap.Fits my 65 stock rad perfect.No problems.Rocky

Thanks Rocky, I see there are at least two sizes(dia)for those depending on the year, I'll have to be smarter on the application guide. It was listed as being a "Universal" application, I needed to drill down to it with my specific car and year.

Jim

Some info I found online about radiator caps.
http://turbobuick.com/forums/threads/radiator-cap-tech.98760/

Found this too. http://www.slantsix.org/forum/viewtopic.php?t=12606
With lower ring only, with free-hanging centre valve (Partial-pressure, open system)

With lower and upper ring, with free-hanging centre valve (Partial-pressure, coolant recovery system)

With lower ring only, with spring-loaded centre valve (Full-pressure, open system)

With lower and upper ring, with spring-loaded centre valve (Full-pressure, coolant recovery system).