There are two standard heights of radiator fill necks that will cover probably 90% of every American made vehicle for about 50 years. Is there any reason someone can't use a tape measure or a ruler, measure the inside depth of the neck, go to the FLAPS, and do some measuring of the caps they have in stock? "This ain't rocket surgery!"- - - - -or maybe I'm having a Mr. Spock moment- - - -"That is not logical!" Getting OCD about specific part numbers doesn't make the cut in the real world of auto repair.
Jerry
In the interest of saving time and frustration at this parts store counter, I try to do their thinking for them before I even walk in the door. There is exactly one parts store in my town that’s capable of doing the simple task of measuring and referencing and they keep the shortest hours of any. Measuring caps in stock at this O’Reilly is a fine idea, but strangely they don’t keep 4 lb caps in stock.
I wrongly assumed that a 4 lb cap was a 4 lb cap without even thinking about fill neck depth.
I’m not the least bit picky about part brand or even part number. Was just hoping to find something (from someone here) that is already known to work so I can walk in, make my exchange, and walk out. I’m being lazy, basically.
Jerry’s comment about two different cap heights covering nearly all domestic vehicles is helpful context.
If that’s the case, it would seem that the taller of the two variants has quite a range of actual listed heights: 1-1/16” to 1-1/2.” The cap I bought is allegedly 1-1/16.” I’m not sure how how/where they measure from as that number doesn’t correlate very well with anything when I put a ruler on it.
The short variety is more consistently listed at 3/4.” I’ll try one of those.
Avoid a cheap cap that will expel fluid all over your engine. Air valve may not leak but most I`ve seen do. Thats the dimple on top. Get one if you want. I am trying to save people frustration.
Last edited by Guitplayer; 07/25/202311:15 AM.
~ BD. "You won't find me in an old folks home" Pioneer Florida Cracker 1958 Apache Stepside 1958 Apache 1/2 ton Panel 1959 Apache 1/2 ton Panel
Mine is lower than that (and on the firewall) and it works fine.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
The height looks OK- - - -the capacity is a bit on the skimpy side. I like an overflow tank with a couple of quarts capacity- - - -with about a pint in it cold to be sure the siphon tube stays submerged. If the original cooling system was a "zero pressure" type, 7 pounds might put a bit of stress on the solder joints at the radiator tanks and the heater core connections. 7 pounds will allow the coolant to stay liquid up to 233 degrees at sea level- - - -much hotter than most stovebolters like to run their engines. Each pound of pressure raises the boiling point by 3 degrees. That's why food cooks faster in a pressure cooker- - - -the internal temp in a 15# pressure pot gets to 250+ degrees. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I have a 4 lb cap on my truck with a recovery/return reservoir, 1941 radiator, and a heater. There are no problems with any of the components.
Engine is original, un-rebuilt 216. It, too has a 180 degree T-stat.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
