4-7 psi cap for Griffin radiator?

[flathead 39]

I Just discovered a cooolant leak in one head gasket. I have a Griffin radiator with griffin cap. I dont know the psi rating of the cap but their web site does not offer a low pressure cap. Anybody know what kind of lower pressure cap I can use on the Griffin. No return tank.

[Tinker]

The regular old cap from ford was 4lbs. Well depending on the yr..... I'd guess the cap pressure is not this issue with your leak. You really don't need a return tank on a stock ford, the system will find a level and spit out the overflow.

[51 MERC-CT]

Originally Posted by flathead 39

I Just discovered a cooolant leak in one head gasket. I have a Griffin radiator with griffin cap. I dont know the psi rating of the cap but their web site does not offer a low pressure cap. Anybody know what kind of lower pressure cap I can use on the Griffin. No return tank.

The high pressure caps they offer are because their radiators will tolerate those pressures without expanding.
Why don't you call Griffin and explain to them what you want to do?
Perhaps they know of a source for a cap that will fit their configuration.

[rotorwrench]

The bung designates cap fit by the depth of the bung, the diameter of the spring seal seat, and the outer diameter of the bayonet connection with the cap. It's likely a safe bet that a radiator such as Griffin's can take the pressures of a modern radiator which would be closer to 14-psi but a person would have to confirm that with Griffin. If the Griffin radiator was designed to take a 41A-8100-A or later revision cap then it should take the highest pressure available.

I don't think the 1939 Fords had a pressure cap originally although I believe that the 41A-8100-A cap, & later versions, (perhaps made during the war or later) would fit radiators back to 1938. The early ones just had a cap with a rubber seal and no pressure spring seal. Most folks agree that the early radiators were not meant to take much more than 4 psi of pressure and even less after 80-years or so.

If the head gasket is leaking, I'd suggest removing the head and replacing it. Flatheads need all the help they can get in cooling the engine and any leak is just going to make that situation worse.

[flathead 39]

Originally Posted by rotorwrench

...

If the head gasket is leaking, I'd suggest removing the head and replacing it. Flatheads need all the help they can get in cooling the engine and any leak is just going to make that situation worse.

Repair is on the schedule. I don't think I need a high pressure cap so I'm wanting to fit a low pressure cap on the radiator even after the gasket is replaced.?

[Als48]

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I bought a 4 lb cap for my 54 NAA Ford tractor from the local auto parts store. Those old tractor radiators won't take high pressure either. Take your current cap with you to match up correct style.

Al Hook

[rotorwrench]

My 1956 850 Ford has a modern radiator. They should be similar to the NAA but I'd have to check the parts book. I know my old tractor can take south Texas heat cruising all day at PTO speed even with a 4 PSI cap. I think a 7 PSI will work on it if needed.

The N series tractors like the 9N & 2N had a non-pressure system originally with the slots for the cap on the inside of the radiator bung but most have likely been replaced with the later type from late 1943 thru 8N pressure system which use replacement caps that are 4 PSI.

[flathead 39]

Originally Posted by flathead 39

Repair is on the schedule. I don't think I need a high pressure cap so I'm wanting to fit a low pressure cap on the radiator even after the gasket is replaced.?

7 psi cap installed, repair made, return tank ordered. Acid tested on mountain pass, 6pct grade in places, warm day, no leak, no loss of coolant, temp gauge stayed below 200.

[19ED30]

Tractor supply has low psi Radiator caps usually on the shelf.

[36fordguy]

You are missing the problem with Griffen radiators. The radiator itself requires about 11 lbs pressure (dynamic ) to fforce the water thru the radiator. A external cat (top of radiator) has to be more than this or you will pump water out the over flow. If you less than this on the top cap you water pumps suck on the bottom of the radiator reducing the pressure (dynamic) on the water going into your pumps aloowint the water boil (vaporize) - So the whole system has to be closed loop at about 15 lbs to work correctly like modern cars and radiator system chang the top cap is not the thing to do. Old rad's thhe water flowed thru the rad by gravity. The pumps only got the water to the top of the radiator.I changed to a brassworks rad. that requires less dynamic pressure to the water flow thru the radiator. The you can reduce the top external pressure of the cap. 36fordguy

[19ED30]

Originally Posted by 36fordguy

You are missing the problem with Griffen radiators. The radiator itself requires about 11 lbs pressure (dynamic ) to fforce the water thru the radiator. A external cat (top of radiator) has to be more than this or you will pump water out the over flow. If you less than this on the top cap you water pumps suck on the bottom of the radiator reducing the pressure (dynamic) on the water going into your pumps aloowint the water boil (vaporize) - So the whole system has to be closed loop at about 15 lbs to work correctly like modern cars and radiator system chang the top cap is not the thing to do. Old rad's thhe water flowed thru the rad by gravity. The pumps only got the water to the top of the radiator.I changed to a brassworks rad. that requires less dynamic pressure to the water flow thru the radiator. The you can reduce the top external pressure of the cap. 36fordguy

I am not a engineer, I have used aluminum radiators in a race vehicle only because of weight .open & pressurized (cap) I prefer brass & copper in any year vehicle. Is the Griffin Radiator A poor design ( I know a name brand) small tubs rows , so it needs presser to force flow of coolant ? Is that particular design possibly for high RPMs for long duration of time ? Higher cap pressure raise the Boiling point ? ( there's another name/ action that happens I cannot think of it right now) over the years if I was using mismatch components, I have experiment with different pulley sizes, fans & so on. I was able to come up with a combo that would do what I feel I needed.
Older cars Most of us would get nervous if temps would get over 190 stop & go .
But certain combos make the most power out put from 235-270 degrees.
It all so a factor & depends where you take temp from , and how cooling hoses are Plumed .
Hear on the Barn , I would think its more Original and Purist and maybe slightly modified, ( be forWWII or 1950) But Not a aluminum Radiator ( things of that Nature)
That look like maybe a HAMB question.I float back & forth , I have original slightly modified & I have a HAMB vehicle also .

[flathead 39]

Originally Posted by 36fordguy

You are missing the problem with Griffen radiators. The radiator itself requires about 11 lbs pressure (dynamic ) to fforce the water thru the radiator. A external cat (top of radiator) has to be more than this or you will pump water out the over flow. If you less than this on the top cap you water pumps suck on the bottom of the radiator reducing the pressure (dynamic) on the water going into your pumps aloowint the water boil (vaporize) - So the whole system has to be closed loop at about 15 lbs to work correctly like modern cars and radiator system chang the top cap is not the thing to do. Old rad's thhe water flowed thru the rad by gravity. The pumps only got the water to the top of the radiator.I changed to a brassworks rad. that requires less dynamic pressure to the water flow thru the radiator. The you can reduce the top external pressure of the cap. 36fordguy

When I contacted Griffin about a low pressure cap, no mention of any problem was mentioned, in fact I was told, by Griffin, where I could find low pressure caps that would work with their radiators. Have installed one (7psi) and a reclaim tank and all is working normally. I will continue to monitor the situation.

[rotorwrench]

I know little about the Griffin designs since I don't have a need to use them. I certainly wouldn't wan't a radiator that can't drop coolant through it as fast as if comes into the top tank. Flow is everything to proper engine cooling on a flathead V8. Most radiators have enough tubes in the core to allow proper flow with no pressure. If coolant comes out the bung while idling luke warm with the cap off, the tubes are usually partially clogged. The top tank shouldn't pressure up until it gets hot at road speed. Overheating would push coolant out as soon as it gets to the boiling point. All a pressure cap should do is increase the boiling point of the coolant for those real hot days while the engine is getting a good work out.