I am trying to sort an overheating issue on my AV8... (now that I have the timing issue mostly sorted) I will be replacing thermostats tonight (180 degrees.) I am running a Griffin 2row This one http://www.griffinrad.com/load_details3.php?PartID=175&year=1931&make=Ford&model=&key_id=7-00085 It has a 16lb cap on it now. I am thinking that is high. What is the group thought on the max cap pressure size I should be running on this combo Thanks again Chappy
16 pounds is a lot of pressure both for the radiator and the hoses. You don't want to burst the seams on your top tank or core. What does Griffin say?
I'm not an expert but this is what the various specs mean to me. The 16# rating is the point at which the coolant will begin to boil and trigger the cap to release, not the pressure at which the system will operate all things being in good working condition. With a 180 degree thermostat, you shouldn't normally be seeing that high of pressure unless there are other issues in the cooling system. As always, I am subject to correction by the real experts here.
You're partly correct, it is not the point at which the coolant will boil, it is the point at which the cap will relieve pressure and allow coolant into the catch can/overflow tank.
We all know water boils at 212 degrees. If you raise the pressure, it raises the boiling point. At 16 lbs. PSI, the cap will vent to the recovery tank. I think for an aluminum radiator 16 psi in high. I'm very surprised Griffen Radiator does not have a recommendation on what pound cap to use.
The boiling point of coolant depends on the ratio of antifreeze to water, and the pressure. Here is a chart showing varying boiling points of water/antifreeze mix & pressures: A 50/50 mixture at 16 PSI will boil at 273*F
might give Griffen a call. The higher the pressure, the more force there is trying to pull the tank apart...so if the tank is relatively large, like on early cars, a lower pressure cap is a good idea. But if you have overheating issues where the coolant is boiling, higher pressure can keep it from boiling, as it raises the boiling point. As the chart shows, if you're running 50-50 mixture, and you have a 12 psi cap, you're not going to boil over until over 250 degrees, and you really don't want the engine getting much over 240....so the 16 psi cap is probably overkill.
Be careful. I'd use 7# max. You could start your head gasket leaking. I have a 53 Hudson....I use 7#.
Flathead water pumps can have leaking issues with too high pressure. I think newer units have different seals to reduce that issueI ran 4# cap on my '35, but had original tanks. Other option is no pressure cap and let water find it's own level. Check tension on belt(s) too.
Here is where we stand now. I replaced the cap with a 7lb Installed new 180 degree thermostats. New 50/50 coolant Timing mark is adjusted to just a hair before the pin (better idle than right on the pin) Idle set at 500rpm After 10-15 min at idle from cold (no choke) these are the temp readings I get with my thermal gun See pic for color code. Yellow 256 Blue 259 Green 176 Orange 215 Purple 156 Here is the number 2 and 6 spark plugs after same idle run (new autolite 216's) Any thoughts on why it's running hot FYI, when I drive it, it runs great, revs up quick, and pulls hard, but heats up just as fast or faster. Thanks for the input... Happy Saturday..lol Chappy
Are those plugs indicative of a too lean mixture? A slightly richer mixture should help it run cooler.
I run 7# no over flow recovery, 1" low in the tank, 170 thermostat , no problems, no coolant loss.. Good luck
Does look a tad too lean. Also, are you using an infra red temp gun to get readings? If so, be aware that they will give false readings on shiny surfaces like polished aluminum or polished steel. They will also give false readings on radiator hoses and clamps and non metallic surfaces.. After warm up, what is the temp at the top of the radiator core at the top and what is the temp at the bottom of the radiator core. There should be a difference. Is the temp at the base of your carb cool as fresh gas is running thru there. Check the temp on same places on each side of your engine. Does it run cooler if you loosen the cap? Does coolant reach boiling point? Is your temp gun operating accurately? Also is your engine stock or has it been modified? Place a fan in front of your radiator and see if temp drops when idling. If you increase the idle just a little does it run cooler. If your car is inside a closed area it may not be drawing enough fresh air to cool it down. What is the ambient temp? Are your thermostats operating properly. Take some readings on you everyday driver and see if the infra red gun is operating correctly. Boil some water on the stove and check it. Open the fridge door and check temp. I also have an 8BA in my 40 and will check the temp at various points and share them with you if you desire. One last thing.. Is your hood open or closed when checking the temps?
Thermostat is not opening. Look at the temp differential between Purple and Orange. How can the coolant be hotter exiting the radiator than the coolant entering it? There's no flow. The thermostat is closed, the coolant is blocked right there.
I believe I have solved the overheating issue... I removed the "new" belkamp/NAPA (Isreal made) t-stats and put in a set of Stant 180* t-stats that I tested in water on the stove and drilled two 1/8" holes drilled in them. I topped the block off with fluid at the t-stat housing mount. Topped off radiator with 50/50 and ran it without the cap untill the coolant cycled checking my temps as it warmed up to verify the gauge was correct. At an ideal in the garage it got to about 195-200. Put a 7 lbs cap on and went for a ride, temp stayed aournd 190-195, even waiting for a long light. I will take it for a longer drive later this evening after I mess with the timing and idle. Thanks for all the responses and suggestions. Chappy
They recommend no more than 7 lbs with stock radiators. Your radiator will handle much more. But blowing a head gasket may be an issue I wouldn’t want to deal with.
Drilling holes in the thermostat be avoided by jamming a piece of hard candy to keep it open temporarily, any air pockets in the cooling system will be gone by the time it dissolves.
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