Mine does the exact same thing. This winter is the first winter I have been driving it with thermostats though. I'll see what it does in the summer time.
Last time I ordered something from Rock Auto I ordered me a 10 pack of those thermostat housing gaskets. My first 8BA, a couple years ago, I put in 180 thermostats and that engine's temp does just about what you'd think it should do: runs about 180 most of the time.
My '40 has 180 thermostats in it and usually runs between 170-190 depending on the outside temperature. But when it sits there idling for any length of time I can watch the temp gauge climb and it keeps climbing as long as it idles. If I pick up the rpm it drops about 10 deg. right away. I have come to the conclusion that the stock water pumps just aren't doing the job at idle so I have ordered some of the Speedway pumps to be installed this winter. I also ordered a couple of 160 deg thermostats which I will try only if the pumps don't do the job. I prefer the 180 thermostats because if the engine runs cold you get incomplete combustion. I think 180 is just right for a flathead.
That is not right. A thermostat will begin to open ~5° of it's rated temp. A 180° Thermo should be opening between 175-185°. Thermostat should be fully open 20° above its rated temp, or in this case by 200°(195-205°) During this time the thermostat will vary its opening to regulate flow to keep the heat in the engine at a nominal operating temp. Now if multiple thermostats are doing this there is something goofy going on. Thermostats have incorrect ratings Thermostats are not installed correctly/correct placement Thermostats are defective, build or otherwise. Temperature sender is not placed correctly, Temperature sender is defective or wired incorrectly. First one may be true, if you purchased a batch of bad thermos then they all may be incorrectly marked. But if you have tried various brands at different times and they are physically different(not reboxed/rebranded units) then it is highly unlikely the rating is incorrect. Pan full of water on the stove top with the thermostat submerged and a temp gauge can rule this out. Second may be a possibility. IIRC no one makes the original Ford Flathead thermostat, which was a clock spring flapper valve type. Is it possible that the 'modern' wax poppet type thermostat design does not allow correct placement of the heat motor in the coolant flow? Third related to second. Poppet type causes over-cooling issues? But even a 160° thermostat should still be closed by 160° and a lesser temp should not be seen on the gauge. So why would we see cooler than rated temps? Some kind of funky turbulence and thermodynamics that allows the thermostat to stay open at a lesser temperature? Heat from the head itself is conducting through the thermostat body and artificially heating the heat motor, even though the coolant temp is below rated threshold? Placement of the sender on the inlet side from the radiator will always read lower than what is expected. That is cooled water and is not what you want to measure. It could also be that the sender, especially on an open engine bay hot rod, is getting wind blasted. This would overcool the sender and cause an artificially lower temp reading. Fifth is a good possibility. If it is supposed to be a reproduction Ford unit, it may simply be built wrong and does not operate correctly. If it is an aftermarket unit then the wiring to/from the sender may be incorrect, or mismatched to gauge. With the dual thermostats, IIRC, there were also dual temp sensors on these engines, but still only a single gauge. If you are running two modern senders with a single gauge not setup for two senders then the resistance reading will be lower in total. This would skew the temp reading, depending on if resistance increases or decreases with temp increase, higher/lower than actual. In this case either run two gauges or have a switch to toggle left and right banks using a single temp gauge. A badly grounded/bonded block. Increasing total resistance of the thermo sensor which would cause an artificially higher/lower temp reading(depending on how the gauge uses resistance to temp reading). Disclaimer: I'm not a flathead guy.
Ol blue, Usually anytime an engine is idling and stationary,,,if the temp starts climbing,,,it is airflow over the radiator,,,or lack there of. By increasing rpm,,,it immediately drops temp is the giveaway. Check your fan placement distance to radiator. Sounds like your radiator is fine though,,,,otherwise the temp would not drop so easily. You can even try placing a small electric fan in front of radiator and let it idle,,,you should see the cooling from that if it is the engine fan causing the temp issue. Above 30 mph,,,,,an engine doesn’t even need a fan,,,airflow over the cores cools it just fine. I might be wrong,,,but I would bet your pumps are just fine. Tommy
What kind of radiator are you guys using ? I just would like to know for future reference. Sounds like they are cooling well . I have been nervous about using the stock heads,,,,I figured I needed the extra cooling capacity from aftermarket aluminum. Since reading these post lately,,,I feel better about my heads. They are in excellent condition,,,I really hated not to use them to be honest. Tommy
A lot of information here today. In my case, I'm using one of those chinese Champion radiators. I'd hate to start another conversation about them, but for two hundred bucks this one has been perfect. Except maybe it cools too well. I've got two mechanical temp gauges on it, changed out for another pair to compare. I had another 8BA engine in this car, pulled to put in a truck, that one had a pair of the same type stats and ran as you'd think it should.
So this is my theory for my 8BA cooling issue I posted above. I checked both thermostats on the stove before installing them, both were good. I drilled two small holes in the flange of the thermostats so any air in the system can pass through the two small holes. My theory is: water passing the temp sender is slightly cooler than when it reaches the thermostat because it is upstream of the thermostat and the coolant continues to warmup before reaching the thermostat. In addition, the two holes I drilled in each thermostat flange are allowing a slight bit of coolant to flow through the holes in the closed thermostat and that coolant flow is enough to keep the engine cooler than 180 back by the temp sender. This is why I'm seeing @140 on the gauges and the thermostats are seeing @180 while going down the road. When I'm stopped, the temps stay @180 because the coolant temperature is not brought down as much by just the fan. I'm also at an Idle, so the flow of coolant is much less through the motor allowing it to be hotter upstream of the thermostats (@180).
Well, same here. Sometimes I read too much, so at first I drilled a 1/8" hole in a pair of Mottorad thermostats. Not sure why, I just like to keep up to date. Engine ran as above, so I changed out to another pair with no holes. Same result. So then I bought a pair of Gates and a pair of Delco from Rock Auto, can't remember which I installed but no difference at all. Tired of changing them out.
Thanks for the input Tommy. I suspected air flow problems so I built a deflector for the top of the grille to the radiator just as you often see on '40 Fords and added an electric pusher fan. Neither item made a measurable difference. That is what led me to believe that my problem is in the pumps. The new style pumps have more and better vanes which are supposed to help flow better. Hope it works.
Glad to hear you have already tried it. Well,,,, it sounds like the pumps are probably the culprit. I hope it solves your problems,,,good luck. When you find the issue,,,,please post your results,,it will help others. I plan on using brand new pumps,,,after hearing about cooling issues,,,,I would like to protect my engine all I can. Thanks . Tommy
FWIW, about a year and a half ago, I sold a brand new, still in the Ford logo box complete with installation and operating instructions, flathead Dynamatic fan. When the operating temperature reached 140 degrees, the fan would engage. If I were guessing, I'd say that 140 would be normal for that time period.
Before the better pumps were available, I remember changing them quite often. Mostly for seal issues. Ever since the new ones have arrived, I’ve never had any issues with the new design. Anyone have a new design pump fail yet?? Merry Christmas everyone!! PJ
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