Flathead engine running cold and hot

rhphotord

rhphotord

Senior Member
Been chasing this gremlin for about a year or more now. Starting to think I am stupid. When I first ran this engine I didn't install stats and it continually ran on the cold side. Temps ran up to a max. 170 on a hot day at idle but frankly it never ran well until higher temps. Often had to run it with the choke partially out to prevent hesitation. Put 160 stats in it and tested them before hand, they worked as designed.
Temp ran up to 220 degrees and shut it down and pulled the stats again ran without them all summer.
Well back to square one. Put different 180 stats in this winter and now my temp gauge still won't go above 140 even after idling for a half hour or more. Car runs like crap! Took temp readings with a infrared laser temp gauge and now it appears the DS bank is running at 204 and the PS bank is running 148 degrees Obviously the temp gauge is correct because that's where the sending unit is. Guess I am pulling the stats again! Did I say draining all the anti freeze is a pain in the arss. Well it is and it's a mess.
Only thing I can think of is I have one or both new stats mal functioning. Frustrating as hell! Open to suggestions other than selling it..won't happen
 

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Two suggestion to try:

Don't drain all the fluid when removing a thermostat. Only need to get the level below the stats.

May have air trapped at the bottom of the stat, so stats are not sensing fluid. Many have suggested drilling a small hole in the thermostat to let trapped air get past.
 
I don't see any clamps around the stats ,you would be surprised how much water can be pumped around the stats rendering them ineffective ,as Jay said drill a hole 1/8 only ,I wouldn't have thought the running of it would be affected that much on a FH .Maybe look for something else ,
 
Did you take individual IR temp readings when the stats were out? Was there a big difference side to side like when the stats were in?



I don't put a stat in anything anymore without drilling a small hole in them to vent the air pockets. Most later styles have a small 'burp' vent in them, but they are marginal at best. Not saying that is your issue, but I've seen them cause air pocket problems several times before. If the air gets trapped, water never reaches the stat and they won't open correctly. You should be able to tell when they open by feeling the hoses for when they get hot suddenly. Then compare side to side if they are opening at the same time. All info that will help you determine what's going on.



I've always been a firm believer in running 2 temp sending units and dual gauges, just so you know what is happening on each bank. With the flathead 2 pump system, a single sender and gauge can give you a false understanding of what's going on with the engine. My Dad taught me that years ago, that this was one of the shortcomings of the early designs. I realize nobody likes extra gauges hanging under the dashes of restored cars, but it's prudent to put function ahead of style sometimes.
 
Did drill holes in the 180 stats now installed. Thought that may have been the original problem on the 160 stats. Unfortunately I did not take temp readings with no stats as I just bought the new infrared gauge. Considered running a second temp gauge as well. Tired of doing the same thing over but onward I go. Thanks for the input
 
There’s been a lot of threads on stats not functioning as designed. You said you tested them but you may want to put them in a pan of water on the stove with a thermometer again. What are you doing to make sure the stat doesn’t turn sideways in the hose?.....that’s a nice looking motor....you’ll figure it out!........Mark
 
Ignoring the temperature side of the equation, I'd be more worried about why the engine runs poorly until hot. A bit of choke from a cold start is not unusual but it ought to run well after a few minutes without choke. Do you think maybe the carb is running a bit lean?
What carb setup do you have and what jets/power valve combo are being used?

On the other side of the coin, a car that starts instantly with no choke and runs great when stone cold is probably too rich. Just for info. This is not the situation in your case.

Re the stats I use 160s and check them first in hot water. I also use a small vent hole. It looks like one of your stats is either not working (stuck open) or has dislodged and is allowing coolant to bypass. I have used twin mech temp gauges in my sedan since having a thermostat fail shut on the non sensor side.

Mart.
 
Have to pull the files to determine the carb jetting I ended up with. Had made several changes. Running two Holley carbs on an alum. Edmunds. The spark plugs looked like they should after finalizing jetting. Maybe going at bit richer may help with cold running. One problem at a time to solve.
BTW I did check stat function prior to installing them. Some fun
 
It is fun to play with a 70 year old motor! For what it’s worth, on my ‘50 with an 8BA, I went from 160* to 180*’s and mine ran much better. Fuel mileage went from 12-14 to 17-18 mph. “Seat of the pants” performance also improved. Good luck with your adventure.....Mark
 
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