Flathead runs hot - won't cool

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doowopsinger

Junior Member
I've posted this on the HAMB and it was recommended I post it here also for expert advice.

I've got a running HOT issue. No boil over--just running very hot. 195-210*
Block is a 51 Ford 239cu in, Fenton Aluminum Heads and twin carbs. Hot tanked and magnafluxed. Isky Max-1 Cam.
Radiator is aluminum 2 rows of 1" tubes.
Running 5/8" restrictors. Electric Fan thermostaticaly controlled at 180 degrees.
Have already done an Oxalic Acid flush.
After 30 minutes of driving it will run up to 210 degrees. Once its up there it won't come back.

I've done a number of things and here are some of the results.
All tests done with No thermostats. Used 5/8 hole restrictors.
Using 7 lbs radiator cap.
Cooling system pressure test held at 18 lbs.
Block test for combustion gases checked out OK.
Used a digital temp reader and comfirmed temp on right side and left sides of heads/water outlets/etc are similar around 190*.
On a coolish 55* night the engine idled for one hour with gauge reading 190*
All across both heads temp was 185*-190* ----- Intake manifold reads 220*
Top Radiator tank temp was around 185* and the Lower Radiator tank was around 160*.
Electric fan kicks on about 185* -- Dash temp gauge stays constant at around 190*
Took it out on the road to 40mph at temp gauge instantly climbed to 200*
After shutting engine down, the fan within minutes brought gauge down to below 160*
Intial timing 10* --- Full 28* advance all in at 2500rpm
Plugs are brown
Well there you have it. This is on a cool night. I know things will be worse on an 75 to 85 degree day.
 
What make are the high volume pumps? Why would you buy high volume pumps then restrict the flow, it don't add up?? G.M.
 
I agree with JC. Remove the restrictors. Three major aspects to keep these babys cool: Air Flow, water flow and timing. Looks like you got 2 out of 3 already. You might also set the fan to come on at 160°. A 100° temp rise is about right for a flathead. Are you sure the system is clean? You could try back flushing the rad to see what you get out of it. I have an 16" electric fan that is set to turn on at 160°. On a 50° to 60° day it only comes on if it is sitting at idle for more than 5 minutes. The temp drops below the turn on temp once in motion.

Where are you guys located? (JCWeezer & Doowopsinger)
 
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How much have the cylinders been bored oversize? Thin cylinderwalls are an invitation to overheat. The thinner the cylinder wall the more heat is conducted into the coolant and the less into the exhaust gas flow.
 
41ford1 said:
I agree with JC. Remove the restrictors. Three major aspects to keep these babys cool: Air Flow, water flow and timing. Looks like you got 2 out of 3 already. You might also set the fan to come on at 160°. A 100° temp rise is about right for a flathead. Are you sure the system is clean? You could try back flushing the rad to see what you get out of it. I have an 16" electric fan that is set to turn on at 160°. On a 50° to 60° day it only comes on if it is sitting at idle for more than 5 minutes. The temp drops below the turn on temp once in motion.

Where are you guys located? (JCWeezer & Doowopsinger)
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Sounds like part of the plan. Loose the restrictors and drop the fan trigger temp.

I'm in Massachusetts
 
Your running warm, so try running 160* stats in it. Get rid of about 8* of your total timing if your running a mechanical advance only distributor. You should be 20*all in at 2,000RPM. Try fattening up the main jets a little. Flatties don't like to be the least bit lean. How old is the radiator? It could be the problem. PS Also try and run a good shroud with the fan.
Butch
 
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Butch11443 said:
Your running warm, so try running 160* stats in it. Get rid of about 8* of your total timing if your running a mechanical advance only distributor. You should be 20*all in at 2,000RPM. Try fattening up the main jets a little. Flatties don't like to be the least bit lean. How old is the radiator? It could be the problem.
Butch
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Radiator is a new aluminum 2 rows of 1" tubes.
I was under the impression that it would run hotter with less advance.
 
With mine the timing was a big contributer to an overheat problem. Try setting the idle speed timiing with a vacuum gauge. I know this may create a fire storm. But for me it let me know where the engine liked the timing. Advance the timing until you get the highest vac reading then back it down 1"Hg. Doing that made a big difference in lowering the running temp.

PM me if you want some hands on help.
 
41ford1 said:
With mine the timing was a big contributer to an overheat problem. Try setting the idle speed timiing with a vacuum gauge. I know this may create a fire storm. But for me it let me know where the engine liked the timing. Advance the timing until you get the highest vac reading then back it down 1"Hg. Doing that made a big difference in lowering the running temp.

PM me if you want some hands on help.
Click to expand...

That's just how I set my intial timing to find the sweet spot. The only difference is I left it there instead of bringing it back 1"Hg
 
I would say Radiator. I did a run with another 34 ,at the end at set of traffic lights he was running 140 me 200 .Me 3 rows 5/8 tubes. him new Radiator mutable 4 rows .3/8 tubes. Check your gage.Yes to retarded will run hotter
 
I'm running the same radiator as you. Have stock pumps on a French flathead 239". Dual 94's, Offy heads, stock truck cam, mallory distributor, electric puller fan. Run 190* on a 80-90 degree day on highway, 180* around town.
Butch
 
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