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Old 04-30-2019, 09:39 AM   #1
Rayfry
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Default Hot Engine

My 49 Ford with a flathead V-8 runs on the hot side after about a 30 minute ride. It never reaches the full hot on the gauge but it is closer to the hot than the cold side of the gauge. Is this the way most flathead V-8s run or am I going to have to correct something to cool it down. New purchase and was told the engine was rebuilt.
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Old 04-30-2019, 09:57 AM   #2
Kens 36
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Default Re: Hot Engine

Congratulations on your purchase. Others will chime in but here are some quick thoughts.

Get yourself an infrared laser thermometer. Don't trust your gauge. Take temperature readings at the front and back of the heads to get a good idea of actual temps. Check the radiator at the top and at the bottom to see how the temperature changes as the water moves from the inlets to the bottom outlets.

If you are truly overheating, the first thing I would work on is the radiator. Find a shop that knows how to work on radiators. They can do a flow test and can rod out the radiator if it is clogged.

Good luck!

Ken
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Old 04-30-2019, 10:26 AM   #3
Drbrown
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Default Re: Hot Engine

If your stock dash gauge is showing around the 3/4 temp range when hot, I think your okay. I say that because:

I have a mechanical add-on temp gauge with its sender unit installed in left head, and it shows about 175 degrees when running hot (I am using 160 degree stats). So I took apart my stock dash gauge and re-calibrated it so its needle indicator is at the 1/2 mark when the add-on gauge shows 160 degrees. So the stock gauge indicator now reads just below the 3/4 mark when running hot. When driving up long inclines/hills the temp will climb to the 3/4 mark, but drop back down when I'm back driving on level road.

I assume your engine still has its original two temp sensor units .... one in right head, one in left head. Some on this forum, including myself, note the right/passenger side of the engine runs a little hotter than the left side, apparently due to the way Ford cast its engine blocks. But all things equal-out when the two sides come together at the top of the radiator and the coolant passes on-thru.
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Old 04-30-2019, 11:06 AM   #4
rotorwrench
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Default Re: Hot Engine

Flatheads run a bit warmer than overhead valve engines due to the exhaust gasses flowing through the long ports on the ends and siamese ports in the centers. The radiators can get gooped up over time and may need a rodding out. The blocks sometimes have old core sand and wire stuck in the coolant passages. Cylinder head gaskets can leak compression into the coolant passages. Even the ignition can cause overheating if the vacuum spark control diaphragm goes bad on the distributor.

If its not getting up to the H and blowing coolant out the radiator cap then it may be running normal for its condition. When all conditions are relieved, a person is hard pressed to make them overheat. Now if you climbing up mountain roads on a hot day with a heavy load, even a normal engine will start increase in temperature during the climb but should quickly cool back to normal on the down side of the hill.
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Old 04-30-2019, 11:49 AM   #5
JSeery
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Default Re: Hot Engine

Quote:
Originally Posted by Rayfry View Post
My 49 Ford with a flathead V-8 runs on the hot side after about a 30 minute ride. It never reaches the full hot on the gauge but it is closer to the hot than the cold side of the gauge. Is this the way most flathead V-8s run or am I going to have to correct something to cool it down. New purchase and was told the engine was rebuilt.
I would start with attempting to determine what the temp actually is. An IR heat gun is a good approach. They are fairly cheap and easy to use. Check the temperature at the head connection to the upper hose to top of the radiator. It is also informative to check the top section of the radiator and the bottom section of the radiator. The original gauge is not going to tell you much as far as actual engine temperature is concerned. I would shoot for around 185 to 190 operating range.
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Old 04-30-2019, 12:02 PM   #6
19Fordy
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Default Re: Hot Engine

If it doesn't boil, you're ok. Ambient temperature affects cooling. Where do you live?
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Old 04-30-2019, 01:07 PM   #7
supereal
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Default Re: Hot Engine

The time proven tip regarding engine overheating is that if it overheats while at idle or low speed, low coolant circulation is the cause. If it heats at highway speeds, the problem is poor air circulation through the radiator, usually due to blockage of the fins, or separation of the fins from the tubes of the radiator. All cooling systems lose efficiency over time due to these factors. Overheating was rare when the vehicles were new.
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Old 05-01-2019, 07:55 AM   #8
Rayfry
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Default Re: Hot Engine

Some great advice here. Will be checking out the radiator and the cooling system this weekend. Thanks
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Old 05-01-2019, 05:41 PM   #9
G.M.
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Default Re: Hot Engine

I just went through a bout with my 36 roadster. Have not driven it yet
but know it's good to go. We would drive it 40 or 50 miles and it would
slowly get low on coolant even with an over flow bottle. Looking down
at tubs in the radiator every one looked completely plugged. Took it out
and to the radiator shop, he removed one of the tanks and ran a rod
through them. Put it on yesterday and ran it for 45 minutes with a Lasko
box fan in front of the grill. Temp at top of top tank below water line on
the front with laser gun it ran at 145. Took fan away and it still ran at
150 for another 45 minutes and it 90 degrees outside temp. Looks good,
put hood on Thursday and take it for a ride. G.M.

Found a leak under the bracket on the top of the radiator on the drivers
side. Took a small torch and melted the lead so the bracket popped loose
and leaded the seam on the side of the tank Put the bracket back on and
all is good with no leaks. Warmed it up to 165 and went for a short ride.
85 outside temp and stayed at a little below 165. Hoods back on and new
tires so it looks like it's good to drive. G.M.
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Last edited by G.M.; 05-02-2019 at 04:35 PM.
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