overheating flathead
 

Ok, I have read a lot of things on flathead overheating. I have a 48 Fordor sedan running a mild rebuild with mild Isky cam 3 on the tree, 2 bb l(jetted for the elev 5000ft), dual exhaust, Pertronics ignition, Converted to 12v. Alternator & Vintage Air. New Alum radiator, 160 deg thermostats & 4 lb. radiator cap. Runs great but will get to 212deg and way past that on a grade. I do not(can't)run the air.
1) How hot is hot on a flathead?
2) What can I do to keep the temp gauge from becoming my stress gauge?


Any help will be really appreciated.

Re: overheating flathead
 

I run the following in my 8BA:
Modern water pumps
180 degree thermostats
7 lb. Cap
Aluminum radiator

My flatty never gets over 190 even on the hottest days.
Just some suggestions.

Re: overheating flathead
 

I am happy with 190-195.

Re: overheating flathead
 

I would check that the thermostats haven’t moved and is causing blockage .
Split 10 gauge wire to hold the stat down as you slide the pipe Hose down

Re: overheating flathead
 

Living in the mountains we have a lot of Steep grades.
Ok I had my engine rebuilt by a flathead rebuilder (no longer around). The pumps were on it so I don't know what they are.
I see speedway has what they call modern pumps. Is that what you are referring to?
I can easily go with 180deg and 7lb.
I have noticed that my radiator reserve tank appears to be to small also.

Re: overheating flathead
 

Elev 4800 ft ,8CA motor , 180 high flow thermo, 15 lb cap, closed system(no air)- expansion tank,Brassworks radiator, 8RT late model pumps Never moves off 180 up/down hills live around Lake Tahoe,Ca before I did the complete upgrade of everything I had the same problem your having 36fordguy

Re: overheating flathead
 

Any of the pumps with bearings and improved impellers are good. Speedway, Drake, Carpenter
Are all way better than stock.
I'm using 8RT pumps as well.

Re: overheating flathead
 

My '41 is at sea level with very similar engine and radiator combination. It will peg the gauge and stabilize at about 215 on the IR sensor gun idling or slow moving for any length of time on a hot day. The temp goes up some on a long grade, but not pegged. I added a partial fan shroud and a spacer to move the fan closer to the radiator which improved the situation only slightly.

The same engine, pre-rebuild, ran cool under all conditions with a brass/copper radiator. Those aluminum radiators are rated at like 500 hp, but that is at ideal conditions with huge air flow and water flow. Increasing air and/or water flow will improve cooling. Since you are overheating at speed going up a grade, I suspect water flow. Maybe upgrade your water pumps. Also, if there is an air path from the grill over or under the radiator and into the engine compartment, you might want to block that to keep all the ram air going through the radiator.

Re: overheating flathead
 

First check that combustion gases are not leaking into the cooling system. Next check that ignition timing is not either too advanced or retarded at operating speeds. If all is ok, remove the thermostats and see if anything changes. Report your results. By the way, what heads are you using? It really helps to reduce cooling system heat by raising the compression ratio. If you are using stock heads they can withstand .050 milling cut.

I added an electric fan in front of my a/c condenser for operating in heavy stop and go traffic but never have a problem without the extra fan at cruise speeds. I have stock water pumps on a 276 engine and have been over the Rocky Mountains with the a/c blasting in August and no overheating.

Re: overheating flathead
 

Switch to a 10 pound cap if your radiator and hoses are strong enough to handle the increased pressure. Just for the heck of it try running without thermostats.

Re: overheating flathead
 

What rear axle gears are you running? You ask how hot is too hot? If the coolant boils it is too hot! 212 is pushing it especially at higher altitudes. Of course the pressurized cooling systems help raise the boiling point.

Re: overheating flathead
 

If you come back... You ever clean the block? manual clean is fine? or just bolt stuff to it?

Re: overheating flathead
 

Are you pushing water out the overflow? Have you checked the temp with a heat gun to see the real temp rather than rely on the original gauge?

Re: overheating flathead
 

A lot of data here, Thanks.
3800 miles on a rebuild, tanked and cleaned. Mild Isky cam & mild shaved heads. using all new high quality 12v gauges, elect fan that covers the full size of the radiator. I am going to start with high flow thermostats, up-graded water pumps. larger expansion tank and dump the 4lb radiator cap and start with a 7lb then a 10lb. see if that helps. keeping the alum rad for now and see if that helps. Before I invest $$$$ in a brass radiator. I'll keep ya posted, It will be a while till I can get to it.

Re: overheating flathead
 

With a full shroud electric fan, air flow should not be the problem. The other side of that heat exchanger (radiator) is water flow. I second my own motion that insufficient water flow is the likely culprit. Maybe Haney rebuild, or new Carpenter pumps. Drake is also good, but out of stock right now.

Re: overheating flathead
 

More often than not, a radiator with an internal lime coating will cause overheating. My '47 would peg the gauge until I replaced the radiator. Yesterday the air temp here was 94
and I drove all day with no problem with standard water pumps.

Re: overheating flathead
 

Running mild cam, dual 94"s, alum. radiator, Hurricane a/c system, shrouded temp controlled 12 vt electric cooling fan on my 8BA.
Living in the Tucson area, about 2000' elev., HOT summers with a/c on I may hit 210 degrees, usually run about 195-200. I also have dual temp gauges, one for each head and they stay within 5 degrees of each other. Only get higher temps when having to sit in traffic, but have never had it boil. I am running a 50/50 water-anti freeze mix and 180 degree thermostats.
Hope this helps??? Chap