car will idle at 1000rpm all day 175 F or less but when idle set at 2000 rpm temp goes up to 230 in 8 min and pegs gages in another 4 min (260 +). The guy I bought the car from said it always ran hot but he didnt drive it much. The guy before him said he raced in on dirt and asphalt and never had a heating problem. 8BA 4in crank 1/8 overbore. Sharp manifold with 4 bbl. Straight water for coolant . Isky 400jr cam Dirt track style roadster Here is what Ive done to try to fix the problem: -block magna fluxed and pressure checked at 125 psi in a tank of water -rebuilt engine -changed from Offy to Edelbrock alum heads -tried 2 diff Mallory dist and coils -tried Holley 4bbl instead of Edelbrock 4 bbl on Sharp mani/ switched to 2 bbl Zenith on French Ford manifold - new speedway water pumps -run with no thermostats/ with thermostats/ with and without restrictors -radiator rodded /repaired by 2 different shops - timing and advance verified - 3500 cfm elec fan with shroud - exhaust headers almost straight thru (no restriction) - Mech temp gage in each head -coolant system burped through gage sending units -indicating slight exhaust gas in coolant but I Ksealed it -I just pressure checked fully assembled engine (minus water pumps)through water pump opening blocking off water outlets in heads and it held 100psi for 30 min Any ideas? thanks
Is it puking her guts on the ground at 230? A lot of guys on here say "hot" based on crappy gauges but the car isnt actually boiling over.
Is this an 80 year old radiator ? Even if it has been rodded out,,,,it might still not flow well . Have you done a test drive,,,,,,anything over 30 mph you don’t need a fan . Sounds like you have done everything you could,,,except replace the radiator . Tommy
If it’s in the car in your avatar the nose may not have a big enough opening to provide enough air across the radiator.
Thanks all this radiator was built for this car about 20 years ago. It has always had this rad and engine. It appears to be flowing ok. It has always had this nose. It does boil over at about 220 indicated (depending on what pressure rad cap I have on it). I have run it with a stock full size rad -no change. I've run it with and without thermostats and restrictors - no change. I'm in Arizona so dont need thermostats but trying everything. Driving me nutz for quite a while.
Take that nose off and try it. That's a puny radiator for a big flathead, and an even punier grille opening. A 0.125" overbore is a lot of bore. My flathead is a 286, but when it was built it had all the rust sandblasted from the water jackets. And my Walker radiator has only boiled over on a super hot summer day sitting in traffic. It goes down the highway about 175 in July.
I’m not saying this is your problem and I know why you did it but the shroud is blocking a portion of your radiator and preventing flow from the grille in those areas. With all the bases you’ve already addressed I’m leaning toward a blockage in your block. You indicated you have gauges on each bank. Are both sides heating up evenly at 2000 rpm? Are you losing coolant at speed on the road that’s not related to boil over?? Is the radiator truly pressurized or does it lose coolant at the overflow? Try this…. Drain your coolant and install 100% vinegar in it. Run the engine on the road even at 1000 rpm for a good 50 miles if you can. Drain and flush it. Do it again and again if needed. Ive flushed an old flatty like this 5 times before it cleared out.
^^^ Do this, then give it a flush with baking soda added to the water (to neutralize the acid in vinegar).
Another test for you. I like alchemy’s idea. While you’re at it. remove the shroud and just temporarily attach the fan to the radiator directly. I’ve used zip ties around the edges of the radiator sides. Not through the fins.
Like Pete Joe said I had a problem on a car I built a few years back. It was a 50 Plymouth Suburban that I put a 276 DeSoto Hemi in it and no room for a mechanical fan. So I built a really nice shroud and electric fan combo that looks pretty similar to yours. Sitting it never got hot but started going down the road and it just keep creeping up and up and up and I figured that the Shroud wasn't allowing enough air to pass through the radiator. I took the Shroud and electric fan off so there was nothing and drove it and the thing sat at 180 just cruising down the highway. So I fabbed up some nice brackets to hold the fan onto the radiator itself and no more problems in a bunch of years. Not saying this is your problem but just something to check
Its a 20 year old rad and I have driven it quite a bit but its only good for about 20 min and its way overheated. I ran it with a stock rad but I'm going to follow up on rad thanks
Recommend a heat gun so you can see where your hot spots are . I have about 10 questions for you but for now what are you doing fiddling with idle at 2000 rpm and running it like that sitting still with no air going thru the radiator . I'll have to say your just creating a bad situation I don't care what your reasoning is these Flatties and their cooling systems are not made for this type of treatment . So what I want to know is : Does it throw a spout when coming to a signal ? And do you hear detonation ( deep drumming sound ) ? Your ability to change out parts is fantastic but I question this 2000rpm thing and wonder what hasn't been told here
Are you running thermostats? May be hard to do, but I would like to know the temp of the top tank and lower tank of the radiator when it gets hot. I wonder if the water if going through that small rad too quickly and not be able to cool itself. At speed, the pumps push the water through the system faster than at idle which isn't your problem. Most overheating issues happen in reverse. Meaning overheats at low speed or at idle. You problem seems like the water isn't not dissipating the heat at speed. Did the car sit for any length of time before you go it? Flathead blocks are notorious for collection gunk in the water jackets. I may have missed it, but you checked timing and for a lean condition, correct?
The 2000 rpm idle is because it heats up while driving so I am trying to isolate the engine from everything else (auto trans C4 , driveline)etc. The fan is pulling all kinds of air, in fact at 175 the fan kicks on and if I let it idle at 1000 it will cool off to 160ish. Rev to 2000 annd in 8 min or so its at 220+ With a 16 lb rad cap it will boil over at 220 indicated. I dont see it boilin over at signal unless I stay stopped. I usually try to avoid signals. I have an 8 mile 15 min loop I use as my test run. Mostly stop signs soo no long stops No detonation. thanks
I never had satisfactory cooling with an electric fan on these things. You could have a blockage in the block somewhere that's inaccessible. Be sure the head gaskets have the correct water passages and are installed right side up. Just a thought: the fact that it cools at idle and gets hotter with increased RPM would seem to indicate a lack of coolant flow. Check the water pumps for loose impellers, too.
Hi, After I rebuilt my 59AB, bored and stroked, it ran hot for the first 50 to 100 miles or so, now it runs cold! You mentioned about idling but not about miles. How many street miles do you have on the rebuild? Glenn
This rad was built for this car about 20 years ago and was ok for approx the first 15 years of its life. I had it cleaned and checked I also drove the car with a stock V8 rad -still overheated the following temps are over a 2 week period top tank 9readings avg temp 190 bot tank 9 readings avg temp 168 pass water pump (gage in each pump) 22 readings avg tenp 183 driver water pump 22 readings avg temp 184 all the above at idle while driving (stop and read water pumps) 205 to 220 driving rad temps (24 min run time) top229, bottom 156 -I only have one reading I've put a thermal imaging camera on it and nothing stood out. Lots of data! Now that I'm looking at it the water pump temps while driving seem very high for water that just came thru rad but the water does mix with block water thru the little hole in the water pumps. Is there anything in a rad that can wear out? If the tubes are clear and its not leaking why would its performance change? thanks to all for your ideas
Its been thoroughly cleaned by me and then by machine shop. Its overheated with 3 diff sets of head gaskets and the pumps are new from speedway but it overheated with the old pumps. thanks for your input
Have you checked the plugs or AF readings for a lean condition at 2000 rpms? What induction set up are you using?
The laws of Thermodynamics are finite. Look at it from this angle. If the radiator rejects heat from the coolant into the atmosphere at the the same rate that the engine is adding heat to the coolant, then the coolant temp will remain constant. If the coolant temp is rising, the engine is adding more heat than the radiator can reject. Therefore, you need to increase the heat rejection capacity of the radiator. The easiest way is to increase the mass flow rate of the air across the rad. Larger fan, better shroud, etc. The 2nd option is to use a larger rad with more fin surface area. Everything else in this situation is probably working around the margins, and it sounds like you need to hit it with a big hammer, or a bigger rad in this weak analogy.
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