I have a 1946 flathead, High flow water pump, 2x2 intake with 2 strombergs. new radiator with 1240CFM electric fan, mix of water with 2 bottle of water wetter, no thermostat, 7lbs cap. Original distributor modified with pertronix ignition. I have a strange overheating problem. If I start the engine and let it getting hot at idle it take just over 5 minutes to get to 200, I then start the fan and the temperature goes back down to 185/190 degrees (passenger bank is always 5 to 10 degrees higher than driver side). I can let run at idel like this for 30 minutes with the Los Angeles heat with no problem, If I stop the fan it take 2 minutes to go back to 210 and goes back down to 190 in 3 minutes after I restart the fan. No white smoke or water in oil. the problem come when I drive it, after few miles it start to heat more and more, it look like I loose water (seams to be from the overflow). after 20 to 30miles engine run at 200 and doesn't cool down even if I let it running at idle with fan on. It already went up to 230 last saturday at the end of a 45 miles trip, and this was running not even seating in traffic, weather was really hot saturday tho. I refilled over 2 liter in the radiator after that. the car was running really bad then, miss firing under load, the coil was really hot (the coil bracket is seating on the passenger side of the motor), I barely made it home. Next day fire it up and run great. I'm a bit confused of what to look for,I will do a compression check later on today and try to run 160 degree thermostat in the top hoses.
First, is the gauge correct? Take off the belt so the pumps are not running. Start the car and look for bubbles in the radiator. Also can take the upper hoses off and do the same test. If you have exhaust gasses getting into the cooling chambers you should see bubbles. If that checks out, timing! Retarded timing = overheating. 4lb cap is better. imo What type of radiator? Is it big enough?
Why aren't you running thermostats? I would run a restrictor if you think you don't need them....there needs to be something to control water flow through the cooling system.
Do two things.. Be sure your gauge is correct as stated before and secondly you didnt mention the radiator type,,, A stock one should only be pressurized to a max of 4-7 pounds. Some radiators will need a pressure release valve at the overflow tube because the overflow tube is positioned below the radiator cap neck in the radiator. Losing water at high speeds is common especially with high volume pumps. Your cap should be within that 4-7 pound range. Now if you have an aftermarket radiator. all bets are off. Next area is the timing.... Do you know if its working correctly..? Is it advancing??? How did you set the timing?? As stated a leaned out carb will make an engine hot.. Is the engine a fresh rebuild?? If not have you cleaned it out with vinegar?? If not search flathead vinegar here on the hamb.
Run a combustion gas leak check [Block Check brand in the US] to confirm or rule out that possible problem. Never saw the need for high flow pumps on a flattie,back in the 50-60s we removed every other blade from the impeller because they moved to much water at higher RPMs. Ran a 296CID here in the desert and it would run 180-190 in 110* days set up that way. 180* stats and 48 Cad radiator.
I run no stats in one flathead. It takes 20-30 mins of driving to get over 160. doesnt go over 180 in stop/go traffic, in fl, after driving for an hour. Thought about using stats or restrictors to help heat it up quicker.
Overheating while driving is usually poor flow through the radiator. Take a drive up to Bedford area, Kempston, actually, and see the folks at Kempston Radiators. I can't recommend them highly enough
Id quickly say that if you have a coil that is running hot and it is back firing the coil is wired backwards. This gives very poor spark under high temp and since you let it set over nite and it fires right up and runs correctly Id start there.
On the timing, two immediate things: First, loosen locknut on the vac brake and turn the bolt out as far as it will go BY HAND (so you do not pop the retainer off the bolt with wrench turning) then back in about 1 1/2 turn. Lock down, leave it there unless engine shows pinging. Second, get a timing light and run it up to be sure the advance is moving. The shaft/cam interface in these distribs is sometimes gummed up and so locks advance until cleaned.
update: Removed top hose and fan belt and had no bubble when running. Radiator is new, in brass, 20" tall, 4 cores. I will fit 180 degrees thermostat at the top radiator hose, have to find the right size tho. I looked at spark plugs, they was black, will get a new set. Looked at distributor, noticed that I dont have vacuum. It s a crab distributor with pertronix internal and flame thrower coil, should it have a vacuum? I dont have any plug for vacuum on my intake either (eddy meyer 2x2). Dont really know how to set timing, will try to find a shop to have to check advance.
regarding miss firing, it only happened last week end, never had the problem before, did 150 miles in a really strong heat the week end before, it was running great appart for the over heating problem...
what the problem with air filter? I was thinking to remove them tho, I have those: http://www.prestostore.com/cgi-bin/store.pl?ref=partsnstuff&ct=57116&pd=250044
Check timing on the engine, no shp needed, just make sure it moves a significant space on pullet from 400--2999RPM and set that piston as noted above whether hooked to vac or not. Basic timing by a version of Ford's field expedient system: http://www.vanpeltsales.com/FH_web/flathead_engines_distr-timing.htm takes 5 minutes, just R &R with 2 bolts! Black plugs can be caused by richness or by running retarded. Do all tuning with air cleaners OFF, if running then changes when you put them back on discard them and find a better way to filter your air! The common tiny chromefilters are often restrictive when brand new and clog quickly because of size. Hook up the vac properly when you can, but I don't think it is contributing to heating.
PS...since you have electronic conversion you can't watch the points move... So, leave small primary wire hooked up. Position distributor with the 2 rulers and have the adjuster screw retarded a bit in relation to center of scale. You need an assistant now...advance the timing at that screw until there is a spark from #1 plug wire held close to cylinder head. Distributor rotates CCW, proper timing is right about the center of the scale, sliding screw upward retards, down advances. If this is too alarming, just put the screw about half a line below center of scale and call it good.
So, I have some update on my problem. I added 180degrees thermostat, was running a bit cooler. check for crack or leaks, nothing, all seems good. Done a tune up, changed jet as it was running to rich, got both carbs balanced, timing was off. Car is running way better now, faster on the road and stay cooler when running or at idle... but after 10 miles at 70mph on the freeway, it start miss firing again and loose all his power and run shit, start to run hotter, loose his idle, sounds like if it was running on only few cylinders. let it coole down over night and all is back to normal... really I dont know what to look next, but it seems that this problem is linked to my overheating problem. any advices?
What coil is on the car????? , a low resitance coil will cause the pertronix to miss fire when hot . Measure the coils resistance between the pos and negative. Typically any coil below 1.5 ohms will over heat the coil, we usually suggest a resistor of 1.5 ohms and a coil with 1.5 ohms , seems to work with the pertronixs controller....
If it's flowing too fast to transfer heat to the radiator, wouldn't it be flowing too fast to absorb heat from the engine? Short of cavitation, what is it about increasing the velocity of coolant that diminishes it's capacity to absorb or give off heat? Bob
GMC BUBBA, I have a PerTronix 40011 Flame-Thrower 40,000 Volt 1.5 ohm Coil, as requested on the pertronix doc.... it is brand new....