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I just got my '38 going and drove around some with the hood off. Its got a new Afco aluminum radiator and Moroso aluminum waterpump ,elecric fan on a temperature switch . Did great idleing around with hood off , around 175-195 degrees . Now have hood on and temp gets up to 220-230 ideling but will drop down if I can get over 40 mph for a bit . Is the hood the problem ? It never did this with the previous setup . Or is the water pump not flowing enough at slow speed ? I had a stock 305 with long pump - stock '38 radiator before . 350 with cam and headers and all the chrome/aluminum goodies now !

howziit guy!

Hmmmmmm, is there also a new electric fan? push or pull? what cfm rating? what temp is it set to operate? did it go off, at the prescribed setting? did it go off, at all?

do you also have a motor-driven fan? thermal-activated clutch fan? is it the same distance to the new radiator, as the old setup was?

is your new water pump the long style, as your old motor's was?

DO YOU HAVE A FAN SHROUD, and did you previously have a shroud? is the fan correctly positioned in the shroud?

is the radiator coolant the same mixture, as your previous motor was?

JMO, your car is having a difficult time directing the hot air out of the engine compartment.

i had that problem in my '57 coupe. i installed a marine 12V electric blower in the engine compartment, with ducting, to expel underhood hot air towards the driveshaft. it worked...and it sounded WICKED, at the stoplight!

i also tried rerouting the OEM heater motor...to suck underhood air, and expel towards driveshaft also.(that worked okay too.)

with your hood off, obviously the engine heat exits the compartment easily.

does your hood have louvers?

how far down does the temp drop, while cruising at 40mph?

i presume that you are using aftermarket temp gauge.

i have both aftermarket/OEM gauges, both on the intake manifold in my truck. aftermarket reads 185F(okayyy!); OEM reads PEGGED...RIGHT SIDE!(holy cow!)

Hmmmmmm, bigger hi-perf motor(especially tight-clearanced rebuilt ones) produce more heat(friction)...chrome retains more heat...headers produces and emits more heat into the engine compartment.

do you have A/C now...and did you have it, with the other engine?

come back, over.....

Well ...the old setup had the long pump and now it has a short Moroso . I moved the motor towards the radiator to get the hei off of the firewall . so I dont think I have enouh room now for an engine driven fan . I dont remember the details on the fan , I got i off of E-bay but it is big , fits from one side of rad too other without much extra . its pulling from behind . No louvers on hood to but the side panels have stock vents still in operation . I may pop off the side panels and see what happens . I had stock exaust manifolds before and they had NO room by the frame , now it has headers and over an inch clearance from the frame . I still wander if the pump can't flow enough at slow rpm's,I wander about one of those "flow cooler" disc if it would help ? The temp has dropped 20 degrees in about a mile over 40 mph with hood on. Don't have any coolant other than water in yet , wanted to make sure everything was hooked up and tight before puttin in the green stuff . It never did puke when hot , the fan does kick on around 195 and off (I think) around 175-180 . No shroud yet either , gonna be tight gettin one in and clearing everything .

howziit again guy!

that moroso pump should be okay, as is...not needed to be modified further, i don't think.

i'm presuming the fan-to-radiator clearance is within specs,per instructions.

custom shroud, fitted to your radiator&fan, should help.

running without side panels should help also.

I took the old girl on a little road trip sunday to a town 30 miles down the road and the gauge never got over 175-180 until I got into town and sat at a stoplight for a few minutes . Went by a buddies house and was showing him a problem I am having with the carb (power valve blown) and - with the hood open on one side - the truck didn't get too hot . Looks like the fan can't get the hot air out of the engine compartment fast enough by itself . So , I wont mess with the waterpump , will probably move the electric fan to the front and put a small fan on the pump .

howziit again guy!

now we're getting somewhere. good for you.

QUESTION!!! in the position you now have the electric fan, is it spinning the correct way, so that it's sucking, not blowing?

if it's blowing, that's your problem. correct that by reversing the voltage polarity, or flopping the fan blade.

if the fan was PULLING air into the engine compartment, then make sure it's PUSHING air, when you relocate to radiator front.

please forgive me, if i am stating the obvious.

When checking for a fan, look at the old Mister Gasket fans. I bought one in the package at a swapmeet for $10. It worked perfect for my engine. The pump was less than 1" from the radiator. The fan is flat on the front side clear to the tips of the blades. It's one of those stainless steel flex fans.

I had the same problem you are having, electric couldn't cool it, and it's just a stock 250-6. With the flex installed, it won't go above the 160 themostat, and does it ever move the air. I think it's 18" with out a shroud. I can bearly get a wrench to tighten the bolts. I had to tape the bolts to the fan and put the whole mess in together, thats how close it is. Joe

howziit again guys!

JMO, stainless flex fans are accidents waiting to happen.

the one i had was so sharp, it could cut tomatoes, slice bread, and the backs of my hands...with the engine off.

i had to tape the blades, in order to work on my '57's fuel pump,radiator,etc.

after learning that people have been KILLED/seriously injured by that disintegrating "guillotine", i replaced them with a thermo-clutch fan, or a fiberglas flexfan. :p

Tried a flex fan once. Cooling was worse with it. Try a steel fan as your problem seems to be air movement ie: only heats up at idle or slow speed not on the highway.

howziit again guys!

you're right, Jack; i forgot that the original 4-blade fan on my 283 cooled THE BEST.

sadly, i got caught up in the HP chase, and have been plagued with overheating problems ever since.

Hmmmmm, i wonder if it'll fit on my BBC; i'll go look for it. :p :p :p

I had a small plastic fan on before and it cooled fine , even without a shroud . I had to use the small one to clear the lower radiator hose . Radiator sat high-water pump sat low . I about froze in the winter though , covering the rad. with cardboard , driving it 30 miles down the interstate still wouldnt get it warm enough to open the automatic choke . I always vowed that I would remove the pump fan and run electric on thermastat. I suppose I will go back with the little plastic one. It did move the air ! I know what you mean about the stainless flex fans being sharp , sharper than heck if you get your knuckles around it .

bear, what temperature thermostat are you running? It sounds like its broken- you shouldn't have to cover the rad to get it to heat up.

On my 37 the radiator was also high and water pump low. The lower 1/3 of the fan was missing the radiator. I redrilled the core support and lowered the radiator about 3". The fan clears the lower hose and pulls air through all of the radiator. Joe