The Stovebolt Site Forums The Shop Area The HiPo Shop '52 Panel with 350 overheating

I did a search about overheating on trucks with 350's installed. Also about fan to radiator distance. I found some info but many of the posts are old and the links don't always work. My son just purchased a '52 panel with a 350 in it. Runs great but the seller did tell us that it will get hot if in slow traffic. Today, my son brought it home and drove it through town. It overheated and coolant came out the overflow tube at. I did find out that the fan should be about 1/2 inch from the radiator. The space on this truck is about 4 inches. There is no shroud. A few questions: Am I correct in assuming that the over heating is because the fan is too far away from the radiator? The PO suggested installing electric fans. I have read that a shroud should be installed. Does a shroud from another vehicle work? Are shrouds for this application available? What is the cap pressure for a 350? I don't have any info as to what this engine is from. Are they the same for a 350 or similar? (My only experience with a radiator cap in an Ad is my '47 1/2 ton which has a rating of zero.) Shroud better vs electric fans? Should we install an overflow tank? Thanks in advanced for any information regarding this situation.

'52 Panel

Hy Rusty Shackleford, we must know what the whole cooling system can handle pressure wise, is the radiator a modern replacement capable of some pressure, is there a heater core as well, is it capable of some pressure? A shroud would definitely be a good idea, electric pusher fans mounted in front of the radiator could also cure the overheat problem and if you installed those you could remove the engine driven fan. If you were sure the cooling system components could handle some pressure then a coolant recovery system would also be a good idea, sorry if I gave more questions than answers, but there are more things we have to know to make the best suggestions possible.

I can offer a couple of suggestions based upon real life experiences. First install a fan shroud. The tips of the fan should be about 1/2 inch inside the shroud. There are shrouds to be had from the aftermarket folks (Google) or go to your local salvage yards with a tape measure and some basic hand tools. If you do install electric fans it’s best to get the ones that are mounted in their own shroud. When filling the radiator fill it to 1/2 inch above the cooling fins leaving plenty of room for expansion. Radiator cap pressure 12-14 pounds should work. Others may have a different take on it.🛠

I've got a 305 in my panel with a new desert cooler 4 row radiator. I figure since all cars have electric fans, and I've seen very few "failures" I decided up front to go with an electric fan which is encased in the fan shroud. I've driven it in 100 degree heat in parades and it has never gave me a problem.
Do it right and forget about it.

.....do you think the radiator may be clogged?? just asking.

....FYI, if I remember correctly, every pound of radiator cap raises the boiling point of the coolant by 3 degrees...
if that is wrong someone will let us know!

Is the radiator stock?
Does the overflow tube come out of the cap area or the tank?
Does the fan spin the correct direction? (serpentine belts use reverse rotation fans and water pumps)

As mentioned above, you need to know the limits of the radiator and heater core, the old stock ones may take up to 5 to 7 psi caps or they could be zero pressure units, new modern radiators take 15-17 psi caps. Trying a high pressure cap on an old radiator will likely blow out heater core or the tanks on the radiator.

Try moving the fan closer to radiator, spacers are fairly cheap and you will get better results with a mechanical fan. A shroud would help, but not if the fan is to far from the core, and if you get it close enough you may not need the shroud. If you go electric, buy the best you can afford with the most cfm available. You will need a decent alternator to power the fan at low speeds as they pull a lot of amps. Use heavy, 14 gauge wire with 30-50 amp relay, and a temp control to turn the fan on/off as needed. Manual on/off is a sure way to run your battery down when you forget to turn it off!

Be sure you have 50/50 coolant, or straight water if you are in a hot climate. Flush the system to be sure it clean just for added insurance.

Slow speed over heating is a sure sign of lack of air flow through the core.

I'd suggest spacing the fan a couple of inches closer to the radiator and then installing a relatively short shroud. A fan blade should go half of its width into a shroud, so the point where the fan center meets the water pump pulley or the spacer should be even with the back of the shroud. Going further forward or back seriously affects the volume of air the fan can draw through the radiator.

Electric fans are noisy, especially if you install one that can move enough air to do any good. I'd much rather have an engine driven fan if at all possible. The thermostat sets the minimum operating temperature of the engine- - - -the size and efficiency of the radiator determines whether or not the engine runs at that temp or overheats. The only reason to pressurize the coolant is to allow it to go above the normal boiling point for the altitude and stay liquid. At sea level, one pound of pressure raises the boiling point 3 degrees. A 15 pound cap would let the coolant get up to 257 degrees before it boils, but the radiator, hoses, and heater core would all have to be capable of handling that pressure without bursting.
Jerry

Step 1 is to determine if truck is actually overheating. You do that with a temperature gauge. I assume you have no water leaks. Be sure you don't. You did not say how you determined it overheated. On some radiators, you need to just fill above the coils and leave some expansion room or it overflows a little but that is not overheating. That is why a temperature gauge is needed to see if motor exceeds about 200-210 deg F. 220 F is shut down time.
The wrong cap can let water "boil"/evaporate out while driving. Other things can cause "overheating" besides inefficiency. You can have overheating due to fan not blowing/sucking enough/too far from Rad, motor overheats and pressure lets water out cap or...... you can have loss of water, blocked radiator, radiator too small, collapsing hose, bad water pump, loose fan belt, bad thermostat......... and then overheating.

Step 2 is be sure you have a new thermostat. Use the recommended one for the year of motor.

Hard to say what radiator cap to use. If radiator is original, get a new aluminum one. An old rad and a newer V8 usually does not work.
Your fan is WAY TOO FAR away from radiator. Many shrouds available. Some can be trimmed/modified to mount/fit. As Jerry says, fan should be half in/half out of shroud.
Be sure fan centerline is approximately at radiator centerline in the Y axis.

These updates/new parts/shroud should do the trick with no electric fans needed in your area of the world.

Yes a donor fan from some other vehicle may fit, but finding which one is difficult.

One thing I notice that no one has mentioned is common in V8 conversions: many owners cut away the sloped part of the latch plate panel to move the radiator ahead. The panel is an integral component of the entire airflow engineered system, including the lower front splash apron and the grill bars. Note how it all is designed to catch air and move it upward in an organized flow to the radiator. When owners cut away the front of the latch plate panel that cohesive flow is lost. Yet ironically they think it's opening up the radiator for more airflow.

Thanks for all the information. I've come to understand that the fan is definitely too far away from the radiator. The engine sits low in the engine bay and part of the fan is below the radiator. The radiator looks like an original (It has Harrison on it and I just found some paper work that shows it was re-cored in 2005.) I've purchased a new Northern radiator but can't get the paired shroud with electric fan locally. I found one at Brother's which fits the '47-'54 radiators. So I think I'm on the right track. There are no leaks, I've bought a new thermostat. I was thinking of putting a new cap on (12# or 14#?) as the one that's on there (although it's nice and shiny) doesn't have any indication of pressure on it.

The original radiator is likely a zero pressure system, so no new cap will be needed. Why not move the fan forward? Do you really want to listen to electric fans running all the time? My 250 has a low water pump and the fan blades go below the core and it still cools just fine. Lower the radiator if you have to.

I just completed a 350 swap in a 49 GMC using the stock radiator. I too discovered the engine sat to low to properly cool with a mechanical fan.
I went with a 16" electric fan with a home made shroud, a 4lb cap and an overflow bottle and so far its not gone over 205 and avgs 185-190 in normal driving and I haven't had to add coolant. I'm still experimenting with thermostats and am running a 160.
Something like this elec fan and shroud combo may interest you.

'49 with a 350 swap here too. I cut metal at the bottom of the radiator support at the inside corners to allow me to lower the radiator 2 inches to get more of the fan on the radiator. Mechanical flex fan is 1/2 inch from the radiator. Runs at 185 all day long.

I have a 1-1/2" Derale fan spacer I just took off mine. PM me if you want it.

"Overheating" is one of the most misused terms in our hobby. A lot of stovebolters need a fainting couch anytime a temp gauge goes above 200 degrees. Beginning in the late 1950's, most vehicle manufacturers stopped putting numbers on their temp gauges and replaced them with "C" and "H" designations. Most engines live very happily at coolant temps in the 200+ degree range AS LONG AS THERE'S ENOUGH PRESSURE ON THE COOLANT TO KEEP IT FROM BOILING!

If the radiator was recored recently it's probably pressure-rated for a 15# pressure system or more. Make sure the heater core is rated for that pressure, put a good 15-17 pound cap on it, and drive on. If you want a little insurance for traffic situations, fit an electric fan in front of the radiator with a temp switch that turns on a 220 degrees, and back off at 200- - - - - - -just like a majority of the cars built since the mid-1980's have!
Jerry

I used a fan/shroud from Old Air Products in Ft. Worth. Aluminum shroud is very nice...looks to be 3/32" thick and bent/formed very well. 4 flaps at corners to kick out at speeds over about 40mph and a SPAL 16 inch fan (2070 cfm). Made for these trucks. I got the one with the adjustable thermostat/relay. You will need to make your own mounting tabs, but I expect you would with any of these pre-made shrouds.

You can see it here:

https://tinyurl.com/ybaon6je

Thanks for all your input. With the new radiator and shroud the temperature gauge shows 190 to 200 even in traffic (which, apparently, is in the normal range for a 350. I would say it was overheating before as the temperature gauge was at 230, the engine ran rich and stalled, and coolant spewed out the overflow tube - this hasn't happened since the install. I have since found out that the engine is from a 1970 Caprice - 250 horsepower.

Did you get the universal shroud that you cut the hole yourself?

The shroud is from Brothers and it's made for the '47 to '53 aluminum radiator they sell. It came with the hole already cut, the fan, and the wiring, relay, and temperature switch. The radiator is from Northern Radiator. I got the radiator from a local auto parts chain. I could get a shroud from Northern with two 10inch fans (made for the radiator I got) but it would have taken 5 weeks to get it up to Canada from Minnesota. The Brother's one was shipped in a week.