I'm not sure where to start only to say we have discussed this at least 3 times with 20 or more posts each time.

Not to rehash anything but the questions are always radiator, timing, hoses, thermostat, hot spots in block, and the list goes on. Guys I tried everything rechecked it all.

I can only tell you everything is new factory or better, or at least I thought.

The car would go to 240 degrees + in a heart beat on the freeway. One would conclude that with this amount of air coming through at 70 mph + that should not happen.

I came to the conclusion that I needed to replace the electric fan that came with the brand new Dewitt radiator. The fan could only turn as fast as the elect. motor would let it. I believe the elect fan was fighting the air and not it letting through, and or disturbing the air flow.

I took the radiator out, removed the Dewitt fan and replaced it with a flex fan and installed it as originally designed by GM.

Do I need to say more, I can't even get it to 180 degrees.

I spent untold hours going everything, taking apart, spending $$ by taking it to others to check this and that. I purchased and spent good money for a product that was suppose to be state of art and would work on a stock engine rebuilt to factory specs.

Would like to hear what you all think about this, and how many have been as frustrated as I am right now knowing that again a product that you pay good money for, that is suppose to function as advertised does not.
Dennis

 

Just a WAG of course but I'd say you had the fan wired to run backwards and it was tryig to PUSH air back out the front of the radiator.

What do you think about that?

 

No way was it wired wrong, I thought I said that I checked rechecked and spent additional monies to verify that all was working as designed. You could place paper in front of the radiator and it stuck to the radiator
Dennis

 

IMHO, electric fans are a total waste of money. Use your GM fan.

 

I have seen the same thing several times.

No one ever believes me when I tell them that the stock fan/shroud is the way to go (on any vehicle) and to dump the electric fan.

GM spent millions of $$ at the desert proving grounds making sure these cars would run cool in all conditions. Why people try to modify the stock cooling system for a general purpose vehicle (not race specific) is beyond me---or if it didn't come from the factory with an electric fan, you don't want one!

The only electric fan on my car is going to be the one be the one behind the Earls oil cooler

Doug

 

Straight talk.

A thought, heater/defroster blower motor, did you forget or is yours without one...

 

My 56 has a very healthy SB400 with Rochester FI.
The radiator is stock (copper), shroud is stock, stock water pump and 4 bladed fan. Zip, nada, zero, none, no overheating problems. Although, I DO have a single electric fan in front of the radiator for the specific purpose of providing cooling air during long idle periods in the summer or during very slow moving, heavy traffic on very hot days. On the rare ocassions that I've needed the elec fan, as soon as I get moving again (10-15mph or faster), I turn the elec fan off (I have an on/off switch under the dash).
MY vote, keep the cooling system GM configuration, and keep it in good condition.

An added comment. In the past, there have been many times when owners have had overheating problems and could not ever find the problem. BUUUUUUUUUUUUUT, the engine/cooling system did NOT exhibit symptoms of overheating (BIG CLUE), such as erratic engine operation, puking coolant, etc. As it has frequently turned out, the temp sender did not match the proper resistance requirement for the gauge. It is VERY seldom that temp gauges get replaced, but it is somewhat common for temp senders to get replaced, and that is frequently the source of the gauge showing a hot condition.

 

Dennis, I for one really appreciate sharing your solution and perseverence - it makes sense! We are in the middle of an engine swap with cooling problems.

You said that you used the "GM flex fan"? Did you mean the fan and clutch as was OEM? Glad you are

Regards, Mike

 

Mike
I went back to the way GM designed it. I purchased a 17" Flex-a-lite fan and two spacers.

I used a direct drive spacer[ no clutch fan] to get the right distance. Wanted plenty of air and I got it.

Welded them togeather. I did not weld them, I had that done. The fan blades are suppose to be half in and half out of the shroud for the best performance.
Dennis

 

I went through this back in the mid 70's with my 70 Vette (350-350, A/C, 4 speed, etc.). Had the stock clutch fan go belly up for the 3rd time (2 times before, the clutch was replaced under GM warranty). So I decided to try a dual electric fan system. One trip on the tollway to work was all I needed to see the error of my thought process.

The dealer stated that GM offered a flex fan for Vettes as a replacement for the troublesome clutch fans on Vettes that had heating issues, which mine did not, but I needed something that would last! That flex fan was terrific (and never failed), and I have used the GM type ever since on all my vehicles (when ever possible).

Plasticman

 

Seems to me that there are about 10 million cars on the road today with factory installed electric fans and they don't seem be overheating. The problem is not the electric fan. The problem is the lack of engineering in the aftermarket units.

 

John, I just could not refer to you as plasticman.

I used this forum for everything on building this car, including what I should do about the raidator. The car was a project car that I bought, it reminded me of a kit car. Everone refered me to Dewitt. I purchased the product from him and ordered it from him to include the fan. I should have checked on this but was under the impression anything he sold was right on.

He I'm sure is a very ethical person, as he disscussed on his dime all the cures for this problem which included a new larger radiator. He never once mentioned that the fan was the villian.

I wonder what his thoughts are now that I solved the problem by removing his fan setup. By the way once I removed it, I wasn't real impressed with the blades or their design.

Dennis

 

Dennis,

From what I have heard, your comments on Tom Dewitt are right on, and he certainly knows his heat rejection systems. We see him quite often responding to heat issues, so I expect he will respond when he sees this thread.

It might be an issue with that particular fan design, or maybe a new product? Will let him come forth and provide the answers.

Bottom line is what works for you. Glad to see that you solved it!

John (the Plasticman)

 

Alright, now you guys have got me scratching my head about this overheating/fan problem. I was all set to get a set of dual electric fans for my overheating 283/270 next summer but now I don't know which way to jump. I slipped a bearing on the crankshaft in my 1960 as I was driving it home after purchase a couple of years ago. I had the local engine builder do a complete overhaul with as many new parts as it required (same block & heads but just about everything else new). It has run very hot ever since (1200 miles on the engine since rebuild with no geometry changes in cam, valves, etc.) especially at any speed less than full highway speeds. I can even handle 90+ degree weather at just over 180 degrees on the temp guage as long as I keep the speed at 65mph or better but as soon as I drop down to city speeds, even for a very short time, the temp guage rises to 200...220, etc until I can hear the antifreeze boiling away in the system which is sealed with a 7 psi radiator cap. I am going to have to do something about it but now I am not sure what to do. I read an article in one of my corvette mags this fall about the dewitt dual fan setup with thermostatically controlled fans that sounded ideal for my needs but now I am not so sure. What say you all?

 

Keep the mechanical fan. As was stated above the electrics need a ton of engineering, huge motors, etc to pull enough air!

 

Tony don't waste your $$. Use the factory setup. I saw a fan that I would have loved to use but because of my serpentine belt system, direction[counter clock wise] I had to use the Flex-a lite with reversable blades. The other fan is used on baha trucks and does it suck air, I will get you the info. if you want. Check with someone who builds trucks for this application, Look outside the box, thats what I did. An elect fan is only going to go as fast as the motor was designed, in addition, I feel it inhibited the air flow at highway speed.

If you check an earlier post on this subject one of the solutions was the use of a Lincoln Mk 8 elect. fan set up. claimed to use a lot of air.
Dennis

 

DZAuto already mentioned it, but definitely check your temperature with an infrared thermometer pointed at the thermostat housing to make sure it is not just your sending unit giving your gauage a bad reading. While doing some engine work this week on a '64, I put in a new temp sending unit - it had the gauge reading +/- 205 after 5 minutes of running the engine at idle while setting the timing and adjusting the carb. The infrared temp gauage read only 180 at the thermostat housing. The gauge is 25 degrees off (at a normal operating temp).

After discussing with a local garage owner who repairs/restores classic corvettes, he said all of the new sending units he has tried result in a hot reading from the gauge (he is out of older accurate units). Anyone know where to get a sending unit that works accurately with the old gauge?

 

Tony,

My 62 has a warmed over 350 (dual AFBs, headers, etc.) with an old copper brass non-oem, nothing special radiator, 160 deg. thermostat, and never overheats, including 96 deg. Florida summer weather. It has a GM style 7 blade flex fan, and if it gets to 190 F (highway or stuck in traffic), then something is wrong. Note that it does have a vacuum advance on the dist. and I did add some extra sealing around the radiator and shroud (when I first got the Vette several years ago). And that does not hurt either.

Plasticman

 

Did GM put a solid spacer mounted "flex fan" on any vehicle?

 

The factory electric fans are part of a factory engineered system, which included the motor, tuning, radiator, fan and a few other things.

A SBC or BBC dumps a lot of heat into the cooling jacket as compared to some more modern engines, if you don't have as much heat dump into the jacket, you don't need as much cooling capability.

Doug