As you well know these cars didn`t overheat from the factory. BB or SB it makes no difference. You have a new radiator and the correct thermostat but I would take JohnZ`s advice and dump the flex fan back to the OEM clutch fan as long as everything else is working correctly that others have commented on.

 

I had a friend that put in a 454 into his '66 Chev C-20 4X4 truck. He originally put all this hotrod stuff in like flex fans, additional aftermarket electric fans, trick this, trick that, all the while I suggested he stick with stock GM components, After he got tired of the over heating, he went to a GM 5 blade fan, and fan clutch, again at my urging, properly spaced to the radiator,a nd the over heating stopped.

Doug

 

Yah, but all that fancy high dollar trick stuff looks so pretty. It dont mean that it works though does it.

 

Not to get off track but this motor is not tricked out or shimmering with bling... the flex fan is a $35, 6 bladed, metal race fan without a clutch but compensated for position by a spacer... I am starting to think the missing lower shroud and lower baffle are big time contributors...

Scott

 

And you located the problem all by your self.

race fan= low drag at high RPM, low air movement at low RPM. the electric fan is probably also impeding air flow thru your radiator.

I ran my 327 '61 for YEARS without ANY shroud at all, and didn't have any over heating problems with the factory clutch and fan. I only went to the shroud at a time when I could afford to buy a new one, and I got tired of the engine looking half finished without the shroud

I am sure I have said this before, but GM spent millions of dollars and thousands of man hours to develope a reliable vehicle that works in all climate conditions. In most cases aftermarket parts provide inferior performace unless intended for very specifc appliactions.

Doug

 

Okay...

complete shroud =good
lower baffle install=good

I can certainly give that a try... the fan issue seems to have a lot of differing opinions...

- Some say go back to GM fan with clutch
- Some say the electric fan is the solution.. remove flex fan
- Some say the electic fan could be impeding airflow

My own observations on the fan say that the electric fan is much more efficient at moving air through the radiator than the flex fan ever could... lack of a shroud should not be an issue with the electric fan by itself... agree that the flex fan and electric fan might be fighting each other... especially at idle... my guess is that the hot air is swirling around the radiator at idle causing the temp rise because of the gaps around the radiator and the two fans fighting each other... thoughts?

Scott

 

I'm getting a headache!!! DITCH THE FLEX FAN!!!!!

I don't mean to be obligerant (sp?), but your whole problem sounds like air flow and the flex fans just don't get it. This is 35 years of hot rodding talkin'. I've used flex fans, water wetter, STP (gawd, that was crap!), and every fuel additive made and I wish I had all that money back!! The factory knew what they were doing.

Try using just the electric fan and see if it doesn't work. If not, unhook it and use the original fan and clutch. Good luck!!

 

 

When I added AC to my car, I also added the electric fans. I did not remove the stock fan and shroud. The electric fans are there to augment the stock fan when driving at slower speeds. I don't think my electric fans could handle it on their own on a 100 degree day.

Get rid of the flex and put the original back on.

Dave

 

You guys who are so adament against flex fans need to understand one important fact. There are good flex fans available. My 62 is an example (and being in FL I should know), and so were the GM big flex fans used during the 70's and 80's on some AC vehicles. There was also a flex fan issued by GM as a "fix" for big block Vettes that overheated during the early 70's. It was a monster 7 blade design that would cool just about any vehicle (large blades with lots of pitch). If I was not in a rental home (with just about everything not "important" put into storage), I could find the p/n in an instant. I used that particular fan on my 70 Vette with AC (driven every day for 15 years), and it NEVER overheated, including many a hot day stuck in construction traffic on the Illinois Tollway - where summer season has replaced by "construction" season. Flex fans can be very effective. But the design has been cast in a poor light by the crap produced by the cheap designs put out by the "hot rod" crowd (you tend to get what you pay for - in most cases).

However, a 6 bladed flex fan does not sound like a "good" fan. Any fan will generate noise, but an even numbered fan will create a noise that sounds like a fast beating drum at certain speeds (harmonics and all). "Good" fans should have an uneven number of blades (5 or 7 being the most common), and the blades will NOT be spaced evenly. If your 6 bladed fan is spaced evenly, then I agree that it should be ditched. But not necessarily for a cluth fan.

Plasticman