C2 Ai Conditioning fanblade

[Dino L.]

What effects other than looks, would a 1964 AC 7 blade fan have on a L76 versus the stock 5 blade in total stock configuration....Regarding air flow at idle in traffic, at speed? Does the clutch need to be swapped also? would it keep the car cooler in traffic? My car runs at 180 except when it is idling in a traffic jam and the temp will gradually increase upwards to 220, it doesn't boil over, but I thought with a boiled stock block, new water pump, new Dewitt radiator, new rad cap and hoses, proper ignition timing that the car could maintain 180 on a hot day in traffic...but it cant. Would the 7 blade help airflow at idle? Not too concerned over loss of horsepower.

[Joe L.]

Re: C2 Ai Conditioning fanblade

Dino-----

I think that you will find that the 7 blade fan might make some small difference, but it won't amount to much of a difference. MANY years ago, I changed the original 5 blade fan on my 1969 (which is the greater pitch fan also used for most 66-69 big blocks) to the 7 blade "AC" fan, GM #3955182. I noticed very little difference, at all.

If you do change fans as you suggest, you will not have to change fan clutch. Your existing clutch will work with either fan.

[Dino L.]

Re: C2 Air Conditioning fanblade

Is it accepted performance for these cooling systems to perform in that fashion...Gradual temp increase at idle on a hot day? My 93 does the same thing except as it climbs to 230 a set of e-fans come on.... is a mid year design that ineffecient...Keep in mind the car I am talking of has been totally gone over...shroud, rubber, rebuilt fan clutch, etc etc

[Kevin M.]

Re: C2 Air Conditioning fanblade

Try driving in a parade in 80 degree weather, you never take your eyes off the gauge. My 67 SB does just what you describe 180 except when stiing still then it climbs stays out of the red though.

Kevin

[Barry K.]

Re: C2 Air Conditioning fanblade

yep, I drove my '65 L76 is a parade ONCE.............will NEVER do it again!

[Joe L.]

Re: C2 Air Conditioning fanblade

Dino-----

The pre-73 Corvette idle and low speed cooling performance is now and always was marginal, at best. There are a number of reasons for this, including shroud design, lack of shroud seals or lack of effective shroud seals, and fan clutch design/performance. Suffice it to say, the performance was marginal.

By the mid-70s, idle and low speed cooling was greatly improved. Some of these improvements can be retrofitted to earlier models, but it can get quite complicated to do this, especially for small blocks. And, of course, much original configuration will be lost in the process.

[Jack H.]

Add-on...

To amplify what Joe said about Shark era cars, that's one of the little feature/function side effects of the TCS (or '71 only CEC) system. There's a thermal switch in the RH cylinder head that has three positions: (1) cold engine, (2) normal operating temp, and (3) above normal operating temp. The switch closes under either #1 or #3 conditions and this causes the vac advance solenoid to open and gate vac to the distributor to modestly boost engine RPM and circulate coolant plus air through the radiator at a faster rate.

Of course we don't test the 'overheat' feature of these systems during performance verification, but I once had the opportunity to see my car's system go to work! It was during a local July 4th parade when it was pushing +90F outside. The temp gauge would steadily climb above 180F heading toward the red zone.

Once the needle entered the bottom end of the overheat range, there was a solid CLICK from the engine compartment as the CEC solenoid engaged and engine revs climbed about 125 RPM. As time passed, the temp gauge slowly wandered back down to roughly 195F and CLICK, the engine idle decreased as the CEC disengaged.

I watched the sequence repeat about four times during the 1.5 hour parade and marveled that the system actually worked! BTW, three other Corvettes from a competing Corvette club puked their radiators and had to be pushed to the side of the parade route to cool down. This competing Corvette club had held a pre-parade instruction session and told their members to turn engines OFF if temp gauges started to climb...obviously the WRONG advice!!!

[James G.]

Re: C2 Ai Conditioning fanblade

Not to confuse you ,but make sure the temp sending unit is the correct one and reading proper tempurature. Many units on the market were GM units for other applications and were calibrated for different dash gauge.

If possible, have a tech check your coolant temp with a modern 'radar' type temp gun. They point it to the radiator, top hose, lower hose and get readings off the item being shot. Compare that to the gauge. Many sending units mis read the actuial temp by 20 degrees.....and we all worry over a false reading.

Todays gasolines make an engine run hotter also. So watch your timing, radiator cleanliness, radiator cap condition, and coolant mixture as well. Some aftermarket additives, like RED LINE WATER WETTER can help lower temperature by as much as 15 degrees.

Generally, if the overflow bottle is not puching, especially after shutting off the engine, all should be OK.