After performing a frame off restoration i removed the original cooling fan and i installed a thrmostatic fan clutch, and i am having a problem after driving for a while the engine coolant light is blinking if i am standing still at idle the light comes on but after i start to move the light goes off. I am not sure if there is a specific fan clutch i need to purchase but it seems as this fan is not engauging, i am not sure since this is not factory is the fan cluch too far from the radiator and it is not sensing the heat from the radiator,is there a spacer that is needed that im not aware about, if someone has seen the same problem or if someone can guide me in the right direction it would be appreciated thanks for taking the time and reading my post

 

A couple of things:
1) I thought all 442s (400 ci) used a fan clutch setup from the factory. I take it yours was not this way? If not, be sure you are using a deep-pitch fan with this new clutch.
2) Make sure your fan shroud is properly installed, and that the fan extends at least part way into the shroud opening.
3) Make sure your radiator is properly sized for your engine, 3-rows at a minimum for a BBO (4 if you have A/C). If you didn't have a clutch fan to begin with, the radiator may not be properly "stock sized" either.
4) Check your temp sending unit to be sure it's not closing (turning the light ON) at too-low of a temperature. I'm not sure what the stock sensor trigger point is, but I'm sure someone on here does.

Post a picture of your setup if you get a chance.

 

Thanks for the quick response, i have a new 4 row radiator installed , the vehicle is not equipt with a/c, i dont have the vehicle in front of me now so i cant tell if the fan blade is inside the shroud but im pretty sure it is, the shroud is installed properly, i have the factory fan blade installed would this be considered deep pitch or is this a aftermarket fan blade that needs to be purchased, i may try to locate the proper coolant temperature sensor and start from there is there a specific place that i should try fusick or somewhere else thanks again

 

Get a cheap aftermarket gauge to screw into the intake to verify the actual engine temp. Hopefully you have a defective sending unit and are trying to slice a problem that isn’t there. Is all the air out of the cooling system? Jack up the pas side front of the car, as high as possible. Leave the radiator cap off overnight. Hopefully the next day the coolant level has dropped considerably. Those are all the simple things I can think of.

 

68 used a 4 blade fan without a clutch for standard cooling. All 68 A-Bodies had a shroud except W30's and W31's.

I like to use an infrared heat gun. It does a great job at telling you the exact temp anywhere on the block you can see and they're cheap

FWIW I have a 70 455 with a five blade clutch fan in my 68, with a shroud, single core aluminum radiator, and I've never have had a problem.

 

A/C and Heavy Duty Cooling:

 

I have a 7 blade fan, I think I got it from a mid 70s Chevy truck. When the fan clutch engages, there’s a mini tornado in the fan shroud. I’m guessing the 7 blade fan from other big cars would work. Im guessing A fan with more blades won’t make much difference with your issue, but couldn’t hurt. I’m thinking you either have a gauge calibration issue, a coolant fill issue, or maybe a water pump problem. The light doesn’t come on until about 235ish, there definitely has to a issue if it’s coming on, assuming the light works as designed

 

Mike, thanks for those figures. My car (no A/C) came w/ the 4-blade fan/spacer and a 2-row radiator. When dad added an under-dash A/C in '76, he swapped the fan blade w/ one of those "horsepower saving" aluminum fans that supposed to flatten out at high RPM, which didn't pull much air at all at idle and it always struggled with overheating when not moving in traffic. In the mid '80s when I re-cored my radiator for 4 rows, I swapped that worthless aluminum fan for a clutch and deep pitch fan (like the factory one). Never had a cooling problem since.

Curious why the W30/W31s didn't use a shroud? Seems those cars especially could benefit from the improved cooling efficiency provided by a shroud. Weight savings?

 

I just went back in looked. It was only M21 equipped W30's and all W31's that didn't get them. It wasn't added until 1/29/68. so earlier W30's would have had a shroud. No idea why they stopped installing them. Maybe the high rev's were causing the fans to hit the shroud.

 

I had a similar issue during the past year, I have a 455, 4 speed, 391 gears, new everything and it seemed like it was running way too hot at times. The rad wasn't boing over, seeing the temp gauge moving so high was getting me worried. I tried a thermal clutch fan instead of the fixed 4 blade fan and found the 4 blade to cool more effectively. I made sure the 4 blade fixed fan was set 1/2 into the shroud, got the right seals for the shroud and picked up a laser thermometer. When the rallypac temp gauge reads 1/2 way the temp on my rad is 185-190, 3/4 on the gauge and my rad is at 195-200, almost to the top on the gauge and the temp on the rad is 215-220. Those temp reading were taken from the front of the rad at the top by the inlet to the rad from the motor. In all the cases there was a dramatic drop in temp to 150-165 at the bottom of the rad where the fluid leaves to go back to the motor.I don't like to see it get that hot but when it does I just make sure its not there for very long. hope this helps. In my case the temp gauge stays right in the middle most of the time, but if I get stopped on traffic it will rise after a while, so knowing those number make it a bit easier to relax.

 

Do you have the rubber strips installed around radiator that force the air to be pulled thru the radiator?

 

Do you have the air dam installed between the bumper and the rad cradle?

 

The above are good points, make sure sell the shrouding is installed. Make sure all the air entering the grille is forced thru the radiator.