7 blade fan for72 GS Stage 1 with AC.

mdp427

New Member
I am restoring a 72 Stage 1 with AC, and the original fan and shroud were missing when I bought the car. I've been told that it should have a 7 blade fan but none for a 455 is shown in the assembly manual. Anyone out there know the diameter,# of blades, part #,etc. for what is correct on this model. Can I assume that the shroud is the same as other GS 455's? Thanks, Mike
 

LARRY70GS

Active Member
The correct fan has 7 blades and is 18" in diameter. It uses a thermal fan clutch. The fan shroud is the same for the 1971 and 72 GS455 whether Stage1 or not. Not sure how anal you are about your restoration, but there was a 19.5" fan that has 5 blades that is a better choice IMO. The fan shroud has a 22" opening, so the 18" fan gets lost in there IMO. The 1970 and earlier shrouds had a 20" opening and fit much tighter to the radiator, so the 18" 7 blade is a good match. You can get the fan clutches on rockauto or any parts store. They won't look exactly like what came on the car from the factory, but again, not sure how anal you are:)


Here's the 5 blade, it is weird looking.

 

IN71GS

Member
I have a 71 455 with AC. I was told the factory fan was a 20" 5 blade, and I found an original one a couple years ago and replaced the junk 18" flex fan a previous owner had put on the car. Also put a fan clutch back on the car. Car has no problem staying cool in traffic now.
 

mdp427

New Member
I have a 71 455 with AC. I was told the factory fan was a 20" 5 blade, and I found an original one a couple years ago and replaced the junk 18" flex fan a previous owner had put on the car. Also put a fan clutch back on the car. Car has no problem staying cool in traffic now.
Thanks for the reply. According to the 72 factory assembly manual, a 455 with AC or heavy duty cooling takes a 20" 5 blade fan though most people I ask tell me it should have a 7 Blade fan. I have located a 5 blade fan and the correct fan shroud. Right now I am using an 18 inch 7 blade fan and a repop fan shroud with a very large aluminum radiator. The car runs cool when moving but heats up in traffic on a hot day. When I get some time I'll try the other combination. Thanks again, Mike
 

LARRY70GS

Active Member
If the car heats up in traffic, look at your ignition timing. 1972 Buick v8's used relatively retarded ignition timing, 4* BTDC with no vacuum advance at idle, 1st and 2nd gears. That alone will cause the engine to run hot. If you have the original distributor, part number 1112110, that distributor only has 14-18* of mechanical advance. Using 4* of initial timing will give you 18-22* of timing at full throttle. That will also drop engine power. Buick V8's like 30-34* of full throttle timing. If you have that distributor, I would set the total timing to 32* which will move your initial timing to somewhere around 14* or so. Get rid of the pollution device that does not allow vacuum advance until 3rd gear, and run a line directly from the carburetor to the vacuum advance so you have full time vacuum advance. Switch it from ported vacuum to manifold vacuum, and the engine will run nice and cool in traffic.

1972IgnitionSpecs.jpg
 
I have a '72 GS455 with a/c here, and it has a 5 blade that would be best described as 19.5" as mentioned previously. It looks a little shy of 20", but they are a little harder to measure when everything is in place.
 
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