1973 Fan Clutch
Thread Starter
Intermediate
Joined: Nov 2005
Posts: 38
Likes: 0
1973 Fan Clutch
Can somebody tell me how to determine when a fan clutch needs to be replaced? It is on a SB engine and is the orginal clutch. It does not turn very freely when the engine is off, maybe 1/2 revolution.
Also, what happens when it doesn't work?
Does somebody make a spacer to replace it, or should I replace it if it is bad? If I replace it, who has a quality unit?
Also, what happens when it doesn't work?
Does somebody make a spacer to replace it, or should I replace it if it is bad? If I replace it, who has a quality unit?
Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Basis fan clutch test.
Start with a cold motor, turn on car for 2 minutes then shut it off. See how much resistance it takes to turn the fan by hand. Turn on motor and run untill it's hot (10 to 15 minutes) turn off motor, there should be more resistance to turn the fan when hot. Also fan should stop within 1 or 2 revolutions when you turn off the motor when at normal operating temp. PG.
Burning Brakes
Joined: Jul 2008
Posts: 923
Likes: 37
From: Green Bay Wisconsin
[QUOTE=trsulliv;1569659473]Can somebody tell me how to determine when a fan clutch needs to be replaced? It is on a SB engine and is the orginal clutch. It does not turn very freely when the engine is off, maybe 1/2 revolution.
Also, what happens when it doesn't work?
Three things can happen:
1). Seizes up and runs at full speed of engine all the time (robs horsepower) Should spin easily when cold, give it a spin with engine off.
2). Bearing gets bad, check with engine off, grab fan and push toward the radiator and pull back toward the engine, the fan bearing should have no play in it.
3). Start engine and run with engine bay open and wait for car to reach operating temperature. You should be able to hear fan clutch engage (you will hear it blow harder when it engages). If your car begins to overheat and you never hear fan engage you might have a bad thermostat spring.
Hope this helps,
Douglas in Green Bay
Also, what happens when it doesn't work?
Three things can happen:
1). Seizes up and runs at full speed of engine all the time (robs horsepower) Should spin easily when cold, give it a spin with engine off.
2). Bearing gets bad, check with engine off, grab fan and push toward the radiator and pull back toward the engine, the fan bearing should have no play in it.
3). Start engine and run with engine bay open and wait for car to reach operating temperature. You should be able to hear fan clutch engage (you will hear it blow harder when it engages). If your car begins to overheat and you never hear fan engage you might have a bad thermostat spring.
Hope this helps,
Douglas in Green Bay
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
trsulliv-
You might also check for oil around the main shaft of the clutch fan. Usually if you are seeing oil, the fan will not pass the suggested test Douglas gave you.
I think four seasons has a direct service replacement for your car under part number 2714. You should be able to pick this up at most parts stores. I'm not positive this is the correct number so take your old one with you and make sure both bolt patterns are the same as well as the center hole in the hub for the water pump. The current delco replacement part number (twice as high) is 88961763.
Willcox
You might also check for oil around the main shaft of the clutch fan. Usually if you are seeing oil, the fan will not pass the suggested test Douglas gave you.
I think four seasons has a direct service replacement for your car under part number 2714. You should be able to pick this up at most parts stores. I'm not positive this is the correct number so take your old one with you and make sure both bolt patterns are the same as well as the center hole in the hub for the water pump. The current delco replacement part number (twice as high) is 88961763.
Willcox
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Can somebody tell me how to determine when a fan clutch needs to be replaced? It is on a SB engine and is the orginal clutch. It does not turn very freely when the engine is off, maybe 1/2 revolution.
Also, what happens when it doesn't work?
Does somebody make a spacer to replace it, or should I replace it if it is bad? If I replace it, who has a quality unit?
Also, what happens when it doesn't work?
Does somebody make a spacer to replace it, or should I replace it if it is bad? If I replace it, who has a quality unit?
Don't replace it wit a spacer, use the proper clutch.
Thread Starter
Intermediate
Joined: Nov 2005
Posts: 38
Likes: 0
Thanks. took it for a drive to warm it up, and then shut it down. The blades spun, Iwould guess 4-5-6 revolutions before it stopped. As soon as the motor was shut off, there was some resistance when I turned it by hand, but not a lot - it was not free spinning, but it wasn't real hard to turn either. Sounds like I need a new - right?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Intermediate
Joined: Nov 2005
Posts: 38
Likes: 0
Thanks. I took it for a drive to warm it up, and then shut it down. The blades spun, Iwould guess 4-5-6 revolutions before it stopped. As soon as the motor was shut off, there was some resistance when I turned it by hand, but not a lot - it was not free spinning, but it wasn't real hard to turn either. Sounds like I need a new - right?
Melting Slicks
Joined: Mar 2006
Posts: 3,456
Likes: 102
From: Piedmont Va
St. Jude Donor '11-'12-'13,'19-'20
Thanks. I took it for a drive to warm it up, and then shut it down. The blades spun, Iwould guess 4-5-6 revolutions before it stopped. As soon as the motor was shut off, there was some resistance when I turned it by hand, but not a lot - it was not free spinning, but it wasn't real hard to turn either. Sounds like I need a new - right?
What symptoms are you chasing? is your car overheating regularly?
Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
4 or more revolutions when hot is to many, I have a 1990 article from Corvette World that shows how to adjust the clutch fan for less slip, PM me your email and I'll send it to you. PG.
Thread Starter
Intermediate
Joined: Nov 2005
Posts: 38
Likes: 0
On the street I have no overheating problems, but running at Road America the temps really get up there, although I have been able to keep them at about 210 with the heater going to. The engine is a ZZ3 with Hooker headers and a Q jet. I am running it through a 5 speed, but have an orginal Automatic radiator. The rad has been cleaned out.
Last edited by trsulliv; Apr 11, 2009 at 10:12 PM. Reason: Adding more details
