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Discussion Starter #1
I've had a pulsating engine vibration regardless of whether the car is moving or standing still and I've reved it up. Just for grins I removed the (fairly new, but too old to return) steel fan and thermal fan clutch and ran the engine standing still - presto, no vibration. I put on the old aluminum flex fan and still no descernable vibration. Clearly the relatively heavy steel fan or clutch unit was the cause. Has anyone heard of this? Seems a bit odd given that this was the OEM setup on the '69. It's hard to believe that one of these two components is that far out of balance. For now, I'll just roll with the flex fan, but I wondered if this was a semi-common problem or others had encountered it. The fan mount on the front of the water pump has a nose that forces the pulley and fan clutch to center when mounted, so they aren't mounted off-center.
 

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Yes I have heard of people finding out that they have a vibration coming from the fan or clutch. I would call the people from where you purchased it and tell them you just now finished restoring your car and starting it up. Tell them you have a terrible vibration coming from the fan and clutch. What have you got to lose? I read where some people get lucky and get help. It is not like you want your money back ask for a replacement fan and clutch. BTW who did you get them from?
 

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Some fan clutches need a shim on the front of the WP to center it perfectly. If it is not there the fan can be off center. Does your clutch have or need one of those?
 
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I had the same thing happen on a vehicle. Not sure why all of a sudden it started happening but I chunked it and put another fan assembly on.
 

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Actually its a bushing not shim like I said above.
 
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Not so much out of balance but about to lock up and come apart! Hello Mr Radiator
I have seen these fluid clutches do this. Going to a flex fan is worse as the thin metal blades have been known to come off and maybe thru the hood.
Get a standard Delco or Hayden.
 

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Discussion Starter #7
Thank you all for the feedback. I have a Hayden fan clutch, heavy duty as recommended by Hayden for my car. It's about 7 years old, but minimal mileage (hope to change that now that I've installed the T56). The fan is a TorqFlo that I purchased from Autozone, so I suspect it's more imported junk from China. I also noticed that an OEM '69 fan had 7 blades, not evenly spaced, but my fan has 6 blades that are evenly spaced relative to each other. Given the rotating mass and angular velocity of these things, I'd think that the fans would need to be well balanced, but I also suspect that they are not balanced by the manufacturer, but only rivited together and stuffed in a box for sale. As you guys probably already know, the way the mount on the fan clutch is configured, the snout of he water pump fits through the pulley and is a snug fit into the clutch mounting flange. The clutch has 4 slotted holes so when you install the 4 bolts it forces it to be centered as the mounting slots are obviously 90* to one another so I don't see how I could mount it off center. The car had the flex fan on it when I bought it years ago. I wasn't thrilled with the flex fan and that's why I switched, but the steel clutched fan weighs a ton compared to the light aluminum-bladed flex fan. I suspect any imbalance is coming from the fan and not the clutch, but I hate to spend money for a new fan only to find out the problem returns as soon as I bolt it on. Does anyone make a certified balanced fan for a clutch fan setup or are they all Chinese junk?
 

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Chris, I think someone on this site posted a no-no using the HD fan clutch as it made too much noise for one thing. I believe most gm cars used the 7 blade fan on a fan clutch. I have seen a few 6 blade that were giving guys problems. Just saying.
 

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I also noticed that an OEM '69 fan had 7 blades, not evenly spaced
I'm a bit confused by this statement as it doesn't make sense. Can you clarify on how an OEM 7 blade fan was not evenly spaced?
 

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The link below shows the 7 blade fans and they are balanced 1969 - 1974 Camaro Engine Cooling Fan Blade, 3947772 Date Coded G

This is the fan blade I use, with a Delco standard fan clutch. I don't think I am the only one that uses this blade.
Agree with Don...I too use that blade with the standard clutch. When discussing with the vendor regarding a regular vs heavy duty, he also mentioned about the tendencies with the HD to be a bit noisier and louder.
 

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Discussion Starter #13
Again, thanks for the input. Unless it's an optical illusion in the photo, it looks like the blades on the 7 blade fans are not equally spaced around the hub. Maybe this is how they are balanced or perhaps this is done for acoustic reasons. I recall looking at these when I bought my cheepo 6 blade fan ($40); might have been a penny wise and pound foolish choice. I suspect that the fluid in the heavy duty clutch is more viscous than the standard model that would have been a better choice. Are the more expensive ($120) fans guaranteed balanced?
 

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Chris, here's my original 7 blade. (772) Note that it's made with aluminum blades. Yes, the blades are staggered. It's done to move more air. Think of it as a law of physics.
 
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