67 big block 7 bladed fan?

[jack katz]

Just purchased a 67 427/400 with factory air (4 speed, ps & pb). Car has a 7 bladed fan on it and when the engine revs up, it sounds like a truck (that is, there is a "roaring" sound as a result of the fan speeding up) ! I've considered replacing the 7 bladed fan with the correct 5 bladed fan, but from what I've heard the 5 bladed fan will not keep the engine cool enough, especially with the a/c running. I was told that one way to correct the fan noise would be to get the "correct" 7 bladed "Corvette" fan.

Anyone have any experience on this? Looking for some advice. Thanks.

[Wayne W.]

Re: 67 big block 7 bladed fan?

I have never had any trouble with the 5 blade keeping mine cool.

[Michael W.]

Re: 67 big block 7 bladed fan?

You might want to check your fan clutch also. The only time any fan should 'roar' is when the clutch is engaged. Even a five blade fan can make a surprising amount of noise when the clutch kicks in.

[Eric Fairclough]

Re: 67 big block 7 bladed fan?

I have a 72 454 with a 7 blade fan and it does the same thing. The only way to eliminate this noise is to get rid of the fan cluth and bolt on a direct fan with a spacer. I have had this problem with other cars as well and getting rid of the fan cluth has cured it from the noise. The only reason i did not change my vette fan is orginality.

Eric

[Jerry M.]

Re: 67 big block 7 bladed fan?

I thought all 66 and 67 big block cars with a/c or automatic trans came with 7 blade fan.?????

[Michael W.]

Spacer-

Eric,

Why would having a fan clutch (malfunctioning or not) create more noise than having a direct drive spacer? Or did I misread your post?

[Roger Legge]

Re: 67 big block 7 bladed fan?

Sure sounds to me like the fan clutch is bad. That roar is what it sounds like when the fan clutch is engaged/locked. If you hear this noise when the car is cool, turn the engine off and see if the fan will spin. There should always be some slight drag when you try to spin it.

Roger
#36316

[Jack Katz]

Re: 67 big block 7 bladed fan?

I guess that's really my question. Did the 427/400 (4 spd with a/c) come with the 5 bladed fan originally or a 7 bladed fan, and is it a 7 bladed fan for the Corvette engine? I know that my fan clutch is working properly. I think part of the problem here may be that this was originally an Arizona car, and maybe the 7 bladed fan on the car now is a "heavy duty"(?) fan because it gets so darn hot out there??

I checked the NCRS Information & Judging GUide and didn't see anything about the fan. Did I just miss it, or is there no reference in the Guide.

Thanks to all of you for your great input.

[Eric Fairclough]

Re: Spacer-

Mike, That was what my experiences with fan clutches have showed me. Maybe all the fan clutches i have seen were bad and were locked into the enganged mode. My corvette fan clutch makes alot of noise when you get on it. It's louder than the exhaust ( stock mufflers ) but it cools the car down quite well so i havn't changed it yet. My friend had a 84 trans am with a fan clutch that was very loud worked good but loud and he changed it to a aluminum flex fan with a spacer and it was silent. Eric

[Michael W.]

Re: Spacer-

For your theory to be true (clutches cause more noise than solid spacers) the clutch would have to be capable of turning the output side faster than the input side, in other words driving the fan faster than a solid spacer would. This of course is not possible.

I think you'll find that the reduction in noise was due to the aftermarket fan, and not the substitution of a solid spacer.

[John H.]

Re: 67 big block 7 bladed fan?

'67 JG sez all BB's used a 5-blade 17-1/2" diameter fan.