70 seven blade fan

[Justin S.]

I found a seven blade fan for a '70 with air that has bent tips. Although they look uniform, I've never seen one like this. The seller told me an NCRS judge told him that they were bent on purpose for balancing. I was just wondering if there was any truth to that claim. Help please?

[Jim T.]

Re: 70 seven blade fan

Justin I just took a look at my original owner 1970 with factory air. The fan blade tips are not bent. I did not count how may blades my 70 has.

[Joe L.]

Re: 70 seven blade fan

Justin I just took a look at my original owner 1970 with factory air. The fan blade tips are not bent. I did not count how may blades my 70 has.

Jim and Justin------

There are 7 blades on these fans and I don't think any were made with bent tips for balancing. For one thing, I don't think that tip bending could even be used to balance the fans. However, these fans had aluminum blades which could easily get bent "accidentally". This applies to both the 1970 and 1971-74 "spike-tipped" AC fans.

[Ken K.]

Re: 70 seven blade fan

Were the 454 with AC bent at the ends? My 1973 454 with AC had bent fan ends.

[Terry M.]

Re: 70 seven blade fan

There is a reason 1970-74 454/C60 has shims on the motor mounts. It is to center the 7-blade fan in the shroud. Once the engine mounts become deteriorated the engine moves enough, on acceleration, to allow the blade tips to strike the shroud. If the mounts deteriorate slowly, the tips strike the shroud slightly and may make enough noise for the driver to become aware of the problem and the result, if properly and quickly diagnosed, is bent tips. If the mounts fail suddenly, the result is damage to the fan and shroud and possibly even the radiator. There are a lot of these fans out there with bent tips from incidents during use.

[Kenneth B.]

Re: 70 seven blade fan

My 70 454 with AC dose NOT have Bent tips on the fan blades but as Terry said it has shims on the motor mounts & seems to have plenty of clearance above the fan shroud.

[Justin S.]

Re: 70 seven blade fan

Thanks for the help everyone. I thought the ad smelled a little. Do you think the tips could sustain annealing and straightening?

[Monte M.]

Re: 70 seven blade fan

Justin,

I think you would have no problem straightening the tips. Taking some steps to relax the metal will go a long way in preserving it if it were to get bent again.

They were trying to get every bit of air across that radiator they could.

It has come up from many owners, of cars with this fan, that the fan seems a bit too close to the shroud.

The big blocks had the tendency to overheat a bit anyway. Put an automatic trans and A/C and that air flowing across that fan had a lot to do.

The fit was so tight that they even had to go to shimming motor mounts as was mentioned earlier.

In 67 when you had a big block, automatic trans, and A/C, they went as far as moving the licence plate to under the passenger side bumper to allow more air to flow over the center of the radiator.

My guess is they may have addressed this solution with the C-3 as well, but for whatever reason they never ended up doing it.

The real question is the price of the fan. If you are getting a good/fair price, then, yes. it might be worth the investment.

If you are paying top dollar because they just do not come up for sale that often, I would pass. One will eventually come up for sale.

What is the date on the fan? Or do you care about such things. The fact that you want a correct fan on the car tell me you care a little.

Whatever you decide to do, best of luck and have some fun doing it.

Monte

[Joe L.]

Re: 70 seven blade fan

All-----

I believe the reason for the "spike tips" was the result of an effort to quiet the fan noise generated by a fan designed to move as much air as possible. With fans, the more air moved, the noisier the fan.

Also, and incidentally, C3 Corvettes are "bottom breathers". That's the reason for the chin-mounted air dams (which significantly increased in size in later C3's)

[David L.]

Re: 70 seven blade fan

Justin,

Are there any numbers stamped on the 7-blade fan?

The 1968 Chevrolet models (exc. Corvette) w/AC were issued a 7-blade fan, 18" dia., 6 1/8" X 4" aluminum blades with curved tips, 2 3/8" hub hole, 3.00" bolt circle, stamped "3931002", "913894" and a date code. The 3931002 fan (made by Schwitzer) was issued only during the 1968 model year and then as an over the counter replacement for the 3789562 5-blade steel fan in May 1972.

Dave

[Patrick H.]

Re: 70 seven blade fan

Justin,

I think you would have no problem straightening the tips. Taking some steps to relax the metal will go a long way in preserving it if it were to get bent again.


Monte

I would suggest that trying to straighten bent tips may be a recipe for disaster. One of those tips flying off due to stressed metal could wreak havoc on the car - or a bystander. A photo of the fan would go a long way towards showing us if this is a factory designed tip or if this was owner-inspired later in life - and either way I'd not straighten them.

[David L.]

Re: 70 seven blade fan

Does the fan look like the one in the photo below?

[Justin S.]

Re: 70 seven blade fan

The numbers on the fan are 3969926-914386.D70 making an April of '70 date.seven blade fan.JPG

[Joe L.]

Re: 70 seven blade fan

I would suggest that trying to straighten bent tips may be a recipe for disaster. One of those tips flying off due to stressed metal could wreak havoc on the car - or a bystander. A photo of the fan would go a long way towards showing us if this is a factory designed tip or if this was owner-inspired later in life - and either way I'd not straighten them.

Patrick------

Yes, with a fan a lot of centripetal force is created. If a piece happens to fly off and hit one in the head it can even be worse than an attack of gout! Personally, I don't recommend trying to repair a fan.

[Patrick H.]

Re: 70 seven blade fan

Patrick------

If a piece happens to fly off and hit one in the head it can even be worse than an attack of gout!

LOL!!!