Quote:
Originally Posted by Midwest Tin
Hi, What are your thoughts on the Late 31 fan blade. Has anyone had any trouble with running a late 31 fan blade? Jim
|
This type of fan was simply an alternate design (supplied by Holley I believe). It was used concurrently with the Ford design and was not chronological replacement.
I haven't studied that later fan closely but it appears to be essentially the same design in the hub area. The biggest advantage to the Holley design is there is no place for internal corrosion in the main blade area as it's a single thickness. This DOES provide one major benefit. The Ford design fans typically (probably 95%+) have substantial internal corrosion between the layers. If you look closely at one you will see the outer 2-3" of one or both blades bulged and distorted. This causes imbalance among other problems.
That single issue seems to provide the later type fan with a significantly reduced failure rate. However some still fail. The other issue that contributes to failure is bent/distorted fan blades. This is NOT obvious with a purely visible inspection. The problem with these unique looking propeller fans is that the neatly shaped fan blade make a very comfortable HANDLE! Over the years (or decades) most fans have been used to turn (or attempt to turn) the engine over when trying to zero in on the timing mark with the pin. I can't believe the number of times I've seen this done! How much can these fan blades take before the blades become distorted? Of course it will not occur with the two blades evenly. Besides the undesired stress placed on the blades at the hub, this creates a functional imbalance between the blades. Yep, MORE problems!
All these problems can be identified with proper inspections but I only know of 3-4 people that have ever done so. A decent machinist will measure crankshaft journals to see if they are round and/or tapered, or measure ring gaps before assembly. However they will likely look over a fan closely, say "gee, that looks good" and assume it is! Magnafluxing wont mean a thing except to tell you if you need to have your eyeglass prescription updated!
One thing I find very interesting is the number of folks that claim "there was no crack there this morning but but the blade just went!" I've seen MANY (abused) fans on swap meet tables over the years with a crack measuring 1/8"-1/4" long. Funny, the fan blade is still attached. How can that be if they fly right off when the crack begins? Hmmm, I'll have to figure that one out.
With all that said I won't recommend anyone else run an original fan. I don't want to be called to task for the decisions of others and the resulting success or failure. It also won't hurt my feelings to have more fans to choose from on the swap meet tables!
As a final note, I had a friend that I helped complete the restoration on his '30 Deluxe Roadster in 1975. He put the original fan back on the car at that time. Before he died he had put about 90k miles on top of the 70k miles already on the car. Yep, about 160k miles on the fan! He drove the car across the USA as well as many "short" trips of 1500+/- miles each way and he DID NOT have an overdrive! Yes, I'm sure that fan will eventually fail but when? 200k miles? 250k? I have no idea.