Updating to 11 bladed fan.

[mingmong]

Hi all,

Finally got hold of an 11 bladed fan for my '77 C3. (Hoping this is going to keep the temps down in London summer traffic!) I've given the 'new' fan a good clean and I was about to fit it all together when I came across a possible problem. The original 5 blader had a smooth surface area where the fan belt runs.(Second pic, where I'm pointing the pencil)




However the new 11 blader has three distinct grooves in this area. (Arrows on third and fourth pics). Question for the experts is...is this actually a problem? I'm thinking it might be an idea to get this area re-surfaced on the lathe. Yes/no? Your thoughts always appreciated.
M

[mingmong]

And here's something else I've found...




The first photo shows the original fan surround that the 11 bladed fan came with. The surface that the alternator sits on (pencil pointing again) is higher than the second picture (which is my original casing). There's about a 5mm difference between the two which means that if I used the dirty old one my fan pulley's going to be out of line with the engine pulley by the same distance. Obviously I'm sticking to the original one BUT(..and here's the curious part)...both fan casings have exactly the same part number on them..901 601 101 5R ? Anyone else come across this? Seems odd.
M

[304065]

The mounting boss for the fan was made thinner over the years to facilitate increasing the capacity of the alternator from 55A to 75A. As you correctly note, the fan would stick out too far with the earlier housing and a thicker, later alternator.

The grooves are, obviously, wear caused by the belt. The danger is that if you have the belt tensioned on an outer groove, and then you drive the car and it slips to an inner groove, you will lose belt tension. Turning the surface to a taper to match the outer pulley is a good start, but you may find that you have to remove ALL the shims between the fan and pulley in order to achieve proper belt tension, and even then it might not be enough.

Unfortunately the pulley is riveted to the fan and so it's difficult to swap the center sections. Some have utilized allen bolts to do so, search here under "Henry Schmidt" and "allen" for one professional's solution to this problem.

Good luck! I don't envy Londoners for their traffic and this is coming from a New Yorker! (Albeit an old Oxonian. . . )

[dtw]

Cramer's info is good. I'd be very reluctant to turn down a fan pulley surface.

Regarding the part numbers - the number you indicate is actually a casting number. That casting may have been used over the years in a few different applications that would have been assigned different part numbers.

[mingmong]

Many thanks for your replies. Not going to turn the surface down. The idea of drilling out the aluminium rivets and swapping the inner fanbelt surfaces had occured to me. I'm assuming this is what Henry has achieved. (Unfortunately I can't get the search to work...I'm having one of those days!) Any chance you could post the link?

[304065]

Henry Schmidt- help please

[mingmong]

Fantasic! Thanks John. That engine of Henry's is something else! Wow and there's little me thinking I'd got my fan clean! Think I'll drill out those rivets and bolt on the original plate. Anyone else ever done this?
I just knew this '2' rated 4 hour job in Waynes 101 Projects Book would turn into an epic...it's always the same with anything I do to my car.
'Oh while I'm there I'll just....'

[Wil Ferch]

Here's some more reading if you want to make your head spin on all the possible fan combo's-->

Engine Fan Drive Ratio

- Wil