Topic: 68 San Jose S code - PS Pulley 7AA or AF?

[Oz390]

Dec 67 build, PS, PB, GT no AC.  Have a few on the shelf and forget which one came off it all those years ago... assuming one is correct???

[craig429]

From this site
http://www.stangerssite.com/fordpumppulleyID1.html
It appears it should be 6AA.

[Oz390]

Great....  more spares...

[Oz390]

... and why does AC change the pulley?  The AC would put more load on the engine, and some wieght on the car.  But why would you go with a bigger pulley with AC, which slows the pump speed..   

[TLea]

For one thing it is a different offset because its driven by different pulley. I think the theory of the larger pulley is that it requires less hp to turn a larger pulley

[Bob Gaines]

For one thing it is a different offset because its driven by different pulley. I think the theory of the larger pulley is that it requires less hp to turn a larger pulley

That theory goes hand in hand with the fact the larger pulley cuts down on the speed or revolutions. The need for the decrease in speed depends on the application. For instance the hipo alt pulley is larger because of the intended higher rpm operating conditions and the need to keep the RPMS down at the alt hub at high operating speeds. The 67 GT500 P/S pulley has a huge pulley on a A/C car application to keep the speed down on the pump . Just explaining the reasoning .I am not a engineer and can't explain in detail what constitutes the need on each individual item. Bob

[Oz390]

The rpm issue is moot, e.g. on a 390 they used two differnt diameter puleys for AC vs non-AC, so same RPM range as its the same engine.  As an engineer I can't see why they would alter the pulley offset on the PS and make assmebly more complex, and the cost of more parts, and not just accomodate at the AC pump???  Very odd... but....

Off to try to find a 6AA....

[Bob Gaines]

The rpm issue is moot, e.g. on a 390 they used two differnt diameter puleys for AC vs non-AC, so same RPM range as its the same engine.  As an engineer I can't see why they would alter the pulley offset on the PS and make assmebly more complex, and the cost of more parts, and not just accomodate at the AC pump???  Very odd... but....

Off to try to find a 6AA....

The size issue on the pulleys is just how it has been explained in the high performance reference books for the last 45 years.  Some engineer had to justify his keep at Ford. The 6AA isn't that hard to find but if you can't find one PM me I have one. Bob