I am installing them on a very rare BMX frame.the bottom bracket shell measures 66mm.I believe I'm looking for a spindle length of approximately 110mm.it also has to have English threads.my question to you campy gurus as what part number am I looking for or combinations of measurements that I can shop for? also any leaves and or ideas on exactly what I'm trying to do.
You are going to struggle a bit with this one unless you can find the correct BB of that vintage, which is a big ask insofar as Campagnolo didn't make a huge number of these cranks to start with and information on them, even at the factory (with whom we are very closely connected) is very thin on the ground.
The biggest problem that you will have is that the square taper used on the inside of the cranks was neither an ISO standard or a JIS, as at the time these standards didn't really exist - all manufacturers, campagnolo included, used proprietory, in-house standards.
The 2 degree taper angle was generall standardised but the starting square size and the length of the taper was not - so it was recognised by mechanics and assemblers at the time that some crank / BB axle cominations were a "go" and some were a "no go" and that the best thing to do to be sure of not only a good taper match, but also, consequently, a good chain line, was to use the crank manufacturer's matching BB set.
If you mismatch, the consequences are generally cracked cranks, either because the area bearing the load is not enough (happens with accurately made ISO cranks on JIS axles) or the crank migrates too far up the tapers so the crank bottoms out on the taper, and in some cases splits as the fixing bolt pushes it hard against the shoulder of the taper which is curved. Much less commonaly and in some ways less seriously - but just as useless - the taper can emerge out through the opening square of the crank so the crank bolt bottoms against the end of the BB axle before it's washer comes into contact with the inside of the crank.
So, if the axle length in your case looks to be around 110, I'd guess it's actually 109 (Campag Pista type, look for BB axle 120-PP-68 and use a 1mm shim under the matching Pista fixed cup) or you could "try" the current Pista BB (which still uses the Campagnolo proprietary tapers) or finally, some of the last generation of "FAG" style BBs, the AC-H and AC-S 111 mm BBs might do the trick. All would need a spacer or two to account for the 66mm BB width.
I've sent a query to our colleagues at the Campagnolo factory with regard to this but I would be surprised if the information can be easily dug out of their archive ...
HTH Graeme Velotech Cycling Ltd Campagnolo Main UK Technical and Service Centre