View single post by Esprit2
 Posted: 12-26-2007 02:58 am
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Esprit2

 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 572
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 Just dropping in for a quick clarification on some confusion I may have caused before checking out over a year ago.   I had expressed concern that there may be a diffference in keyway position between early Jensen Healey 907's and the later Lotus-spec 907 such that they aren't interchangeable.   Working back through the math for the J-H 115-110MOP pulley and for the 110-100 MOP Lotus pulley suggested that the keyways "had" to be in different places.

Well,  I now know there is no keyway difference and the early & late cams and pulleys,  and they are functionally interchangeable.

My earlier calculations were based upon the published MOP numbers.   However,  I've recently been corresponding with an Engineer at Lotus Cars,  and he mentioned in a sidebar comment that the Lotus 100 MOP is really 97 MOP.   All the others are as advertised,  and he has no idea why the 97 was rounded up to 100.   "It must have been a marketing number".

Running backwards through the numbers using 115/110,  and 110/97,  everything works out perfectly.   The keyway location is the same.

So why did the part numbers change?   In 1979,  Lotus re-drew the part drawings to "lucidate and metricate".   While they were at it,  they assigned new part numbers to match a new number format that would be used going forward.   No significant part changes (some minor ones), and the parts are effectively interchangeable.

The only caution remains with the early J-H pulleys.   They were not hard annodized,  and the raw aluminum pulleys wear out relatively quickly.   For replacement,  the later, annodized pulleys are the way to go.

Regards,
Tim Engel

Last edited on 12-27-2007 06:51 pm by Esprit2