View single post by Mark Rosenbaum
 Posted: 01-01-2007 04:00 pm
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Mark Rosenbaum

Joined: 03-12-2005
Location: Kingman, Arizona USA
Posts: 532
You can determine a cam's nominal lift by measuring the lobe height (the distance from the tip of the cam lobe to the belly of the base circle) and the diameter of the cam's base circle, then subtracting the latter from the former.  By comparing your result to the likely alternatives you may be able to determine which cam grind you have.  For example, I just made some not-very-accurate measurements on two lobes of a stock JH cam, as follows:
Lobe A: lobe height 1.552", base circle 1.210", calculated lift 0.342".
Lobe B: lobe height 1.550", base circle 1.205", calculated lift 0.345".

For 907 engines, the various Lotus-developed cams are listed below.
0.340" - Type C or 101 cam, 907E0101G (stock JH).  No special markings.
0.350" - Type D or 102 cam, 907E0102G.  One groove at front of cam.
0.344" - Type E or 103 cam, 907E0103G.  Two grooves at front of cam.
0.410" - Type 104 cam, 912E0104E.  Marked 444.....
0.378" - Type 107 cam, 912E0107F.  Marked 777.....

In addition to the above, there are many aftermarket cams, mostly for racing of one sort or another:
0.416" - Delta Motorsports' current Type 104 variant
0.361" - Delta Motorsports' current Type 107 variant
0.420" - Dave Smith type DS2
0.420" - Dave Bean Type BLL-104
0.425" - Dave Bean Type BLL-105
0.375" - Dave Bean Type BLL-107
0.360" - Paeco Type JH-7000 Intake Only
0.420" - Paeco Type JH-7000 Exhaust Only
0.370" - Paeco Type JH-7800 Intake and Exhaust
0.415" - Paeco Type JH-8600 Intake and Exhaust

Thanks go to Tim Engel, Garry Kemp, Kurt Housh, and Judson Manning for most of the data presented here.  The photo in the previous posting came from somebody's eBay offering of quite some time ago, not from parts I have on hand.

Attachment: cam measurements.jpg (Downloaded 546 times)

Last edited on 01-01-2007 04:02 pm by Mark Rosenbaum