WEll I've been wrong before so I'll try again
I first thought the thumper style cams were a fix for low compression motors
but now I think just for those that want a lopey idle and are not aware of the torque they leave behind.
An Oxymoron
Comp lists their thumper lobes on page 12 of their lobe catlogue
surprising they have different lobes for .842, .875, .904 all good- but why, comp turning over a new leaf? Here's the two basic thumps for .842 and Mopar size lifters at 1.5 rocker
........................006.........050......,200........lift w/ 1.5
Thumper SBC 279/297 227/241 138/148 479/465 107 PONTIAC
Thumper SBM 279/296 227/241 142/149 .486/473 107 BBM AMC CRS lobes int & ex/
note with the same seat timing the Mopar version has enough additional duration @.200 to make a difference (AMC and Magnum will have more lift with 1.6 rockers)
Neither has a lot of lift at those durations, either .006 or .050
Why?
not having to trim the guides? springs? target "poser" market?
any ideas on why the large spread between intake and exhaust durations?
