DeTomaso Mailing List: August 98, Message #279

In a message dated 8/6/98 3:31:56 PM, wpk@fc.net wrote:
snip...
<<...What's the story on this and also what's the deal with the bronze gears
vs the steel ones ? They particularly emphasize the need to change the
distributor
gear if going from a hydraulic tappet to a roller tappet cam. Why ?>>

Don't know why anyone would arbitrarily change a stock dist drive gear. Check
it for condition, maybe reshim it for play if there's too much, but thats all
I'd do. 
Stock cams are cast iron; roller tappet cams are made of (usually) 8740 steel
and thus the integral steel cam gear is not compatible with stock iron dist
gears. Bronze gears are cheap to make by the aftermarket guys but wear
rapidly, giving the effect of a worn timing chain. I'd change a bronze gear
about every 15000 miles (check first). Be careful swapping dist gears- its
easy to put the gear at the wrong height on the shaft, thus not engaging the
cam gear properly & destroying the cam as well as the dist gear. I've seen
brand new bronze 351C gears that had the pin hole at the wrong height. Also
saw one set too low- the dist gear got hot & seized against the block! Cheers-
J DeRyke