Robert Dardano wrote:
>
> Thanks John It is the drive gear I am asking about . Can these gears be
> messured to determine wear or is it just done buy an exper. engine
> builder that looks them over and decides if they are good or bad Are
> drawings availabe to check how much wear there is. Are there specific
> tools used to check the pitch of the gear? thanks rob
Robert--
I doubt there are prints commonly available today. It's mostly a matter of
parts inspection and making a sensible judgment
about whether or not the part should be replaced.
There needs to be some end play in this gear, but it's mostly a matter of the
life of gears. Any pair of gears in hard
contact with each other will wear excessively--it doesn't matter if it's the
distributor drive gears, the ring and pinion or
the transmission gears contacting the lay gear. The factory recommended
clearance of the distributor gear is meant to ensure
that there's no unnecessary wear, or excessive force placed on the drive.
It should not be necessary to check the pitch of the gear. That is determined
by the grinding done by the original
manufacturer to print specification. It's possible that a badly-made
replacement part might fail, but it's more likely that
the failure is related to hardness or surface finish than from the wrong gear
pitch.
Any machinist should be able to determine that excessive wear has occurred, and
if so, some idea of the cause. If one is
fairly certain about the rightness of the surface treatment and hardness,
spalling (flakes coming off the gear's surface) are
an indication of excessive clearance, allowing the driven gear to hammer
against the drive gear. Galling (torn and smeared
material) on the surface of the tooth is an indication that there's not enough
clearance for oil to lubricate the surface or
that the local pressures exceed the capacity of the lubricant.
It's a matter of careful examination of the parts. Out of curiosity, does this
question arise from the failure of the
distributor drive in your engine, or the drive gear on the cam?
Cheers.
--
Michael D. Porter
Roswell, NM (yes, _that_ Roswell)
[mailto:mporter@zianet.com]
Don't let people drive you crazy when you know it's within walking distance.
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