Esteemed Gearheads,
I have a question about static vs. dynamic ignition timing on my TR250
that has probably come up before, but I've been unable to find an answer on any
of the usual web pages. Could someone please help?
My Haynes manual calls for static ignition timing to be set at 10 deg
BTDC (page 511). It then calls for the vacuum advance and retard lines to be
disconnected from the distributor (Lucas #41202B), and the dynamic timing to be
checked at 4 deg ATDC at 800-850 RPM (pages 513,521).
I understand the principle of vacuum retard on idle/overrun for
emissions
purposes, but I can't understand how the static timing could be set at 10 BTDC,
and how the idling engine gets to 4 ATDC with both vacuum lines disconnected.
Page 513 of the manual shows the 41202B distributor has a nominal 4-6 degrees of
centrifugal advance at 850 RPM. I would expect to see a healthy distributor
idling at about 14-16 deg BTDC with everything else properly set and vacuum
lines off, no? Obviously, there are other variables at work, but can anyone
explain this to me? (I would not be able to follow an explanation along the
lines of the points/condenser thread a couple of weeks ago.) TIA.
Best Regards,
Tom Marincic
'68 TR250 CD3574L
P.S. Regarding the TR6 seatbelt thread, all cars sold in the USA that
were manufactured after Jan 1, 1968 were required to have provisions for
attaching a 3-point belt, even though shoulder belts themselves were not
required until much later. I put the new Moss 3-point static belts in my car,
and they fit wonderfully, though I need to trim off a couple of feet of excess
webbing. The lap belts have eyelet type mounts, and clip into the stock fittings
in a minute. The shoulder belts fit the factory anchor perfectly. I prefer
static belts because you can cinch them tightly for spirited driving and they
compensate for any lack of lateral support from the front seats. $0.02.
|