DeTomaso Mailing List: April 2001, Message #225

hi all,

as ewe may recollect, i recently bunged-up my old distributor's ancient
aftermarket electronic ignition trigger.  as no replacement parts were
awailable, i yust bought a gnu dizzy w/the more modern (mid 80's?)
electronic ignition trigger.  well, being lazy, i yust plugged it in & timed
it by seat-of-pants feel.  i got it down pretty good after a couple tries -
good idle, strong acceleration, but it would still buck-n-stumble at w.o.t.
anything short of wot was ok.

so, since i had the front of the engine exposed to replace the heater hoses,
i thought i'd do the timing correctly.  now, i have a couple of questions...
:>)

1st - the li'l blue owner's manual (which is for closed-chamber heads, i
tink, as it sez bhp is 310) sez that, w/hoses disconnected, adwance should
be 6 deg btdc.  under the decklid, the tag (for my open-chambered cj motor)
sez 16 deg btdc.  which is it?  sweet ol' bill recommended 12 deg btdc...

2nd - now, i know why i was having stumbling at w.o.t. - when i adjusted it
seat-of-pants-style, it was w/the carb wacuum line & the manifold wacuum
line both connected.  now, when i disconnect/plug both lines & adjust the
timing at anywhere *near* 6-16 deg btdc, the car will immediately stall-out
when the manifold wacuum line is connected to the back of the dizzy
diaphragm.  (no problem w/the carb wacuum line).  the manifold wacuum line
pulls such a strong wacuum that the timing has to be retarded a *ton* in
order for the car to idle when it's connected.  w/its current setting of 16
deg btdc, and the manifold wacuum line disconnected & plugged, the timing
adwances to ~26 deg btdc under throttle to ~3.5k-4k rpms.  drivability is
now great thruout the range, except for a backfire upon initial acceleration
off idle.  is this gnu dizzy set-up w/a different wacuum adwance from the
old one?  should i yust back off the adwance a bit & leave the wacuum line
plugged?  is the backfire from something else?  or???

any/all help is appreciated; respond direct as well as to the list, cuz i
only get the digest once-a-day...

doug s., #2602