What follows is to my knowledge undocumented details into the
proper placement of the TR6 distributor.
Problem:
1. missing due to improper postion of rotor to stake in cap
2. tach cable binding due to dist position for proper timing
3. plug wire placement differs from the manual.
4. dwell/timing changes at speed, worn base plate, retard
5. dwell/timing unstable, worn shaft bearings, worn lobes
6. timing marks wrong on most TR6's
7. PI vs. carb emission distributors, which is best?
Reference:
A. Bently 12.10.22, shows dist drive cog placement
B. Bently Fig 77 page 28, owners manual section, plug wire placement
C. Bentley 86.35.00, Lucas 41219,41202,41306,41306M,41352,41385
1,2,3: The distributor drive cog is driven by the cam worm gears and drives
the oil pump in one of 2 positions. The cog gear itself has 14 teeth
meaning that its posible to insert this one tooth off and foul the
final dist final position. I believe moving it 2 teeth will allow
the wires to be rotated one stake in the cap, but as its a 2/12 vs.
2/14 movement, the rotor position relative to the cap is fouled
even though the dist position appears correct. Meaning the rotor
fires when off about 5 degrees from the center of the stake position,
i.e. a high speed miss... and darn impossible to find. One other
related problem is a dist with enough vertical play in the shaft
to actually pull OUT of the slot, grab rotor, pull up and attempt
to rotate... I've seen two cars that exhibit the symptom of a
backfire, miss fire, and back running again, on these cars the
dist shaft rotated 180 degrees backfired and popped back into
position... believe it or not!
If you'll note the reference 2 above, my cars with retard plugged
and timing set to 12 BTDC have the #1 stake turning 1/3 of a stake
position forward of that pictured. In this scenerio the dist is
rotated slightly in a clockwise direction from that shown till
#1 and #5 are more even, but #1 still protrudes more. If all
else is perfect, this should be enough to get the car running
with NO other devices.
If you follow the instructions in reference 1 above by placing the
timing marks on TDC (correct one of the 2 possible) and pulling the
dist drive gog plate, note the final position of the drive slot
is supposed to be aligned with the two fake knobs on this plate.
To obtain this position, lift the shaft (#13 in the drawing) with
your finger and insert with the shaft perfectly vertical
(note I recall placing the oil drive shaft either horizontal or vertical)
**editor note - verify this
This shaft should rotate as inserted and drop down over the oil pump
shaft...
READ THIS TWICE ELSE MAJOR DAMAGE WILL OCCUR: its usual for this
cog to drop down most the way but not drop on the oil pump shaft,
this is NOT obvious, feel under the plate for a 1/8" gap, if so,
then put car in 4th and push forward/rear till it drops prior to
inserting the bolts!!!! The "sweet spot" for the oil shaft is
either perfectly vertical or horz, this will take a couple of
tries, but its possible to have it all drop together if done
correctly. See torque settings, these bolts are not tightened much,
a new gasket is recommended, see prior notes for end float or
replace per existing gaskets.
Your dist will now look as in reference 2 and the tach wire will
easily clear the fuel pump top and not bend too much, i.e. perfect!
You can actually insert the dist, set timing to 12 BTDC, turn on
the ignition and with points or Ignitor, turn dist clockwise till
back one stake and then counter clockwise till it fires (screwdriver
hanging out of #1 1/16" from the valve cover bolt, same for coil
wire if you cannot tell if anything is in action...) tighten the
adjustment bolt, its correct.
4,5: As you'll note from the curves and actual info, these are designed for
a idle timing of 12 BTDC. The retard vacuum device is for spoofing
the idle emission laws of the early 70's. It likely increases emissions
during run-time, but as this wasn't checked, its a mute point. This
mechanism will increase idle heat, decrease fuel comsumption, cause
hesitation during low RPM gear changes and cause excess wear in the
distributor base plate.... "if functioning correctly..." on cars with
"retard" induced wear in the base plate pivot point, retard shaft hole
and retard mechanism itself, a variable dwell/timing is produced by
the torque of the base plate at the pivot point making dwell/timing
setting impossible. Actually, its worse as the setting "appears" perfect
until the retard falls off at which point the base plate movement
disturbs the dwell/timing, meaning the car is ONLY tuned at idle
and has a variable dwell/timing sequence at any running speed... not
what anyone would want. I suggest using a piece of 1" rod the size
of the fitting on the carb and a 1" piece of tubing to leave the
elbow attached, but sealing the carb vacuum port. Now you can tune
the car's dwell/timing. The proper answer is the installation of
an electronic ignition conversion (I like the Ignitor, pls note these
are digital devices and WILL not handle arc'ing, broken plug wires, and
other forms of problems in the ignition circuit. They will NOT cure
any miss or other major problem, i.e. fix the ignition to 100% perfect,
then swap in the Ignitor. The Ignitor will maintain the 100% perfect
ignition, the car starts faster, idles faster, and you can gap the
plugs to 0.035 to take advantage of the 10% hotter spark due to
the optimized dwell angle and lack of losses during the point arc'ing)
The electronic conversion will correct any lobe wear and due to the
pickup method is mostly immune from bushing wear which causes the
shaft to wobble (push rotor back and forth, there should be NO
movement possible, I run with 1/8" movement with the conversion
with no noticable ignition errors).
6. The damper on the TR6 has a rubber piece between the inner and
outer shells. Over time the rotten rubber and start/stop motion
can cause the timing marks to slip. This means that some TR6's
appear to like up to 16 BTDC timing, I suspect this is due to
the slippage of the damper and actual timing is 12, meaning there
has been a 0 to 4 degree slippage of the marks.
7. Distributor 22D-6, unit Lucas 41219 TR5 150HP dist. vs. 41385 76 US dist.
(info on dist PI vs the latest emissions dist.)
As you'll notice from the curves, the PI distributors and Carb dist
apply about 14 degrees advance by 2500 RPM, so for most running these
are the same. The PI and early carb dist advance more at earlier
RPM's, so some run-time difference may be encountered at 1200-2000RPM,
but once things start rolling, there should not be a notice-able difference.
Faster springs are available from TRF as part of a kit. Be careful removing
the single LARGE spring as its possible to loosen the post as these are
just riveted in, the distributor will later explode if these are not
tight!
Net result, there is NO special tuning of the mechanical advance for
either the vacuum advance or vacuum retard versions and all can be used
in HP engines with equal results. HP springs from TRF may help 1000
to 2500 performance, but I could feel no difference after the effort
and work required... not to mention the extra dist that exploded.
--
Roger G. Bolick, rgb@exact.com 512-794-9567, FAX 512-345-2879
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