Good Write up Brian! I've attached Tom's Distributor FAQ Below. The mixture
of your's and his tells all. One comment I would add is, buying a recurved
Distributor from our vendors is a great way to go. I bought one from Ross
and it came all set up and ready to install with new OE Hitachi points,
rotor and cap.
*************************** Tom's Distributor
The air/fuel mixture takes a certain amount of time to burn, igniting the
mixture needs to take place before full burning is desired. Too much in
advance will cause problems, too little in advance will reduce power and
cause drivability problems.
The total amount of advance should be around 35 degrees at the crankshaft,
so the initial setting of timing should be 35-centrifugal advance. The 68
and later roadsters came with a distributor with 17.5 degrees advance, which
is 35 degrees CRANKSHAFT ADVANCE, requiring the engine timing to be set at
TDC (Top Dead Center). While the engine will idle with this setting, it
isn't producing enough power at the lower engine speeds to get moving from a
standing start. You either to rev the engine into a higher power band, and
slip the clutch. While this will get you moving, it won't help your clutch
By advancing the distributor to 10 BTDC (Before Top Dead Center) you'll
notice the improvement in drivability, especially getting off the line.
HOWEVER, you'll have way too much total advance leading to all sort of
nasty problems in the engine.
After reading the above, why not do away with all the mess of the advance
weights, springs, cams and just WELD everything together, and be done with
it! That is fine for engine speeds above 4,000 rpm, and is commonly done
with racing engines, but not ideal for a street driven car. If you try to
start the engine with too much advance, the piston is moving slowly enough
that the mixture starts producing pressure before the piston makes it past
TDC! This will push rotates the engine in the wrong direction! Great way to
blow the lid off the aircleaner, or mess up your timing chains!
So to give a reasonable power slightly above idle, and not exceed to total
maximum spark advance will require a small centrifugal advance in the
distributor. Thankfully this is what the '66-67 1600's were running! They
have a maximum DISTRIBUTOR advance of 7.5 degrees, for a total of 15 Crank
degrees. So with an initial setting of 16 BTDC, and an advance of 15
degrees, gives us a total of 31 degrees.
the '68 and later roadsters (both 1600 and 2000) can benefit from a simple
rework of the distributor, provided they do no retain the original smog
To convert your '68 and later distributor to the earlier specs, use:
cam part number: 22132-14605 (for METRIC engines!)
light spring number*: 22110-14600 --> May have interchanged
heavy spring number: 22110-25600 --> these to numbers!
weights, if needed : 22109-71300
*Part number has TWO SPRINGS in it, one light and one VERY HEAVY.
New weights were used, as 20 years of rubbing between the springs and
weights had resulted in the spring cutting a slot into the weight mounting
ear... the weights could flop around at will! Made for a very interesting
For a 2000 engine, the ideal way would be to order a brand new '67 model
distributor. But they have been NLA for some time. You could order a '66
1600 model one, which will have the correct advance, but comes with the
wrong vacuum unit attached to it.
Rebuilding is straight forward. I highly recommend leaving the distributor
cap, with the plug wires attached, in the car! Seems odd, especially if you
always have 1-3-4-2 (the firing order) memorized.
Pop off the cap. Note the direction the rotor is point in. Make yourself a
little sketch of the direction. Now look at the bottom of the distributor,
make a note of which way the "offset tang" is.
To disassemble the distributor, start with removing the vacuum advance unit.
Two screws, and wiggle it to make it pop lose of the little tang (on the
contact plate). It is almost best to have either an egg carton to hold the
screws, or thread them back into the correct holes, so you know which ones
went were later (they are different length).
Next check the smoothness of the breaker plate pivot. the little tab, for
the vacuum unit, should move back and forth smoothly. A common problem is
too long of a hold down screw holding the points down, and the plate
Next slide the little plastic block out of the way. Inspect the wires going
to the points, and the little ground wire.
Remove the two screws holding the breaker plate [Assembly - breaker in the
parts book]. Lift it up and out of the way.
You know can observe the weights, and springs. If you hold the bottom pivot,
and twist the top you should see the operation of the weights move out. Let
go, and they should snap back into place.
You should disassembly everything, clean, inspect, and grease everything
lightly to make sure it does the "twist and snap back when released". Now
you'll be glad you made notes, as you could have easily put the top cam back
180 degrees off. If so, the rotor will be pointing at the wrong place, and
one reassembled, you'll spend more time trying to figure out what went
wrong. (Not that I would do such a thing At least not TWICE)
Reassemble, noting the correct screws in the correct holes.
Even if you buy a BRAND NEW distributor, I still recommend disassembling it,
and regressing everything. I did just that, the grease was 25 years old, and
dried rock solid!
It is spring time, time to take the roadster out to your favorite swimming
hole and enjoy a peaceful afternoon.
I'm off to my favorite skinny dipping hole & sauna this weekend, so I'll be
back next week if there are any questions. (hopefully not as hectic as the
past two weeks! When is that project due? :-) ).