It was one of those "What the heck am I missing??" weekends. Lots of
head scratching and no racing.
Three separate timing lights tell me that the timing on my 1296 Spitfire
motor is at 55-57 deg advanced. I'm not typically in the habit of
disputing such compelling evidence, but I don't know what to think at
this point. The car shouldn't RUN at almost 60 degrees of advance, let
alone run BEST at 60 degrees of advance.
Based on the various observations detailed below, it seems to me that
the timing is ACTUALLY around 30 deg of advance, while the timing lights
all say it's at almost 60 deg of advance. Is that possible?
Is it possible that 3 timing lights are simultaneously wrong, but all
give the same erroneous reading? They're all the type with the dial on
the butt end - we need that since the earlier Spitfire has just a narrow
single pointer at the pulley, not a broad pointer with 25 or 30 degrees
marked on each side of zero.
1. The car runs when the timing lights say it's at 57 degrees of
advance and it WON'T run (will barely idle and is non-responsive to
throttle inputs) when it's set back to 30 degrees of advance according
to the timing lights.
2. When the engine is at TDC #1 firing, the rotor is pointing JUST past
the position for the #1 plug wire (nowhere close to the 30 degr. or so
past which it would be if the timing was actually 57 degrees advanced).
3. The distributor drive gear appears to be in the correct position.
When the engine is at TDC #1 firing, the drive gear is pointing
3:30-9:30, with the wider side of the slotted gear "down" (towards your
knees as you're sitting on the tire, cursing and mumbling to yourself
because you were just certain this was going to be the answer). It
looks just like the picture in the manual.
4. We also did the "set the timing by ear" thing, where you run the
car, rotate the distributor to advance the timing as the revs pick up
until it starts to stumble a bit, then rotate it back to retard the
timing until it quits stumbling and the revs drop just a bit. The car
runs best when the timing is set there. Checked with the timing lights
-- you guessed it -- 57 deg advance.
5. Watching the rocker arms move up and down, the openings and closings
look right for the cam specs -- no dial indicator in the track boxes,
but the movements are at least approximately in the right place and
concentric-ish around TDC.
6. As a further check on the cam installation, we measured the distance
before TDC on the crank pulley at which the intake starts to open.
Intake is supposed to open at 19 deg BTDC at 0.050" lift off the seat.
On a 4.75" pulley that should be a little more than 3/4 of an inch on
the rim of the pulley when the valve has just started to go down
(measured by eye on the valve and with a carpenter's tape measure on the
pulley -- yeah, we're gettin' reeeeeaaal scientific here) (4.75 *
3.14159 / 360 = 0.042 * 19 = 0.798 inches). It looked to be in
approximately the right spot, or at least as close as you can check with
no dial indicator to see when you're at 0.050" of lift and using a steel
tape measure on a round pulley.
7. And using the same extremely scientific methods, we looked to see
that the distributor rotor was pointing approximately at #1 plug wire
location when the pointer was just about 0.5 inches before TDC #1 firing
(18 degrees of mechanical advance in the Mallory so 12 deg static
advance). (4.75 * 3.14159 / 360 = 0.042 * 12 = 0.497 inches).
What the heck am I missing here? Can the timing actually be at 30 deg
adv, while the timing lights are saying it's at 60-ish? And if that's
possible, how? what would cause it?
Scott B.
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