[Fot] Fwd: Re: Bad Time

[Tony Drews]

I recently found the same thing, and have stopped using the dial back 
timing light.  I put an extra mark on my pulley at 30 degrees.

In my case, the cause is an ignition system that sends and extra 
(unneeded) spark to each cylinder during the exhaust stroke.

This causes an actual advance of 28 degrees to appear to be well over 
50 degrees on the dial back timing light.

I have no idea why you would have that effect with your ignition 
setup.  It seems that a double spark confuses the timing light.

- Tony

>At 07:10 AM 6/11/2007, Barr, Scott wrote:
>>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).
>>
>><snip> to make it through the list



>>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.