<VV> Warning: synapse firing

[Larry Forman]

Hi Padgett,
Humm, let's think about this some more.  A fouled plug has SOMETHING in there.  The real question is whether it is conductive and thus shorting the spark, or open and the spark rises attempting to break through the increased insulating material with a higher dielectric constant than air.  If it is conductive, opening up the gap might help create a more robust spark that might tend to blow out the crud.  Opening it up for an insulating material might also increase the spark energy and blow through that too.  The scope trace should tell you whether it is open and thus has a shorter and higher spark pulse OR is shorted and has a lower and longer spark pulse.

When the idle goes down, the signal traces should lengthen since the horizontal sweep is set at some constant value of so many centimeters/second.  Thus a slower idle takes longer for things to happen and thus the traces should grow longer.

Kevin Willson, aka Unsafe, suggested using the COIL wire to trigger the timing light.  While that timing light firing will happen three times as much, the other timing flashes will be 120 degrees off and will not matter.  Try that approach and see if it works for you.

Pulling number 1 spark plug wire should NOT kill the engine!   Remember that when you did the cylinder balance test by shorting out individual cylinders it did not kill the engine.

Let's step back some more.  Have you performed a cylinder leakdown test on this engine?  This would be an excellent starting place to determine if the engine has various leaks for different cylinders.  You can then listen to the carb air horns, oil filler and the exhaust to determine where most of the leakage is for each cylinder.

Finally, swapping in a higher output coil only takes a couple of minutes.  Worth doing, versus thinking much about.

-- Larry
----- Original Message -----
From: Padgett <pp2 at 6007.us>
To: virtualvairs at corvair.org
Subject: <VV> Warning: synapse firing
Date: Tue, 22 Nov 2005 13:16:52 -0500

> 
> Suddenly occured to me that a fouled plug is really shorted and not 
> open so more volts and a larger gap will not help (in fact a 
> smaller gap might be advised). For a really lean (emissions 
> controlled) idle, then lotsa voltages and a wide gap might be more 
> likely to find an ignitable charge but that is not the case here. 
> Mixture should be plenty rich but getting carbon fouling 
> theoretically from leakage through the exhaust valve guides 
> (explains crankcase blowby with good compression as well but would 
> just a worn guide have a big enough leak ? 6 of them ?)
> 
> This would explain why the Heathkit display seemed to shorten a lot 
> when the idle would drop - the plugs were dampening the spike below 
> the trigger point.
> 
> This also explains why my timing light stopped flashing - or does 
> it ? The timing light lead was on #1 and when in the reduced idle 
> mode, pulling #1 would kill the engine so the plug was still firing 
> at 350-400 rpm but the timings light was not picking it up ? More 
> questions but think I may put the 60 KV coil on hold for a bit, 
> sounds like it will not help here.
> 
> Padgett
> 
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