REFLECTOR: Lycoming IO 360 Timing

[Dave Dent]

As I wrote earlier, don't use a timing light. They are very inaccurate with
this type of ignition.  They work good with a point system and some C/D
systems but with the JR use a volt meter.  Just attach the red lead of the
volt meter to the adv. of the computer and the black lead of the volt meter
to ground and you can read the advance.  Be sure to do this with the vacuum
disconnected from the advance box that is screwed to the top of the
computer.  Plug the hose so you don't have a leak and then start the engine
and you will be able to see what the actual timing is.  Your data plate
should say 25 degrees before TDC.   If you don't see this on the meter,
adjust it with the small adv. knob under the box.  This is the key piece
that Jeff builds and adds to the General Motors computer and coils.

The coils in the system fire both on the compression stroke as well as the
exhaust stroke.  This is done by going through the ground side of the
engine. The electronic system compensates for this but the timing light
can't.  This seems to be the reason for the fluctuation in the light
reading.  Giving a sense of jumping all over the place.  That is why I don't
recommend using the light.  It will be just be pot luck if you get it right
on.  There are a few timing lights that compensate for this but are very
costly.  Good auto repair shops have them.  Volt meters are very cheap and
do the job just fine.

Dave

----- Original Message ----- 
From: "steve korney" <s_korney at hotmail.com>
To: <reflector at tvbf.org>
Sent: Tuesday, August 24, 2004 6:35 PM
Subject: Re: REFLECTOR: Lycoming IO 360 Timing


> Dave...
>
> Can you give a good reason why the timing light jumps all over the place
> while checking the timing on a J.R. ignition...???
>
>
>
> Best... Steve
>
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