For some reason this was sent to me rather than vintage-race@autox.team.net.
Reply to author, not me.
mjb.
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Date: Sun, 07 Apr 2002 11:21:41 -0500
From: Wes Campbell <wes@texas.net>
Subject: Re: finding TDC with the heads on
I sent out a post earlier asking for help in finding TDC with the heads on
the car. I have a 1600 CC Kent Ford cross flow set up and I'm mounting the
crank sensor for an Electromotive (distributor-less) ignition system. It's
a precise system and I had to be sure I had the sensor exactly at TDC for
it to work properly.
I tried using my valve feeler gauge to figure out TDC with valve action,
but, that proved to be too difficult if not impossible. It wasn't very
exact; I could rotate the engine several degrees without knowing exactly
where TDC was. So, I gave it some serious thought and came up with a
creative solution that perhaps others can benefit from.
The solution:
The solution would require some concentration in hand rotating the engine
because of the unevenness of the back pressure. I need to free up my hands
to concentrate on just that. So, I took a multimeter that has the audible
tone option for continuity or a short. I attached one probe to the chassis
and the other I wrapped tape around it to insulate it and provide a
in-place-fit friction mount. I inserted that probe in the #1 spark plug
hole with the piston as high as I could tell.
I rotated the engine by hand as slowly and as evenly as I could. When the
piston comes up and touches the probe, I get a audible tone and I stop
rotating the engine. I marked that spot with a little masking tape and a
mark. I then REVERSE the engine rotation 300+ degrees until the same thing
happens. I again mark that spot with a little masking tape and a mark. I
take a easy to read precision ruler and find the mid point between the two
marks. My TDC mark is now mid point between those two marks.
I now have my engine at TDC. This method proved to be very exact. I could
repeat the process several times and the marks were always on the same
spot. Plus, with just a little hand pressure on the wrench use to rotate
the engine, I could set the tone off and on. The engine rotation for this
action was unnoticeable by human eye.
Hope this helps someone else in the future.
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