So the current summary of the distributor cap discussion is:
1. Big cap or small cap is mostly a function of the spark plug gap you run,
not what you use to drive the coil. Either cap setup will fit early or late
distributor bodies.
2. Optimal plug gap is probably in the range 0.040 to 0.050, which still
allows the use of the small style cap.
3. Whatever spark you see if you pull a plug, and ground it with the engine
running (or just arc from the coil wire to ground), is not representative of
what happens under high-speed running conditions.
I disassembled three distributors over the weekend and learned some
interesting things.
First off, two of the three had worn the upper distributor bushing so badly
that the mechanical advance drive plate had worn into the distributor body.
Why does this happen? Doesn't the thrust from the oil pump drive push the
shaft up? Does the distributor drive get oiled mostly by accident, and the
buildup of varnish and other cr*p causes it to run dry? There's a helical
groove in the distributor shaft but unless I've got my thinking backwards,
it's there to pump oil back down so it doesn't squirt into the distributor.
What assembly lube can we use that will alleviate this (bushing end wear) as
much as possible?
Second thing: Are the numbers stamped into the advance plates, measurements
in crankshaft degrees or distributor degrees? Unfortunately I only have one
plate to choose from that has a reluctor assembly (the other two have points
cams), but it does have a choice of 21 degrees or 16 degrees advance (in
whatever units they are measured in). Which should I use, or should I try to
dig out a different one? The application is a warmed-over 289 (cam, headers,
600 CFM carb on an F4B manifold). The distributor will be a mechanical +
vacuum advance, reluctor style pickup for an MSD6AL amplifier.
If you have any comments I'd be most interested to hear them.
Theo Smit
-----Original Message-----
From: Bob Palmer [mailto:rpalmer@ucsd.edu]
Sent: Saturday, October 07, 2000 11:57 AM
To: DrMayf@aol.com; rpalmer@ucsd.edu; larry.p@erols.com
Cc: theo.smit@intel.com; tigers@autox.team.net
Subject: RE: Dist. Cap
Mayf,
Like any subject, there are a range of opinions. Here are some I found on
the Web:
<snip>
|