Re: Question For Dave Ray (Astro Van Plug Gap)...
Those vans run .045 maximum spark plug gaps. The .060 was set by emissions techs trying to get a larger spark area to light off a fuel molecule that was less/leaner than earlier .045 gap systems. In these years, GM had to warrantee replace massive amounts of both coils and modules because of the .060 and .080 spark plug gaps that emissions techs insisted they needed to fire the popcorn fart lean mixtures off. Changes to the EFI systems and programming took care of the too far open gaps, plugs went back to a reasonable gap, and the world rotated right again.
When that van was supposed to go back for dealer servicing, the plugs should have been re-gapped down to .045 maximum, and a new emissions specs sticker should have been installed, obviously, it didn't get any of that. If it didn't tear a coil/module up, you are very lucky, indeed.
The throttle body EFI 4.3 engine in my 1986 Safari has an emissions sticker that shows a spark plug gap for that feedback EFI module (8 pin), at .035.
With those distributor caps, a story, true, but, tells it like it is. GM didn't design, nor start them, a company called "Cross Fire Caps" did, years before GM. They made caps for GM point distributors, and inside them, to move spark from one side of the cap to the other, they used a magnetic suppression, spiral core section of spark plug wire, nice stuff, the caps were good quality, worked, lived long lives and prospered. One day, owner of the company decided to retire, and sold the company to, whom else, a person only interested in profit margins, high ones. New "engineers" came into play at the new business, and they changed the cross over media, from the good spark plug wires, to the much easier to do, and seriously less expensive PRINTED CIRCUIT media. Cap quality went from great, to worst in the industry ASAP with the change.
GM "engineers" working on their cross over ignition project didn't have enough common sense to pay attention, and designed the stock cross over caps with UN-INSULATED PRINTED CIRCUITS. Instant junk. What Tom experienced with cylinder 5, was the ignition system attempting to fire off two separate spark plugs at the same time, because of RF energy transfer from one printed circuit plug "wire", to another inside the cap, to fire BOTH plugs at the same time. Probably one cylinder firing when it should have, another firing too early, both of them fighting each other.
Same basic thing happens when a really bad set of RF leaking spark plug wires are run together on an engine along side and inline with each other. This is why we need to run a GOOD set of magnetic suppression, spiral core wires, 8mm if possible, on any and all of today's ignition systems, and not run them parallel with each other, cross them over each other, form an X.
OK, what else did all you guys do, this is getting fun...again.