3/14/09
Today I had the wheels I referred to last month mounted on the car. This set isn't perfect either, but after all the work they turned out much nicer looking (up close) than the previous set. Since it's raining pretty steadily this aternoon, I don't have any new pictures, and besides, the difference from any distance or in a picture will be rather subtle. Here is a picture I took comparing the two sets fairly late in the refurbishing project.
Plugging along
3/21/09
Found my high speed miss/lack of revs this morning. Finally! And it was neither fuel nor timing.
One of my former 240Zs (can't remember which) came with a very old, tattered copy of a service manual. Very generic looking, inside it says it was published by Henley in 1971. Fairly complete as far as mechanical data, most of its info and pictures appear to be copied straight out of the factory manual. (Apparently nobody paid attention to copyrights back then.) Some of the text was obviously rewritten by native English speakers, and the entire troubleshooting tree is totally generic and applies to any car of that vintage. They probably used the same troubleshooting tree in all their manuals.
I hadn't looked at this manual since I got it, but last night for no apparent reason I picked it up and started paging through it. Looked at the possible causes for "Engine misses on acceleration". The first cause listed was bad points, which obviously doesn't apply with my recent electronic ignition.
But second on the list is "Dirty, or gap too wide in spark plugs". Got me to thinking.
The plugs weren't at all dirty, they were almost new, in fact. But...
Conventional wisdom has always been that after converting to electronic ignition, and especially with a hotter coil, you can use wider gap plugs to give a larger flame front. Most modern cars do just that. There are many advantages to this from more complete combustion. So naturally I have been using NGK BPR6EY-11 V-Power plugs as specified for a late 280ZX. Considerably wider gap than stock - stock calls for .032" or so, these are .044". Hmmm....
Since I had a fairly fresh set of stock BP6ES that I had been using with the points ignition, I swapped them in this morning and took it for a drive. Perfect. Pulls hard to 6000+, no fuss at all.
Now I see why I kept blaming this on the ZX ignition that I tried several times, and also why it didn't always show up immediately. I'd swap distributors and take it for a drive. It would be fine, so I'd then "finish" the swap by tidying up the wiring and installing the wider gap plugs. Then I wouldn't notice the problem immediately since I don't routinely rev it past 4000. At some later time I would try that and start scratching my head.
Don't know if this might apply to other cars or not. Might have something to do with the shape of the early 240Z combustion chamber. But it is interesting, now that it's fixed.
