Once I had the analyzer working properly, it was interesting to play with the cylinder cancelling function. You can short out individuals spark plugs and then measure the drop in RPM. All the cylinders should drop the same RPM when shut down. I had two cylinders, #3 and #2 that barely dropped 100 RPMs when shut down. The rest would give a 350-400 RPM drop. Once I replaced the Autolites with the NGKs, they all dropped the exact same amount of RPMs: 400.
One thing to note on these machines: you have to think about what your firing order is when doing the cancelling test because the numbers on the cancelling buttons dont neccesarily correspond with that same number cylinder in your engine. You read the spikes from left to right in this order: 8-4-3-6-5-7-2-1 on most GM and Chrysler V8s.
By the way, here are the Autolite 65's I removed. They are about 3-1/2 years old. The trouble with diagnosing plugs on a hemi is that when you loosen then plug, a tablespoon or so of oil seeps down from the aluminum sealing tube onto the plug. It is hard to get the plugs out without them dripping oil onto the electrodes. The two wet looking plugs got oiled during removal.
They all look pretty similar in burn pattern. Any plug diagnosticians out there? How do they look?
The one thing I did notice is the lack of consistency of manufacture in these Autolites. At least 2 of them have different height insulators and slightly different width center electrodes. That doesnt make for a smooth running engine. At least the NGKs all looked the same.
Plugs 2, 4, 6 and 8 are on top from left to right and plugs 1,3, 5 and 7 are on the bottom from left to right.
