Spark plug change interval

[ew1usnr]

Dennis, as long as you are spending this much attention to the plugs and ignition system it may be worthwhile to try indexing your plugs. This article says a 1-2% performance loss can occur from poorly oriented plugs.

Hello, Jeff.

You planted a bug in my brain and I had to take another look at my plugs to see what was going on.

Ford Muscle recommends aiming the open end of the plug at the exhaust valve.
See: https://fordmuscle.com/archives/2000/07/indexplugs/

Ideal position to exhaust.JPG

I removed the plugs and marked them to indicate the open end:

3 On engine.jpg

A friend at work had given me a pair old 260 cylinder heads. I screwed a plug into one of the old cylinder heads to get an idea of how the plug would be situated and set it to the same position as the one installed in the car:

1 Outside old head.jpg

That showed that the open end of the plug was aimed at the black exhaust valve, exactly as was recommended by Ford Muscle as being the ideal spark plug position. I shuffled the plugs around so that the open sides of all the spark plugs on the left side were pretty close to this same position.

2 IInside old head.jpg

The plugs on the right side of the car, however, all tended to be aimed at the intake valves. That is evidently alright also. Another web site recommended positioning the open side of the plugs towards the intake valves:

Ideal position towards intake.JPG

See: http://www.enginelabs.com/news/getti...-indexing-101/

So, the open ends of my spark plugs are aimed at either the intake or exhaust valves, which is good. None of them are positioned so that the spark is shielded from the combustion mix, which is bad.

The Wonder Falcon has indexed spark plugs!