Re: Spark Plug Gap

Posted by 55PackardGuy On 2014/7/20 19:21:47

JW,

You're right on the gap. I test drove it. Doesn't start right off like it did, and less power and acceleration with the .030 gap. You learn something new every day. The previous plugs were identical, AC 45R, although I doubt if they were made in Mexico, as the current set was.

Compression (cylinder pressure) test: varied between 115 and 125. I have all the readings written on the head in pencil and the car is in the garage for now so can't give them cylinder by cylinder here right now.

The compression test done the day after an oil change with 6 1/2 quarts of Valvoline 30 wt Conventional and 1/2 qt of MM oil. The car was driven about 15 miles after the oil change. The compression test was done the following day when the engine was almost stone cold. I just started it, backed out of the garage, took the old plugs out, did the compression test, and put new plugs in.

I think those are OK compression (cylinder pressure) numbers, but don't know for sure. It doesn't ping, but then I've got 95 octane clear gas in it. I guess variation between high and low cylinder pressure of 10 lbs or less is OK. It comes out to less than 10% variance.

(Also, before doing any of this, I did a good ol' fashioned Marvel Mystery Oil "soak and smoke" to try to break up carbon and loosen up rings/valve stems. After that, I drove it about 15 miles and changed the oil.)

All the old plugs looked pretty good. Gray ash, no wetness or oil fouling.

Thoughts? especially on the cylinder pressure readings, will be appreciated very much.

Thanks!