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These spark plugs are from the Vista Cruiser. '72 350 2 bbl engine, the previous owner put an HEI distributor on it and the plugs are AC R45SX, he had them gapped at .055. I think I have an issue with some really worn rings on #3 but overall I am trying to figure out what to do tune up wise to fix the build up issue on most all of them unless that is all oil blow by too.
Or maybe I am wrong and there isn't any oil blow by but because the mileage on the odometer is 127,000 I am assuming the rings are worn. At least they aren't oil fouled. Number one is top right.
Well that is good then. The fuel is new and I have put quite a few tanks in it since I bought it but the previous owner didn't drive it much so the fuel most likely was old most of the time. I am thinking then to just clean them up and re-gap them. For the standard distributor for that year the gap was .035 but does it need to be that wide for an HEI distributor? Might as well check compression while they are out and determine exact TDC as well.
Spend the $15 and buy new plugs. HEI doesn't "need" a wider gap - that was done for compliance with EPA requirements to meet emissions standards after 50,000 miles without a tuneup. The wider gap and higher coil voltage allowed emissions motors to fire crusty plugs that look like this and avoid that crud bridging a smaller gap and shorting the plug.
I'm not certain how long the engine sat for any extended period of time, but IMO it looks like H2O condensation; which, most often would normally not occur on a daily driver. Sitting for an extended period of time on a vehicle which is seldom driven you might expect to get H2O condensation. Based upon the exterior of the plugs (as well) I'm suspicious it's H2O condensation. Don't know the previous driving history, but a new set of plugs would be in order.
Thanks for that, Joe. Just wondering -- in the first paragraph the author makes reference to the higher intensity of a blue flame. I had an eighth grade science teacher who told us that a blue flame is actually cooler, because the blue indicates more unburnt fuel. This has stuck with me for nearly fifty years now. Was my teacher lying?
Thanks for that, Joe. Just wondering -- in the first paragraph the author makes reference to the higher intensity of a blue flame. I had an eighth grade science teacher who told us that a blue flame is actually cooler, because the blue indicates more unburnt fuel. This has stuck with me for nearly fifty years now. Was my teacher lying?
I wouldn't pay a lot of attention to that first paragraph. The author is trying to make an analogy from a butane cigarette lighter flame to an electric spark. They are not the same thing. Your hottest, strongest spark from a spark plug is a thick blue-white arc (it's not a flame). The pale yellow thin arc is not your best igniter.
Interesting article Joe thanks for sharing, I just got in from doing a compression test and cleaning all the plugs (now it may be moot because thinking of getting new ones anyway). By the way TDC was right on within 1 degree, I didn't bother to check for timing chain stretch because I expect there to be some if it is original with nylon teeth anyway. Here is the rundown on the compression results. #1 - 145 #2 - 130 #3 - 130 #4 - 145 #5 - 118 #6 - 125 #7 - 118 and finally #8 - 132. That is a difference of 27 between the smallest and largest numbers and about a 20% error if I did my math correctly. I always heard that 10% was safe so is it reasonable to conclude that the engine is very tired, not just kind of tired?
I had an eighth grade science teacher who told us that a blue flame is actually cooler, because the blue indicates more unburnt fuel. This has stuck with me for nearly fifty years now. Was my teacher lying?
I was in an advanced chemistry class junior year in high school and we were taught to ignite things such as magnesium strips at the top of the blue flame on the bunsen burner as that was the hottest part of the flame.
It is a 50 year old motor. Those numbers, while not ideal, aren't terrible either. Those plugs look worn, which would make the gap bigger. Most of us run .045" to .050" with a HEI.
It could be oil or bad fuel causing that buildup on the plugs. As the others stated, it's time for a new set. As far as gap, I've always run .040-.045 with an HEI, next time I'll try a smaller gap and see.
I haven't been to my favorite auto parts store yet to get a new set but in the meantime considered doing an experiment. Gapped the plugs at .035 and ground down the tip per the suggestion in the video. I think I will put them in and see what happens, after cleaning them with a Dremel tool and rotary wire brush they came real clean and there wasn't much wear on them at all. I won't be losing anything by doing it and may learn something one way or the other. Maybe this thread will continue after a few more hundred miles with the same plugs in them. Who knows?
Last edited by Oldsguy; October 16th, 2022 at 05:12 PM.
Reason: spelling
October 15th, 2022, 07:48 AM
