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Discussion Starter · #1 ·
Had a previous question, but unfortunately the the solution didn't work or I did something wrong.

My friend has been looking for the right spark plugs for a long time now. He's tried 3 different types that stores have told him will work, but they obviously didn't. They would not fit. They all seemed too big.

I'm thinking that something must be off with his engine, or it may not be completely original or stock DBScar-DI Diagnostic Connector.
Its a 1965 Chevy Truck C10 Half Ton.

The last time he got spark plugs, was from an old repair place, which used his firing order to get them. Firing Order# 18436572 He remembers the mechanic telling him that they were NOT metric, if that helps.

Any idea what exact type of spark plugs he needs?

Went to the parts store and asked about the tapered R45S or the R45TS but they mentioned that they don't make tapered versions of the 13/16th plug I was looking for.

We took out the old plug and tried to match it up. We tried the same numbered ACDelco plug R45S and it didn't fit. We tried a Autolite, but it also didn't fit.

I noticed that the old plug plug seemed slightly thinner than both new plugs. Right after the threads, and after the compression ring, there is a steel base. The diameter of the old plug is slightly smaller than the new plugs, as the parts store guy was able to see using a digital gauge. (Autolite was slightly thicker than the ACDelco, ironically) It looks like to me that the newer plugs were not going in because of this reason. In the head, there is a small little lip which looks to be stopping the plug from going all the way in. Therefore the threads are unable to reach. I'm almost positive that the metal base (of the plug) is hitting this lip (in the head) preventing it from going in.

Anyone have any idea if this is normal? What are my options? I tried sanding down the new plug, but sand paper wasn't working too well. While waiting for an answer, I'm going to start looking for lathe to slim the new plugs down.

Thanks again.
Update: We looked at a tapered peanut plug, but that was obviously smaller than the big plug. He does have the big plugs, and not peanuts.
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