So, I have a set of AFR 195s on the engine that I'm just finishing up a re-rebuild on (thank you Comp R's).

In its previous incarnation, with the same heads (straight plug) and headers (shorty block huggers) and Autolite 3924s I was having a serious problem with melting plug boots. Even with insulating sleeves on the wires/boots, after ~100 miles the boots would turn into mush. I'm new to the SBC performance world, so I didn't realize that shorty plugs would possibly have helped with the problem, getting me a little extra clearance between header and wire, and I'd like to give it a shot this time around.

I've done a bunch of searching, and it seems that there isn't an off the shelf shorty plug that will fit AFR heads. I've read mention of customizing plugs by cutting off the porcelain and threading the center electrode. I've attempted this so far on 2-3 plugs.

The 3924s I bought won't work, as the plug cap isn't a screw on style and is all one piece and will snap the center electrode off inside the plug if you try and unscrew it. I looked at the FR3LS (whatever the y call it now), and it appears to be the same deal. I bought 10 Bosch Super Plus plugs as they have the screw on tip, but when I ground down the electrode found it's much bigger than the threaded portion and would be more involved than simply retapping.

So, since all the links to customizing plugs appear to be dead, can anyone tell me what plug to use for this mod, or point me in the direction of a functional write up?

Thanks for any info!

 

You're right- you can't get shortie plugs in that style (I looked for a long time, too). I did see a while back somebody compared the length of different brands of plugs in that same style and found that one of them (NGK??) was slightly shorter than some of the others. Not by a ton- maybe 1/4" at the most, but that could be the difference between burned plug boots or not.

I beleive it was someone over on Nastyz28.com who had posted up this information probably a year or so ago- might want to head over there and throw a post up about it.

 

AC 41-629 is what I use. They're technically not shorties but they thread in so much farther (AFR approved) that they become shorties.

 

Hmm, interesting. Those are the FR3LS replacements. I guess I buy one and compare.

Thanks for the tip.
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I'll check out the NGKs as well, I don't think anyone in town had them in stock.