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Old 07-14-2012, 05:16 PM
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Spark Plug Application SBC

Hi All,
I have a question regarding spark plug compatibility. I have recently got my 11:1 comp 355 sbc with 294S cam up and running using Autolite 23 plugs and all the other recommendations from F'Bird-88 (thankyou F'Bird-88 for all your online assistance - i did get the HEI dist) including locked out timing, transfer slot exposures etc and the thing runs great, idles CLEAN! And goes llike a rocket. However I have an issue with the long Autolite 23 plugs clearing the headers. One in particular #8 cyl is that tight that I have to pry the header pipe away from the head with I jimmy bar just to get the pug in!
And then when I fit the plug wire on, the boot touches the header pipe and shorts out - causing a miss under acceleration. I believe that the AR series autolite range are shorter and are considering running the AR23 plugs for more clearance, however when I check the comparability tab on the Summit catalog, it says that these are for V6 engines. I posed a question to Summit about this and they replied that the AR23 plug is NOT SUITABLE for sbc and that I must use the AR25? This plug is gonna be too hot for my application. My question is, is there any difference between the two plugs other than the heat range? Is the reach, thread size and wrench size still the same? Do Summit know what they are talking about? I'm confused! Are there two types of AR23's? Can any one clear this up for me please...

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