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Old 02-26-2021, 07:15 PM
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posulli88 posulli88 is offline
258 I6
Join Date: Dec 18, 2016
Location: Denver, CO
Posts: 322
Help me Diagnose Spark Plugs

Well, I just pulled my spark plugs and I am concerned. I have an amc360 that Rick Jones built to have just under 10:1 compression (I run 91 octane here in Denver). Its run by a Holley Sniper (which I think is probably running a bit too rich). Its a full MSD Ignition system and I probably only have around 400 miles on it total. Between a big move and other projects Ive been working on on the J10 I just havn't been able to drive it as much as I would want. Although I have now buttoned everything up and it's ready to see some miles. You can see the detailed build of the engine here:

It did bend a push rod (very minimal bend) due to the guy who machined my heads (before it got to Rick) not doing a great job and missing some measurements. Again Rick has been amazing through this entire build and the quality in his work is evident.

Anyway, Ive just pulled the plugs and most of them seem to be fouled. I know reading plugs over images is hard but Ive done my best to capture high quality images below. A couple notes:

I am most concerned with plug/cylinder 1. That cylinder probably hasn't been running because of fouling. Im trying to convince my self its fuel fouled and not oil fouled. It does smell heavily of fuel. Cylinder/plug 2 has 5 minutes run time on it. I replaced it the other day because I noticed the exterior ceramic was cracked and arcing outside the cylinder. I am running NGK FR5 plugs. Also the silver you see on some of the edges of the plugs is anti-sieze from when I pulled them. Thoughts?

77' J10 w/ 360, T18, Dana 20 TC
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