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Spark plugs

2K views 8 replies 9 participants last post by  nashcar 
#1 ·
I’m curious what spark plugs you guys are running in your 396’s. I need some recommendations on what to use.
 
#2 ·
I'm interested in this as well, as I'm about to do a tuneup on my 396.

Some of the data I've found suggests a lot of guys are running AC-44s.

Someone had this to say, and I'm sorry I didn't grab who wrote this when I found it. If it's someone out here, kudos!

AC- 42- high RPMs ( good for tuning race engines, KOLD plug)
AC- 43- Chevy calls for this in 454s ( It will foul if you idle a lot)
AC- 44- Using this plug in my 454 since 1971 works fine.
AC- 45- good for a high milage engine
AC- 46- good for an oil buner
AC- 46X- Will dam near fire in Diesel Oil
 
#3 ·
Every engine is different depending on the modifications, tuning, and driving habits. Personally, i would would start with the factory recommended plug and make sure your tune is correct and then inspect the plugs and go from there. The standard plug in 1968 for the 396 was AC 43N.
 
#5 ·
I like the AC Delco 45's in stock to mild builds.

With my old combo running angle plug heads and large tube headers, I had to go to use shorty plugs... I used Autolite AR 132's I think it was. (race plug)
 
#9 ·
Another one for 45’s here. When I first got my z28 I used 43’s as per the book, they fouled. I read a post by John Z where he said to run 45’s as the 43’s were too cold for today’s street use, of course he was correct.
 
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