Spark plug gap???
Pro
Joined: Jun 2005
Posts: 593
Likes: 1
rule of thumb is for about every 75 HP gain gap should be reduced by .004.
But you cannot change the gap more then .004 +/_ of what the plug was designed to so if you wanted to go with a .040 gap you would have to use a different plug that was designed for about that gap.
If your running a header with mods also best to drop down one step colder so a NGK TR-6 is a step colder and designed for 0.40 gap.
Newest GM plugs are designed differently then what C5s used to use where they ran a .60 where new ones are .40 but are still a hotter plug.
But you cannot change the gap more then .004 +/_ of what the plug was designed to so if you wanted to go with a .040 gap you would have to use a different plug that was designed for about that gap.
If your running a header with mods also best to drop down one step colder so a NGK TR-6 is a step colder and designed for 0.40 gap.
Newest GM plugs are designed differently then what C5s used to use where they ran a .60 where new ones are .40 but are still a hotter plug.
Safety Car
Joined: May 2000
Posts: 4,811
Likes: 344
From: Albuquerque NM
My motor is simular to yours, but with 11.4 cpmpression. I'm running .050" gap. Runs good, but then it ran good with the stock plugs even after the pucks came off and the gap was .070" 
What do you guys think it should be?
What do you guys think it should be?
Heel & Toe
Joined: Jun 2005
Posts: 21
Likes: 2
maybe gap is my problem.
I just removed the stock plugs and installed a set of boshe paltinum plus 4 plugs and the car barely runs, at Idle it misses and under a load it bucks and feels like it is running on 4 cylinders. I verified all electrical connections and verified all plugs were firing (at idle), but the car runs like hell! Maybe It has somthing to do with the preset gap on the 4 electrode boshe plugs?. Does anybody want to chime in about this one? Is it a must that I use these NGK tr55's in my car? the stock plugs were .080 
and seem to run ok?
and seem to run ok?
