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Projected or non-projected + indexing

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CGASTON

Well-Known Member
Joined
Oct 11, 2009
Messages
1,881
So can anyone tell me what the benefit is of running a non-projected plug versus a projected plug? What the benefit of the two? Stock heads on modified engine? Does anyone index there plugs? Pros and cons? I have been told that non-projected plugs help with detonation.
 
Projected plugs do not belong in a blown engine. Even a slightly modified GN should be using a race plug.

Unless you have an all-out, must have every HP you can find engine, you will never experience any power increase by indexing spark plugs. :)
 
Nick Micale said:
Projected plugs do not belong in a blown engine. Even a slightly modified GN should be using a race plug.

Unless you have an all-out, must have every HP you can find engine, you will never experience any power increase by indexing spark plugs. :)

Nick, I know that we talked this before. What plug are you running? Autolite 145?
 
The typical projected tip plugs are supposed to provide a hotter spot for detonation to occur, whereas a non-projected tip plug sits much shallower in the chamber and is cooled more by the cylinder head.

I have run both and found my best results using a non projected tip.

Autolite has a wide variety of non projected racing plugs available with a 14mm tapered seat.
Here's a few P/Ns

.460" reach for iron heads
Warm
AR135 (NGK 7 heat range)
AR134
AR133
AR132 (NGK 9 heat range)
Cold

.708" reach for aluminum heads (champion GN1)
Warm
AR474 (NGK 8 heat range)
AR473
AR472 (NGK 9 heat range)
Cold

Note cold means "really cold", and warm is still a step or two steps colder than a regular non-racing type plug.
 
I see you run E85. I run an AR474 on E85. May run an AR473 at the track.
 
What about a AR24? I have used NGK UR-5 for years. Been thinking about trying the Autolite Racing Plug.
 
The ar3933 works great

I run them in my race car with TA alum heads, NOT in my street car with iron head as those plugs are too long and can cause serious issues projecting too far into the combustion chamber. :eek:
 
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