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Discussion Starter · #1 ·
Does anybody here index their spark plugs? if so, wich way do you turn them? toward the intake, mid cilinder,or exhaust.
Just curious.
 

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I don't and never have , not even on race engines.
Do you really think there is anything to gain?
 

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Discussion Starter · #3 ·
well,in my other life as a US muscle car guy,it was a good thing to make the spark available to the best side of the spray,just wondered if that is true w/the b mill
 

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it does have its benefits in all motors, some more then others. in our motors it would probably be less than 1hp though, so its kind of pointless

if anything though, i would say turn towards the intake
 

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88SE Lude said:
I don't and never have , not even on race engines.
Do you really think there is anything to gain?
its not solely for hp gains as much as its for burning the mixture more thourally (sp?). as for which waw to turn them, turn em towards the intake side of the head. thats the "correct" way of doing it.
 

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burning the mixture more thoroughly does give hp gains, also gives gas mileage gains. gotta love when you can get both at the same time haha

power is directly related to how much fuel/air is burned while the valves are still closed, and if the mixture burns more thoroughly, you burn more of the air/fuel before the exhaust valve opens which in turn creates more power. and when more gas is burned before exiting the exhaust, it also creates better gas mileage
 

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do it toward the intake valve. or was it the majour thrust side of the cylinder....................... im thinking 80% towards the intake valve. we discussed this in school a few days ago.
 

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Much less effect on a hemi-head ( like our twin cam engines) than with a wedge head. A hemi-head has the spark plug in the middle of the combustion chamber and the compressing air/fuel charge is evenly formed so there isn't much to be gained by aiming the spark in a particular direction.
 

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Indexing is more about burning the mixture completely and even the most seasoned racers see less than 1hp from it. With our engines I can almost garuntee seeing no gain. Indexing is something you'de want to do in a Mid Cam 2 valve setup like a Corvette, etc... No point and plus, its a bitch to do with all those special washers and stuff
 

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Yep... a Corvette is an excellent example. The plain vanilla chevy V8 has a wedge head that creates a lot of turbulance as the air/fuel mixture is being compressed. They are also known as "slow-burn" heads (the reason they sound so nice and mellow...you should have heard an old ford flat head V8 )

Because the ground electrode "shrouds" the spark there is an advantage to aim the unshrouded spark in a particular direction to start the flame front in the turbulance. I have no idea what that direction would be , but engine tuners do.
 

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I believe the goal is to aim it at the exhaust valve... atleast thats what I remember being told, but again the gain is so miniscule unless you're racing pro-stock or something there really isn't a reason
 

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But if you aim the gap towards the intake you risk blowing the flame out with the intake charge.


But TBH I agree with J-willie :emthup:
Completely pointless excercise.

On our engines taking the plugs out and cleaning them will have far more benefit than where you put the gap.
 

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The reason I say aim it towards the exhaust valve is because after the intake stroke and the compression stroke the air/fuel charge will be all over the cylinder not just the intake. People aim their spark plug on the exhaust side because that side of the cylnder/valve runs hotter and it ignites the air/fuel charge easier allowing a quicker and more efficient flame front. With a 4 valve setup though you will not see a gain in power, since there was twice the curtain area of the 2 valve engine. Maybe minor fuel economy gains but that's it. It's really just an extra thing to do with you need that extra thousandths of a second.
 

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Huh ??

The piston is going upwards on the compression stroke and the spark plug fires at say 25 degrees before T-D-C. Do you really think that ANY valves are open at this time ??

Let's go back to the Chevy V8. The spark plugs are located by the exhaust valve in the combustion chamber. Look where they screw into the head...between the exhaust ports.

So you would want to aim the naked spark TOWARDS the center of the combustion chamber or as motoxxxman says "towards the intake valves".
 

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The intake valves have been closed for quite some time when the plug fires.

That said, the intake side of the cylinder has a cleaner mixture, so thats generally where people point them.

Of course, it's worth maybe 00.5% power increase, so it's really in the why bother region of things.
 

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:emthup:
What I was implying with this comment.
88SE Lude said:
On our engines taking the plugs out and cleaning them will have far more benefit than where you put the gap.
 
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