Spark plug indexing - what orientation is optimal?
#1
#2
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#3
I've read this question a few times trying to see what I've missed so if I've misunderstood, please come back and explain.
What difference do you expect this to make?
They plugs are torqued 25-29 Nm and not a set number of turns so you have no control over which way it's facing once torqued up. Regardless of the way it's offered up to the head, it only starts to screw in when the lead thread on the plug engages with the lead thread in the head.
Graham
What difference do you expect this to make?
They plugs are torqued 25-29 Nm and not a set number of turns so you have no control over which way it's facing once torqued up. Regardless of the way it's offered up to the head, it only starts to screw in when the lead thread on the plug engages with the lead thread in the head.
Graham
#4
Some say that orienting the open-end of the gap towards the inlet port gives some tiny increase in power output. Legend has it that there are available washers of variable thickness, to facilitate this sort of twiddling without interfering with the correct spark-plug torque.
Personally I'll give it a skip!
Personally I'll give it a skip!
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#6
It's really astonishing how much bogus hot rod/racing lore is out there that guys think has application to street performance cars. I would add a few cases in point but I didn't sign on to start any trouble.
O God. I can't help myself. How about plug indexing, fancy air cleaners, purple motor oil, $38/qt transmission fluids and miracle fuel/oil additives just to get the ball rolling. Let the games begin. We should start a comprehensive list.
O God. I can't help myself. How about plug indexing, fancy air cleaners, purple motor oil, $38/qt transmission fluids and miracle fuel/oil additives just to get the ball rolling. Let the games begin. We should start a comprehensive list.
Last edited by user 2029223; 05-30-2014 at 07:09 AM.
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Brutal (03-25-2013)
#8
It's really astonishing how much bogus hot rod/racing lore is out there that guys think has application to street performance cars. I would add a few cases in point but I didn't sign on to start any trouble.
O God. I can't help myself. How about plug indexing, fancy air cleaners, purple motor oil, $38/qt transmission fluids and miracle fuel/oil additives just to get the ball rolling. Let the games begin. We should start a comprehensive list.
O God. I can't help myself. How about plug indexing, fancy air cleaners, purple motor oil, $38/qt transmission fluids and miracle fuel/oil additives just to get the ball rolling. Let the games begin. We should start a comprehensive list.
The following users liked this post:
Bob OB (03-25-2013)
#9
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It's really astonishing how much bogus hot rod/racing lore is out there that guys think has application to street performance cars. I would add a few cases in point but I didn't sign on to start any trouble.
O God. I can't help myself. How about plug indexing, fancy air cleaners, purple motor oil, $38/qt transmission fluids and miracle fuel/oil additives just to get the ball rolling. Let the games begin. We should start a comprehensive list.
O God. I can't help myself. How about plug indexing, fancy air cleaners, purple motor oil, $38/qt transmission fluids and miracle fuel/oil additives just to get the ball rolling. Let the games begin. We should start a comprehensive list.
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#11
How about $400 after mkt induction air cleaners with $1200 exhaust systems that dump the HP at low rpms and add a hand full of HP over 6 grand at which point the engine blows.
But the sound is marvelous - while it lasts. Hoo Haah! I'm so funny I can't stand it! P.T. Barnum was right.
But the sound is marvelous - while it lasts. Hoo Haah! I'm so funny I can't stand it! P.T. Barnum was right.
Last edited by user 2029223; 03-25-2013 at 05:46 PM.
#13
Theoretically, you should direct the gap toward the incoming charge. Accel used to offer a threaded tool that simulates the cylinder head threads so you can trial fit the various copper washers so the plugs will be "indexed" correctly before actually installing the plugs. It's a lot of fooling around for nothing on a street engine. How about this... Do they offer a multi-electrode plug for our cars? Several manufacturers offer a 2, 3 and even a 4 electrode plug. I don't know if any list one for the Jags.
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This is from NGK
4. Indexing
This is for racers only !!
Indexing refers to a process whereby auxiliary washers of varying thickness are placed under the spark plug's shoulder so that when the spark plug is tightened, the gap will point in the desired direction.
However, without running an engine on a dyno, it is impossible to gauge which type of indexing works best in your engine. While most engines like the spark plug's gap open to the intake valve, there are still other combinations that make more power with the gap pointed toward the exhaust valve.
In any case, engines with indexed spark plugs will typically make only a few more horsepower, typically less than 1% of total engine output. For a 500hp engine, you'd be lucky to get 5hp. While there are exceptions, the bottom line is that without a dyno, gauging success will be difficult.
4. Indexing
This is for racers only !!
Indexing refers to a process whereby auxiliary washers of varying thickness are placed under the spark plug's shoulder so that when the spark plug is tightened, the gap will point in the desired direction.
However, without running an engine on a dyno, it is impossible to gauge which type of indexing works best in your engine. While most engines like the spark plug's gap open to the intake valve, there are still other combinations that make more power with the gap pointed toward the exhaust valve.
In any case, engines with indexed spark plugs will typically make only a few more horsepower, typically less than 1% of total engine output. For a 500hp engine, you'd be lucky to get 5hp. While there are exceptions, the bottom line is that without a dyno, gauging success will be difficult.
#16
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#18
I can offer (to Members Only) French Plug Locating Snake Oil
Not only does this permit precise orientation of the plug electrodes it also allows choice of plug insertion depth.
This increases the number of variables to the point where you will NEVER find a satisfactory solution.
Also labour saving since the next set of plugs can be oriented on the workbench in the (required) new cylinder heads.
Not only does this permit precise orientation of the plug electrodes it also allows choice of plug insertion depth.
This increases the number of variables to the point where you will NEVER find a satisfactory solution.
Also labour saving since the next set of plugs can be oriented on the workbench in the (required) new cylinder heads.
#19
This is from NGK
4. Indexing
This is for racers only !!
Indexing refers to a process whereby auxiliary washers of varying thickness are placed under the spark plug's shoulder so that when the spark plug is tightened, the gap will point in the desired direction.
However, without running an engine on a dyno, it is impossible to gauge which type of indexing works best in your engine. While most engines like the spark plug's gap open to the intake valve, there are still other combinations that make more power with the gap pointed toward the exhaust valve.
In any case, engines with indexed spark plugs will typically make only a few more horsepower, typically less than 1% of total engine output. For a 500hp engine, you'd be lucky to get 5hp. While there are exceptions, the bottom line is that without a dyno, gauging success will be difficult.
4. Indexing
This is for racers only !!
Indexing refers to a process whereby auxiliary washers of varying thickness are placed under the spark plug's shoulder so that when the spark plug is tightened, the gap will point in the desired direction.
However, without running an engine on a dyno, it is impossible to gauge which type of indexing works best in your engine. While most engines like the spark plug's gap open to the intake valve, there are still other combinations that make more power with the gap pointed toward the exhaust valve.
In any case, engines with indexed spark plugs will typically make only a few more horsepower, typically less than 1% of total engine output. For a 500hp engine, you'd be lucky to get 5hp. While there are exceptions, the bottom line is that without a dyno, gauging success will be difficult.
BUT - this only works within 200 RPM either side of peak torque. Always consult your pharmacist.
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Jon89 (03-26-2013)
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