The Spark Plug Dilemma

Monday

Member
Joined
Jul 21, 2021
Messages
213
Reaction score
86
I bought a set of Brisk Premium LGS Spark Plugs (GOR15LGS) for my mustang. Weather is getting better here, and I have all the parts for my spring build up. I thought of putting these in so I'm not having to index these plugs.

Anybody have experience with these? I could use your opinion.

Thank-you
 

lwarrior1016

Mr. Secondary Timing Chain
Staff
Joined
Sep 22, 2014
Messages
8,481
Reaction score
4,234
Location
South Mississippi
I’ve heard good things but have no actual experience with them.

Side bar, what in the world do you have to index the plugs for? Is it a really close tolerance build?
 
OP
OP
Monday

Monday

Member
Joined
Jul 21, 2021
Messages
213
Reaction score
86
When I did the diligence, it made sense to me, as the narrator spoke, "... [] you don't want the backside of your plugs" to the intake valve and fuel mix.

It just seemed logical. Sensible.

Honestly.

AND, I am wrong ALL THE TIME!! when I buy shit because "it made sense".
 

lwarrior1016

Mr. Secondary Timing Chain
Staff
Joined
Sep 22, 2014
Messages
8,481
Reaction score
4,234
Location
South Mississippi
When I did the diligence, it made sense to me, as the narrator spoke, "... [] you don't want the backside of your plugs" to the intake valve and fuel mix.

It just seemed logical. Sensible.

Honestly.

AND, I am wrong ALL THE TIME!! when I buy shit because "it made sense".
Hey man, I get it. Every little bit makes a difference. I just didn’t know if you had to keep them oriented because of them hitting pistons or something.
 

RAU03MACH

Legend
Joined
Apr 23, 2019
Messages
6,717
Reaction score
6,510
Location
NEW MEXICO
Are those plugs a little longer than a stock motor craft
The indexing is sort of like a shim copper washer
And mark the plug how many turns to getting to the sweet spot before hitting the piston
Something like that
 

tinnocker

Member
Joined
Apr 12, 2021
Messages
153
Reaction score
71
Indexing from what I understand has nothing to do with the build. A very slight gain in the speed of the burn is accomplished by having the flat part of the electrode pointed at the intake valve so it fires as the gas mixture sprays into the combustion chamber. If the flat part is pointed away from the intake valve, the gas/ air mixture has to flow around the spark plug to get to the spark. The indexing is accomplished by marking the plug with a marker on the side that the flat electrode is pointing to. By knowing where the intake valve is located in each cylinder, the plug can be screwed in until it points in that direction. Each cylinder's plug will require different thickness shimmed washers to accomplish this. Some plugs may get tight right on the money, pointed at the valve. I have never tried this, figuring it was worthless unless you were wanting every horsepower that is possible out of an engine. I haven't seen a comparison of indexed vs non-indexed on the dyno but there may be one on Youtube.
 

badass98svt

Well-Known Member
Joined
Jan 11, 2006
Messages
4,114
Reaction score
1,800
I'd like to see them cover that on Engine Masters.
See how much dyno #s are improved (if at all)
 

NEURON

Member
Joined
Nov 10, 2016
Messages
160
Reaction score
43
Location
SOCAL
Indexing from what I understand has nothing to do with the build. A very slight gain in the speed of the burn is accomplished by having the flat part of the electrode pointed at the intake valve so it fires as the gas mixture sprays into the combustion chamber. If the flat part is pointed away from the intake valve, the gas/ air mixture has to flow around the spark plug to get to the spark. The indexing is accomplished by marking the plug with a marker on the side that the flat electrode is pointing to. By knowing where the intake valve is located in each cylinder, the plug can be screwed in until it points in that direction. Each cylinder's plug will require different thickness shimmed washers to accomplish this. Some plugs may get tight right on the money, pointed at the valve. I have never tried this, figuring it was worthless unless you were wanting every horsepower that is possible out of an engine. I haven't seen a comparison of indexed vs non-indexed on the dyno but there may be one on Youtube.
I thought that the mixture starts coming in as the exhaust valve closes. Then the intake valve closes and the piston comes up then the mixture is ignited, right?
 

lwarrior1016

Mr. Secondary Timing Chain
Staff
Joined
Sep 22, 2014
Messages
8,481
Reaction score
4,234
Location
South Mississippi
I thought that the mixture starts coming in as the exhaust valve closes. Then the intake valve closes and the piston comes up then the mixture is ignited, right?
Yes. The mixture is ignited after it has come in to the cylinder and then been compressed in the chamber completely surrounding the spark plug.
 

tinnocker

Member
Joined
Apr 12, 2021
Messages
153
Reaction score
71
I guess the theory is that it is not 100% surrounding the plug since everything is happening so fast. The mixture would have to go around the plug to get to the spark, so have the spark facing the oncoming mixture. I've never tried it. Too much trouble for so little gain....if any. Looks good on paper.
 

lwarrior1016

Mr. Secondary Timing Chain
Staff
Joined
Sep 22, 2014
Messages
8,481
Reaction score
4,234
Location
South Mississippi
I guess the theory is that it is not 100% surrounding the plug since everything is happening so fast. The mixture would have to go around the plug to get to the spark, so have the spark facing the oncoming mixture. I've never tried it. Too much trouble for so little gain....if any. Looks good on paper.
But the mixture is coming up from the inside of the cylinder at that time. It’s not incoming from the intake valve, that motion has already happened.
 

Steven

Legend
Joined
Jun 3, 2007
Messages
8,177
Reaction score
118
Location
SC
I'd only be concerned with Indexing if you were running 20lbs of boost, or large nitrous shot. Indexing doesn't accomplish anything in a mostly stock motor.
 

Michael Plummer

Active Member
Joined
Feb 20, 2007
Messages
517
Reaction score
111
Location
Brockton, MA
I have no experience running those spark plugs you mentioned (Brisk) but as long as you're not having any misfires I would look elsewhere for more HP.

Indexing spark plugs for more HP: Without going into a full-out explanation it depends on how the combustion chamber is shaped and where the plug is located inside the combustion chamber. Then you have to determine if indexing helped or didn't via a dyno. But if you're bored here you go......

1. On a heart-shaped combustion chamber point the flame front at the majority of fuel.....basically the larger segment of the combustion chamber.

2. On a Ford engine (non-heartshaped) anything facing away from the combustion chamber wall.

3. Want more HP than that, don't use heart-shaped combustion chambers in performance applications.

And I'm sure there is a ton more information on the internet but this practice was done back in the day on higher compression engines that had issues with piston to plug tip interference.

In closing, it's my opinion that this procedure isn't worth the effort or the minimal cost to do.

Good luck with whatever you decide
Michael Plummer
 
Joined
Mar 7, 2021
Messages
146
Reaction score
62
Location
Seaford,Del
Brisk plugs are one of the best plugs out there as well as NGK. Do not use those plugs with no ground strap, Not saying they are junk but they belong in different engines like an outboard boat engine or a rotary engine. The two plugs I mentioned are the only plugs I use and never indexed either of them. Only the big boy racers index plugs. Think about it look at how many boosted Coyote engines either it is from the factory or swapped, I'd bet MAYBE two% index out of thousands. Even the Lunds that are running 7.40s or 30s and aiming for high 6 sec 1/4 don't index plugs.
 

Latest posts

Forum statistics

Threads
77,438
Messages
1,502,150
Members
14,919
Latest member
Alida81

Members online

Top