Spark plug tricks?

[85_SS_302_Coupe]

I just read an article where they talked about filing down the tip of a spark plug to be rounded instead of square and to be right over top of the electrode underneath it. I've heard guys talk about this before, and the mag claims you can gain as much as a tenth in the quarter and 5lb/ft of torque all through the RPM range just by doing this.

My question is, does anyone routinely do this and have they seen any real improvements over just gapping them and going?

Also is there anything other than that that you guys are doing to your plugs?

Lastly, now that i've got heads and a cam and i'm running faster, what kind of gap should i be working with?

 

[Mustang5L5]

The theory is correct. Electricity travels to points rather than broad flat surfaces. So filing the plug to a tip gives is a more precise strike zone. '

Will you gain a tenth? I seriously doubt it. I would be shocked if you gained 1 HP

 

[Maryland Stang]

You can also index the plugs. That's where you make sure the gap of the plug is pointed towards the center of the combustion chamber on all cylinders.

These spark plug tricks do work but we're talking about the type of things you do when you're looking for that last 1 or 2 horsepower. On a street car it's kinda pointless.

 

[85_SS_302_Coupe]

Well, i found this page about side gapping, which is really interesting:
Performance Unlimited 4-Wheel & Off Road Center - Hartford, Wisconsin - USA

And then, as far as indexing goes, i found these washers that make it a lot easier:
Spark Plug Indexing Washers - summitracing.com


I did the side gapping thing and i did the best i could with the 8 plugs i already had in it to get them all as close to the center of the chambers as i could. Now, i don't know about making more power but believe me when i tell you, it's the best throttle response my car has ever had. For a carbed car the throttle response is as "EFI" as it's ever been if that makes sense.

 

[MaxTheHooker]

hmm, this is particularly interesting to me 85! good find! i'll have to go out and give this a try tomorrow! the only question is, did you leave the ENTIRE electrode exposed? if so, how the hell did you gap it afterward? also, what did you end up gapping them at?

 

[Vipersix]

IMO...

I would place more emphasis on determining the correct plug and gap than attempting to index your plugs. The rate of return for a properly indexed set of plugs is likely to be in the range of 1 - 2% which is essentially worthless unless you're a competition racer and need the extra .01 seconds. I have seen more harm done using improperly gapped plugs than because they are facing random directions.

But let's assume that you deem it worth your time. Each engine, or more accurately each cylinder, reacts differently from indexing and requires a different position. Based on final runner direction and swirl, the incoming air passes through the intake valve in a calculable speed and direction which is then theoretically turned and aimed towards the exhaust valve as the piston travels towards TDC. So, depending on the direction of rotation and center of compression (contrary to popular opinion, there are varying levels of compression within the combustion chamber), the plug face needs to be oriented towards the oncoming slug of air in order to facilitate a more complete and thorough ignition. Based on the factors just discussed, this may mean the plug needs to be oriented toward the intake valve, towards the exhaust valve, or some angle in between. The only way to correctly determine this is through airflow models and dyno tuning.

Of course, if you have a mild case of COD (Obsessive Compulsive Disorder) as do I, you'll index the plugs simply because you can't stand the thought of them facing in completely random directions. But honestly, I think you'll get a better drop in quarter time if you take a large dump before you race.

 

[stykthyn]

taking a dump for teh win.


dont forget to tighten the belt an extra notch afterwards.

 

[85_SS_302_Coupe]

hmm, this is particularly interesting to me 85! good find! i'll have to go out and give this a try tomorrow! the only question is, did you leave the ENTIRE electrode exposed? if so, how the hell did you gap it afterward? also, what did you end up gapping them at?

I did them on a little miniature bend grinder that i have and i only ground them down so that the ground strap tip is centered over the electrode. That site that talks about cutting all the way to the side of the electrode...i dunno about that so i started with this just to see what happens. I also couldn't get any good info as far as gapping...some people say 54, some say 44, i went with 50 and it seems to be running pretty killer. I'm open to other gap suggestions though.

 

[NIKwoaC]

This is all interesting, and seems to have some theory behind it, but I've bought the best of the best plugs and had the cheapest of plugs and I can't say I've ever noticed much of a difference. I personally think its a placebo effect on a NA street car. Are you sure the reason your car is running so well isn't from the cooler fall air?

Not to be completely pessimistic, but I'd just like to see some dyno numbers before I go hacking at my electrodes or buying special washers and indexing plugs.

 

[85_SS_302_Coupe]

That's why i hit the plugs that are already in my car instead of doing a new set. I figure, for me personally it's no big deal to spend 20 minutes on my grinder shaping the ground strap on each plug if that'll get me at least better throttle response.

I think i can rule out air temp because i had the car out the same day before i did the plugs and noticed the difference. I'm not real concerned with getting the indexing washers...i think the side gapping and getting them as close as possible to pointing towards the intake valve is good enough on my engine.