Gap spark plugs to .050" or .054"?
05-14-2008, 05:28 PM
#11
1st Gear Member
Join Date: Apr 2008
Location:
Posts: 62
RE: Gap spark plugs to .050" or .054"?
ORIGINAL: camaroeater
I think I'll just flip a coin I guess....tails=.045" and heads=.054". I hate doing **** when I not 100% sure about something.
I think I'll just flip a coin I guess....tails=.045" and heads=.054". I hate doing **** when I not 100% sure about something.
05-14-2008, 05:30 PM
#12
Join Date: May 2008
Posts: 10
RE: Gap spark plugs to .050" or .054"?
ORIGINAL: xB1u3xF1v3xO
somewhere .054 or a little below...you'll be fine.
ORIGINAL: camaroeater
I think I'll just flip a coin I guess....tails=.045" and heads=.054". I hate doing **** when I not 100% sure about something.
I think I'll just flip a coin I guess....tails=.045" and heads=.054". I hate doing **** when I not 100% sure about something.
05-14-2008, 06:55 PM
#13
6th Gear Member
Join Date: Apr 2007
Location: California
Posts: 10,468
RE: Gap spark plugs to .050" or .054"?
If it's n/a then gap larger, say .054. The larger gap makes for a larger longer spark that's a bit hotter and more likely to ignite the local air/fuel mix and generate a strong flame kernel. The problem with larger gaps is that they can cause increased electrode wear, so when they get excessive the plugs wear out faster(for reference some newer cars are running stock gaps of .060 in order to generate a large enough spark to "catch" some fuel in the lean mileage mixtures) and in higher compression and boosted applications the problem can be the hotter spark keeps the plug tip too hot and can possibly cause pre-ignition or you can get spark blow-out, where the force of compression literally "blows out" the flame kernel as it's trying to ignite the fuel charge. That's why any engine with too much gap for the setup will get high rpm misfires. Not enough gap and you'll have poor performance, fuel consumption increases, power may be low and throttle response can suffer. The only thing is that in order to run larger gaps you need higher voltage ignition systems to generate enough voltage to jump the high resistance gap(bigger gap = more resistance = more voltage required), that's why older cars with poor ignition systems ran much smaller plug gaps, usually less than .035 whereas modern vehicles or older vehicles like my 67 with modern high energy ignitions run .050 or more.
05-14-2008, 07:49 PM
#14
RE: Gap spark plugs to .050" or .054"?
if i was you and weren't sure i'd gap them at .052, right in the middle. that way your only 2 thou out of spec for either one, and come on 2 thou is so small you wouldn't notice any difference.
05-14-2008, 10:07 PM
#16
1st Gear Member
Join Date: Apr 2008
Posts: 52
RE: Gap spark plugs to .050" or .054"?
ORIGINAL: ctgreddy
if i was you and weren't sure i'd gap them at .052, right in the middle. that way your only 2 thou out of spec for either one, and come on 2 thou is so small you wouldn't notice any difference.
if i was you and weren't sure i'd gap them at .052, right in the middle. that way your only 2 thou out of spec for either one, and come on 2 thou is so small you wouldn't notice any difference.
I had extensive conversations with the local machine shop and to my dismay... they put down the NGK's and said go with Autolite AR series plugs. I have a '94 GT 5.0Lthat is Naturally aspirated and I asked for the plug application for my car. They told me AR13's were the way to go.
The AR series Autolites are constructed with a ground that only protrudes half way to the electrode to give a more open spark for better combustion. The machine shop told me hands down these performed better than the NGK's in every dyno runthey tested them in.
Oh... and they told me the gap ona Naturally aspirated 5.0L should be .052 for optimum performance.
They weren't kidding about those AR series plugs... My car ran betterwith the AR's thenit ever did on any of the other plugsI tried.
05-14-2008, 10:10 PM
#17
1st Gear Member
Join Date: Apr 2008
Posts: 52
RE: Gap spark plugs to .050" or .054"?
ORIGINAL: stang8689
What if you have a MSD 6AL, dizzy and coil, what would you gap them at?
What if you have a MSD 6AL, dizzy and coil, what would you gap them at?
Now if you run NOS or have forced induction, that's different. That would call for an entirely different gap setting and heat rating.
05-14-2008, 10:14 PM
#18
1st Gear Member
Join Date: Apr 2008
Posts: 52
RE: Gap spark plugs to .050" or .054"?
ORIGINAL: 67mustang302
If it's n/a then gap larger, say .054. The larger gap makes for a larger longer spark that's a bit hotter and more likely to ignite the local air/fuel mix and generate a strong flame kernel. The problem with larger gaps is that they can cause increased electrode wear, so when they get excessive the plugs wear out faster(for reference some newer cars are running stock gaps of .060 in order to generate a large enough spark to "catch" some fuel in the lean mileage mixtures) and in higher compression and boosted applications the problem can be the hotter spark keeps the plug tip too hot and can possibly cause pre-ignition or you can get spark blow-out, where the force of compression literally "blows out" the flame kernel as it's trying to ignite the fuel charge. That's why any engine with too much gap for the setup will get high rpm misfires. Not enough gap and you'll have poor performance, fuel consumption increases, power may be low and throttle response can suffer. The only thing is that in order to run larger gaps you need higher voltage ignition systems to generate enough voltage to jump the high resistance gap(bigger gap = more resistance = more voltage required), that's why older cars with poor ignition systems ran much smaller plug gaps, usually less than .035 whereas modern vehicles or older vehicles like my 67 with modern high energy ignitions run .050 or more.
If it's n/a then gap larger, say .054. The larger gap makes for a larger longer spark that's a bit hotter and more likely to ignite the local air/fuel mix and generate a strong flame kernel. The problem with larger gaps is that they can cause increased electrode wear, so when they get excessive the plugs wear out faster(for reference some newer cars are running stock gaps of .060 in order to generate a large enough spark to "catch" some fuel in the lean mileage mixtures) and in higher compression and boosted applications the problem can be the hotter spark keeps the plug tip too hot and can possibly cause pre-ignition or you can get spark blow-out, where the force of compression literally "blows out" the flame kernel as it's trying to ignite the fuel charge. That's why any engine with too much gap for the setup will get high rpm misfires. Not enough gap and you'll have poor performance, fuel consumption increases, power may be low and throttle response can suffer. The only thing is that in order to run larger gaps you need higher voltage ignition systems to generate enough voltage to jump the high resistance gap(bigger gap = more resistance = more voltage required), that's why older cars with poor ignition systems ran much smaller plug gaps, usually less than .035 whereas modern vehicles or older vehicles like my 67 with modern high energy ignitions run .050 or more.
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