Spark Plugs??
- Thread starter daviszx3
- Start date
-
Sponsors (?)
MustangLX-5.0
Founding Member
Are you running stock plugs? You'll want to go to a plug that's one or two heat ranges colder than stock.A copper plug will do just fine unless you don't mind spending the dough for iridium plugs.If you go with copper plugs,gap them down to .040".Factory gap setting is .050".If you go with the iridium plugs then you can gap them to stock .050".Also,what do you have your timing set at?
The reason your engine is cutting out at 8 - 10 psi boost is most likely because your plugs aren't gapped properly for the SC.With higher cylinder pressures it takes more electrical energy from the coil to jump the plug gap and "SPARK".The gap is your resistance.Higher cylinder pressure creates higher resistance.So when the boost gets near 8 -10 psi,it cuts out on you,or more specifically,the plugs can't fire because there's too much resistance.This is why it suddenly picks back up after a second or two.The pressure drops and the plugs can now fire again.Decreasing the plug gap will decrease the resistance and will allow them to fire even at 10 psi.The only problem with this is that you lose a little power from the shorter gap.You can keep the stock gap if you go with iridium plugs.More specifically,the ones with the U-groove in the ground electrode.The primary electrode is tipped like a sharp pencil.That's supposedly how it gets more power without having to increase the gap.They are expensive tho.
The reason you want plugs with a colder heat range is to prevent detonation or premature misfires.The plugs dont get as hot so they can't pre-ignite the gas.
It may also be a good idea to upgrade your ignition system to something like an MSD 6AL especially since you have a SC.You could probably keeps the same gap and get more power from your SC at the same time.
As for WHAT brand of plugs.Not sure really.Probably best to stick with Motorcraft.Stay away from Autolites.They are garbage.Also stay away from the platinum tipped plugs.Useless and may actually make your problem worse.Platinum makes a better insulator than a conductor.
The reason your engine is cutting out at 8 - 10 psi boost is most likely because your plugs aren't gapped properly for the SC.With higher cylinder pressures it takes more electrical energy from the coil to jump the plug gap and "SPARK".The gap is your resistance.Higher cylinder pressure creates higher resistance.So when the boost gets near 8 -10 psi,it cuts out on you,or more specifically,the plugs can't fire because there's too much resistance.This is why it suddenly picks back up after a second or two.The pressure drops and the plugs can now fire again.Decreasing the plug gap will decrease the resistance and will allow them to fire even at 10 psi.The only problem with this is that you lose a little power from the shorter gap.You can keep the stock gap if you go with iridium plugs.More specifically,the ones with the U-groove in the ground electrode.The primary electrode is tipped like a sharp pencil.That's supposedly how it gets more power without having to increase the gap.They are expensive tho.
The reason you want plugs with a colder heat range is to prevent detonation or premature misfires.The plugs dont get as hot so they can't pre-ignite the gas.
It may also be a good idea to upgrade your ignition system to something like an MSD 6AL especially since you have a SC.You could probably keeps the same gap and get more power from your SC at the same time.
As for WHAT brand of plugs.Not sure really.Probably best to stick with Motorcraft.Stay away from Autolites.They are garbage.Also stay away from the platinum tipped plugs.Useless and may actually make your problem worse.Platinum makes a better insulator than a conductor.
fiveohwblow
Official Member
- Jul 21, 2005
- 2,169
- 145
- 135
Very good information above and I would agree with most. Only thing is I use autolites and have for years. They work great for me at around 500hp...
Very good information above and I would agree with most. Only thing is I use autolites and have for years. They work great for me at around 500hp...
+1, i run autolite 3923's, they make a racing plug that costs a little more that i am going to try out this season also. Im not sure if you can use this same plug with a stock head, but i used these on my old motor with a Novi 2000 with good results. Naturally Aspirated i run a .045'' gap and on the Blower motor i was using .035''
what plugs are in the car now?
MustangLX-5.0
Founding Member
What do you have them gapped at?
The only reason I said Autolites were garbage was because when I worked at Sam Galloway Ford,I had asked numerous techs over the years about the plugs I was using.I was also using Autolites and they had been fouling up too easily.Most of the other techs blamed it on the AL's.Said they are pure crap.That they weren't made to run in Fords.The same thing goes for Champions and ACDelco.Perhaps they were born to believe that only Motorcraft plugs should be used in Fords.I'm currently using NGK Iridium tipped plugs in my V6 and have no problems with them.Now I suspect I was probably having fouling issues with the AL's because they may've been the wrong heat range.Perhaps..then again maybe they are crap.All I know is I had 3 different sets of AL's.I picked a different heat range and even re-gapped them to .060 .Yep..big gap.It ran quicker but they still fouled up fast.
Posted via Mobile Device
MustangLX-5.0
Founding Member
Those plugs are fine.And so is the gap.You may have an ignition problem.It sounds like a lack of coil energy.What sort of coil and Diz are you using? And what do you have your base timing set at? Are you using stock injectors and MAF?
MustangLX-5.0
Founding Member
millhouse
Founding Member
Considering the OEM Motorcraft plugs are nothing more than a rebadged Autolite, I’d say that was a typical case of Ford tech’s saying anything they can to get you to buy up. If Motorcraft plugs are good enough for Ford, Autolites are too…as they are the same plug.
With that said, if you are running boost I highly recommend stepping up to a recessed tip plug for a few reasons.
First off, it pulls the tip away from chamber a bit which can greatly reduce your chances of getting spark blowout. You don’t want your d!ck hanging out in the wind on a cold day.
Another advantage is you shouldn’t have to run quite as cold of a plug, as the recessed tip cools things down a bit by itself. If you were running 2-steps colder in a standard plug, you may be able to get away with a 1-step colder recessed tip plug.
One more advantage is the actual ground strap length is of a correct size for smaller gaps. Anyone that has gapped a standard plug down below .030 can see that the ground strap overhangs the electrode a TON! What no-one ever tells you is you are supposed to cut that strap down after you gap it that low to get the strap centered closer to the electrode. If not, you’ll need more energy to create a good spark, otherwise your spark can actually get less intense…as that .030 gap will act larger. The recessed tip plugs have a MUCH shorter ground strap and come gapped MUCH closer to what most run with forced induction setups. When you gape them down to .030 or smaller, the tip is still fairly close to the center electrode.
Similar threads
