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Can someone give me a gap or guidelines for gapping plugs: 351W alum. block bored/stroked 4.125"/4.00", 427 c.i., aggressive cam, EFI, AFR 205cc alum. heads, tring to make a streetable daily driver, Autolite 3926 plugs.

Thanking everyone in advance, Adlai
 

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You go by the manufacturer of the ignition system you are using.
 

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I was truly wondering if someone was going to say something about the ignition system.. That is the deciding factor and an unknown with the details given....
 

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I would imagine most install them right out of the box, no gapping tool used... :frown:
 

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I would imagine most install them right out of the box, no gapping tool used... :frown:
I've always checked mine but have found that more often than not they are really close to where I want them at .035 anyways.

John
 

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I've always checked mine but have found that more often than not they are really close to where I want them at .035 anyways.

John
So do you gap them or just screw them in?
 

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I've always checked mine but have found that more often than not they are really close to where I want them at .035 anyways.

John
That is true but not knowing what ignition system he has there is no way to 'guess' what plug gap to use... can start anywhere that gives spark, but is it correct?
 

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I usually use a rule of thumb: stock ignition system, stock gap; higher energy system aftermarket, wider gap. How wide, is often stated by system manufacturer, if not, I'll add 5 thou. I just did a Pertronics II dizzy with the Pertroinics II coil and some of the literature stated to use stock gaps, other info implied gap may be increased but didn't say to what. I called Pertronics and the guy said I "should" be able to increase it but was reluctant to commit to a figure. Finally he broke down and said some users have reported good results with up to 10 thou over stock. I went with 5 and all is well. However, if going with wider gaps, make sure the plug leads are able to handle it.
Unless in an emergency, I can't image installing plugs without checking the gaps first.
 

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That is true but not knowing what ignition system he has there is no way to 'guess' what plug gap to use... can start anywhere that gives spark, but is it correct?
I've used .035 for as long as I can remember and it's always been fine. Perfect? Heck, I don't know since I don't own an engine dyno to test it out. Could I make ___ more power if I opened them up, or tightened them down a few thousandths? Probably, but since I'm not looking for an extra hundredth of a second, or a fraction of a mile an hour at the track I really don't care.

Unless you're running back to back engine diagnostics in a very controlled environment, I seriously doubt you'd ever see a real performance difference. Just my humble opinion.

John
 

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I have to say, for spark plug gap, I've always used .35. For points, I've always used my drivers license. I've owned quite a wide range of Ford muscle, from 289 4v to a 460 4v. All of 'em purred like kittens with those specs.
 

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Use E3plugs and don't worry about it.
I might just do that next time! Although I have a set of Motorcraft platinum's with only a few miles on them (long story) that I should probably use next time I change them out. Since the car only gets a few hundred miles a year that could be a LONG time though! :D

John
 

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Can someone give me a gap or guidelines for gapping plugs: 351W alum. block bored/stroked 4.125"/4.00", 427 c.i., aggressive cam, EFI, AFR 205cc alum. heads, tring to make a streetable daily driver, Autolite 3926 plugs.

Thanking everyone in advance, Adlai
An Autolite 3926 is quite a hot plug--is that recommended for use with an aluminum block?

Typically a good place to start is .035".
 

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An Autolite 3926 is quite a hot plug--...
+1. I just caught this thread and that jumped-out at me too. I would have started with 3923s and moved from there with testing. Hmmm...
Typically a good place to start is .035".
Anything will spark at .035, so that is safe to start with. Your final gap will depend not only on your ignition setup, but your engine and what the ignition must fire through. There is a thread around here on how to test and set your optimum gap. It is wise to tune your gap along with everything else that gets tuned.

David
 
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