Cutting and indexing the plugs

[vld]

Any advantage to cutting and indexing the plugs on a 4.6? ie trimming back and hining the electrode and 'aiming' the spark? what about gap?can the stock ignition handle a wider gap?

 

[Gearbanger 101]

It's an old hot rodder trick from the '60's. It does help to some small extent, but nothing that's going to drastically improve your power. As for a wider gap....maybe slightly, but there's really no advantage with a stock engine in doing this. Opening it up too much will cause spark blow out, which works against you, not for you.

I say if you want to index the plugs (and go with copper plugs BTW) and cut back the element to center it over the electrode, go ahead....but don't expect miracles.

 

[Kilgore Trout]

Good article on indexing spark plugs:
http://www.bullittarchive.com/html/modules/articles/article.php?id=30

 

[Mirrahasmycar]

the best thing you can do is get some NGK copper plugs, spark plugs won't make that much difference

 

[Mike97gt]

i doubt it would make that much of a difference but i am going too try the method in that article on my car and see what it does..

 

[vld]

anybody know if they are indexed from the factory? also as i look at the engine it looks to me like i am going to have to pull the fuel rails to get to the plugs. is that right?

 

[Kilgore Trout]

anybody know if they are indexed from the factory? also as i look at the engine it looks to me like i am going to have to pull the fuel rails to get to the plugs. is that right?

No need to remove the fuel rails.

 

[Gearbanger 101]

anybody know if they are indexed from the factory?

No....are you kidding, the bean counters would never go for it.

 

[MatthewP]

I've personally tried this on the dyno. with a 5.0 or 351W, plug indexing is definitely worth it. I gained 5 HP from indexing on my 351W and another 3 HP from upping the gap from .045 to .055. I tried the same stuff on my 02 GT and got 0.

I also noticed that the threads in the cylinder heads on my 02 GT all start in exactly the same place, which means for any given plug it's orientation when installed is the same in any cylinder. All of the 5.0/351W style heads that I have tried have variances in the threading so you have to try each plug in each cylinder until you find a match.

You do not need to remove the fuel rails to install the plugs when using the stock manifold.

I would also recommend using anti-sieze on the threads when installing new plugs in any aluminum cylinder head to avoid problems with removal later.

-Matthew

 

[vld]

thanks!