Spark plug gap?
Thread Starter
Le Mans Master
Joined: Apr 2001
Posts: 7,410
Likes: 252
From: Little Elm TX
Spark plug gap?
Since I’ve been having continuing problems in the higher rpms, I decided to replace the spark plugs today to see if that would help. I was told the spark plugs that were in there should have been gapped at .050. Since they were NGK TR55’s they would have to have been done. Those plugs normally come gapped around .055. On a side note, the ones I just bought were gapped at .057. Anyway. I had thought maybe the plugs were blowing out in the higher rpms so I closed the gap to .045. Took the car out after warming it up and that seems to have helped some. What I’m wondering is this? What effect does the gap have on the way the motor runs? I know you don’t want it to small or it won’t burn all the fuel. To big and it’ll flame out in the higher rpms range. How can I tell by the way the motor is running if I’ve got it right?
BTW, the ones I took out were gapped like this:
1. .059
2. .059
3. .059
4. .060
5. .059
6. .057
7. .060
8. .059
BTW, the ones I took out were gapped like this:
1. .059
2. .059
3. .059
4. .060
5. .059
6. .057
7. .060
8. .059
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Re: Spark plug gap? (R94 LT 1)
.050 is book spec on LT1's. Be careful regapping plugs, you want the ground strap to be as parallel to the electrode as possible.
I have the TR55ix iridiums installed and like them.
I have the TR55ix iridiums installed and like them.
Le Mans Master
Joined: Feb 2002
Posts: 7,858
Likes: 2
Re: Spark plug gap? (R94 LT 1)
Well duh on my part-- just saw your sig. I'm pretty sure that when LPE and MTI do 383's they reduce the plug gap. I'm sorry not to be more specific but I do remember seeing a spec on a 383 where the plugs were gapped 0.035. Maybe you're getting detonation too, and one heat range colder plug NGK TR6 (?) might help?
Thread Starter
Le Mans Master
Joined: Apr 2001
Posts: 7,410
Likes: 252
From: Little Elm TX
Re: Spark plug gap? (Lone Ranger)
Well duh on my part-- just saw your sig. I'm pretty sure that when LPE and MTI do 383's they reduce the plug gap. I'm sorry not to be more specific but I do remember seeing a spec on a 383 where the plugs were gapped 0.035. Maybe you're getting detonation too, and one heat range colder plug NGK TR6 (?) might help?
Burning Brakes
Joined: Aug 2000
Posts: 984
Likes: 1
From: Cincinnati OH
Re: Spark plug gap? (R94 LT 1)
Switching from the stock AC's gapped at factory spec to NGK TR5's (.035) fixed my high rpm misfire. But, I should mention that two of the AC's were missing their pucks, so I don't know if that was the problem. In any case it ran fine with the TR5's for 10k miles. I just got a set of TR55's and will gap them to factory spec to see how that goes, I'm thinking it was bad plugs in the first case, not necessarily the gap.
Also, I called LPE since I was using one of their cams and asked them what they use and they told me .035.
Also, I called LPE since I was using one of their cams and asked them what they use and they told me .035.
5th Gear
Joined: Feb 2003
Posts: 5
Likes: 0
From: apollo beach fl
Re: Spark plug gap? (R94 LT 1)
Spark Plug gap should be determined by the ignition manufacturer..ie if its stock go with what the book says , the plug should be gaped to what the ignition sys is setup to need ....just my .02 :thumbs:
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Thread Starter
Le Mans Master
Joined: Apr 2001
Posts: 7,410
Likes: 252
From: Little Elm TX
Re: Spark plug gap? (purpleTPI84)
Spark Plug gap should be determined by the ignition manufacturer..ie if its stock go with what the book says , the plug should be gaped to what the ignition sys is setup to need ....just my .02 :thumbs:
Thread Starter
Le Mans Master
Joined: Apr 2001
Posts: 7,410
Likes: 252
From: Little Elm TX
Re: Spark plug gap? (AlHale)
I have an LPE 383 and have the paperwork that says to set at .035".
What kind of ignition do you have? ie........wires, plugs, coil?
