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How to determine a bad spark plug?
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From: Houston, TX
How to determine a bad spark plug? What symtoms make a spark plug bad? What things do you look for to see whether a plug is good or not? I currently have roughly 10k miles on my plugs (NGK TR-55) and I have them out right now to see what they look like. I snapped a few shots, please let me know what you think. Replace them or keep 'em? By the way, whats the best way to clean them? Thanks.
Oh yeah...before I forget, what should be the gap on these plugs and as you get deeper and deeper into mods, should the gap be different from stock?
Oh yeah...before I forget, what should be the gap on these plugs and as you get deeper and deeper into mods, should the gap be different from stock?
Thread Starter
9 Second Club NA
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From: Houston, TX
Oh, the pics I included are the plugs after I somewhat cleaned them. I used a steel brush and a rag to clean them a little. I didnt know what else to use. Is that ok, or should I use something else? (ex: a type of cleaner)
02WS6#519: Is that a proven fact or is that just an opinion? Not saying youre wrong or that I dont believe you, just curious. If my car came stock with 320 hp and it now has rought 485 hp to the motor, then thats a 165 hp increase all motor. (bolts ons and cam) Just out of curiousity, why smaller gap?
02WS6#519: Is that a proven fact or is that just an opinion? Not saying youre wrong or that I dont believe you, just curious. If my car came stock with 320 hp and it now has rought 485 hp to the motor, then thats a 165 hp increase all motor. (bolts ons and cam) Just out of curiousity, why smaller gap?
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Joined: Nov 2001
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From: Troy, AL
A smaller gap is easier for the spark to jump. Generally speaking, the more power you're making, the harder it is to jump the gap, hence the need for a smaller gap. However, our ignition systems are quite strong so it's not as big of an issue as it is with lesser ignition systems.
As a rule of thumb, for every 50 HP increase in power, close the gap .004. So you'de want to close the gap about .013 from stock. Stock is .060 so that puts you at .047. Again, this is just a general rule of thumb thought up a looooooooong time ago. IMO, it is a VERY conservative rule of thumb when speaking of the LS1 ignition system. A .055 gap will work just fine at your HP level if only running NA (the wider gap you can get away with, the more power.)
As for looking at the plugs to tell if they're bad...sometimes you can't. Not long back I had to replace a TR-6 that looked PERFECT but was causing a skip under load. I had narrowed the other possibilities down and then decided to change all of the plugs on one bank. Problem solved.
As a rule of thumb, for every 50 HP increase in power, close the gap .004. So you'de want to close the gap about .013 from stock. Stock is .060 so that puts you at .047. Again, this is just a general rule of thumb thought up a looooooooong time ago. IMO, it is a VERY conservative rule of thumb when speaking of the LS1 ignition system. A .055 gap will work just fine at your HP level if only running NA (the wider gap you can get away with, the more power.)
As for looking at the plugs to tell if they're bad...sometimes you can't. Not long back I had to replace a TR-6 that looked PERFECT but was causing a skip under load. I had narrowed the other possibilities down and then decided to change all of the plugs on one bank. Problem solved.
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From: Troy, AL
Factory ratings are one thing, reality is another. Consider that they rated them at 305 HP at the flywheel....but yet they dyno that and very often more TO THE GROUND. Also, GM rated basically the same engine at 345 HP just because it was installed in the Corvette....but yet when dynoed it does no better than the 305 HP F-body LS1. Gee, wonder why they would misrate them? 
305 RWHP / .85 (approximate driveline loss with an M6) = 359 FWHP
If they actually had only 305 FWHP then they would dyno only about 260 RWHP with an M6.
305 RWHP / .85 (approximate driveline loss with an M6) = 359 FWHP
If they actually had only 305 FWHP then they would dyno only about 260 RWHP with an M6.
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From: Waldwick, NJ
[QUOTE=Colonel] Also, GM rated basically the same engine at 345 HP just because it was installed in the Corvette....but yet when dynoed it does no better than the 305 HP F-body LS1. Gee, wonder why they would misrate them?
QUOTE]
The reason why they underrated the F-body was because they want the Vette owners to think they have a far superior car, hence the price tag....C'mon you should know that you NOOB 
QUOTE]
The reason why they underrated the F-body was because they want the Vette owners to think they have a far superior car, hence the price tag....C'mon you should know that you NOOB
