spark plug gap suggestions
Thread Starter
Registered User
Joined: Jan 2003
Posts: 23
From: Lafayette, IN
spark plug gap suggestions
I have a 93Z28 with 3:73 gears, hypertech 160 , hypertech chip, hooker lt's, tb bypass, morosso cai and I just bought NGK tr55 plugs, the guy at napa told me to gap them at .045, others have told me .050 and I just read a post from about a year ago on here from a 385lt1 or something like that that said stock heat range requires a gap of .060 So which do I use? Thanks for looking at this.
Registered User
Joined: Jul 2001
Posts: 718
From: Wichita Falls,Texas
Originally posted by my94blackz
I just replaced my plugs with ngks and they came gapped at bout .55-.57. My old ones from the previous owner was gapped between .65-.73, i was like
what was he thinking?
I just replaced my plugs with ngks and they came gapped at bout .55-.57. My old ones from the previous owner was gapped between .65-.73, i was like
what was he thinking?
Well over time the plug gap increases. All the NGK Tr55's I have bought were gapped at .060 and above. The only ones that were gapped were the NGKTR6's at .035.
Registered User
Joined: Feb 2002
Posts: 79
From: Cincy, OH USA
Since the gap size has a direct affect on the spark plug's tip temperature and on the voltage necessary to ionise (light) the air/fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need.
A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximises burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.
With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think.
In reality, computer controlled vehicles do such a good job of lighting off the air/fuel mixture (as evidenced by the ultra-low emissions), added ignition capacity would do little to burn more fuel since the stock configuration is doing such a good job. Older non-computer controlled vehicles or those that have been modified with higher compression or boosted (nitrous, turbo, supercharged) engines can certainly take advantage of a more powerful ignition system.
A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximises burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.
With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think.
In reality, computer controlled vehicles do such a good job of lighting off the air/fuel mixture (as evidenced by the ultra-low emissions), added ignition capacity would do little to burn more fuel since the stock configuration is doing such a good job. Older non-computer controlled vehicles or those that have been modified with higher compression or boosted (nitrous, turbo, supercharged) engines can certainly take advantage of a more powerful ignition system.
Registered User
Joined: Jan 2001
Posts: 2,148
From: Bay Area, CA
Originally posted by my94blackz
My old ones from the previous owner was gapped between .65-.73, i was like what was he thinking?
My old ones from the previous owner was gapped between .65-.73, i was like what was he thinking?
Registered User
Joined: Jan 2001
Posts: 2,148
From: Bay Area, CA
Originally posted by Stealth Z
The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximises burn efficiency.
The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximises burn efficiency.