Ripper415

iTrader: (6)

i'm in the middle of a LT install and as i just changed my spark plugs last year to a new set of ngk tr-55, i was planning on reusing them. only thing is i dont have the original boxes where it listed how much to tighten them to. i seem to remember for mine (part # 3951) it was something like "turn by hand until snug, then turn an extra 1/8 of a turn with wrench", but i'm not sure. can anyone who has a ngk 3951 box post a picture of the back where it says all this info?

also, should i lower the gap now that i'm going to a LT/ORY setup? i have a few basic mods (lid, ssra, ported tb) so i think i lowered the gap from the factory .055 to .050 last time. since i'll be adding an additional 20 or so hp should i lower it to .045 or even perhaps lower?

finally, i plan on getting a dyno tune in the near future. should i adjust the gap now even lower in preparation of the extra power that will give me or will their tune make the most out of whatever gap i have them at?

01redws6ta

Just tighten them until snug with wrench or socket...do not overtighten. Torque spec is usually around 20 ft/lbs...I'd have to look it up for sure. I think I gapped mine to around .050" too...that should be fine to leave them there.

94'BLKBRD

iTrader: (76)

Leave the gap alone.

Ripper415

iTrader: (6)

thanks for the torque spec but i dont have a torque wrench. i'm pretty sure it was just snug by hand then a lil bit more with the wrench.

i actually went on ngk's website to try and find info and they now say the tr-55 come at a stock gap of .040? that seems oddly low, considering they used to be .055

00pooterSS

iTrader: (40)

You wont be increasing power near enough to change the gap, also remember each plug has a dedicated coil on these cars, its not going to be hard for the spark to jump that gap. You are talking about 20ish hp on a near 500 flywheel hp car, if you were adding over 100hp+ then you would need to adjust.


AND never "leave the gap alone", you ALWAYS check the gap to make sure its proper before you install the plugs. Boxes get dropped etc, I know they have the protector but that still does not garuntee perfection 100% of the time. Plugs are not made for only one car either so you mast check the gap. When you start ordering plugs in different heat ranges then they are definately not made for your specific car, thats another reason why you must always check the gap.


Try searching too I found this thread in about 30 seconds, it says the original gap was .060 then GM put out a bulletin to lower that to .040 for rough idle issues, me I think I would go .050 because I know those coils put out alot and can handle it. GM will want to be on whatever side creates the most comfort/least complaints so that explains the .040 but thats a little low for my taste.

https://ls1tech.com/forums/showthrea...light=gap+plug

00pooterSS

iTrader: (40)

And I believe its 1/4 turn after snug. Ill try to see if I can find that.

found this pretty quick try this, man you suck at searching.

http://www.ngk.com/faqmain.asp

http://www.ngksparkplugs.com/techinf...=US#installing

Direct from NGK
"3. Gapping

Since the gap size has a direct affect on the spark plug's tip temperature
and on the voltage necessary to ionize (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 maximizes 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."

Ripper415

iTrader: (6)

thanks for the help man. i actually ended up going to my town's autoparts store and asking to see a box for the 3951. it said tight by hand then an extra 1/16 turn by a wrench. and i ended up gapping them to .050.

00pooterSS

iTrader: (40)

Damn we both swung and missed on how much to tighten lol. I just know how tight they should be from feel, from doing it for so many years. Glad you got it fixed.