I have heard a million and 50 different responses to Spark plug gaps on a non N20 LS1. i heard .60 .58 .55. .50 .45 and .40 !

Is it true that GM has changed the reccomended gap on our cars to .40?

I went on NGK's website and put in 1998 camaro ss and all the plugs they offer are gapped at .40 so maybe yes?

Help me settle this before i go insane, thanks.

 

i usually gap non nitrous cars to about .40

 

Interesting. Can some ones chime in and share some info

I have heard the same thing . Stock gag used to be .060 so i gaped my to .059 .

What is the benefit if any on the gap .040 on non n20 LS1???

 

out of the box gap on tr6's

 

thats .40 right?

 

Also whats better for a bolt on car?

TR6IX

or

TR5IX?

 

GM revised the plug design and gap specifications for all gen III engines mainly due to idle instability. Per TSB 30604060, iridium plugs gapped at .040" are the new recommended plugs. I've been putting NGK TR55 gapped at .040" for years for Corvette customers with idle problems.

 

Damn, wish I'd seen this before I did my plugs and wires.

 

out of the box tr6 are .40 gap . just put some in my ride a few weeks back . also suppose to go down a step to a colder plug for every 100 horses you add to your engine in a all motor setup . the ngk tr6 is one step colder than the ngk tr55 .
hers some info from the nitrous faq from the nitrous forum sticky :
LS1 Stock and AFR
Thread – 14mm
Reach - .708”
Socket – 5/8 hex
Seat - Taper
Stock Heat Range: 5
Gap: .060
Plug: NGK TR55 (stock number 3951); NGK TR55IX (stock number 7164); Autolite 764; Denso IT-16 (stock number 5325)

Nitrous (one step colder)
Heat Range: 6
Gap: .035 - .038
Plug: NGK TR6 (stock number 4177); NGK TR6IX (stock number 3689); Autolite 103; Denso IT-20 (stock number 5326)

Nitrous (two steps colder)
Heat Range: 7
Gap: Consult
Plug: NGK BR7EF (stock number 3346); NGK TR7IX (stock number 3690); Autolite AR94; Denso IT22 (stock number 5327)

Nitrous (two and a half steps colder)
Heat Range: 8
Gap: Consult
Plug: NGK R5724-8 (stock number 7317); NGK TR8IX (part number 3691); Denso IT-24 (stock number 5328)

Nitrous (three steps colder)
Heat Range: 9
Gap: Consult
Plug: NGK R5724-9 (stock number 7891); Autolite AR93; Denso IT-27

Nitrous (four steps colder)
Heat Range: 10
Gap: Consult
Plug: NGK R5724-10 (stock number 7993); Autolite AR92


LS1 w/ Edelbrock and Dart Heads
Thread – 14mm
Reach – 3/4”
Socket – 5/8 hex
Seat – Gasket

Stock – MFG Recommendations: approx under 9:1 compression
Heat Range: 4
Gap: Consult ignition mfg.
Plug: NGK FR4 (stock number 5155); NGK BKR5EIX (stock number 6341); Autolite 3926; Champion RC12YC (stock number 71); Denso IK16 (stock number 5303)

MFG Recommendations: approx 10.5:1 compression
Heat Range: 5
Gap: Consult ignition mfg.
Plug: NGK FR5 (stock number 7373); Autolite AR3924 (Racing Plug); Autolite 3924; Champion RC9YC (stock number 2075); Denso K20PR-U (stock number 3145); Denso IK20 (stock number 5304)

MFG Recommendations: approx 11:1 compression
Heat Range: 8
Gap: Consult ignition mfg.
Plug: NGK R5672A-8 (stock number 7173); Autolite AR3911; Champion C63YC (stock number 796); Denso IQ24 (stock number 5314)

MFG Recommendations: approx 12:1 compression
Heat Range: 9
Gap: Consult ignition mfg.
Plug: NGK R5672A-9 (stock number 7405); Autolite AR3910; Champion C61YC (stock number 785); Denso IQ27 (stock number 5315)

MFG Recommendations: approx 13:1 compression
Heat Range: 9 - 10
Gap: Consult ignition mfg.
Plug: NGK R5671A-9 (stock number 5238); Autolite AR3933; Champion C59CX (stock number 296); Denso IK27 (stock number 5312)

MFG Recommendations: approx 14:1 compression
Heat Range: 10
Gap: Consult ignition mfg.
Plug: NGK R5671A-10 (stock number 5820); Autolite AR3932; Champion C57CX (stock number 295); Denso IK-31 (stock number 5321)

 

N/A car NGK TR55 gapped @ .058-.060. I normally go .058.

For nitrous, NGK TR6 Gapped @ .038-.040. .038 preferred.

I had good luck with the TR55IX plugs as well.

 

I have recently installed longtubes with ory and a ported tb along with the other mods in my sig. What would you gap your tr55 plugs at?

 

In a non nitrous application, I run the TR55, with the out of the box gap. I just check them all to make sure tha gap is the same. So far the gap is always been the same. Car runs great with them right out of the box.

 

Arn't you suppose to not gap iridium plugs? I think i'ma go with TR6IX

 

Same here

 

I ran TR55s in CETA when it was stock and also ran them in my old 02 Z. Gapped them at .058 in both cars.

Then I ran TR6s in them with the gap at .038

 

TR55's @ .55 right out of the box.. (usually)

After reading this, i may try .58 in my H/C bolt on car...?

 

the TSB says .40 i'm gonna do .40 lol

 

I gapped my TR55's at .038, I guess I was used to installing TR6's. My car ran good with them like that. I regapped them to .058 & haven't noticed any differences.

My best NA run was with them gapped .038, but it was in better air, the MPH was within .5 with both gaps, I'm not thinking I was losing or gaining much.

 

Ideally you want the largest gap you can run. The original spec was .060 but people complained about idle issues. Narrowing the gap to .040 helped address those complaints. Did it do anything for power? Probably not but it shut up the complainers. I run .060 on my NGKs and don't have any issues with idle.

 

Just check them out of the box to make sure they are the same. But, you run the same gap with the irridium plugs.