TR-6 vs TR-55 NGK

[AVIDMOTION]

I got 8 plugs from Pep-boys , they are NGK TR-6, these are one colder then stock.($2.29 each) Some people said with my mods, I should not have to go to one colder and it would make my car run richer. Currently I am perfect 14.7 stoeic.... with my mods is it ok, beneficial, nuetral or detrimental - what is others opinion?

[GRRRR8]

The TR55 should be a Iridium which is a better, longer lasting plug. I would say your true estimated HP if your sig is correct is probably 360-370 so there would not be a need to go 1 step colder. A TR55 is about a 1/2 step colder and would be perfect. Make sure to gap them correctly.

The computer will keep your AF 14.7 regardless with your mods. You would want to look at ST/LT fuel trims if anything.

[johnbell2]

http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp

I think I see why I ended up w/ a plug one range colder... ignition timing changes, 10% ethanol content in fuel, safety factor for stop & go driving in Texas heat, etc.

[GT Drew]

"A TR55 is about a 1/2 step colder " 100% wrong. NGK does not do 1/2 ranges. the TR5 and TR55 are the same heat range BUT the TR55 has a wider gap, .060". They are commonly used in the 3800 vehicles that require a wider gap.
Trying to close the gap on a TR55 to .040" is a big mistake. You get too much overhang over the electrode. Spoils the design of the plug.

[GRRRR8]

Correct on the .060 gap, but it IS about 1/2 a range colder then a factory plug. Not going by a cross reference chart. I guess you have never cut a plug back to expose an electrode. But what would I know...