So i went to mti and picked up a set of tr-5 spark plugs, i asked for the tr-55 but the guy said they were out of them. He said that i wouldnt have any problems with the "hotter" plugs but i just wanted to verify if this was true. As it stands the car is pretty much stock except for mac headers, an ory, bassani catback, a lid, and no egr stuff. Any advice?

 

The only difference between the tr5 and tr55 is the gap. tr5s are factory gapped at .032 or .035 tr55s are gapped at about .050
You'll have a hard time gapping tr5s out to a proper gap for an LS motor.

 

Exactly.

The TR6 has a different heat index.

 

The guy told me to gap them at .040 so i did, is that ok, thanks for the information

 

Well that's 2 strikes for him. Factory gap is .060 so .040 is quite a drop in spark size.

 

That factory specified gap of .060" has been changed. LS1s in general run like crap at .060" gap. I've been installing NGK plugs closed down to .045" for years for finicky Corvette customers. Seems GM finally caught up and released a TSB for this in February, for a new plug design at .040"

 

so then theyre gapped correctly?

 

I would leave it at .040" Like I said, I've had lots of success with .045" gap on stock Corvettes where the customer complained of an uneven/rough idle. .040" should be OK even for a mildly modded engine like yours. FWIW - that's the gap I run on my current TR6 plugs in my very well modded N/A LS1 and it runs better and made more power with the smaller gap.

 

I gapped my 55s at about .055" and it's been running fairly well. But from what everyone's been saying, .040" works well too and may cause less problems. It's best to run the largest gap you can without ignition problems. The gap change was also accompanied by a switch to an iridium spark plug, fwiw...

EDIT: here's the info from the TSB:

A new spark plug has been released for use in the above vehicles. The new spark plug has an Iridium tip instead of the current Platinum tip. Due to the different tip design, the gap of the spark plug has also changed. The new spark plug, P/N 12571164 with AC Delco P/N 41-985, is gapped to 1.01 mm (0.040 inches) when the spark plug is made. The spark plug gap is set during manufacturing and should not be changed or damage to the spark plug may result. Any new spark plug found to not be properly gapped should not be used.