I've read here that NGK TR55's are the way to go especially for the money.
A local auto parts store said the NGK TR5 is the plug for an 03 LS1, not the TR55.
Specs for TR5: G-Power Resistor Spark Plug
14mm x .708" Reach
5/8" Hex
Projected
Tapered seat
(No gap specified)

Specs for TR55: G-Power Resistor Spark Plug
14mm x .708" Reach
5/8" Hex
Projected
Tapered seat
.059" Gap

Then there is the TR55-1GP: G-Power Resistor Spark Plug
14mm x .807" Reach
5/8" Hex
Extended projection
Tapered seat
.059" Gap

I'm guessing the plug of choice is the TR55-GP w/o the extended reach?
Are you gaping these to .059 and not .040 like the factory Delco's?

Thanks

 

TR-55 is the one you want. Not sure what "Extended Projection" is though. The last digit is the gap, hence the "55" vs the "5".

 

best plug I ever used

 

I'm certainly not a spark plug expert, but I think TR6 gapped at .040 is stock. When I had a blower cam installed, the recommended plugs were NGK TR55, which supposedly operate at a slightly cooler temp (don't know how they do that - that's just what I was told). After the cam and BEFORE I installed my s/c, the TR55 plugs were gapped at .040. AFTER I installed the s/c, when my tuner was trying to dyno tune my car, the plugs which were gapped at .040 would not allow the car to run higher than about 4500 rpm. After a few hours of head scratching, the plugs were changed out for a new set (same TR55s), but the gap was set to .032. Then the car ran perfect. My tuner's explanation was that the increased airflow (from the s/c) passing through the valves into the cylinder was "blowing the spark out".

 

TR5 is equivalent to stock. Pre-gapped at .040".

TR55 is the same heat plug as TR5, just gapped at .055"

TR6 is one step colder plug, (also gapped at .040") commonly used with boost or high compression apps.


For most, TR55 is a good choice, we have the ignition power to make the larger gap work.

 

My box says TR55 Stock Number 3951 gapped at .050 I had gapped them at .035 and the car ran sluggish. I was told the number is the heat range. The TR6 is a colder plug for supercharged, nitrous, and higher compression engines. They gap at .035

 

Need more input

 

NGK has a downloadable catalog that explains their part numbers. As I stated and stated above, the "55" and "5" are the same plug, the second "5" in "55" designates a larger gap. Before H/C, I ran the TR55. Now I run the TR6 as NGK recommends one heat range drop for every additonal 100 hp from the stock baseline.

 

Jeeze Bob your staying up late!

I went to the NGK website http://www.ngksparkplugs.com/ and didn't find the catlog you mentioned, I'll keep looking. NGK's site says to use the TR5GP as well not the 55 so thanks for clearing this up for me.

Thanks to everyone for all the great info!

I'm 90 RWHP over stock...I'm wondering if I should try the colder plug as I'm running approx. 10.75CR.

This whole spark plug thing started because I went to SEMA this year and met the Pulstar rep and he was nice enough to give me a set of Pulstar's to try out (ad1's).
There was nothing wrong with my stock Delco's but I finally put the Pulstar's in recently anyway, gaped them to the recommended .040. It might be my imagination but I thought my car felt sluggish, again probably my imagination. We have been having cooler weather so I've also been playing with my AFR (using HPTuners) at about the same time. So to clarify... I'm in no way putting any blame on the plugs.
So I figured I'd try some NGK's you guys have been raving about since they aren't too expensive. It's either that or put my iridium's back in again and see what happens.

 

Hmmm, my 2000 came with platinum AC 41-952, gapped at 0.060, which is per the manual. These are the infamous "puck-dropping" plugs. Did they later reduce the gap to 0.040 when they changed to the irridium plugs?
For the last 7 years I have run the NGK TR55's, which are factory-gapped at 0.055, with good results.

DG

 

Actually, at work early

Seeing your setup and location, I would be inclided to use the TR6. Not sure what those other Pulstar plugs are, but I like plain ole copper core.

 

One thing I can tell you about them is they are pricey...$25. per plug retail.
Here's a link to them: http://www.pulstar.com/

In an old thread TLewis did some dyno testing with them and actually came up with a small HP increase on stock or mildly tuned C5's/C6's.

 

3951 Is what you are looking for in the TR55 plug...i believe. I just bought them myself from my local autozone....they dont show up as working on the car...just tell the guy you want em.

 

I used Tr55 plugs, gapped at .050, all the way up to 450 rwhp before I switched out to Tr6s. Ask for the 3951 stock number NGK plug to get the Tr55 plugs. I have found my best price to be O'reilly Auto at around 1.60 a plug. The second best place has been Advanced and they were around 1.90 a plug. If you have more than 450 rwhp or nitrous use the Tr6, stock number 4177, gapped at .035.