I know it’s been covered many times but I’m not seeing anyone with my set up.i have a sleeved LS1 base block finished to a 447ci with LS7 top end . Car made 580 on a dated tune. I have a 11.1 CR.
anyone have an idea on the best recommended plug to run ? And at what gap . I THINK the car came with tr6’s but unfortunately,after a top end rebuild ,I misplaced the plugs . Any care to chime in ?
thanks !

 

I am not only a modern day LS tuner but also am from the old school when we read spark plugs

My opinion I always recommend a TR5 on any N/A engine and maybe a TR6 ONLY on an engine with boost--
GM used to recommend a .060 gap on a N/A engine--but then about 10 years ago they came out with a bulletin advising a .040 on all their LS engines
A TR6 is a COLDER plug meaning it will take more heat and compression before fouling However during street driving it will be so cold that it will not heat up enough and cause plug fouling--Yes on a dedicated race engine with no street driving and with boost a TR6 is a good choice However on even a highly modded N/A engine with cams and hds etc A somewhat hotter plug is your best choice
In the old days this i how we read plugs and it still applies today's modern computer controlled engines
To read TIMING you look at the color change on the strap of the plug----Ideally you want the color change to be right on the "bend of the strap" the further the color change is towards the threads means you have too much timing---The further the color change is towards the tip means you have not enough timing
Then as far as fueling goes---You would want to look at the center porcelain with a magnifying glass---and ideally you would want come "tan/brownish" color only about 1/4 " above the center of the bottom of the porcelain---Less color means it is LEAN More color up the porcelain means it is RICH
PS There is NO HP advantage in choosing spark plugs The key is to having the correct heat range based on what I have mentioned earlier-

 

TR6 work perfectly in a well tuned modified engine.

 

I would also choose TR6 for that application. A little colder plug will foul up a little faster if not driven hard regularly, but these plugs are so cheap, not a big deal. Running the colder plug helps protect against pre ignition too for if/when you really want to push it hard. In my mine it's the safer more conservative choice. If you don't want to replace as often, look at the TR6IX--iridium equivalent for a few bucks more.

 

This is exactly what I said--- On a daily driver not driven hard a lot--- with a highly modded engine the TR6 will have a tendency to foul out quicker--owners have to be honest about their car's MOST use and make that decision--