The spark plug debate 99 Ls1
12-23-2016, 07:52 PM
#2
Coffee or Tea?
Many like the stock platinum plugs as they can go 100,000 miles before changing. Others like copper plugs that seem to run a little better but need to be changed after about 20,000 miles. Iridium has its fans too.
When my TA was brand new back in 1999, we pulled the factory plugs which turned out to be NGK TR5 Platinum due to a GM/AC Delco strike. The gap spec was .060 but the gaps ranged all over from like .053 to .063 or so. I forget the exact gaps but basically, no two plugs had the same gap. We replaced them with NGK TR55's gapped at .055 and the car idled better and gain a little gas mileage.
I re-dyno'd the car and there was a slight hp gain of 3-4hp.
I've stayed with the TR55's and the car has 155,000+ miles and 7-8 plug changes. We always use anti-seize and a torque wrench to ensure the plugs aren't overtightened.
Thats my .02 worth.
Many like the stock platinum plugs as they can go 100,000 miles before changing. Others like copper plugs that seem to run a little better but need to be changed after about 20,000 miles. Iridium has its fans too.
When my TA was brand new back in 1999, we pulled the factory plugs which turned out to be NGK TR5 Platinum due to a GM/AC Delco strike. The gap spec was .060 but the gaps ranged all over from like .053 to .063 or so. I forget the exact gaps but basically, no two plugs had the same gap. We replaced them with NGK TR55's gapped at .055 and the car idled better and gain a little gas mileage.
I re-dyno'd the car and there was a slight hp gain of 3-4hp.
I've stayed with the TR55's and the car has 155,000+ miles and 7-8 plug changes. We always use anti-seize and a torque wrench to ensure the plugs aren't overtightened.
Thats my .02 worth.
Last edited by 99 Black Bird T/A; 12-23-2016 at 07:59 PM.
12-24-2016, 02:45 AM
#3
Depends on your application, but for anything stock or slightly modified, OEM plugs are best.
ACDelco in a GM, Champion in a Dodge, NGK in a Honda, etc.
When you run into drivability problems it at least eliminates the brand of plug as a possible cause.
I can't tell you how many cars I've taken the wrong brand plugs out of, especially those Bosch 4 ground deals, to put stock ones in because it ran like ****.
I see parts stores list 41-805, 41-962, or 41-985 as original platinum plug for LS engines.
They won't show the iridium 41-110 for early LS engines. Someone can correct me if I'm wrong, but I believe there was a bulleting about these superceding the platinums. I recently put these in my truck and TA.
I don't know if iridium is necessarily better than platinum. They cost about the same.
For a heavily modified engine, that's a different story. I'd talk to someone that builds similar engines and get their input.
ACDelco in a GM, Champion in a Dodge, NGK in a Honda, etc.
When you run into drivability problems it at least eliminates the brand of plug as a possible cause.
I can't tell you how many cars I've taken the wrong brand plugs out of, especially those Bosch 4 ground deals, to put stock ones in because it ran like ****.
I see parts stores list 41-805, 41-962, or 41-985 as original platinum plug for LS engines.
They won't show the iridium 41-110 for early LS engines. Someone can correct me if I'm wrong, but I believe there was a bulleting about these superceding the platinums. I recently put these in my truck and TA.
I don't know if iridium is necessarily better than platinum. They cost about the same.
For a heavily modified engine, that's a different story. I'd talk to someone that builds similar engines and get their input.
12-24-2016, 08:23 AM
#4
Here is a good thread on copper vs platinum vs iridium for more reading.
https://bobistheoilguy.com/forums/ub...pics/2583605/1
One of the key sometimes over looked issues is none of these plugs will perform well if the plug wires/boots/connectors are in poor condition. Likewise, for coil(s).
Regarding Bosch +4's I used them in my stock 91 RS many times, as long as all of the other items in the ignition system were in excellent condition, the Bosch +4's performed very well. I used them for probably 250,000 miles of the 390,000 miles I put on the little 305. The cars best mpg results were with Bosch +4. 35.5 mpg highway, typical was 32 to 33 mpg. When the mpg started to drop a little it was tune up time. This was usually about 50,000 miles. The Bosch platinum & Bosch +2 also performed well but the mpg would drop off sooner in my experience with my 305 RS.
https://bobistheoilguy.com/forums/ub...pics/2583605/1
One of the key sometimes over looked issues is none of these plugs will perform well if the plug wires/boots/connectors are in poor condition. Likewise, for coil(s).
Regarding Bosch +4's I used them in my stock 91 RS many times, as long as all of the other items in the ignition system were in excellent condition, the Bosch +4's performed very well. I used them for probably 250,000 miles of the 390,000 miles I put on the little 305. The cars best mpg results were with Bosch +4. 35.5 mpg highway, typical was 32 to 33 mpg. When the mpg started to drop a little it was tune up time. This was usually about 50,000 miles. The Bosch platinum & Bosch +2 also performed well but the mpg would drop off sooner in my experience with my 305 RS.
