WICKEDFRC

Greetings all -

I just wanted to get some feedback from those with Heads/Cam setups what you were set up for in regard to Spark Plugs and Wires, or, for those who would like to classify themselves as "Subject Matter Experts"

Iron Block 402 LS1
AFR 225 Heads Milled for 10.89:1 Compression
MAHLE Pistons (Flat Top)
G6X3 Camshaft
GM 12495519 8mm Spark Plug Wires
NGK TR6 Spark Plugs gapped at .035

My questions, initially my spark plugs were replaced with newest GM part number, using Iridium spark plugs. This was just an oversight. But on the test drive, the car was sputtering, staggering as I ramped up. It was identified that these spark plugs were running way too hot and that I needed to simply reinstall the NGK TR6 spark plugs.

So, we did just that, but.....The car is still sputtering a slight bit at take off in first gear. Once the car is moving hard, I don't feel the sputtering any longer.

Can this be the result of incorrectly gapped spark plugs, or at least one or two of them?

Could this be the result of poor choice in spark plug wires for my setup? (8mm GM Red)

Could this be the result of a new, but cracked spark plug?

Also, what is a safe cool down period for the heads before removing the spark plugs?


Any ideas, suggestions greatly appreciated.

Last C5

Sounds like a bad plug or wire. Except for the iron block, your setup is very closeto mine and I'm running TR6s gapped to 35 along with some MSD wires without any problems.

vettenuts

TR6 here as well. Also using the C6 Z06 wires with the 90 degree boot.

I would expect that cam to be a bit dicey off idle, not sure if that is what you are describing.

WICKEDFRC

Interesting. And thank you for the input. Could the 8mm wires be effecting the electrical connections? I believe (if not mistaking) I had MSD Wires which were 8.5mm.

I'd hate to pull everything out when everything is brand new. Can this be tested with TECH II and, what kind of test is this called? Maybe I can swing it back over to the dealership and let them run a diagnostic. I just don't know what that diagnostic is called.

VetteNuts - What does "dicey" mean? I think the best way to describe it is, the same sputtering I had when I had teh Iridiums in there running way too hot. Pulled them out and replaced with NGK TR6 at .035. At the upper RPMs I feel a strong pull. Down low between 950-2000 at take off it just feels "hesitatnt" until it starts to get up around 3k RPMs, then it feels "normal".

I once had a cracked spark plug which was easy to tell under extremem loads at higher RPMs (about 5k). The car would ramp up and almost hit what felt like rev limiter. This was my #5 spark plug misfiring under extreme load but not under normal driving.

If anyone can tell me the name of a test I can have the dealership perform, I could start there. After that, I guess I could change the plug wires and see maybe one of the wires was bad.

vettenuts

Is this cam new to you? What you seem to describe is the motor coming "on cam", i.e., at low RPM you are out of the power band and the overlap of the cam will cause the sputtering you seem to be describing.

Careful of the dealership, if they flash the computer you will have bigger problems. Saw this done once with a twin turbo car, needless to say the car was dead until the owner could get the computer reflashed with the aftermarket tuning.

WICKEDFRC

Vette,

The cam is not new. It is the same cam. The only change was new spark plugs and spark plug wires. That's it. I thought a diagnostic check doesn't change anything, just ensures all electrical pulses/charges are in the proper specifications.

baxsom

The stock C5 ignition system down to the plugs and wires can handle a lot more than you have going. Something else is wrong. In fact I have right at the same compression and am using standard TR55s gapped at the newest service manual recommendation of 40 thousandths pushing 450 rwhp and never had an issues. The dealership can't do much that you can't do yourself. If you are getting a misfire code P0300 will show up on the DIC. It sounds like a tuning problem more than anything. You need to get it on a dyno with a tech that knows what he is doing. On this test drive you were talking about, what tuning had been done to the car prior because many many people use stock plugs on a simple head/cam car and never have any running hot issues. It sounds like it is running too lean and needs some fuel in it.

WICKEDFRC

Good input Baxon, Thank you. Prior to the swap, there was no other tune changed or tweaked. It was only the plugs and wires. When I checked my DC, I am not throwing any codes.

The Vette was tuned at LG Motorsports for a conservative 91 Octane. If anything, it is running on the richer side. Like mentioned, no issues prior to the new plugs and wires. My hunch says it is the wires or the gap on the plugs. I am still debating if I should go back to 8.5mm wires which were on the car during the time of the tune. As remote as this may be, it may be a slight difference.

madmatt9471

NGK TR-55 gapped at .055 (Your current gap seems way to tight for a NA motor)

MSD or equivalent wire 8mm - 8.8mm jacket

"IF" heat is indeed the problem then you could buy some cool socks for the wires!

Thanks,Matt

Mr. Jones

I have the GM red wires and run tr55 at 38 gap no issues with spark.
I also hit it with a 75HP NOS shot now and then.
I would start with new plugs TR55 at 40 gap for your setup
(car has forged pistons, AFR heads, rods but stock block)

Bill Curlee

LS engines are NOT picky about the plugs and wires that you run. The GM Red Performance wires are excellent wires! As long as they are installed properly (fully seated on to the plug and coil tower) and the plugs are not damaged, they shouldn’t cause any issues.

Most NA heads cam intake engines do well with copper core plugs but irridums also work excellent. When you run copper core plugs you MUST change them a LOT more often. I run the irridums in my heads cam Fast 90 LS6 and the GM red performance wires. 450 RWHP, NO ISSUES !!

Sounds like you have a damaged plug or a spark plug wire that isnt seated all the way on the plug or coil.

Each GM Red performance wire will read around 300-350 OHMS. Ohn them out and look for any damaged insulation. If you don’t find any, you have other issues.

Remove them and inspect. Use a mirror and look for cracked damaged ceramic plug insulators:




BC

vettenuts

Not sure why the TR55 plugs are being re-gapped. The TR5 is the same plus, smaller gap. The second "5" in the part number denotes the larger gap.

WICKEDFRC

Last night, I went back in and ensured all the plug wires were seated correctly and it seemed as if one may have been a tad off. This morning the car felt a little "better" but I wasn't really aiming to test it out on my way to work with hundreds of other cars around me at rush hour..... I will see how this makes out over the next few days. Checked again, no codes except the standard LDCM BS and HVAC. (I think this is due to an out of tolerance specification). No other codes.

All_Motor_C5LS6

isnt .55 too wide for a HCI setup. Wouldnt it cause spark blow out up top.

baxsom

Depends on compression. Back when I had a boosted Mitsubishi eclipse running 20lbs of boost and pushing 400 fwhp I had to worry about blowing out a spark and exact plug and gap. With the LS1 in the years I have been here and the mods I have done to mine ignition has never been a problem once I figured out that MSD wires were a pain in the *** to keep clicked in place and went back to GM reds.

madmatt9471

In short - No!

In a Forced Induction set-up, Yes it would, but in a N/A motor and H/C set-up there is no need to close the gap as much as the OP does.

With the Coil on Plug set-up you get a very hot spark and can and should run the gap in this range for best performance!

You will blow the spark out on F/I - which should be from .023 - .028

Thanks,Matt

Mr. Jones

So on a HC car they should run plugs at .055 ?
I would feel better at .040 but I will listen to good experience.
I always run them .038 due to the NOS shots.

blackdak318

I have a H/C/Fast 90 car that makes 444 rwhp on a mustang dyno and I run the TR55's with the stock gap no problems at all.

madmatt9471

If you are shooting NOS you will not want the. 055 gap.

NA cars for. 055

All_Motor_C5LS6

I run mine at .050 as I felt .040 was too tight, my compression is 10.65:1, H/C/Fast 90 setup as well. I just don't feel comfortable widening it to .055.



What's the benefit of running a .055 gap over a .050?