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Spark Plug Help

Old 01-01-2018, 06:55 PM
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KJL
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Default Spark Plug Help

I am currenlty have issues with my 95 passing the Nox portion of the GA emissions test. One of the things I am reviewing is the plug and heat range I am currently running. The plug I am using now is a NGK TR55GP. This has a heat range of 5 which is considered HOT on the NGK heat range chart. The recommended replacement plugs on Jerry's web site are ACDELCO 41-913 or 41-602. Unfortunatly I cannot seem to find much if any heat range info on ACDELCO plugs let along a cross reference chart. While the NGK plug I have listed is not shown on the NGK website as one of the recommended options, all recommended options did have a heat range of 5.

I guess I am hoping someone out there has some inside info regarding the best plug I should use.

The car is top end ported, headers, Haibeck chip at 400 rwhip.
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Old 01-05-2018, 07:30 AM
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Running NGK TR7IX plugs in my '91. Gapped at .050". Headers and custom tune on my car. Idles and runs beautifully. Have been in 20 to 105 degree weather with them so far. No regrets. Others are running NGK 6 and NGK 5 heat ranges. You'll need to check the ground strap with a new plug to see what your setup likes best. Marc's recommended setup is the NGK 7 gapped at .050" from what I have read.
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Old 01-05-2018, 11:24 AM
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Originally Posted by jss06c6 View Post
Running NGK TR7IX plugs in my '91. Gapped at .050". Headers and custom tune on my car. Idles and runs beautifully. Have been in 20 to 105 degree weather with them so far. No regrets. Others are running NGK 6 and NGK 5 heat ranges. You'll need to check the ground strap with a new plug to see what your setup likes best. Marc's recommended setup is the NGK 7 gapped at .050" from what I have read.
Thanks for the info, I already purchased the AC Delco R44LTS6. It was cross referenced by several different sources. It seems that this whole spark plug industry is out of control. I go to several different sources and get different recommendations for the same vehicle. If you go the cross reference charts with source 2 plug recommendations, they often cross reference the other plugs source 1 had originally listed. Way to confusing.
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Old 01-06-2018, 09:35 AM
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I was running AC Delco 41-602's. Once I put on headers and retuned the car, I noticed the idle quality wasn't quite as good. I pulled the plugs and while they looked ok, I decided to go with a colder plug with my setup. The NGK 7's were an immediate improvement. Gapped them at .050" and took the car out for a very spirited drive. Noticably smoother and felt stronger throughout the entire RPM band. Read the timing on the ground strap on #1. It was closer to the tip than the base, slightly, so left them in. Very happy with them.
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Old 01-06-2018, 09:59 AM
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Last edited by jss06c6; 01-06-2018 at 10:02 AM. Reason: Typo
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Old 01-06-2018, 10:37 AM
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Originally Posted by jss06c6 View Post
I was running AC Delco 41-602's. Once I put on headers and retuned the car, I noticed the idle quality wasn't quite as good. I pulled the plugs and while they looked ok, I decided to go with a colder plug with my setup. The NGK 7's were an immediate improvement. Gapped them at .050" and took the car out for a very spirited drive. Noticably smoother and felt stronger throughout the entire RPM band. Read the timing on the ground strap on #1. It was closer to the tip than the base, slightly, so left them in. Very happy with them.
Is NGK 7 the actual part number? Or just the heat range value? I can not seem to find NGK 7. Also, what do you mean by reading the timing on the ground strap? I read the color as an indication of performance but do not understand reading the timing.
Oh I see it in your first post 7IX. Maybe I should just swap those in and hang on to others for back up set.

Last edited by KJL; 01-06-2018 at 12:35 PM.
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Old 01-06-2018, 08:15 PM
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Timing needs to be checked with a new plug and WOT (wide open throttle). Ideally, you are on a Dyno to do this, but if not, you need a safe section of road to allow you to install a new plug in Cylinder 1 (or whatever cylinder you chose), then start the car and get into 3rd gear (on the road) or 4th gear on the Dyno, then floor it to at least 6500 rpm. Clutch in and bring the car to stop and shut the engine down immediately. Pull the new plug you installed. You read the timing you by where the discoloration is on the ground strap. As spark advance increases, the discoloration band on the ground strap moves toward the base (away from the tip). Ideal timing will be when the discoloration band is in the curve of the ground strap. Extremely advanced timing will cause severe knocking and you will begin to see small specks of aluminum from your piston on the ceramic of your spark plug. At that point you're sustaining permanent engine damage.
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Old 01-06-2018, 08:55 PM
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Originally Posted by jss06c6 View Post
Timing needs to be checked with a new plug and WOT (wide open throttle). Ideally, you are on a Dyno to do this, but if not, you need a safe section of road to allow you to install a new plug in Cylinder 1 (or whatever cylinder you chose), then start the car and get into 3rd gear (on the road) or 4th gear on the Dyno, then floor it to at least 6500 rpm. Clutch in and bring the car to stop and shut the engine down immediately. Pull the new plug you installed. You read the timing you by where the discoloration is on the ground strap. As spark advance increases, the discoloration band on the ground strap moves toward the base (away from the tip). Ideal timing will be when the discoloration band is in the curve of the ground strap. Extremely advanced timing will cause severe knocking and you will begin to see small specks of aluminum from your piston on the ceramic of your spark plug. At that point you're sustaining permanent engine damage.
I found a set of NGK 7s and installed. The cooler heat range should help my NOX. My 5s ran very well. I may put them back in if I pass emissions.
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Old 01-13-2018, 08:49 AM
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Keith,

What was the outcome? Did you pass emissions? How did your car run with the NGK-7's?
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Old 01-13-2018, 01:45 PM
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Originally Posted by jss06c6 View Post
Keith,

What was the outcome? Did you pass emissions? How did your car run with the NGK-7's?
Not yet. The holidays are over and now it is back to traveling for work. I am also putting new cats on the car. The NGK-7's are installed, new oil. new cats, new O2 sensors, some water injection & Marc's emissions chip. Not much more I can do. Looking to get the cats installed today or tomorrow.
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Old 01-23-2018, 01:39 PM
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Originally Posted by KJL View Post
Not yet. The holidays are over and now it is back to traveling for work. I am also putting new cats on the car. The NGK-7's are installed, new oil. new cats, new O2 sensors, some water injection & Marc's emissions chip. Not much more I can do. Looking to get the cats installed today or tomorrow.
I think the NGK7s are going to be too cold. I've tried them and the 6s.
Settled on the 5s now. Next I am going to try a bit wider gap, ~.043".
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Old 01-27-2018, 12:03 PM
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Originally Posted by Dominic Sorresso View Post
I think the NGK7s are going to be too cold. I've tried them and the 6s.
Settled on the 5s now. Next I am going to try a bit wider gap, ~.043".
Now that I passed emissions I will leave the 7's in for now. I will check them to make sure the color is good after some more miles. The 5's worked fine so I will likely just go ahead and put those back in and save the 7's for my last emissions test this July.
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Old 01-27-2018, 12:08 PM
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Originally Posted by jss06c6 View Post
Keith,

What was the outcome? Did you pass emissions? How did your car run with the NGK-7's?
Passed emissions!!!

New cats
New NGK plugs heat range 7
New O2 sensors
Oil change
Increased the windshield washer bubba injection from 30 gauge syringe to a 25 gauge.
1 quart of denatured alcohol in a near full tank
Slightly over tire pressure
No EGR

Old numbers (water inject only w/30 gauge needle):
Nox 25/25 998
50/15 1096
New numbers:
Nox 25/25 422
50/15 533

My initial numbers before any of the above changes, the old numbers above were just using water injection so you see there was an improvement just using that:
Nox 25/25 1255
50/15 1448
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Old 01-27-2018, 12:30 PM
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Originally Posted by KJL View Post
Passed emissions!!!

New cats
New NGK plugs heat range 7
New O2 sensors
Oil change
Increased the windshield washer bubba injection from 30 gauge syringe to a 25 gauge.
1 quart of denatured alcohol in a near full tank
Slightly over tire pressure
No EGR

Old numbers (water inject only w/30 gauge needle):
Nox 25/25 998
50/15 1096
New numbers:
Nox 25/25 422
50/15 533

My initial numbers before any of the above changes, the old numbers above were just using water injection so you see there was an improvement just using that:
Nox 25/25 1255
50/15 1448
Congrats. BY the way, I just installed new NGK 5's gapped at .045".
I did this along w new O2s also. Did some datalogging and it seemed to have made a big difference in getting the BLMs in line. I suspected that my left side O2 had been compromised by oil consumption last year due to broken compression ring on #7.
With the motor back together, I wanted to start from scratch w a clean slate and new components. Turned out, I was right.
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Old 01-27-2018, 07:28 PM
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Would be inetresting to have u pull the 7s and see what the geound strap looks like.
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Old 01-28-2018, 11:14 AM
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I will check and post some pics. Also, was it you that siad you could help me dial in the chip? Now that I have the car officially back on the road and this .ADX file thing figure out....I hope....just downloaded the file and uploaded into the program...I would like to do that with my 95 and 92.

What is your opinion of the 415 cuin performance packages by Marc?
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Old 01-28-2018, 12:56 PM
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Originally Posted by KJL View Post
I will check and post some pics. Also, was it you that siad you could help me dial in the chip? Now that I have the car officially back on the road and this .ADX file thing figure out....I hope....just downloaded the file and uploaded into the program...I would like to do that with my 95 and 92.

What is your opinion of the 415 cuin performance packages by Marc?
Yes I can help u out w the calibration. We can discuss the specifics when u r ready. Of course u need 2 different .adx’s for the 92 and 95. I sm currently working w Ccmano on his 90ZR.As for the 415, I do not have much experience w it, but of course I have great respect for Marc’s work. There are others on the Registry that do own a 415. I also know others here in Chicagoñand that have 427 and 445s using a Closed Deck. One of our group is putting together a “budget” big bore 391 package. So u have a number of options available to u should u decide on more displacement. My motor is a stock displacement 5.7L fully ported w Pete’s Intake and Exhaust cams generating ~ [email protected]
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Old 01-28-2018, 01:00 PM
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Originally Posted by Dominic Sorresso View Post
Yes I can help u out w the calibration. We can discuss the specifics when u r ready. Of course u need 2 different .adx’s for the 92 and 95. I sm currently working w Ccmano on his 90ZR.As for the 415, I do not have much experience w it, but of course I have great respect for Marc’s work. There are others on the Registry that do own a 415. I also know others here in Chicagoñand that have 427 and 445s using a Closed Deck. One of our group is putting together a “budget” big bore 391 package. So u have a number of options available to u should u decide on more displacement. My motor is a stock displacement 5.7L fully ported w Pete’s Intake and Exhaust cams generating ~ [email protected]
I just uploaded the file for the 92. Now to see if it all works!

Are you doing the cam install work yourself? Who ported your heads?
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Old 01-28-2018, 04:05 PM
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Originally Posted by KJL View Post
I just uploaded the file for the 92. Now to see if it all works!

Are you doing the cam install work yourself? Who ported your heads?
Now that u have the .adx just follow the sequence I posted.I do some work on my motor and drivetrain but for more involved work such as head porting and cams, I’d rather have experienced hands and eyes do that. Dr. Greekenstein or Pete the Greek does the work on my motor. And I don’t have a lift for removing the motor. He’s built the 427s, 445s and massaged 368s/380s etc. His cams are a standard in the LT5 world and the ones I have.
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Old 01-28-2018, 07:21 PM
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Originally Posted by Dominic Sorresso View Post
Would be inetresting to have u pull the 7s and see what the geound strap looks like.
Here it is. Remember I had 50/50 windshield washer fluid getting sucked into the intake and a quart of denatured alcohol in the gas tank and Marc's emissions chip which runs a little richer. If you look closely you can see the needle I used inside the tube as my calibrated orifice.
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