Spark Plug Heat Range

[XfireZ51]

I did a scan of a standing start going thru 3 gears last week. I got Knock retard at top of third gear. So now I’m wondering if that was happening at track at BG. I pulled plugs to see if there were signs of pre-ignition or was it false knock. There were some tiny specks on porcelain but sooty not metallic, and right at the edge of porcelain as it goes horizontal towards center electrode. Also, looking at the ground strap, it changed color at the weld suggesting heat range was hot. Base ring color was black telling me WOT fuel could be leaned out.Plugs were barely torqued so I took care of that. I may do another scan and see if I get same results. If I do, I may go to a slightly colder plug. Right now using AC 41-630 having replaced the NGK Irdiums TR5IX (Came with car, so no idea how long they'd been there) that were there.
Anyone want to chime in on which plugs and heat range they're using?

Here's a very interesting quote from this article

http://www.articlealley.com/article_467790_31.html

"...When an engine is modified for high performance and its power is increased, the stock spark plugs very often result hottest than necessary due to the new power reached at higher RPM and the gasoline would end up pre-igniting or detonating without the need of an electric spark, creating an uncontrolled explosion that would severely damage the engine.

Be aware that never! Never a high performance modified engine, can continue using the stock spark plug, because more power is more energy, and more energy always is more heat.

Unfortunately, even very experienced mechanics have difficulty in detecting the differences in these situations that are very often misunderstood, misleading them to search the origin of the troubles that the spark plugs are showing, in the supposedly wrong air/fuel mixture, cooling systems troubles or other mechanical failures.

It is absolutely clear that is doing lack more information about the true one and transcendental importance of the heat range of the sparkplugs. This exact selection is critical!

Only with the proper Heat Range will spark plugs sustain the perfect combustion process that keeps your engine's top efficiency and functional reliability.

But only a few of the most selected and experienced engine tuners know how to select the spark plug with the proper heat range best suited to match these different conditions, or the specific engine's level of modification, but them reach it only after long hours of expensive and difficult testing by trial and error with different spark plugs sets of different heat ranges.

What you need to find is the spark plug with the heat range, best suited to the combination of your own specific, individual and particular driving habits, traffic, weather, and engine operating conditions, fuel quality, that can be affecting your engine performance; tailoring this selection exactly for you driving habits or life style.

This is the only way that guarantees to achieve the peak power, performance, endurance, better mileage and the lowest emissions."

[flyin ryan]

o.k., i'll bite. i didn't cross the AC number over yet but are you sure the NGK's you had were 5's & not 55's? 55's in our cars is common. the way your reading the plugs sounds like you almost right on the money. i would go one range colder than you are now. i see guys jump to colder heat rangers way too quick most times IMO. it sounds like in your case your on top of the situation & have a good idea what your doing though. i use NGK's in all my stuff, Zee's & the engines i build. 4's are hot & 10's are ice cold. for example the Competition Eliminator engines i do make anywear from 2.35 to 2.5 H.P. per cube & i use 8's & once in a while 9's in then. off coarse that's all naturally asperated stuff. 10's are strictly maximum effort power adder combinations. now there are thousands of factors that make up your plug choice & i don't know 999 of them right now. in a nutshell i think your close.

[-=Jeff=-]

I used 41602 Ac Delco in my car, why did you go with the 41630?

[XfireZ51]

I used 41602 Ac Delco in my car, why did you go with the 41630?

Your car meaning the 89 or the ZR? That's what Al suggested and I believe they are the equivalent of the NGKs. There must be some other difference between 630's and 602's. If its heat range only, one of us if WAY off.

FR,

The NGKs I had were the TR5IX Iridiums. As the article said, the more power you're making, the more heat your putting in. Therefore the need for colder plug. I don't think I'm that far off either. But its enough to make a difference and worth investigating.

[-=Jeff=-]

Your car meaning the 89 or the ZR? That's what Al suggested and I believe they are the equivalent of the NGKs. There must be some other difference between 630's and 602's. If its heat range only, one of us if WAY off.



Sorry the 41602s are in my Z

[XfireZ51]

Sorry the 41602s are in my Z

Jeff,

Isn't there also an issue about the plug seat on the 90 head being different?

[flyin ryan]

90-92's are flat seat. 93-95 use a taper seat. some guys use a taper seat in 90-92's, it'll work but it's not right.

[Pete]

Dom,you sure you have 41-630 or 41-603.

Our cars came with FR2LS (replaced by 41-602) the NGK is FR5.

The only one colder is FR1LS NGK 6962/BKR6E

The 41-603 is NGK FR4.

Pete

[Paul Workman]

Mine had the 41-602s in it when I thought I might be having plug problems (turned out to be mouse-chewed wires). I replaced them with the (Pt) 41-800s, but I did notice my insulators were almost pure white, after about 3-4 hundred miles. No signs of knock, but it occurred to me that it might be running a little lean????

Anywayz, the AC/Delco site lists 3 plugs for the LT5, 41-800s (in Pt), and the standard 41-602. and one other. 41-630 is not listed on their site as a standard replacement for the LT5.

P.

[-=Jeff=-]

Nope no issues with the 41602 in my 90

[jonszr1]

i on a whim am trying that e 3 spark plug . i have about 2k miles on them but seem to get about 1.5 mpg better milage on the freeway and dont have as many knock events .could be just that they are new plugs . i could be nuts but these things just might work. just thought id throw it out for ya :hello:

[Aurora40]

The NGKs I had were the TR5IX Iridiums.
The NGK Iridium plug listed for the '93-95 is the TR55IX. I wonder if the TR5IX is just some older identifier? I believe one range colder is the TR65IX, and two is the TR75IX.

This is a tapered seat plug, which is not correct for the early LT5. However, if it's already in there, I wonder if you'll need to use tapered plugs from now on?

[XfireZ51]

Pete,

I'm positive its a 41-630. But I will look again when I get home. One other
possibility is that if I do have heads with tapered seats, it would give more evidence that the motor had in fact been replaced as I was told. Supposedly, original motor had cam seize issue and GM replaced it with a new one. Sepaking with Ron Kreigh at BG, he said that the service engines were all 4 bolt, 93+ motors. Curiouser and curiouser.

[Aurora40]

Sepaking with Ron Kreigh at BG, he said that the service engines were all 4 bolt, 93+ motors. Curiouser and curiouser.
Wouldn't it depend on when it was done? If it seized in 1990, I doubt it would be a '93 engine. :)

[-=Jeff=-]

Wouldn't it depend on when it was done? If it seized in 1990, I doubt it would be a '93 engine. :)

Agreed, but in Dominics case, being a 92, it is more possible that he might have a 93.. but then IF it was swapped for a 93, when they replaced the motors, was it Complete? meaning then his IH and plenum he took off would have been from a 93 then right?

[jonszr1]

The NGK Iridium plug listed for the '93-95 is the TR55IX. I wonder if the TR5IX is just some older identifier? I believe one range colder is the TR65IX, and two is the TR75IX.

This is a tapered seat plug, which is not correct for the early LT5. However, if it's already in there, I wonder if you'll need to use tapered plugs from now on? i cked with corey and he said you could go back and forth . i have used the ngk tapered in my car for over a year then when i tried the e 3 and found they were the old style with the metal gasket . and have had no ill effects at all . hope this helps

[Aurora40]

Agreed, but in Dominics case, being a 92, it is more possible that he might have a 93.. but then IF it was swapped for a 93, when they replaced the motors, was it Complete? meaning then his IH and plenum he took off would have been from a 93 then right?
Ah, I don't know why I thought he had a '90...

[-=Jeff=-]

Ah, I don't know why I thought he had a '90...

No problem, but you know you made a valid point.. obviously anything for MY 93 to 95 had a MY93 motor anyway, the service assemblies were also MY93.. now did GM allocate x amount of motors for each MY as Service Assemblies? Then at what point would those have been used before going to the MY93 Service Assembly replacement?

Lastly, if I understand right, te Motor if replaced for warranty was a complete motor right? so if a 92 got a replacement 93 then it should have the IH and plenum for the 93 model right? would that then mean that the early cars were fitted with EGR if using a later motor?

I am curious more then anything one how that was all settled..

Dominic do you know what mileage your motor was swapped at?

[XfireZ51]

Guys,

A couple of clarifications. The car is a 92 #474. It was built in June of 92 so it was built in the last few days of that MY. The information I had received was that the motor had been replaced at 16K due to camshaft seizing. The owner (unknown) insisted and supposedly GM showed him a motor with a good dyno sheet. Wouldn't mind having that myself. I'll need to check out the heads and see what numbers are stamped on the back. According to Graham Behan, GM had decided to phase out the LT-5 during the 92 MY. Mercury Marine could build motors economically ONLY at a 1500units/annum pace. So they basically built all the motors that were going to be used for the next 3 MY in 1 year plus whatever would be needed as service engines. I have the same question as =Jeff= regarding the top end.
OTOH, IH were definitely 90-92 as was plenum. When I port matched the cylinder heads this past winter, the primaries were smaller than the secondaries. Secondaries were about 37mm. Primaries needed basically a crescent moon cut to match with 36mm IH.

As for the spark plugs, I pulled several and they were 41-602s. My mistake because I still had 41-630s in the cabinet. Those I had used with the 84. However, the ground strap still indicates that I could go with a colder plug and lean out WOT fuel.
Currently running .040" gap.

[flyin ryan]

This is a tapered seat plug, which is not correct for the early LT5. However, if it's already in there, I wonder if you'll need to use tapered plugs from now on?no you can go back to flat. that's what i would do. i've seen guys use taper plugs in flat seat heads & they crank it down to force a seal, next thing you know the top thread or two is squashed, go to take the plug out & grabs the thread, gall's, now you've got a problem:cool: . while i'm on it always use a bit of anti-seize on the threads but don't let it get on the ground strap, center electrode or any part of that area.

[flyin ryan]

Dom,you sure you have 41-630 or 41-603.

Our cars came with FR2LS (replaced by 41-602) the NGK is FR5.

The only one colder is FR1LS NGK 6962/BKR6E

The 41-603 is NGK FR4.

Peteif you can't get FR5, the plug i use is NGK BKR5EIX, stock no: 6341.

[jonszr1]

ryan do you think that would be a good plug for a fully ported car? what would you suggest gap wise .you have seen so much in developing motors ,it would be really neat if you shared your thought s . thankyou for any insights you share

[Pete]

if you can't get FR5, the plug i use is NGK BKR5EIX, stock no: 6341.

Thanks Ryan
I use AC Delco 41-602 gap @.035.
I have tried different gaps and have found .035 works best for stock ignition system.
I don't think there is much HP to be had in our LT5's from spark plugs, if anyone has experienced any differance (more power) i would love to hear about it.
I know plugs make a differance on race motors.

Pete

[jonszr1]

pete i have a set of those e3s in my black car.getting about 1.5 mpg better on a steady cruize. i ahve 1 150 stretch that i just put it on cruize . if i am getting better fuel milage ,plugs only diff wcould that transfer into a little more power. are those acs colder than the ngk? thanx for any insight

[Pete]

pete i have a set of those e3s in my black car.getting about 1.5 mpg better on a steady cruize. i ahve 1 150 stretch that i just put it on cruize . if i am getting better fuel milage ,plugs only diff wcould that transfer into a little more power. are those acs colder than the ngk? thanx for any insight

I think it might be more efficient at the rpm you set your cruise at,it does not mean you make more power at peak.

I don't think there is much power if any to be seen on the dyno from our LT5's from just spark plugs.
I'm always willing to hear peoples results.

My Z will be going on the Dyno in a few days i'll try this on the dyno if some one can tell me which plugs are best for more power NGK or Denso.

Pete

[flyin ryan]

ryan do you think that would be a good plug for a fully ported car? what would you suggest gap wise .you have seen so much in developing motors ,it would be really neat if you shared your thought s . thankyou for any insights you shareoh...i would go a touch colder, one heat range, that's all. porting is one thing but compression & cams ( cam timing ) are another & i'm assuming you haven't messed with that? plug gap wise i'd stay around .035" to .040". nothing to be had there, except the more gap you have the more it taxes the entire electrical system, wires, coils etc.

[XfireZ51]

oh...i would go a touch colder, one heat range, that's all. porting is one thing but compression & cams ( cam timing ) are another & i'm assuming you haven't messed with that? plug gap wise i'd stay around .035" to .040". nothing to be had there, except the more gap you have the more it taxes the entire electrical system, wires, coils etc.

FR,

That's what I am planning of doing is go a heat range colder. What would be the equivalent of a 41-601 or 41-600?

[jonszr1]

ryan, thanks a bunch . i have been doing it all wrong have been running ngks at the strip with 50 thou gap . well off to the store for the one step colder and close up the gaps one last ?what type of plug do you like to run or would run when taking a zr1 to the strip. thankyou so much also what are your thoughts on the E-3 plugs . snake oil or maybe good stuff?

[jonszr1]

pete thanx for the input . guess sometimes i think i find the genei in a bottle , i should know better , give me something good to think about though . let us know what you find out thanx ps have you been to the strip with the 41o yet. it would be neat to hear that you got the 10.99 run :thumbsup:

[XfireZ51]

I think it might be more efficient at the rpm you set your cruise at,it does not mean you make more power at peak.

I don't think there is much power if any to be seen on the dyno from our LT5's from just spark plugs.
I'm always willing to hear peoples results.

My Z will be going on the Dyno in a few days i'll try this on the dyno if some one can tell me which plugs are best for more power NGK or Denso.
Pete

Pete,

I think there are a number of articles that suggest there is. Based on what I've read and the kind of power your motor is putting out, you would benefit from going 1 or 2 steps colder. Be interesting to look at your current plugs. Maybe with a colder plug you could be a bit more aggressive with timing.
I think I may try the BKR6E which is supposed to be the equivalent of the FR1LS.

[XfireZ51]

Well I installed the BKR7E and right from the key on and idle I could tell something was different. Gapped at .050". Idle was way smoother. I have a Fidanza in the car, and the "box of rocks" was not to be heard or barely. I have pulled one plug to check heat range, and it actually looks as if I could go one step colder. Any thoughts on that? One of the gurus on 3rd Gen would say just give the motor what it wants.

[We Gone]

Been running the same plugs (BKR7EIX) for about 6 months now, very happy with them.

[XfireZ51]

Been running the same plugs (BKR7EIX) for about 6 months now, very happy with them.

Is that on a stock or modded motor?

[We Gone]

Is that on a stock or modded motor?

Stock...with headers & chip

[XfireZ51]

Should have asked this earlier, but what gap? Of course, yours are the Iridiums so that could make a diff.

[We Gone]

Should have asked this earlier, but what gap? Of course, yours are the Iridiums so that could make a diff.

.035

[flyin ryan]

Well I installed the BKR7E and right from the key on and idle I could tell something was different. Gapped at .050". Idle was way smoother. I have a Fidanza in the car, and the "box of rocks" was not to be heard or barely. I have pulled one plug to check heat range, and it actually looks as if I could go one step colder. Any thoughts on that? One of the gurus on 3rd Gen would say just give the motor what it wants.no chance i'd go colder, 7's are pretty cold already. your happy with it now, let it be. how are you checking the plugs anyways? if you've idled around for any amount of time at all you know your readings will be in-accurate, right?

[XfireZ51]

FR,

I have pulled the plugs after doing a scan that included WOT run and driving around to read various points on the VE table. Looking to read ground strap, which now shows a line much closer to arc of ground strap.
I'm running .050" gap. Any comments on that?

[flyin ryan]

were you looking at the plugs after a WOT/clean shut off run? i'm not sure what your looking for in heat in the ground strap but it sound about perfect right now for me. i'd go away from the .050" stuff myself. if you want to pursue the larger gaps your better off to clip the ground strap back & side gap. NGK iridium plugs actually come with the groung strap cut back a tiny bit.

[jonszr1]

would .40 be better ? any thoughts on the E-3 plugs that are out now?

[flyin ryan]

well, again, understand there is no definitive good, better or best, lots of ways to skin a cat as it were. everybody that comes to me all want that perfect combination & i tell them the same thing, it depends. lots of factors involved, LOTS. that's why those desk top dyno things don't work. i just want to make it clear i'm not saying what you're doing is wrong & what i'm saying is right, i want to help best i can but i have minimal information about your deal to be fair. based on my testing & what my friends in the engine building world are using these days i'd stick closer to .035"-.040". now for the E-3's? i'm a loyal NGK guy, never heard of these? don't know anything about them. i'm chasing power in a lot of areas but spark plugs are not one of them lately.

[XfireZ51]

FR,

Not a problem. Fully appreciate your help or anyone else's on this forum.
As part of tuning the motor, I wanted to make cetain I had the proper heat range plug in the motor. With the right heat range, you can tune the motor with greater accuracy. Having read quite a bit on the subject, heat range for a plug is determined by looking at the ground strap and seeing where the color change appears on it. Too close to the tip of the ground strap, plug is too cold, too close to the base ring of the plug, then its too hot. My color change on the AC 41-602 were right at the base ring. I'm going thru explaining this for the benefit of some of the others, not necessarily you.
The 7 heat range plug, based on how to read the ground strap, seems to be closer to the arc of the ground strap and so closer to correct.
Having said that, I now find that I have a problem with a Code 55 or Lean exhaust. Something is causing the injectors to drop out and therefore a lean condition. I have a scan on it. Lgaff and myself checked the fuel pumps and they both turn on to 48psi then drop off to 42 with Key on, motor off.
I am currently suspecting a flaky TPS or something having to do with timing. Its not the Port Throttle. No code and it has the right signal to stay on. Something else caused the injectors to close down at around 7100rpm. When it went lean, that set the code and so the ECM disabled secondary. My only other suspicion is the Fuel Kill which was set at 7175.
I'm also going to close the gap on the plugs on the off chance the wider gap is taxing the coils.

:icon_scra :confused:

[flyin ryan]

can't hurt to try:dontknow: might help. interesting problem:icon_scra

[jonszr1]

maybe i am nuts but i just love trying things when tuning to try to get as much as possible out of the combo. cant do a throw a cam in it like a standard small blk chev. so trying things tune wise keeps an ole guy happy

[ZWILD1]

I use AC rapid fire #8's gapped to .045 th. I changed over to NGK BKR5EIX's . I wanted to go back to the rapid fires and I get tappered seats no washers. I swore the #8's I had before had washers. I accidently threw the old ones out. Am I crazy or just mistaken.

[Aurora40]

You need #5's not #8's for a '90-92. Why would you want to go back to them from iridium plugs, though?

[ZWILD1]

Eights are one range colder and seemed to work good for me. I posted a new problem though have you had problems with rough idle and lose of power with your car.