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Colder spark plugs for GT40p heads

Post by cgrey8 » Wed Mar 11, 2015 8:31 pm

I installed some Autolite copper plugs into the engine a few years ago for diagnostic purposes thinking one of the plugs I had in there might have been bad causing some horrible intermittent misfires. The problem turned out to be something else, so I left the cheapos in the engine anyway just out of laziness not wanting to swap them back since they were working just as well as the ones I pulled.

Well today, a few years later, the cheap Autolites are starting to give me trouble. I'm getting intermittent misfires & partial fires at cruising conditions as well as sluggish and unstable cold takeoff...even with the MSD ignition box. My guess is without that box, they would be performing far worse. Or perhaps because of the ignition box, they are going bad prematurely??? I don't know. Regardless, I'm fairly sure they need to be replaced. After all, they are Autolites and the cheapest plug AutoZone sold for a 97 Explorer 5.0L.

Since I'm replacing them, one of the things I would like to do is replace them with colder plugs since it's a high compression engine. With a 160 degree T-stat and some spark retard, I can actually run 87 octane on the engine, but just barely. I'm thinking a cooler plug would work better particularly as the spring and summer months start returning.

So earlier this week, I went to AutoZone to get some Champion PN 13 (aka RS14YC6) plugs with a heat range of 14, which at the time, I thought made them a cold plug. But looking at the plug, the construction looks far more like a hot plug than a cold plug. Getting suspicious of this, I decided to do some research and sure enough a Champion 14 appears to indicate hot, not cold according to some heat range charts I found on the Internets showing a number of different plug mfgs and their numbers.
Image

So I'm taking them back.

Doing some further Google searching, I found a similar thread from about 2003 on a different forum:
DFW Stangs>Colder Plugs with GT40Ps (supercharged)

From that thread, the guy there is recommending:
Motorcraft AWSF-22C
NGK 4177

The one thing I did learn from that post is that mfgs assign heat ranges differently. Some lower numbers are hotter and others lower numbers are colder. As you can also see from the chart above, there's no consistency thus you shouldn't attempt to compare plug heat range values from different mfgs. This makes AutoZone's declaration of heat range kind of useless and actually misleading when you use the compare feature on their website. Add to this, the Autozone desk guy (a store mgr) didn't seem confident in what the number was either but that didn't stop him from telling me he believed those Champions to be cold despite my pointing out the construction of the insulator being deep...what I'd expect from a hot plug. He just shrugged his shoulders and was like, are you gonna buy them or not?
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', GUFB, Moates QuarterHorse tuned using BE&EA

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Re: Colder spark plugs for GT40p heads

Post by Paulie » Wed Mar 11, 2015 11:36 pm

I don't know about Champion or NGK but for Autolite and Motorcraft, the lower the number, the colder the plug. The stock Motorcraft plug for a 97 5.0L Explorer would be an AWSF32 and one step colder would be an AWSF22.
1990 Mustang 5.0, HCI, Vortech S-trim, FRPP 42# inj., PMAS MH95, A9L, Moates Quarterhorse, BE/EA, Innovate LC-1.

decipha

Re: Colder spark plugs for GT40p heads

Post by decipha » Thu Mar 12, 2015 8:40 am

NEVER use champion plugs on anything not even a lawnmower

toss a set of autolite 103s in it and be done

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Re: Colder spark plugs for GT40p heads

Post by cgrey8 » Thu Mar 12, 2015 3:22 pm

Thanks to all the responses. I got a set of Autolite 103s. Hopefully they'll be in by the weekend.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', GUFB, Moates QuarterHorse tuned using BE&EA

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Re: Colder spark plugs for GT40p heads

Post by cgrey8 » Wed Mar 18, 2015 7:30 pm

I got the plugs installed and I found some issues that were likely the real cause of the intermittent missing.

First of all, the plugs all came out looking pretty decent. No major or obvious issues and all looked pretty consistent in appearance. The insulator on all of them were rather dark gray, not brown. But they were not glazed, caked, or charred looking. I'm not 100% sure what that means, but I'm throwing it out there so if someone does know what that's a tell-tale sign of, they can enlighten me (and the other readers that stumble across this post).

The main problem was the #6 plug wire that's been draped right across the steering shaft. The boot is straight and is about an inch from the shaft, so the wire runs right over the top of the shaft. The rotation of the shaft wore a notch in the wire which was getting deep enough it might have been intermittently arching to the steering shaft instead of arching across the plug's electrodes. Although the notch was not down to the inner sheath or core. I fixed that by zip-tieing the wire up a bit and covering the notch with electrical tape so if it does work its way back down onto the shaft, it'll have to wear through a fairly thick wrap of electrical tape. If that doesn't work or causes problems in the future, I've got enough old wires I can replace that 1 with. I think I have a wire that has a 45 degree boot, but it's from a 9mm blue wire kit. The wires on the engine now are 8mm black.

The next problem was some moderate corrosion on the tip of one of the plugs. I doubt it was actually causing any issues. Even with the corrosion, I'm fairly sure the sheer closeness of the plug tip and wire connector were such that the voltage could easily make the jump. To combat that, I put anti-seize on the tips of the plugs so the wires hopefully don't allow corrosion on the new plugs.

The other problem I noticed is I never gapped the plugs that were in there, which were Autolite 768. The Autolite 103s were gapped to ~0.50". And that stands to reason given the 768s came out at roughly ~.55". I gapped the 103s down to ~.35". I generally like the idea of a wider gap. But I decided I'd see how a smaller gap works.

So far so good with the 103s, but it's way too early to make any kind of judgement on whether the colder plugs are actually doing anything better or worse. I'll give them a thousand miles or so and pull one to make sure they aren't caking or fouling. If they are, then I'll know despite the high compression and MFA lean burn, the colder plug just isn't working. But my gut feeling is a high compression can benefit from a colder-than-OEM plug particularly given the stock Explorer 302 is a rather LOW compression engine.

The intermittent missing is gone and loaded idle is noticeably smoother (i.e 1st gear, closed throttle, clutch all the way out). Prior to the plug change, I could feel the imbalance in cylinder power production causing the truck to jump or surge. It still does that a little, but not nearly like it did, and always has since I got the 331 installed...but the surging had gotten worse with the 768s.

The cranking stumble is still there, so that's something else. I just need to take the time to figure that out and determine if cranking is too rich, too lean, or if I'm just dropping the ISC closed a little too far at lower ECT cranking conditions. That's a relatively easy fix. I was just hoping it had something to do with the plugs.
...Always Somethin'

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Re: Colder spark plugs for GT40p heads

Post by 89mustangnotch » Mon Jun 26, 2017 12:49 am

Any update on how the .35 gapped held up I'm thinking of switching to 103s for my 10psi boosted gt40p setup. I was reading something about xp103s how they have a better kernel flame and take less energy to spark. Which sounds a lot better. Anyone have any input on these news xp103 autolite plugs
89 coupe 302 eagle I-beams, sealed power pistons, gt40p heads, Anderson n-21 cam , 1.7 crane rockers, professional products typhoon intake, BBK 75mm TB, 3" pmas hpx-e maf, 60lb dekas, moates QH with tuner pro vortech v1 s-trim intercooled. Stock t-5, spec clutch,35 spline strange axles and full spool, 4:10 gears, c clip eliminators,BBK shorty headers, BBK x-pipe to flowmasters, EGR,Smog, AC, PS, deleted. Sitting on MT 28x10.50 stock tubs.

decipha

Re: Colder spark plugs for GT40p heads

Post by decipha » Mon Jun 26, 2017 5:07 am

ive never run the x's

I use the autolite double platinums exclusively and never found a reason to use anything else

let us know how it works out

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Re: Colder spark plugs for GT40p heads

Post by cgrey8 » Mon Jun 26, 2017 6:29 am

89mustangnotch wrote: Mon Jun 26, 2017 12:49 am Any update on how the .35 gapped held up I'm thinking of switching to 103s for my 10psi boosted gt40p setup. I was reading something about xp103s how they have a better kernel flame and take less energy to spark. Which sounds a lot better. Anyone have any input on these news xp103 autolite plugs
They are still in the truck and doing well. Although I could probably go back to normal plugs now that I've transitioned back to a 180 degree Tstat. When my 2nd or 3rd 160 died, I said to heck with this and put a 180 in. I never had issues like that with any of the 180s or 195s I ever used in the past. So I've been running with a 180 which did force me back to premium. The 87 octane just couldn't tolerate the high compression AND higher engine temp without pinging. And the cooler plug was intended to further aide 87 octane in working in a 10:1 engine. The Tstat had far greater affect on whether I got ping than I can say the colder plugs did. To be honest, I can't say whether they did anything or not. They certainly didn't make anything worse so I've had no motivation to swap them.
decipha wrote: Mon Jun 26, 2017 5:07 am...I use the autolite double platinums exclusively and never found a reason to use anything else...
I thought you ran old school coppers? Also wasn't there some issue people were talking about with Platinums and boosted engines hence the migration of the industry to Iridum?

BTW, the only purpose (that I'm aware of) for the double platinums was to be an easy replacement for people with coil pack EDIS. From the factory, coil pack engines usually had 2 different spark plugs installed (different part numbers). One set had the platinum disc on the electrode. The other had it on the hook. That was because coil packs send power into a plug, then to the block, then from the block (i.e. hook) into the electrode of the corresponding plug, then back to the coil pack. Thus one plug always gets electricity flowing in the "opposite" direction hence why the platinum disc was on the hook. The double-platinums just put a disc on both electrode and hook so it was dummy-proof. But from my understanding, there was no need for them on distributor-based engines OR COPs. And for those that aren't aware, the direction of current flow does matter when it comes to which end of the spark does more "damage."
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decipha

Re: Colder spark plugs for GT40p heads

Post by decipha » Mon Jun 26, 2017 4:32 pm

nope I use the APP which is the double platinum series, I don't think I've ever use any of their copper stuff

I have a full list of plugs I recommend in my pre tune info

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Re: Colder spark plugs for GT40p heads

Post by cgrey8 » Wed Nov 03, 2021 1:13 pm

Old thread followup.

For the past few months, I started noticing that the engine was having a harder time cranking sometimes and wasn't idling, light throttle running, and accelerating as smoothly. And when I say accelerate, I mean typical 1st & 2nd gear take offs, not tire-screeching WOTs. It was really starting to get annoying particularly the "floating" light throttle where the engine couldn't decide if it wanted to run faster or slower than the truck, the result being the engine chattering the gears in the trans & rearend back-n-forth. But it never acted like a misfire...just not smooth. I even tried reducing the spark advance at light-to-mid throttle conditions at the low RPMs where this happened. That actually helped for a few months, but then degraded right back to where it was.

The datalogs didn't reveal anything telling with the fuel mix. So I thought I'd start with the simple stuff...like the cheap Autolite 103 copper plugs I installed back in 2017. I kept the Autolite Platinum plugs (AP764) they replaced since they seemed to be in excellent shape when I removed them. And add to that, the colder 103s were just an experiment to see if they would burn lower octane fuel any easier. And as it turns out, they never really made any difference I could tell at all. And because of that, there was no reason for me to bother pulling them back out.

But now, I had a reason to think maybe they were the cause OR at the very least, pulling them might be able to tell me something about the condition of the engine that might explain the rougher engine running condition I was experiencing. So this weekend they got pulled. And looking at them, they revealed nothing unusual or of concern. They all had a fairly similar look. No plug stood out as being noticeably different than the others. They all had tinted brown porcelain near the tips with a hint of sandy char on the hooks indicating the engine burns a little oil which most likely is from oil in the PCV air. The gaps were all pretty large, but not overly so...plenty of tip still showing although rounded as you'd expect from a copper plug. I believe brand new, they were .055", so the gaps weren't exactly narrow to start with.
Plugs1-4
Plugs1-4
MI_03112021_132628.jpg (39.1 KiB) Viewed 10355 times
Plugs1-4, view2
Plugs1-4, view2
MI_03112021_132559.jpg (31.22 KiB) Viewed 10355 times
Plugs 5-8
Plugs 5-8
MI_03112021_132529.jpg (26.96 KiB) Viewed 10355 times
Plugs 5-8, view2
Plugs 5-8, view2
MI_03112021_132412.jpg (32.62 KiB) Viewed 10355 times
Otherwise, they don't really look bad...just a bit used (~41kmiles).

Being the engine isn't boosted and has a CD ignition box (SUM‑850610), jumping a large gap shouldn't have been a problem which is probably why I never experienced misfires. Although I guess the larger gap could add more randomness to where the spark jumps on each fire and that MIGHT account for rough engine running? For those experienced, how likely is that? Or is there something else that's more likely? I don't see nearly enough coating/glazing to cause the spark to travel to the side or up the porcelain.

Anyway, I put the Platinums back in which were in great shape and didn't have 1/2 the browning the copper plugs are showing. But like the 103s, they still were gapped for Stock Explorer 302 specs of .055". Being this is a high compression 331 stroker, I closed the gap down to .040" on all 8 before installing them and actually measured each using a gap gauge. The engine is back to running noticeably smoother. I've only driven it a few times, but so far, the plug replacement seems to have improved driveability...no difference in hard-accel that I can tell. Based on the pics, does anybody have any words of wisdom they can share about what these plugs might've been doing and why?

On a slight tangent, notice how the brown spots are not on the same place of the porcelain relative to the hook. I'm assuming the location of the brown spot is relative to where the intake valve was when the plug was installed.
Do the plug mfgs make any effort to locate the hook electrode relative to the threads?
Do the car/head mfgs do anything to ensure plug landings and threads are consistent cylinder-to-cylinder and head-to-head?

Obviously NOT to one or both in the case of this set of plugs & my 90s era GT40p heads. But the need for precision & consistency in modern engines is much higher than it used to be. I thought perhaps somebody might know if modern engine components consider details like where the hook will be in the combustion chamber.
...Always Somethin'

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Re: Colder spark plugs for GT40p heads

Post by LeadHead » Sun Nov 07, 2021 9:38 am

I looked at a bunch of different pictures of spark plugs, and it appears that the thread starts are pretty random.

I know it used to be (or still is?) an old racer's trick to have different thickness washers to put under a spark plug to get the electrode in an optimal position.

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Re: Colder spark plugs for GT40p heads

Post by cgrey8 » Tue Nov 09, 2021 9:06 am

LeadHead wrote: Sun Nov 07, 2021 9:38 amI looked at a bunch of different pictures of spark plugs, and it appears that the thread starts are pretty random...
That's kinda what I was suspecting, at least as it relates to plugs intended for my generation of head.
LeadHead wrote: Sun Nov 07, 2021 9:38 am...I know it used to be (or still is?) an old racer's trick to have different thickness washers to put under a spark plug to get the electrode in an optimal position.
Back when I had the heads off the engine, I took my plugs and test-fit them into various cylinders to see where each one put the hook. I tried to find a combination that would locate the hook closest to the top of the cylinder in an effort to keep it out of the incoming airflow as much as possible. Is that what the strategy was for the old racers using the washers? If not, what was the intention/strategy they were trying to accomplish with the washers?
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', GUFB, Moates QuarterHorse tuned using BE&EA

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Re: Colder spark plugs for GT40p heads

Post by LeadHead » Tue Nov 09, 2021 8:30 pm

No idea. I think maybe to have the open end point into the chamber?

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Re: Colder spark plugs for GT40p heads

Post by jamie from oz » Thu Dec 16, 2021 8:07 pm

hi.
on the E-tec outboard motors the spark plugs are indexed to a particular angle to help the ignition flame propagation and for the direct injection fuel spray pattern from memory .
the plugs have a line marked on them and if the line doesn't fall into a particular zone you try another plug from the carton .
I have used 10 plugs to get the 6 plugs into the specified index zone .
my conclusion to this is yes it dose matter in hi performance for that last 0.1% but for street cars/trucks it would not make any difference.

Jamie
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Falcon XH v8 5.0L ute 1996 / NVMG84 and 6DGD.bin using sailor bob Def/cry ( ho engine185kw)
Falcon AU2 v8 5.0L ute 2000 / NGVB5 and Y3EE / WALG (factory GT40P heads and intake 200kw )
Falcon EL v8 5.0L with 6cyl SD EEC-V HWAD and 6dbd ETV-513 (JSA'S help with 6dbd_56k_x bin and 6dbd_56k_x Xls)

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Re: Colder spark plugs for GT40p heads

Post by MrsJones » Tue Nov 21, 2023 7:22 pm

I know this is an old thread but perhaps my experience with the P heads will find some value to someone.

I ran the P heads on a 306 combo with flat top pistons and zero deck height. The heads were milled ~.120 or to the point of starting to remove some of the thread boss in the chamber where the plugs screwed in. I forget what head gasket I used but there was wire involved. This equated to ~14:1 compression ratio. I used the Autolite 103's with this combo. I started out gaping them at .035" as preventive to blowing the flame out at that level of compression. On a wheel dyno, I discovered that opening them up to .045" gained 10 rwhp.

The old school spark plug gaskets, made of copper, were used to prevent the piston from touching the ground strap and closing the gap. Marking the porcellen (magic marker) where the ground strap was located then installing a washer to make sure the strap was directed away from the piston, called indexing. Trial and error with different thicknesses of washers is necessary. This process will have to be repeated each time you replace a plug. You'll find one thickness doesn't satisfy all the plugs due to the fact that the plugs are assembled at random.

Also, just for the sake of telling, my "race gas" of choice was Shell 93 octane. Timing was initial set at 14 deg and let the STOCK A9L do the rest of the work. This was with 30lb injectors and with a 65 mm Pro-M MAF with what is now known as the "Optimizer". This MAF unit had the adjustable gain and offset ACTUALLY in the sensor. Fuel pressure was set at 60 psi but was adjusted accordingly for air conditions, DA.

As for the 103's, the one's in the photos above looked very similar to mine after about 15-20 passes plus the running around the track. They are a cheap plug and the electrode would wear away, round off, and performance would drop off.

I hope this answers some questions regarding the subject.
1993 Mustang Coupe, Boss block low compression 331 cu/in, Victor Jr. heads, TFS Stage 2 cam, GT40 tubular intake, 30# injectors, 65 mm Pro-M MAF w/balance of induction stock, BBK shortys and 2 1/2 exhaust. A9L GUFB w/Moates QH, BE and EA.

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Re: Colder spark plugs for GT40p heads

Post by cgrey8 » Wed Nov 22, 2023 7:51 am

MrsJones wrote: Tue Nov 21, 2023 7:22 pmI ran the P heads on a 306 combo with flat top pistons and zero deck height. The heads were milled ~.120 or to the point of starting to remove some of the thread boss in the chamber where the plugs screwed in. I forget what head gasket I used but there was wire involved. This equated to ~14:1 compression ratio...
I had my heads decked as well, but not that much. What I was surprised at is that my GT40p head chambers seemed much larger than advertised sizes. I think advertised, they are supposed to be somewhere near 58cc. My heads ranged from 60-62cc AFTER being decked. I can't remember how many thousandths were taken, but it was no where near .120".

My intention for this 331 build was to get a tight quench with the flat tops and the heads. But stock Explorer gaskets measured way thicker than I expected...something near .060" IIRC. So I went with some FelPro aftermarket gaskets that measured .039". They were double the price of stock Explorer gaskets, but worth it given my intentions for quench and compression. With the additional stroke, CC measurements, gasket thickness, and measured pop of the pistons above the deck, I estimated my engine somewhere around 10.2:1. It's enough that running a 180 degree T-stat forces me to pull timing compared to stock A9L (or X3Z) numbers even with 93 octane pump gas. This weekend, I've got to replace the timing cover gasket because the gasket has pushed out and is leaking coolant. So I'll be going back together with a 160 Tstat so I can hopefully get back some of the timing I've had to pull when daily-driving in Atlanta summers.
MrsJones wrote: Tue Nov 21, 2023 7:22 pm...I used the Autolite 103's with this combo. I started out gaping them at .035" as preventive to blowing the flame out at that level of compression. On a wheel dyno, I discovered that opening them up to .045" gained 10 rwhp...
Good to know. Next time I replace them, I'll try opening them up a bit. I'll also test how far they've opened just due to wear. Since I'm not racing and use this engine as a daily, I might still need them gapped tighter just so they don't wear too far open. I tend to replace them every 30k, although now that I work from home, that takes a good bit longer than it used to when I was driving to the office everyday.
MrsJones wrote: Tue Nov 21, 2023 7:22 pm...The old school spark plug gaskets, made of copper, were used to prevent the piston from touching the ground strap and closing the gap. Marking the porcellen (magic marker) where the ground strap was located then installing a washer to make sure the strap was directed away from the piston, called indexing. Trial and error with different thicknesses of washers is necessary. This process will have to be repeated each time you replace a plug. You'll find one thickness doesn't satisfy all the plugs due to the fact that the plugs are assembled at random...
I do something similar. I mark them as you describe so I can see where the strap ends up landing when threaded into the head all the way. And I mix-n-match the plugs to get the strap pointed somewhere up/away form the piston. I didn't do this for clearance as much as it seemed like a good idea to have the spark's flame front unshrouded by the hook. I usually buy 12 plugs in hopes that I can find a combination of 8 that locate the hook somewhere up. I'm curious as to how much actual benefit this extra effort results in for performance AND fuel economy.
MrsJones wrote: Tue Nov 21, 2023 7:22 pm...As for the 103's, the one's in the photos above looked very similar to mine after about 15-20 passes plus the running around the track. They are a cheap plug and the electrode would wear away, round off, and performance would drop off...
Since my engine isn't a race engine, but rather a daily driver, the plugs stay in WAY longer than that, but get a far less of a beating. It's interesting that the porcelain patterns look so similar given the radically different duty.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, FMS Explorer (GT40p) headers, aftermarket T5 'Z-Spec', GUFB, Moates QuarterHorse tuned using BE&EA

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Re: Colder spark plugs for GT40p heads

Post by MrsJones » Wed Nov 22, 2023 7:23 pm

I will admit that 14:1 presented problems with keeping the seal, hence the wire I spoke of. But even that was no guarantee.

The procelene carbon patterns are likely due to the incoming air/fuel cooling the area where there is less buildup. I learned of the indexing program from an "older than me" racer who claimed it was done to use the strap as a block to the incoming mixture as it helped prevent "blowing out the spark". This was before the hi tech ignition systems we have today. For a NA engine, high compression numbers were the rule of the day. Domed pistons were the rage but caused their own issues, hence another reason for indexing.

I mentioned the Shell fuel only because the engine didn't run as well on 93 from any other source that I tried. I tried some 104 octane no lead but there was no gain there. If anything it hurt performance. As you probably know, as octane ratings go up the slower the burn. I needed a fuel that would burn the fuel as quickly as possible without melting a piston or something else. The fuel we get these days is simply not as optimum as it could be. We just have to live with it.

As for the plugs, remember, they are ALL produced for general production engines for the auto industry and, simply put, some are better than others. When gapping the plugs, the ground strap gets deformed enough to not be parallel with the end of the center electrode. Spark jumps off that sharp edge of the electrode and is eroded over time and use, thus the rounding. Always gap with wire type gapping tool for best accuracy, if you're into that, and, you can tell where the spark will be occurring initially. I have looked at some of the platinum plugs with the small electrode as possibly lasting longer than others. Problem, as I see it, heat ranges for those are limited.

Nice chat.....
1993 Mustang Coupe, Boss block low compression 331 cu/in, Victor Jr. heads, TFS Stage 2 cam, GT40 tubular intake, 30# injectors, 65 mm Pro-M MAF w/balance of induction stock, BBK shortys and 2 1/2 exhaust. A9L GUFB w/Moates QH, BE and EA.

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Re: Colder spark plugs for GT40p heads

Post by 85GT » Sun Dec 31, 2023 12:55 am

cgrey8 wrote: Wed Nov 22, 2023 7:51 am I think advertised, they are supposed to be somewhere near 58cc. My heads ranged from 60-62cc AFTER being decked.

I do something similar. I mark them as you describe so I can see where the strap ends up landing when threaded into the head all the way. And I mix-n-match the plugs to get the strap pointed somewhere up/away form the piston. I didn't do this for clearance as much as it seemed like a good idea to have the spark's flame front unshrouded by the hook. I usually buy 12 plugs in hopes that I can find a combination of 8 that locate the hook somewhere up. I'm curious as to how much actual benefit this extra effort results in for performance AND fuel economy.
You guys know you can do that indexing off the engine right with an indexing tool? Get the straps right once in the engine, then mark the tool with each cylinder's plug. Next round, you just see which plug lines up the best for each cylinder in the tool.
PS - I've never found any HP or fuel differences lol.

Chris, did those heads get a valve job? Lazy/cautious grinders can sink the valves quite a bit grinding the seats costing you CCs. Even facing the valves will make the heads protrude less into the chambers to cost some too.
85GT, 302 w/Dart Windsor Jr heads, Crane 2030 equiv. Performer 5.0, 75mm TB, 88mm slot MAF, 34lbs injectors, BBK shorties, 5spd converted to 4R70W with Baumann controller, 9" rear w/3.25s
A9L running A9P bin via Quarterhorse w/LC-1 WB

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