Spark Plug Life with HEI Distributor?? - JeepForum.com
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post #1 of 18 Old 07-16-2021, 07:46 AM Thread Starter
mikwallace
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Spark Plug Life with HEI Distributor??

Here’s the engine related Stats:

1990 YJ, 4.2L engine rebuilt @ 246,00 miles bored .040 over

“PFI” Systems Kit, TBI, ECU, all associated components, and HEI distributor.

Here’s the issue:

Was Starting good, running good; however, after about 4,500 miles on rebuilt engine it began to run rough when cold (ecu code was mixture rich at the O2 sensor), then after warm up it ran ok. Pulled one of the plugs and tip burned down to about .060+ gap. A New plug gap should be .033-.038; .035 set when new plugs installed after rebuild. Re-gapped all old plugs, helped but not fixed.

Today I Installed new plugs gapped at .035, checked and reset timing. Starts good, runs good, no CEL.

Here’s a pic of old and new plug.

img_0532.jpg

The old plug has burned down quit a bit!

So, does the HEI system increase voltage so much it causes a short lifespan for the plugs?? If so, looks like the Champion plugs are a no-win! I’m running the OEM type plug - Champion RFN14LY.

Input and opinions requested!!!

Thanks


Follow up:

After plug Change and timing adjustment, started good idled good in shop. Drove when engine cold (not operating temp) and ran awful, CEL rich mixture, stalled, and barely ran above idle speed (20 mph). Once engine at operating temp all is well. So what will make it run bad above idle speed when cold, but yet when warm it’s ok.

- Faulty temp sent to ECU?
-ECU not setting spark correctly?




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post #2 of 18 Old 07-16-2021, 10:01 AM
bpounds
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I am not familiar with the PFI product, so I went and looked it up. Apparently it does control spark.

I have the Howell system with a CRT HEI distributor. It does not control spark in any way.

So I'll just throw out some things that come to mind, and I reviewed my maintenance schedule.

I also use the OEM Champion copper plugs. But I gap them to .045". Been doing that since the day I put the HEI in there, which was 8/2015. Not sure where I got that, but I'm sure it was recommended somewhere, probably by CRT.

I use non-standard spark plug wires, which need to be at least 8mm. Stock smaller gauge wires won't handle the higher voltage.

I've replaced plugs once since installing the HEI (new plugs at time of install). That was at about 8k miles on those plugs, and they looked perfect. I pretty much stick new plugs in any time I have a reason to pull them, because they are cheap and easy, and I just don't see a reason to stick used plugs back in the head.

So therefore, no I do not think the HEI burns up plugs, but I would take a look at the recommended gap and your wires. Also take a look at your timing. I have run between 7° and 11° BTDC, and it has run about equally well anywhere in there, but emissions has been impacted which is why I have tried different values. Chasing pinging issues too. I do not know how or if the PFI system adjusts timing, but incorrect timing will burn plugs.

As far as running rough when cold, I would look at all the components that read temp, including coolant temp and air temp/density. Make sure your MAP is mounted correctly oriented AND above the level of the throttle body. Don't forget the factory temperature vacuum control valve, which I assume your system still uses for EGR and timing advance functions.

Bill

1988 Wrangler,4.2L I-6, Howell EFI JP-1,CRT HEI Ign,AX15 ext slave conversion, Zone 2" lift + 1" BL + 1/2" booms, BFG 31 x 10.5, Bestop.
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post #3 of 18 Old 07-16-2021, 11:39 AM Thread Starter
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BPounds - thank you very much for the input. I do have the bigger plug wires as you mentioned. The PFI system does adjust timing. It has a timing wire that you unplug then set timing to “0” degrees and plug the timing wire back in, turn of ignition, wait minimum of 30 sec before starting. The ECU will then adjust timing. I’ve double checked all vacuum lines. I’m trying to find out how to check the temp sensor to ensure it’s working properly. It send info back to ECU. I may have a spare and just change that out to see if it fixes it. All the egr stuff is gone. In fact I have a Clifford Performance intake and headers, so all the EGR sensor stuff is gone.
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post #4 of 18 Old 07-16-2021, 12:04 PM
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The RF14 is a little 'hot'. RF12LYC is probably a better plug for your 4.2 (Autolite 985 as well.)
Yes, HEI plug gap is .045...Much better idle just doing that.
You do have the distributor supplied by PFI???

Regap and try that cold before you change anything else.
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post #5 of 18 Old 07-16-2021, 02:13 PM
timatoe
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I gap them to .045 as mentioned and run the "stock" Champion or Autolite plug. I've been running mine for about 10 years with HEI and I've changed the plugs once after the initial install.

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Originally Posted by George Orwell
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post #6 of 18 Old 07-16-2021, 07:35 PM
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Came across something strange while looking into the subject. All of Champion's platinum and iridium plugs are listed (in both their catalog and Rockauto's as well) to be one heat range colder (12) than the copper (14). Same heat range as what @gutthans recommended. Never heard of an HEI burning up plugs either.....and I've owned a few GM's over the years.
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post #7 of 18 Old 07-16-2021, 10:27 PM
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I think we've gotten the answer already but it's very possible to melt or deform the tip of the spark plug if it's too hot/the heat range is too hot for the engine. If you run a really hot coil and the spark plugs are on the hot side of the allowable range, it may be necessary to run a colder plug but this is kind of rare. Hopefully, this didn't cause any knocking or pre-ignition that damaged the pistons but it may be worth looking if things continue to run poorly with the new plugs.


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post #8 of 18 Old 07-17-2021, 06:01 AM
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Just for giggles I went through about 20 different sources. I've noticed that the numbering systems are getting more complex, even with the charts. There are about 50 different recommended plugs!

Two things: Watch which plug you get. The Autolite copper ATL-985 sells for $2.99; the Autolite ATL-A985 (same plug/same vendor) lists for $3.99
Champion is moving to a simple numbering system. The 412 is the RC12LYC

IF you operate near idle a lot, don't drive far at one time, hardly do highway...the 14 heat range is a good choice. IMO 12 is a better range for typical use.

https://www.sparkplugs.com/champion-...mbering-system is an older chart that was standard before the newer changes. Good luck finding cross-references and making sense of how they keep you confused.
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post #9 of 18 Old 07-17-2021, 10:16 PM Thread Starter
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Thanks guys! Great info, as usual, from the Forum. The only reason I’m running 14’s is that’s what’s in the Haynes Manual for pre ‘96 models with carb six cylinder. Although I no longer have a carb, I assumed the difference between the carb and FI was the heads? So, I went with the Haynes info for carb’d engines. I did have some pinging under load (I.e. highway speed up long hill climb. But it went away after I switched from 87 oct to 91/93 oct fuel.
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post #10 of 18 Old 07-17-2021, 10:39 PM
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Yeah unless you've done some major engine work, you shouldn't have to run anything more than 87 octane to prevent that engine from knocking with the right plugs.


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post #11 of 18 Old 07-18-2021, 03:24 AM
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When we talk about a spark plug's heat range we aren't talking about how hot or cold a spark plug sparks. We are talking about how well the plug transfers heat from the tip to the engine head.
Adding horsepower is adding combustion heat. No EGR also adds heat.
A hotter spark plug wears faster.
I would try one heat range colder plug and go from there. You should be able to run 87 octane.

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post #12 of 18 Old 07-19-2021, 07:24 PM Thread Starter
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Thanks guys. You continually amaze me!! I’m entourages to CO now and the YJ is on the trailer. I’ll see how it does in Denver and will evaluate there before going to Silverton. Look forward to riding Black Bear Pass down to Telluride. Will send pics!


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post #13 of 18 Old 07-24-2021, 03:22 AM
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Secondary ignition voltage is a very misunderstood thing. Compare a stock HEI coil to a performance one. The peak voltage in the stock one is 32KV IIRC. Some of the newer coils produce over 60KV. Electricity is lazy and when a spark plug fires there is a lot of things that make it resist firing and cylinder pressure is a big one.. The coil will provide just enough KV to make it happen.

If you hooked a stock coil to an old Sun Oscilloscope and ran the engine at idle you would probably see 10 to 12KV to fire a plug. If you swapped the coil to the hotter one you would still expect to see about the same result. As the engine speeds up or is accelerated more air fills the cylinders and increases the cylinder pressure which requires more KV to fire. This would be evident on the scope. The KV lines spike or get taller showing the increased voltage as you hit the throttle. If you were to have lower compression in one cylinder, that cylinder would show a lower KV line.

In a nutshell, upgrading a coil does not mean that you ever use more voltage or supply more voltage than you did before. It is only going to use what it needs. I am not saying that coil upgrades are useless or bad either and many vehicles do benefit from them. Especially at higher RPM's or when boosted.
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If you cannot fix it with a hammer then it has to be an electrical problem.
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post #14 of 18 Old 07-24-2021, 10:41 AM
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I'd bet at least half the members of this forum have no idea what an O-scope is.....

Not this thread, but the forum in general (for clarification)

Quote:
Originally Posted by George Orwell
We sleep safe in our beds because rough men stand ready in the night to visit violence on those who would do us harm.
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post #15 of 18 Old 07-24-2021, 12:00 PM
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We control the vertical. We control the horizontal...
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