Hey all, I pulled my plugs and checked them after running them for about 4 months, just curious if im using the right plugs with the right heat range. I'm using NGK iridium IX part num: UR4IX. With a gap of 0.460. Have a little bit of shudder on idle but I don't think it's related to the plugs. Picture included!
Engine mods and whatnot here:
305 tpi
Hedman mid length lengths
Hawks mototsports ram air boxes installed
gutted air boxes
8mm denso plug wires
Accel hei super coil

Don't know if any of this would affect the heat range but and help is good help!

 

Think you should be fine with stock heat range NGK 4. The old rule of thumb is every 100hp over stock 1 colder but it's a general guide and not a sure thing. My modded C4 is still using the stock heat range and i did try 1 colder. Heat range is effected by increased compression, power adders and sometimes aftermarket ignitions like MSD CD boxes(read instructions). Your accel supercoil is hotter but not exactly multi-spark CD hot(you don't have a upgraded HEI control module either). Still the common problem with the accel super coils, is not having a good ground. The MSD HEI's have a dedicated ground wire from the dist body.

I just bought an 83 TA with vortec heads on a 355, the parts add up to 10+ comp and they had the stock 305 plugs in it. Deff too hot! and incorrect reach! Need to edit that vid LOL

Had a pretty low comp combo making near 400hp and i needed the hottest plug even on 87 octane. So sometimes it wants what it wants but again i think your combo is fine stock heat range.

All that said, do you know if it has a clean fuel filter or good fuel psi??? Looks kinda Lean. MAF TPI if your profile info is correct. So i wouldn't be like super "needs tuned" concerned with those mods. Not that it wouldn't help. Think I rem the stock regulators being sketchy/issues, so I'd check the PSI. Still these cars are getting old, could be dirty/clogged injectors, do all the plugs look like that? Have the stock cat? Any codes? Got a better pic of the plug? Check for intake vac leaks? Check the timing?

 

no cat, no codes. Previous owner removed the codes for the downstream 02 sensor, egr valve and cold start injector. He already got to the cat before i could lol, i did recently replace the fuel filter but i have not checked fuel pressure...
is there a way to check for a faulty or leaky injector without pulling them? And how to check for intake vac leaks? Not sure about the timing. Not exactly something I think I'm ready to mingle with yet lol.

 

Heat range of the spark plug has nothing to do with performance for the most part at least, it has to do with the self cleaning effect of the plug so that It doesn’t foul out, the reason you would want to go colder is for safety/ to prevent pre ignition and detonation, you see a hotter plug sticks out more into the chamber and absorbs more heat, so if a given engine was designed with x temp plug and you add more compression or boost etc etc.. if that plug gets too hot and glows well you get the picture.
So the hottest plug you can run without causing pre ignition is best to keep the plugs clean.
Use the grounding electrode to check if your timing is correct.

 

Last night it popped in my head that i had issues looking up the right plug for my 86 C4. Not heat range but because of it being a half year of short reach plugs iron heads and long reach plugs alum heads. So made me think maybe actually you may have the wrong plug. Occurred to me that they may use diff plugs CARB, TBI & TPI I know the 83TA 305 Carb is NGK 4 heat range but the 86 TPI 350 alum head was NGK 5 heat range.

and according to this post they do https://www.thirdgen.org/forums/tech...park-plug.html

Also Summit shows diff plugs for the engine VIN code BUT Summit shows both those plugs for my 86 C4 or an 87 C4(all alum heads long reach plugs) sooo......
https://austinthirdgen.org/thirdgen-vin-decoder/#8586
https://www.summitracing.com/parts/n...maro/year/1986
https://www.summitracing.com/parts/n...-size/5-0l-305

Short answer yes/maybe you prob are 1 too hot and need a UR5 maybe??? They don't like to make it easy LOL and one site says it's right, another will say it's wrong. Don't suppose you have your factory manual???

 

sadly I do not have my factory manual, but I will see uf running ur5 is better

 

No it's cool, can't trust forums, parts stores or other sites to be accurate always. How i looked up my C4 plugs when the C4 forums was just a jumbled mess of this or that plug. I used the manual that came with it(where ever it is now???) And even now when i go to look at my notes(gotta keep car notes when you have multiple projects), then check my C4 plug AGAIN online and what the forum/sites say, is still confusing AF! My notes said NGK 4 is what i have in the car atm thought it was 5 but if you cross ref some Acdelco plugs on some sites you get 5 or 4 heat range for the alum head long reach plugs.

Even worse after i looked up your plug on the NGK cross reference(1st pic your plug). My C4 plug is weird!!!(2nd pic) So now I don't trust the NGK cross reference chart 100% either LOL

 

And just for anyone reading this, to be clear there are 3 types of plugs for SBC, so make sure you got the correct plug! The 83 TA i bought has short tapered and needs long for it's 96+ Vortec heads

-Short reach tapered .460 NGK UR
-Long reach tapered .708 NGK TR
-Long reach Gasketed .750 NGK FR

Had to bring that up since I also brought up C4 plugs and don't want to confuse anyone. Annoys me that NGK cross reference chart shows heat range 4 for three diff heat range AcDelco

 

hmmm, not sure what type I need exactly, if it helps i have stock heads on? Original engine too.

 

Stock heads i think are short tapered for the LB9 but you could always pull a valve cover, to check the casting number, to be 100% what heads you have. Still if it looks factory, it's prob stock heads. My 3 plug reach/type post, was more for who ever digs up this thread, later and sees me talk/post a pic of C4 plugs cause those are long reach gasketed.

Sorry to be confusing LOL

 

you're good man, guess I'm down to testing ur5 plugs lol. Dunno if a lean condition could be because I only have my upstream 02 sensor. The downstream is completely removed from the computer and car. Previous owner stuff I'm dealing with right now

 

The NGK UR4 goes in stock cast iron head F-body TPI engines and the NGK UR5 goes in stock cast iron head F-body TBI engines. I'm wrong.

NGK heat ranges are backwards for other sparkplugs companies.

Run the NGK UR5 spark plug with the 0.035 gap it calls for.

Your car nor any other V8 3rd gen F-body came with a downstream O2 sensor. They came with 1 unheated narrowband 1 wire O2 sensor in the driver side cast iron manifold.

 

According to the Engine VIN code letter on Summit Racing(links from my earlier post)
https://www.summitracing.com/parts/n...maro/year/1986
https://www.summitracing.com/parts/n...-size/5-0l-305

https://austinthirdgen.org/thirdgen-vin-decoder/#8586

 

ohhh very helpful, thank you man. I will try running UR5s lol, any chance it might fix my rough idle?
if it doesn't then checking my fuel pressure is next

 

It's possible but it could be a lot of things, vac leak, bad ground, something loose. But that's the fun of cars LOL Add testing the voltage to your list. Simple cheap test Vacuum gauge, can help point you in the right direction sometimes.

 

yessir, this car is alot of fun, fixed too much in 2 years. Somehow is still running and is my daily.

 

Well Hell maybe it got it backwards. I'm always thinking the of 87+ F-body by default because it's all my friends and I own these days.

If it's that way for the 87+ cars then I put the wrong plugs in a lot of them and about to put the UR5s in my 92 TBI tomorrow.

Looking at NGK's application guide I put the wrong ones in some of them. Some of the years call for a UR4 and some a UR5 for the same engine.

My 1992 TBI calls for the UR4s but I'm putting in the damn UR5s I already got.

 

I was wrong and you are right. Sorry my bad.

Thanks for pointing this out to me.

 

would you happen to know what the ngk ur5 equivalent is to an ac delco plug?

 

Don't ask me, I'm the idiot that has been proven wrong. LoL

Back when I bought all my NOS GM distributors and Delco-Remy distributor caps and a bunch of other stuff I bought all the NGK UR4 and UR5 sparkplugs that U-Haul had. Like 25,000 of them. I'm glad now my ad used the application guide and I told people to verify on their own which plug they needed. LoL

 

Looking at that picture of the plug, the heat range is fine. You can very easily see the color transition halfway down the ground strap which is perfect.

Technically, you want the coldest plug possible that doesn't foul up. Too cold a plug will cause deposits to build up since it doesn't get hot enough to burn them off. Too hot of a plug and things start melting. If the engine is stock, then the stock heat range is fine. If the engine has been modified then you may have to try different heat ranges to find the best range.

 

the engine is stock all internally, all ive done to the engine is an intake, headers, and an accel hei super coil. I do have a rough idle, dunno if the plugs are fouling out because of the heat range apperently being slightly off lol

 

So I don’t want get into a pissing match and I definitely don’t want to knock your knowledge, I try to live by always a student, so 34 years in the business and from every that I was taught I disagree with this statement but please feel free to correct me.

So the ground strap is used to determine ignition timing, for example you could have an extremely cold plug that fouls after a few runs but has perfect timing indications on your plugs. Temperature of plugs only controls the self cleaning effect.
Also from everything that I was taught the oe’s use the hottest plug possible, this is for maintenance purposes.
But I do agree you should run the coldest plug you can that doesn’t foul out quickly.

Again if I’m wrong please enlighten me, I’m always open to lean something new.

Thank you
George

 

No matter the heat range, within reason, with a set of new plugs that properly fit in his heads it will idle like a kitten all day long in a properly running engine.

Dude you got some problems that ain't the difference in heat range between a NGK UR4 and a NGK UR5.

 

I am sadly aware, just anything to make her run slightly better yknow. Probably gotta get new everything on that motor lol

 

I agree it’s not your plugs unless you have a broken one or two, I’ve seen people drop the plug while installing and crack the porcelain causing misfires.
To check the injectors you will need a multimeter, you will need to ohm test each injector you will also need a fuel pressure gauge to make sure they are holding a prime.
As for your plugs to me they look like the temp is too cold and your ignition my be a little low so I would get the correct plugs and also check ignition timing, this requires a timing light.
One invaluable tool with these cars is an ALDL connector with TunerPro software and logging all the vitals

 

what is an ALDL connector?

 

Assembly Line Diagnostic Link

It where the GM dealership service technician would connect their GM Tech 1/1a dealer level scan tool too to diagnose problems with your car at. It's also one of the places workers on the assembly line would connect to to test things as the car was being built on the assembly line.

I just noticed something. You live in Kentucky. Where at do you live in Kentucky if it's not some big secret? Or if it is a secret how far away from me do you live?

 

The aldl cable in an interface between your car and a laptop, most people that aren’t part of the third gen community think that all you can pull out of these old gm ecu is codes but in fact for years now we’ve been able to pull live data just like an obd11 car, it really help when you can watch the live stream for diagnostics.
You will need the aldl, software like TunerPro RT and the ADX file from the site to be able to connect.

 

so you are talking about the obd port? I live in georgetown so you are about 2 hours out from me. Not gonna decline an offer if you wanted to come down and run some tests on ignition timing/aldl live feed lol.

 

FYI, just checked injectors this morning, all reading 16 ohms or a little above so they should be alright in that area, still dunno if they are leaky or dirty. Gotta get a pressure tester for the fuel rail lol

 

Yeah the ALDL port is what people call the OBD I port.

Yeah two hours each way is a little bit more than I had in mind. Was worth a shot because you might have been in my backyard or in a neighboring county.

 

ah well, I will definitely look into using the software you mentioned though for live feed

 

Yeah I was going to respectfully suggest something similar
The ground strap in this case is useless, it does not give much information. The mark on the strap is an indicator for ignition timing but only when the plug is new and been used for a single run at a time.

The heat range is indicated by the color change of the threads bottom up. I like to see a few threads turning gold.

From NGK.com.au


I've been reading used plugs for over 25 years.
The picture of a single plug is very little to go on but here is what I see
1. There is some oil fouling on the threads, appearance of dark sticky color from burning oil in the threads. It is quite common to have some oil on spark plug threads and entirely acceptable but I do not like to see it turning dark burning color - this is telling me plug is a bit too hot I think. At least it is a single diagnostic marker of possibility.
2. The carbon ring looks 'chewed and browned' to me. This is another indication of a too-hot-plug, look at the top picture from NGK. Then look at the dark carbon ring on the hot plug vs the good condition plug, with its lighter ring unbroken and unchewed appearance.

Here is example of ideal plug NGK with 30k miles , notice dark black carbon ring unbroken and clean and flat



very slightly browning to grey (prefer light gray on one side of the white) on the porcelain is ideal
The strap can only really tell us if its being melted or pelted by globs of aluminum or whatever when its been used many miles, marking on the strap loses meaning after a couple runs, the marks begin to average and overlap

IMO the plug presented has some issue. It seems too hot to me. And either its got really poor air filtering or some issue with the fuel or heat to have that kind of brown cruddy appearance I think.
In my LS swap turbo app I use NGK Iridium 8 for about 80k miles
In 2L and 3L turbo apps I usually use the same plug but 7 heat range, those engines are a little better about heat management in the chambers and pistons
In an N/A app for LS or SBC something around 6 I would think is a reasonable performance threshold

 

So admittedly I did not zoom into the picture to look very closely at his plug and now realize (but picture is a little blurry) I see some peppering on the insulator, so we have signs of detention. I disagree on the temperature though I still think it’s cold for this motor but I’m also assuming a lot of things, so most sbc with mileage burn oil so to me that would explain the oil and my thinking is that if in fact it burns some oil in the combustion chamber then I would expect the oil on the plug to look more cooked, I would also expect to see the thread discolored.

 

The problem in the picture is you cannot see the gold thread color, how many threads up it is. Five? Seven? The oil burning makes it impossible from that angle. So there is no way to tell from the threads if the heat range is correct. All we have to go on is the appearance of detonation and oil burning - both of which indicate too hot of a plug. So the scoreboard is too hot: 2 evidence wise, and too cold: 0, it isn't carbon fouled, there is no sign of ash deposits unburnt, only oil being burnt

Oil is normal but they should be slightly oily with a golden clean oil sheen, not burnt dark black oil in just a couple weeks of driving. Burnt oil on threads after a couple weeks is not typical and diagnostically relevant as hell given the other plug appearance issues

 

of course dark oil is strange after a few weeks of driving with new plugs, but I've had these in for atleast 4 months. Do note that I do have a motor with 220,000 miles and has been rebuilt once by the previous owner. On top of that I have oil leaks absolutely everywhere.

 

Good point, you have changed my mind, Kingtal0n for the win!

 

your OP stated
So its actually 4 months? Burning oil on plugs and lots of oil leaks in 4 months is fine. But if you want to know heat range you need to carefully identify the golden discoloration on the threads, count how many threads. I Like to see 3 threads of gold on a performance engine, not 5+

Random image searching should lead you to this kind of observation

here is another



Oil raises compression ratio, leads to detonation
Too hot plug (too many gold coloration threads) leads to detonation
Too much timing advance at wide open throttle with too lean of a mixture causes detonation

 

I did indeed say a month, i didn't check when i ordered and installed them i should edit that now that i see it.

 

Well a 'month' could be 200 miles or 2000 miles. So it doesn't really matter, it isn't actually useful information. I just assumed 1 month was maybe 500 to 2000 miles, so its a bit early for so much oil burning on the threads I think/thought

If you want to state in terms of miles on the plugs, and at what air fuel ratio, this would be more useful information. But they look so rough it doesn't really matter either; It needs new plugs, cleaning (remove as much oil as possible) and to fix whatever is causing them to appear that way (heat range, oil burning, etc...) at some point the issue may be more mechanical, sealing (rings, valve seals, etc...) showing up on the plugs than actual tuning or heat range related, causing problems

 

my fix is just getting an entirely new motor, previous owner didn't really tell me what happened to cause the motor to have to be rebuilt. There is a crack on the wall of it too that he was aware of too. Im not trying to save my motor in any way, just trying to make it run a little longer (thankfully these things are decently reliable) until I can get a new motor.
It wouldn't surprise me at all if I tore it down and everything was worn. I expect it to be.

 

Hate to put thoughts in your head but if you get a chance look into an LM7/4l60e swap from a crashed truck with 100k miles

 

No no man don't worry about it, im constantly aware of those thoughts and not much i can do, just gotta take it as it comes yknow. On that note, would it be a direct hookup to my car? Different harness/computer?

 

Its something you would research for six months
Plan every part and purchase, produce a list of the current cost to buy everything you need all at once

You can diy the entire thing, if you can wire, weld, tune, etc...
As you begin to outsource these things, the reliability coefficient begins to decrease unfortunately. Not only because aftermarket, exogenous and ulterior implications, also because for each thing you do not diy you will not understand where wires go or why behaviors are and have that deep connection for diagnostics that speedy recovery as you move from one aspect to the next, for example say the fuel pump starts acting funny, you should know exactly which wires and where, how the relay is pulled closed, what amperage the pump pulls at max load, what is the voltage of the pump at max load as measured directly on the wires near the pump, why you selected the diameter wire that you did, even the temperature of the wires is important. If you just buy a harness and plug it in and have some issue you won't know where to even start looking. You won't be able to say 'hmm I remember when I was wiring the pump one of the wires felt funny in the connector, maybe it came loose' etc...

If you have all the parts and a plan the actual swap can be done in a matter of days to weeks, since it is a basic straightforward goal as first timer diy novice, just don't get fancy with parts, keep all the factory stuff, unlock the computer and get used to HPtuners, start learning how the transmission works, read the service manual for the 4l60e and look at some trans-go upgrades for it. You don't need to buy many or much if any for a reliable daily stockish swap but it helps to understand the common failure points and how to avoid them.