Spark Plug Questions

[Gary Lewis]

I have and fired it up, but haven’t had a chance to drive it yet. We may take it for a spin this weekend.

[Rusty_S85]

Gary Lewis wrote

You'll see a parallel post entitled Exhaust Noise Questions, which was caused by noise in the headers I've recently noticed.  And that prompted me to pull the plugs today in an effort to rule out a fouled plug or an overly-rich mix.  But as you'll see, the plugs say the mix is not rich.

I'll show two pics of the plugs below, but my question is what to go back with.  These are NGK UR5's, but I recently bought UR4's to replace these, and I just discovered that these are one notch hotter than the 5's.  So I'm thinking that I don't want to go hotter give the state of these plugs - would you agree? 

The plugs on the left have been turned to show the color, which isn't all that much.  And on the right the color is turned away from the camera.  But the white is about as white as the new plugs I bought.

Comments, please!

Late reply just saw this, but what I am seeing is the plugs you have in now are too hot and you need a colder plug not a hotter plug.

You have nice colorization on the electrode strap indicating you have good heat, but the clean white porcelain is showing your plug is running too hot and is burning everything off preventing a nice fuel ring around the base of the porcelain.

The black specs on cylinder number one is a sign of detonation, carbon is being blown off the piston and is sticking to the porcelain.   Cylinder three has some slight speckling on the porcelain indicating it has some detonation as well.

Another thing is your timing mark on the electrode strap is not too bad, depending on the source they want that timing mark on the electrode strap to be from between the ninety-degree curve and the fire ring where it is welded at.  Some like cylinder seven I feel is a bit too close to the weld while cylinder eight I feel is about ideal close to the ninety-degree curve.

I wouldn't mess with the timing however, I would try running one plug colder temp wise try and get some color into the porcelain, that should knock down on your slight detonation issue, it also has a very good chance at moving your timing mark on the electrode strap closer to the ninety-degree curve.

[Gary Lewis]

Thanks.  I did go one notch colder on the plugs and we took a ~200 mile trip today with no problems.  I'll pull the #1 plug one of these days and post a closeup of it beside the previous #1 plug.

As for detonation, I think I can tell a little bit of difference.  Before it rattled a bit when I got it below 1000 RPM, but today it didn't seem to do that.  However that is quite subjective so I'll drive it more and see if that observation holds.

[Rusty_S85]

Gary Lewis wrote

Thanks.  I did go one notch colder on the plugs and we took a ~200 mile trip today with no problems.  I'll pull the #1 plug one of these days and post a closeup of it beside the previous #1 plug.

As for detonation, I think I can tell a little bit of difference.  Before it rattled a bit when I got it below 1000 RPM, but today it didn't seem to do that.  However that is quite subjective so I'll drive it more and see if that observation holds.

You should be good on the detonation, when you pull the plugs out now you should have a tan color porcelain which means you are not too hot and not too cold.

I suspect what was happening is your electrode was getting hot enough on some cylinders to cause a slight detonation.

You didnt have what appeared to be silver pyramids so you weren't knocking metal off your pistons, you were detonating just enough to rattle some carbon loose.

Heres an old diagram I got about timing indicator mark on the electrode strap.


Its one of those things that I am kind of dreading to do for my build, considering the proper way to do a plug read is to do a hard full throttle pass then kill the ignition system then pull the plugs.  No way for me to do that unless I do it on the side of the road away from home.

[ArdWrknTrk]

Plug chops are a pain now that we have knock sensors and AFR meters..

God I used to loathe the time spent for hundredths, and costly teardowns when you missed, or the weather bit you in the butt.

Top fuel guys have the almost unlimited budget to be on the ragged edge.
I'd rather be safe than sorry.

[Rusty_S85]

ArdWrknTrk wrote

Plug chops are a pain now that we have knock sensors and AFR meters..

God I used to loathe the time spent for hundredths, and costly teardowns when you missed, or the weather bit you in the butt.

Top fuel guys have the almost unlimited budget to be on the ragged edge.
I'd rather be safe than sorry.

Yep they are a pain, for me I will have to do it cause my engine is all new and nothing from the factory so I have to figure out what plugs mine need.  My starting point is what AFR recommended for my heads and they state they are a pretty commonly used plug with my head so I should be fine.  I still want to do a chop to make sure everything is good.

I dont have knock sensors nor computer controlled timing but I do have an aftermarket EFI system to take over my fuel so I am not too concerned about AFR, I am more concerned about my plug heat range and my ignition advance as well as if I am detonating or not since my timing is going to be a bit on the edge of what all sources state I should be running for fast burn cylinder heads.

[ArdWrknTrk]

Aluminum heads really change things.
They can sink so much heat you may find you need to go two steps hotter than with CI and the same build, but I suppose you'll find out.

Always good to start with manufacturers recommendations!  

[Rusty_S85]

ArdWrknTrk wrote

Aluminum heads really change things.
They can sink so much heat you may find you need to go two steps hotter than with CI and the same build, but I suppose you'll find out.

Always good to start with manufacturers recommendations!  

Yes, aluminum really pulls heat away, plug AFR recommended as a starting point was Autolite 3924 copper plugs.  From the Autolite tech sheets I found online there is no clear-cut way to rank Autolite plugs to compare them, but my plug is the 392 family, it is a resistor plug and it is a 4 on the heat range.  This family consists of plugs 3922, 3923, 3924, and 3926, so my 3924 plugs are on the hot side of the family range and even summit states for mild small block aluminum head builds the 3924 would be used in many of these applications.  I just need to make sure because in my case once I move 90% of my driving will be at 65 - 75 mph on the highway for hours on end turning between 2,400 and 3,000 rpm.  So, I might need to go with a 3926 if the aluminum heads, 7 bladed flex fan, and aluminum 2 core radiator draws too much heat out of the plug.  On the flip side it might be too hot and I need to go down to a 3923 plug.

One thing I found interesting is the 3924 plug translates to a RC12YC champion or a FR5 NGK plug.  What caught my eye was the 12Y for champion, my old Fairlane took 14Y Champions when new which sadly is no longer produced since I wanted to keep with champions.  Just like these 3924 plugs I tried to find a Motorcraft cross over I prefer Motorcraft plugs over autolites but there is no cross over.

Yes, it is good to start with what the manufacturer suggests, they built whatever you are using, and they know a good starting point if not what to use regardless.

[ArdWrknTrk]

I've had problems out of the box with Autolite.
Ceramic not crimped into body, cracked insulators, twisted ground or flat against the center conductor.
And I can never seem to get 8 that are correctly gapped.

I've been using NGK V-power since the mid '70's in dirt, and then street bikes.
Now the bikes take crazy $25 plugs but I keep using V-power in my truck.
I use UR4, and am surprised that Gary needed to go colder with his far more efficient F3TE heads.

Some people don't understand how they change the heat.range....
The ceramic cone in the plug goes deeper, making for a longer path to the head, where the heat is pulled away.
Therefore the tip stays hotter.
Like you said, if you read the carbon ring you can tell where it stays hot enough to burn away.

[Gary Lewis]

Rusty - Your plug diagram matches what I've read, and both say the timing is about right - for part throttle usage.  I've not done any full throttle runs in a long time, and certainly haven't stopped on the side of the road to read the plugs.

And I agree that the UR5's may have been causing pinging or detonation at low RPM.  I have a corner in the neighborhood that is fairly tight and the engine would rattle if I took it in 3rd and gave it any throttle at all.  That was down just below 1000 RPM.  But yesterday I tried it after we'd been on the highway for 90 minutes and it didn't rattle.

Maybe tomorrow I can pull #1 and see what it looks like.

[Gary Lewis]

Here are pics of the new UR6, on the left, and the old UR5 for #1 cylinder.  Just about 200 miles on the UR6, and all of it running 10% ethanol.

[Rusty_S85]

ArdWrknTrk wrote

I've had problems out of the box with Autolite.
Ceramic not crimped into body, cracked insulators, twisted ground or flat against the center conductor.
And I can never seem to get 8 that are correctly gapped.

I've been using NGK V-power since the mid '70's in dirt, and then street bikes.
Now the bikes take crazy $25 plugs but I keep using V-power in my truck.
I use UR4, and am surprised that Gary needed to go colder with his far more efficient F3TE heads.

Some people don't understand how they change the heat.range....
The ceramic cone in the plug goes deeper, making for a longer path to the head, where the heat is pulled away.
Therefore the tip stays hotter.
Like you said, if you read the carbon ring you can tell where it stays hot enough to burn away.

Ive heard horror stories about Autolites but I have used them before, they just arent my prefered plug.  I do have a NGK DSII Coil for my truck but I never been a huge fan of NGK for plugs, I do like their O2 sensors how ever.

I know some plugs are hard to read the carbon ring, I found out that if you are careful a band saw at the threads can remove the threaded portion and separate it from the porcelain so you can see the band, this is something youd do more with a hot plug that has the porcelain a lot further down and out of view which mine would have.

Correct, people dont fully understand that a hot plug has less porcelain in contact with the metal body so it doesnt dissipate heat as easily and a cold plug has more contact to dissipate heat more easily

If I change my plugs to another brand when I will most likely destroy this to chop the threaded portion off to inspect the porcelain I dont know what brand I will go with but I will probably stick with copper plugs however as they seem to be highly recommended for daily street use.

[Rusty_S85]

Gary Lewis wrote

Here are pics of the new UR6, on the left, and the old UR5 for #1 cylinder.  Just about 200 miles on the UR6, and all of it running 10% ethanol.

The bluing by the weld, Id keep an eye on that, if I am remembering right thats a sign of too much timing that is causing the ground strap to get hot enough to anneal the metal creating a blue line on the strap at this point..  You are still good as the bluing is above the weld still, but you are at about the limit you can advance your timing before the bluing will disappear from the strap and the ground strap is super heated and has a good chance of causing detonation.

[Gary Lewis]

The timing is the same as with the hotter plugs, and it is controlled by the computer so I won't be adding any.  But I'm wondering if it is just too early to really read the plugs.  The hotter plugs had some color to them, but this one looks brand new.

I'm hoping to drive the truck more soon, but there aren't any longer trips in the near future.  Maybe this fall/winter we will take it to Arkansas and do some of the forest service roads.  So it'll be quite a while before I get enough miles on it to make much difference.

But I've not done any WOT runs with these plugs.  How long does any color added then stay on the insulators?  There were quite a few WOT runs done with the hotter plugs, so maybe that's where the color came from?

[ArdWrknTrk]

You want to read a fresh plug.
Not one that's had time to eat oil or wear at all.

WOT is only because if you're racing that's where you hope to be all the time.

In that case idle doesn't matter, and for many types of racing you're only concerned that you'll run lean on top and hole a piston or seize.
Throttle response matters in road racing, but you are never pulling hard enough for the computer or injectors to be overwhelmed.

[Gary Lewis]

I'm only asking 'cause I'm trying to figure out where the little bit of color came from on the UR5, therefore hotter, plugs.

The AFR sits at about 14.9:1 when crusing, gets down to 13:1 on a steep hill when the cruise tries to make up speed, and maybe as low as 11:1 at WOT.  The UR5's had some WOT runs on them several thousand miles ago, but since then it has all been cruising and maybe dipping to 13:1 every once in a while.  But they have a bit of color.

The colder UR6's have the same cruising and maybe dipping to 13:1, but only for ~200 miles, and no WOT runs.  And at least the #1 plug has no color - and the hotter #1 did.

So did the color on the hotter plugs come from the WOT runs several thousand miles ago?  Or is it just too early to see color on the colder plugs?  

This isn't a big deal, I'm just curious - tan, not yellow.