The middle picture has plugs I just pulled out this morning. You can see I'm still a touch rich at cruise with just a quick look. The porcelain should be a dull white.

The bottom picture are a couple of plugs I pulled and cut apart last summer. You can see tha shading on the upper part of the porcelain so I was still a touch rich, but if I went much leaner at a cruise I had a tip in issue. So you have to compromise sometimes.

In the bottom picture, you can see the fuel ring is better than .125 wide and has what I call a fade to it. IOW, as you move away from the shell, the fuel ring isn't well defined and fades into the middle of the porcelain.

The fuel ring is WOT. Depending on what you are doing, you can get as tight as a .060 wide ring with race fuel or alcohol. You need to be .100-.110 wide on pump gas. And no fade. The fuel ring should be sharp and clean with no fade.

This is an iron head, 11.01:1 pump gas 340. I have a Racer Brown solid flat tappet cam that is 281/281 255/255 .620/.620 on a 105 LSA in at 105. The intake manifold is a fully ported Holley Strip Dominator (I did the plenum back to square by welding it up and did a little welding in a couple of other places...wish I had done more welding) with a 1.437 Venturi BLP B4X carb.

I run Hooker 5303 headers with custom craft mufflers. I also run a Mallory Unilite with the curve locked out and the total at 36*. I also use a Mallory 685 digital ignition box. The plugs are Champion.

That's all I can think of right at the moment.


THANKS DAVE for posting the pictures for me. Hope this helps.

Exactly, EFI maybe but with duration and overlap my Dart falls on it's face when mashed cruising in that zone.........been there, done that........

No problem. Thanks for explaining plug reading. Im gonna try going back to the .055 t slot from the current .059. The .059 was put in to cover a lean tip in which turned out to be fuel and heat related. The .059 did richen things up a bit. Gonna try the rc9yc champion first just for shits and giggles.

With good fuel you MAY like a .052 and don't put all of your faith in the WB like people are saying, get it right and the numbers are what they are......

Ok. The race gas did richin it up a bit. Ill try the .055 first. Ran good with those and go from there. Thanks Dom.

Plus when I ran leaded gas it liked more timing........

You want to stick with 1 fuel grade till you learn the spread from each fuel on jetting.I did a couple 60' launches in my drive and read my plugs till I move on to the next step of jetting.[add pv]I have #7 plugs in.

What fuel are you using and what plug is that?

NGK-7 with pump 93

ok. looks like the the plug in the pick needs to be next step hotter. color change is near the end of the ground strap. I have some fresh plugs in it now. i will see how these color up.

I wouldn't put much stock on doing what you did in the driveway with the accelerator circuit furnishing a lot of added fuel to the launches
I would go drive it at light part throttle now to see what it is running like on the idle and transition circuits and go from there
I would use a G meter or the sixty foot times at the track to tune the accelerator circuits, not how the spark plug looks

I agree and I want to see what his look like with newer plugs side by side when he does.

Me too

What tool are you guys using to cut the plug, in the above pic the cut is nice and clean.

I did that in my lathe here at the shop.

You can do it with a right angle grinder too. You just need to be careful not to get into the porcelain. At least don't hit it all the way around.


This made me think of a customer I had. He would use a hacksaw at the track when he was picking the fly poop out of the pepper. He made a fixture to hold the plug and just got after it. He could do a plug in no time.

You can do it any way you can think of. It doesn't matter how you do it. Just that you can get the shell off and leave all your fingers on.

Thanks, was wondering if someone made a tool to cut the plugs.

I bought a 10x magnifer glass off of a small dental medical tool, that really helps to look closely at all of the spark plug, especially the ceramic insulator below the spark plug body

I light is fine. But when you are trying to measure the fuel ring it's impossible with the shell on.

I called my customer last night and asked him how he made his jig to hold the plug.

He says someone now makes one that clamps on to the bumper. He did give me an on the cheap way to grab the plug to get the shell off.

He says just use an old spark plug socket and grab it in a vise. Cut through the shell and then grab the plug and turn it one flat and cut some more.

There is no reason not to cut the plug apart.

Havent had much time with the car this week, but did take a cruise out in the country, about 25 miles mostly cruising at 3000rpm with alot of stop and go and a few wot blasts. Still on the 110/93 mix and using champion RC9YC plugs. When they start coloring up i will lean the T slots at that time and see if they clean up at all. Engine ran fantastic with very good street manners whole short trip. Only pulled 3 because they all burn the same except #7 which is on the far left.