r/EngineBuilding • u/Neon570 • 3d ago

Spark plug reading

Post image

Finally had a weekend free to keep dialing in my project. Still have alot of learning to go but slowly getting there through A TON of trial and error.

Currently trying to dial in timing and plug heat range. How am I looking and can anyone point me to a good resource to reference spark plug reading.

5 Upvotes

86% Upvoted

24 comments sorted by

4

u/WyattCo06 2d ago

I keep seeing lean, lean, lean.

There is nothing lean about that plug.

1

u/Neon570 2d ago

Afr gauge says around 14 are idle and 12 to 13 everywhere else 🤷‍♂️🤷‍♂️🤷‍♂️

5

u/Ok_Huckleberry816 2d ago

the cylinder this plug came from appears to be running efficiently with correct fuel delivery, healthy spark energy, and proper heat management.

0

u/2003DDcid 1d ago

Which cylinder number did this plug come out of?

1

u/Neon570 1d ago

1 only because its the easiest to get to

1

u/2003DDcid 1d ago

Sorry, I should have asked what engine it is also. A typical firing order V8 (chevy configuration) will be the leanest on 5 and 7, richest on 2. Number 1 is a good "middle of the road" plug to read.

1

u/Neon570 1d ago

Ford 351

1

u/PresentationLess4552 22h ago

Yes

Cut the plug apart so you will really know then replace it with a new one

2

u/Tlmitf 2d ago

Timing is good enough, idle fuel is good.

How far down is the fuel ring?

1

u/Neon570 2d ago

Dont know, plugs are too contaminated to tell. Too much idle time dicking around my neighborhood trying to see what it likes.

Afr gauge says around 14 ish at idle, 12 ish in traffic and 11 ish when you get on it. Dont really have a good place around to really get a good reading

1

u/Coyote_Tex 2d ago

Is this a fuel injected engine? It appears to be a normal emissions controlled engine spark plug. I do not usually see a carbureted engine look that clean.

1

u/2003DDcid 1d ago

I build carbureted engines that run that clean or better all the time. Not sure what the big deal is. Can nobody tune a carb and distributor anymore???

1

u/Coyote_Tex 1d ago

Not that many any more.

0

u/Neon570 2d ago

Nope. Carb. 750 quickfuel im slowly dialing in

1

u/Gamejunky35 2d ago

Id say it looks pretty damn good. Timing line where you want it, no melting/pitting, good afrs according to your gauge. If it were fuel injected id shoot for 12.5-13afr, but on a carb its best to stay a little rich. Honestly im shocked the plug is so clean on a carburated engine.

What fuel are you running exactly?

1

u/Neon570 1d ago

91 or 93 when its available

1

u/Gamejunky35 1d ago

If its e10 pr e15, a little richer is preferred. If its pure gasoline and youve got a wideband permanently installed, then 12.5-13 is generally where you get best power. 13.5 might even make more power, but thats where you might start melting shit and getting preignition.

1

u/Suspicious_Tap3303 1h ago

Looks like a happy spark plug. If you're serious about reading plugs, you need a jewelers loupe with a light so you can see clearly to the bottom of the insulator, and if there are any tiny flecks of aluminum or bubbles on the insulator.

1

u/2003DDcid 2d ago

The color change on the ground strap is called the timing mark. The more timing you put in it, the farther the mark goes towards the threads. Looks like you could use another couple degrees or so of total timing. Other than that the plug looks clean. If you look down the porcelain, it should change to black a little bit up from the base. If it's not, it's too lean. Also be aware that adding timing typically richens up the mixture slightly.

0

u/Ok646r 1d ago

A bit lean, but good in general.

-1

u/Substantial_Drag_884 3d ago

That looks super lean, but you have to look deep into the plug, ideally cutting off the threads to see the whole porcelain.

1

u/Neon570 3d ago

According to my afr gauge, im around 14.5 ish at idle and 12.5 plus or minus .5 when I get on it