How do I read these Spark Plugs?

[Sapper 3]

I pulled my plugs last weekend and this is what I've got. Some look too lean, and one wet (too rich). What could cause this variation? I've gapped all to 42, they were at 54ish. I'm at 14 degrees. I've 4,000 on the car with Taylor 8mm wires. Car runs very well with no hesitation on acceleration.
Thanks for the help.

[skullandbones]

Hi Sapper 3,

Are you using a metric gauge? I think those gaps sound way too high especially "54ish". Most of the plugs I've used are between 0.032 and 0.035 inches. The gaps look wide on the pics but that's just guessing. My Cobra plugs are gapped at 0.032. I'm wondering about the deposits on some plugs and the wet one. Are you getting any oil into your intake from the PCV exhaust. I noticed I was getting a little when I took my intake apart for polishing. I guess it's time for checking the plugs for me too. You say it is running fine. Is it running "Dead Man's Curve Fine" or is it just OK? I too have my EFI setup on 14 degrees which seems to be the sweet spot for it. Also, I'm assuming that the pics are with the plugs grouped as left and right banks so it's not just on one side. What plugs are you running: make and temp/number? WEK.

[Sapper 3]

Gage pic below, I think I'm ok on the gap. I'll do some more reading on the gap, but to date I've read the standard Ford 302 was/is 54 and ones like mine are 42. It wouldn't be the first time I'm wrong, so I'll read some more. No oil from PCV visible. She really does run great without any lag. I do get the occasional back fire when I left off quickly after a hard accel. Yep, I laid out the plugs on the breather in the order on the block separately on the passenger and driver's side. If you hover over the picture I think the Pass / Dr Side pic name will show up. On the Plugs I've Autolite 3924. Details below.

Brand: Autolite
Manufacturer's Part Number:3924
Part Type:Spark Plugs
Product Line:Autolite Copper Core Spark Plugs
Summit Racing Part Number:ATL-3924

UPC:00009100039248
Shorty Spark Plug:No
Resistor:Yes
Manufacturer Heat Range:4
Electrode Core Material:Copper
Electrode Tip Material:Copper
Insulator Type:Projected
Spark Plug Thread Size:14mm
Spark Plug Reach:0.750 in.


Gap Gage.JPG

[skullandbones]

I stand corrected. I have to go back now and see what mine are gapped at. I know some racers will use a tighter gap but all the street performer guys are at 0.044 to 0.045. Sorry for the error. WEK.

Note: Checked the gaps. I'm at 0.052. I must have gotten the memo when I was installing and forgot. BTW why are you changing your gap from 0.054 to 0.044?

[OVCobra]

plug #1 on photo 1 and plug #2 on photo 2 look lean,
plugs #2 & #3 on photo 1 and plugs #1, #3 & #4 look good
plug # #4 on photo 1 has an issue, either fuel or oil fouled (does it smell like gas?)
If fuel fouled, likely a bad plug or plug wire; put in fresh plug and check again. If no change, try changing plug wire. If oil fouled, much more work...does the motor smoke under power or on deceleration?

Plug gap is largely dictated by ignition system; high energy ignition systems (MSD) will fire big gaps, what is your ignition system?

Reading plugs is best done at the drag strip cutting ignition immediately after crossing the traps and coasting to the return lanes; start with fresh plugs. This will provide a very good indication of mixture at full power. Reading plugs during/after city driving should tend to be a little rich due to stop and go etc.

Hope this helps,

Dave

[cobraguy13]

I agree with OVCobra, Check for vacuum leak at the above lean plugs and replace the fouled plug.

[CraigS]

Regarding the black plug read the last two pages of this thread. Ooops maybe I am not allowed to do that. Short version- a guy had a couple of oil fouled plugs. Long, long story is that it now appears that the intake gaskets were not sealing because the intake was bottoming out on the block rather than at the intake ports on the heads. So his intake gaskets were allowing oil to get sucked up out of the valley into the intake ports.

[Desert Cobra]

Check your firing order. The 306 Ford Racing has an HO cam in it that does NOT have the same as a small block Ford firing order. Just a thought.

[Sapper 3]

Thanks all for the recommendations. I've replaced the plug and borrowed a plug wire tester to check the wire. Step 1 is to test the wire and watch the plug over time (I pulled the new plug after about a 20 min run and it was clean). Also I just put new shorty headers on so I'm thinking I'll pull the driver side header to check the gasket is seated properly.... it's only an hour or so of work.

OVCobra - With the black plug out the cylinder smell heavily of gas and the plug was very wet. No black smoke however. I have MSD.

[OVCobra]

Sapper 3
Sure looks like the plug was fuel fouled but overall engine is not running rich. Back to change plug and watch, if stays dry and colours well, you had a bad plug. If not change plug wire and start over.

CraigS makes a good point, two lean looking cylinders could indicate a vacuum leak at the manifold (leaning out just those cylinders)...check it out.

Dave

[Sapper 3]

Thanks all for the recommendations. I've ohms tested all my wires and they ranged from 1.84 to 2.93 resistance (with my meter set at 20K) depending on length, so ok there. I've order new plugs from summit. The local dealer didn't have exactly what I needed (I live in Germany so there's not a lot of Ford parts). But they did have a similar plug with the same heat range. It's 1/2" shorter. I've made 2 short runs and pulled the plug to inspect. There was no sign of fuel, but they were very short runs. She is running much better and there's no fuel smell anymore, but I'm sure the driver's side is still a little rich so I'm hoping it's the shorter plug not burning that cylinder as efficiently as it should. My CAT on this side (driver's side) is glowing a narrow red band so there's still too much fuel. The Passenger side CAT is fine.

I did have a large gap 1/16th inch bulge at it's widest x 2 inches long between the manifold and my breather neck. At some point it was miss aligned and I'd tightened the element cover in such a way as there was a gap at the bottom front passenger side near the cylinders 2 and 3 area. That's about the same location as the two lean plugs so I'm hoping that was the cause. I used cab cleaner to search for other leaks and nothing else was obvious.

Plan now is to replace all plugs when they come in and then monitor the plugs. I'll also keep an eye on the driver's side CAT to see if the new plugs eliminate the red band. If the new plugs don't remove the enriched driver's side CAT I think I'll pull the header to check for a good gasket seal.