Plug reading

• Jun 9, 2025

• #1

Aron Gleason

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So yesterday I took the car out for a cruise, car was running really good. Got home pulled a plug and the tip of the porcelain is white and the rest is black. On another note, when I go to stab the throttle it responds without hesitation.

 

• Jun 29, 2025

• #2

Aron Gleason

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Here's the latest as of earlier today. Took the car out and it was running good. Afrs were anywhere from 12.9 to 14.5 depending on throttle position at normal cruise. When id stab the throttle it would go up to 16.2 for a split second before recovering.

 

• Jun 30, 2025

• #3

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Geoff 2

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The top pic looks like it could have bits of piston on the plug...

 

• Jul 10, 2025

• #4

Aron Gleason

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Update on my plug reading. Looking much better

 

• Jul 11, 2025

• #5

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Geoff 2

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Agree. What has changed? Richer mixture?

 

• Jul 11, 2025

• #6

Canadian1968

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Careful of that lean spike at WOT. Bad things happen when

You said it recovers quickly. But that still means there is a lack of fuel right off the hit. Make sure your accel. Pump is adjusted correctly. You may even need to look into a different pump cam.

The AF meter is a great tool to have .

 

• Jul 11, 2025

• #7

Aron Gleason

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Canadian1968 said:

Careful of that lean spike at WOT. Bad things happen when

You said it recovers quickly. But that still means there is a lack of fuel right off the hit. Make sure your accel. Pump is adjusted correctly. You may even need to look into a different pump cam.

The AF meter is a great tool to have .

Click to expand...

I have a afr gauge. And yes i might need to change pump cam.

 

• Jul 11, 2025

• #8

Aron Gleason

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Geoff 2 said:

Agree. What has changed? Richer mixture?

Click to expand...

I haven't changed anything.

 

• Jul 11, 2025

• #9

Canadian1968

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Aron Gleason said:

I have a afr gauge. And yes i might need to change pump cam.

Click to expand...

Yea , I was just trying to say how handy it is that you do have one !

You don't give to much info on the motor or setup. Is this a new build and carb ? If so you probably just need to go threw the carb and tune correctly. The pump cam alone may not be enough. You may need a bigger pump nozzle as well. Is it mechanical or vacuum secondaries ?

 

• Jul 11, 2025

• #10

Aron Gleason

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Canadian1968 said:

Yea , I was just trying to say how handy it is that you do have one !

You don't give to much info on the motor or setup. Is this a new build and carb ? If so you probably just need to go threw the carb and tune correctly. The pump cam alone may not be enough. You may need a bigger pump nozzle as well. Is it mechanical or vacuum secondaries ?

Click to expand...

The motor has been together for about 32 years. Had a 284 484 purple shaft cam all the way up until this years when I replaced it with a Delta cams 292 495 lift cam. The carburetor is a 950 double pump mechanical secondary carb. Msd mechanical advance distributor. M1 single plane intake, 10.5 compression according to the guy who built it for me.