Please help read plugs, 7 good and 1 black?

[garry viohl]

428 fe with autolite plugs and 7 are tan in color, while 1 is black. What is happening? Its #2 plug (pass side, 2nd back from front)

800 cfm holley double pumper
74 jet main
85 jet secondary

[patrickt]

Originally Posted by garry viohl

428 fe with autolite plugs and 7 are tan in color, while 1 is black. What is happening? Its #2 plug (pass side, 2nd back from front)

Clean it, gap it, put it back in and exchange the plug wire with one of similar length, and make a note to yourself which one you switched it with (uhh, when I say "switch it" I mean at both the spark plug and distributor end ) and see if the problem goes away or switches over to the plug that you switched wires with. That's the cheapest "first step" that I can think of.

[jhv48]

First thing, start the engine and pull the plug wire off of the offending cylinder. Do you notice a change in the engine speed or smoothness. If not, ground the plug wire to the block and see if you can hear a spark jumping from the plug end of the wire to the block. If not, you have no spark to that cylinder. Easy fix. If you hear a spark jumping, you have spark to the cylinder and your problem is more complicated now.

Using any oil lately?

Smoking a little from one side or the other?

Audible missfire?

Time for a compression test. Oil is possibly creeping past rings or valve guides.

[garry viohl]

Its black (too rich) not oil (no oil residue). Will try compression test. Same thing with two set of wires.

[patrickt]

Originally Posted by garry viohl

Its black (too rich) not oil (no oil residue). Will try compression test. Same thing with two set of wires.

OK, possibly a bad terminal on the distributor cap for that cylinder, or possibly a bad plug (cracked insulator that is really hard to see).

[jhv48]

Originally Posted by garry viohl

Its black (too rich) not oil (no oil residue). Will try compression test. Same thing with two set of wires.

If it's fuel fouling, then either the plug is not firing or is defective or a different heat range than the rest.

Good luck!

[garry viohl]

I have tried two set of wires, new plug, all same number and heat range and does the same thing. I will try new cap and rotor, they looked ok when I checked them.

[convincor]

see pg 3, post #45 here Spark plugs: 7 tan, 1 black

[convincor]

the tell tail sign

problem revealed

[Car Lover]

All the above i would check most probably a bad plug wire,by the way 800 cfm double pumper sounds like a lot of carb for a street engine.

[convincor]

Two different sets of wires, same problem.

Originally Posted by Car Lover

All the above i would check most probably a bad plug wire,by the way 800 cfm double pumper sounds like a lot of carb for a street engine.

Originally Posted by garry viohl

I have tried two set of wires, new plug, all same number and heat range and does the same thing. I will try new cap and rotor, they looked ok when I checked them.

[garry viohl]

Compression test results:
1 130
2 130
3 135
4 135
5 120
6 125
7 125
8 130

Number 2 is the problem plug

Intake gasket between #2 and #3 look lifted by 3/4 inch.

Maybe thats the problem?
Should I pull the intake?

[convincor]

Are the gaskets "Fail-Pro printo leaks??
The gasket should be flat with the head. What's happened is they split at the port.
Unfortunitly Victor stopped making the Nitro Seals but someone just told me that FE Specialties has them still.
If you can't get them, Edelbrocks are the next choice as they also have a steel core. Edelbrocks
Take pics when it comes apart..

[jhv48]

You say you've changed plugs and wires, but did you make sure there is spark to the plug?

[CowtownCobra]

It's significant that one plug is a different color than the rest. But with today's crappy gas the actual color is not as significant as it was 40 years ago.