Technical spark plug diagnosis

HELP - just took these out of an sbc that wouldnt rev past 2k (i wonder why) nothing special, roller cam low compression run it on non ethanol gas - clogged injectors leaning out cylinders? oil entering from guides diluting fuel? the plugs were last changed a year or so ago and the motor is always run up to temp and under load (not just idled around) it went from a little hard to start, to a little down on power to this in a very short period of time - will test compression asap - no backfire - ran smooth to 2k

 

What do 1,3,5, and 7 look like? The threads on those plugs look to be way too long for a SBC. Try a set of AC CR43TS and see what happens. What kind of heads are you running, anyway?

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No gap, why are the tips missing, how can it run at all like that?

 

It would also help to know what kind of ignition system you're using.
What the advance is, initial and mechanical, msd or not, compression ratio, more details please.

 

1 3 5 7

 

Wow that is nasty. You may have pre-ignition from carbon buildup. Does it diesel when you shut if off? Does it smoke, what color? Use oil?

 

How does it run with a new set of plugs? How long do they last?

 

as in too much carbon in the chamber raising the compression too much for the 90 octane gas - it did not diesel it started smoking but also smelled like raw gas once it got really bad

 

didnt put new plugs in yet - going to do a comp test first

 

I'd also check to see if the intake gaskets weren't sucked in some where.
Or everywhere!

 

Well it does look rich. FI did you say? You may be washing the rings with excess fuel leading to ring and cylinder wear, also diluting the oil. Carbon can cause pre-ignition, the hot carbon chunks igniting the mixture before the plug.

 

i will tear into it and report back

 

This is all true. But , if this is the engine I'm thinking of, they were prone to intake gasket leaks. Thus, the ecm will over fuel the good cylinders and advance or retard the timing as needed, to compensate for the vacuum leak on the other cylinders, making a complete disaster of the spark plugs. Hence the destroyed electrode's and over rich plug reading's.

 

And if it's like the early Vortec I had, the orange coolant ate the intake gaskets. There was a petition to have GM pay to fix but I don't think it ever succeeded.

 

Had the same good damned problem!

 

yikes! look like they came out of a motor that was in a flood - last time you changed oil ? coolant?