Spark Plugs What is wrong?

[AussieinNC]

Cyl 3,4 and 6 all look like water contamination within the combustion chamber...

Compression test and leak down test...most likely blown head gasket between 4 and 6...

Could also be a lean out due to manifold crack...is this a two barrel or four barrel carb?

Open plenum manifold or closed ?

[Grumpy old man]

I would get a correct set of matched plugs gapped correctly and run it again before you get too crazy trying to diagnose whats wrong , the threads don't even look the same length let alone the heat range can't be the same .

[53chevyforever]

Originally Posted by Grumpy old man

I would get a correct set of matched plugs gapped correctly and run it again before you get too crazy trying to diagnose whats wrong , the threads don't even look the same length let alone the heat range can't be the same .

I had all the same at first...they looked fouled so bought all new ac plugs at beginning...no difference...then this last try...I put in the 3 autolites...still ran the same.

[53chevyforever]

Originally Posted by AussieinNC

Cyl 3,4 and 6 all look like water contamination within the combustion chamber...

Compression test and leak down test...most likely blown head gasket between 4 and 6...

Could also be a lean out due to manifold crack...is this a two barrel or four barrel carb?

Open plenum manifold or closed ?

Manifold is edelbrock performer bought new from oriellys by the guy I
bought truck from....carbs are not the problem both that I have tried run
perfect on my other truck.