Piston Question
 

When I got my drivers side head off, i noticed the #5 piston was different from the others. The others were all black topped, but #5 was black in the middle, and looked like it had a gold colored ring around the edge. What is it?

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Black '90 GT. Flowmaster American Thunder Cat-back.

the black tops that you are describing, is this carbon build up on them? I would think so. Try cleaning and removing the build up on one of the the other pistions. Keep a vacum handy. Check to see. What is the car's history, Service record, accidents, etc.

I think it could be normal. The 5.0 intake starves the front cyliders of fuel. Bad stock design.

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92 GT, 4:10 gears, centerforce clutch, 6# powerdyne blower, bbk h-pipe, flowmasters

If you have a gasket leak then you could be leaking coolant into that cylinder. When coolant is burned it will clean the piston top and make it shiny. Were you losing coolant when the engine was running?