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Zed Head

All brains on deck - an unusual problem

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I had deposits on my 77 EFI on plugs 3&4. It was due to cracks in head.

The exhaust ports on 3&4 are the only two adjacent exhaust ports and heat builds there.

Maybe exhaust valve lash is too tight on 3 & 4allowing reversion.



Here is 3&4 exhibiting darker colour on cracked head (EFI):






Edited by 240260280

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I'd be very skeptical of a plug read based ONLY on a short period of idle. The car is not driven at idle. 

Put in new plugs and GO DRIVE THE CAR aggressively for an hour, THEN read the plugs.

If nothing else you've had an hour of fun driving the car. 

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Actually, his basic problem is an idling problem.  Lots of traffic, and sitting while idling causes the plugs to load up and the engine to run rough.  A good drive and quick engine cut might offer a clue, but the problem is the idling.  I know that my old engine would start to run rough at idle, I'd take it out in the country and give it an Italian tuneup and it would idle smoothly for a while.  Then load up again.  IT was fun for a while but got old eventually.  I put my spare engine in to fix it.

246's issue is similar.  Not clear how the cracks cause the fouling though.

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