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87 3.2 high carbon buildup 7000 mi. since valve-job


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Bought a 87 911 at 87000 mi that I knew needed a valve job (high oil consumption) which was performed by reputable shop. Work included new valve guides, exhaust valves, etc.  Car exercised weekly at all speeds / conditions and put on dyno after 6 mos later when it pulled anticipated BHP and torque.  Now, (3yrs and 7000 miles later) it began running cumulatively more and more poorly. 


Diagnosis including a cylinder leakdown test and borescope review, found 5 cylinders have above 80+% leakage from exhaust valves and a very high carbon buildup on intake, exhaust valves and in combustion chambers.  Two unrelated shops have diagnosed by leakdown tests with same results.  Logically, it will need teardown to determine cause of problem.


All thoughts and comments are appreciated particularly considering the short time since the valve job.

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