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C90 EX valve advice

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Well-Known Member
Apr 22, 2007
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I bought a C90-8 last Fall that was "Majored". I have all the logbooks since day one and it has a total time of 832hrs. The problem was that it was majored by an experimental engine rebuilder not an A+P. I talked with my A/I and he said we could tear it down and send the parts off and rebuild it legally. All the steel is back and the case is also back from Divco. The jugs all measured up to be well within limits. The problem is that the exhaust valves are part number 3921-TP. I can only find one reference to it in the Parts/Overhaul manual. I called "Fresno Airparts" and they said it was a 80 octaine valve. My A/I is away for a week and I would like to get some thoughts on this. Is it mandatory or highly recommended I replace this with a 100 Octane valve or is it OK to use this one.
Thanks for any thoughts on this in advance

Cape Cod

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