Flanges are not flat.
My new IO-540 has slight gaps in the center. Now, after seeing the cause, mine are coming off before first flight to get the flange surface sanded flat then I will reassemble with hylomar.
When we prime our fuel injected engines, the fuel pours right down the tube. The reason for deterioration is from having the gap which allows fuel in and movement during pressure pulses. Hylomar or equivalent should get you three times the hours. Paying as much as we do for these engines, one would expect better fit and gaskets. We don't want any leaks on intake as it is unfiltered/heated air which throws off fuel servo fuel delivery ratios.
For those flying to check for leaks install small shop vac exhaust to fab inlet with filter in place to slightly pressurize intake tubes and use soap bubbles to check for leaks.
Edit: I can fit a .010" feeler gage on every intake tube flange between two bolts.
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Last edited by Wayne Gillispie : 09-27-2011 at 06:06 AM.
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