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Fixing manifold leaks

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Neil

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Lycomings do have some problems with intake manifold leaks and this is how I fix those at the head to intake tube joint.

The upper intake flanges are subject to being bowed. This happens over time or by an assembler not having the tube located properly in the flange clamp at installation. It happens. I installed a 540 that had been rebuilt by a highly reputable shop and the flange of the tube wasn't located in the clamp properly when it was tightened. The engine actually whistled when it was idling.

1. You can check for flatness easily enough if you have a good flat surface. A cast iron table that is blanchard ground like the old wood working tools is great.

2. Resist any temptation the flatten the back with a file. There is a step that the end of the intake tube seats in that must be flat and if you file the high spots off, the recess will not be flat.

3. All you need to straighten the flange is a cheap Arbor press, some shim stock and a piece of scrap aluminum that will bridge the peaks on the flange.

4. I have about .025' shim under each edge of the clamp. With the scrap aluminum across the peaks the flange is easily brought back true with a few good bumps from the press. Just check your progress by seeing if the part rocks when placed on your flat surface. If you should over form a tiny bit, that's alright as it will flatten when you tighten it to the head.

Intake clamp 1.jpg


Intake clamp 3.jpg


Intake clamp 4.jpg


Intale clamp 5.jpg
 
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