IO-540 Baffling Question

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drak130
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IO-540 Baffling Question

Post by drak130 »

Hello All,

Anyone out there replace the baffling on their IO-540 M7? I am in the process of replacing my original baffling piece meal. It all looks straight forward except for the rear section. I can't tell if it is cut curved or if it is stretched or bent curved. Obviously if cut curved I'm gonna need a big square piece to cut it from vice the straight 3 inch roll I have. Pictures enclosed are not the best.

Thanks for any info and/or advice.

Cheers
Tim
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VA Maule
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Re: IO-540 Baffling Question

Post by VA Maule »

Your 3” roll is all you need. The relief cuts break enough tension it let it form the curve. Use the old pieces as a template. A really slick way to make it more cooperative is cleco the peace(s) down to a scrap peace of plywood as you trim and duplicate them, plywood on the bottom, new material, old peace on top, proceed one relief cut at a time then match drill through and into the plywood cleco in place as you go.
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netconn
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Re: IO-540 Baffling Question

Post by netconn »

I replaced my baffling with 3" silicon. I just removed the old rivets, started the baffle strip at one end and worked to the other end. Drill, cleco, rivet. Use the same holes. The baffle will bent around the curve.

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drak130
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Re: IO-540 Baffling Question

Post by drak130 »

Thanks for the info and techniques Fellas!

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krautman67
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Re: IO-540 Baffling Question

Post by krautman67 »

Hi Tim,

I replaced mine recently after cleaning up and re-installing the engine. Ours is a 1975 0-540. I found a few cracks and wear damage that needed to be repaired to the aluminum baffling prior to installing the new 3” silicon. It curves nicely, as netconn and VA Maule stated. It seals much better than your old material. The photo is just as I was done, with a few gaps showing since it was not yet in its final position. The silicon now rests in its proper position with the cowling in place. The cuts that you see overlap to form a tight seal.
Be sure to use rivets with the same large flange you have. I used solid rivets, smaller head. I should have used pop rivets with a larger flange. My old rivets were much smaller than your original rivets. The silicone popped through the rivet heads where the silicone was stretched going around a curve, I had to put a washer in.

Carl
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1976 M5-235C

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drak130
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Re: IO-540 Baffling Question

Post by drak130 »

Thanks for all the suggestions fellas,

One more question....Finished the gaskets but it seems like a big source of air leaking would be the oil access hatch on the top of the cowl. Looks like at one time there may have been a seal of some flavor there but nothing now. Anyone have any suggestions on how to seal that up or even if it is neccessary?

Tim

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Re: IO-540 Baffling Question

Post by VA Maule »

Don’t know how much leakage might be around the oil door, but I suppose you could use a small and soft piece of weather striping like what goes around the swing out windows and doors.

Now some engines I’ve seen there are tremendous leeks around the cylinder bases and the aluminum baffles as well as the front of the engine between the cowling inlets . When you add up the 2 dozen or maybe more quarter and dime size holes a substantial volume of air that should be going through the cylinder fins just escapes out without carrying any heat with it also reducing pressure above the cylinders reducing the efficiency of what does make it between the fins. Place a light above the cylinders and look up through them from the bottom and any light you see that’s not coming through the fins is leaking ( it will probably surprise you how much light you’ll see) it would be just about impossible to trim a peace of aluminum to such a compound shape at the cylinder base and case junction so it doesn’t get done in a factory/manufacturing production situation. The easy fix to all this leaking is to calk up the holes with silicone. The clear common stuff in the aviation aisle of you favorite hardware store that fits the the caulking gun (foot longish) the long snoot helps you reach the needed spots and you might need more than one tube.
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maules.com
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Re: IO-540 Baffling Question

Post by maules.com »

If the baffling and venturi air egress are well done, there should be more low pressure at air egress than ram air at front.
To see the effect, in cruise the top of the top cowl as seen through windshield should be 'sucked' downward.
Jeremy
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