LYC. 540 rods in a 520 Continental

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rowdy1
Southern Airboat Member
Posts: 173
Joined: Thu Sep 11, 2014 10:07 am

LYC. 540 rods in a 520 Continental

Post by rowdy1 » Mon Jul 31, 2017 3:49 pm

I was searching around on the site and found an old thread about putting O540 rods in a 520 Continental to raise the compression ratio. However the thread is 5-6 years old and I don't recognize any of the players. Is this a legitimate option to get a little higher CR, and is it as simple as pulling the jugs and swapping them? This sounds way to easy! Also what power gains could you expect. I am running a stock 520 w/ whatever the carb is that comes on a 540.

PS. I did read the part about mocking up one cylinder to verify valve clearance and possibly needing to fly cut the pistons.

Thank You

mrfixit
Southern Airboat Member
Posts: 189
Joined: Sat Aug 06, 2011 10:21 pm
Location: Dunnellon, FL

Re: LYC. 540 rods in a 520 Continental

Post by mrfixit » Tue Aug 01, 2017 7:19 am

Yes have worked on a few engines done this way. But there are a few problems.
If I remember right one you have to have a small journal continentai crank then you small journal Lycoming rods with Lycoming rod bearings.
But the continental rod is wider on the crank then the lycoming so the rod will no stay centered on the crank.
I have welded up the sides and machined the rods to make them work in the past then rebalance the rods before I put the engine together.
Most of these were on race boats so they do not get the time on then that a ride boat will see.
some people have the case milled to increase compression or go to different pistons.
Depending on what engine you have to start with what you can do.
just remember raising compression will usually makes more heat.

rowdy1
Southern Airboat Member
Posts: 173
Joined: Thu Sep 11, 2014 10:07 am

Re: LYC. 540 rods in a 520 Continental

Post by rowdy1 » Tue Aug 01, 2017 1:06 pm

Thank You!
I had to believe there was more to the story than just what I had read. Im already working on a multi port EFI conversion plus coil on plug ignition. Sounds like I don't need to undertake this project as well.

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