O200 Valve Rocker Cover Question

[farmrjohn]

I'm trying to track down and stop an oil leak on an O200. I've read that over tightening the valve rocker cover can deform them, preventing a good seal with the gasket and a subsequent leak. The mating surface of the cover has a raised bead on it that also goes around the screw mounting holes. Should that bead be even all the way around? On the cover in question that seems to be leaking it appears that the bead around each hole is raised 1/16" or so above the rest of the bead that connects between the screw holes. Is that the deformation the over tightening comment above refers to?

 

[Salty]

Dunno, but it’s pretty common to have a very slow leak from valve covers. Mine always have a tiny drop on the bottom of them. I consider it corrosion protection.

 

[Dan Thomas]

I'm trying to track down and stop an oil leak on an O200. I've read that over tightening the valve rocker cover can deform them, preventing a good seal with the gasket and a subsequent leak. The mating surface of the cover has a raised bead on it that also goes around the screw mounting holes. Should that bead be even all the way around? On the cover in question that seems to be leaking it appears that the bead around each hole is raised 1/16" or so above the rest of the bead that connects between the screw holes. Is that the deformation the over tightening comment above refers to?

That's it. You can reset it by supporting the cap appropriately and tapping that high spot back down, but the support must be right. You can cause further damage by doing it wrong.

Get the red silicone gaskets. Forget the cork gaskets. Cork is great but it hardens and shrinks with age and heat and further tightening of the cap screws just distorts the cap and causes the gasket to split as well. Composition gaskets are a waste of time. Even with the silicone gaskets, overtightening must be avoided. The gasket will extrude and the screw hole gets big and lets oil pass out of the rocker box.

https://www.mcfarlaneaviation.com/products/product/APS-655706-S/

You might also have oil leaking from the valve pushrod tubes at the head end. Very difficult to stop without taking the cylinder off and using a special roller swaging tool to reset the tubes.

 

[farmrjohn]

Dunno, but it’s pretty common to have a very slow leak from valve covers. Mine always have a tiny drop on the bottom of them. I consider it corrosion protection.

The leak is more than a tiny drop-it is spraying a nice coating of oil on the inside of the cowl door just a little below there the baffle contacts the door.

That's it. You can reset it by supporting the cap appropriately and tapping that high spot back down, but the support must be right. You can cause further damage by doing it wrong.

Get the red silicone gaskets. Forget the cork gaskets. Cork is great but it hardens and shrinks with age and heat and further tightening of the cap screws just distorts the cap and causes the gasket to split as well. Composition gaskets are a waste of time. Even with the silicone gaskets, overtightening must be avoided. The gasket will extrude and the screw hole gets big and lets oil pass out of the rocker box.

https://www.mcfarlaneaviation.com/products/product/APS-655706-S/

You might also have oil leaking from the valve pushrod tubes at the head end. Very difficult to stop without taking the cylinder off and using a special roller swaging tool to reset the tubes.

I've tried the Real Gasket which looks the same. They call for 25 inch pounds installed, with clean and dry surfaces. The pushrod tubes have the Real Gasket conversion. The reset sounds like something to gingerly attempt.

 

[Dan Thomas]

The reset sounds like something to gingerly attempt.

Yup.

 

[somorris]

I gave away a complete set a little while back. The new Superior cylinders came with new ones. If I still had them, I would mail you one.

 

[Jdm]

I got tired of dealing with it about 10 years ago. Ordered new valve covers. Installed using quality gaskets and the proper torque. Hasn’t leaked since.

 

[farmrjohn]

I gave away a complete set a little while back. The new Superior cylinders came with new ones. If I still had them, I would mail you one.

Drat, just like comedy timing is everything.

I got tired of dealing with it about 10 years ago. Ordered new valve covers. Installed using quality gaskets and the proper torque. Hasn’t leaked since.

I am leaning that way but TCM apparently now provides the covers painted black which will not match the other three. Superior’s cover is the correct color but of course has the wrong logo embossed on it.

 

[Jdm]

I am leaning that way but TCM apparently now provides the covers painted black which will not match the other three. Superior’s cover is the correct color but of course has the wrong logo embossed on it.

I had to paint them. Nothing to that!

 

[RyanB]

Superior’s cover is the correct color but of course has the wrong logo embossed on it.

Does it matter?

 

[Jdm]

Does it matter?

It would to me, but I’m weird like that!
Just take 5 minutes and spray it with the correct engine color.

 

[farmrjohn]

Does it matter?

It doesn't matter to my but I wonder what eventual re-sale implications it would have for a Superior cover on a Continental cylinder

It would to me, but I’m weird like that!
Just take 5 minutes and spray it with the correct engine color.

All four covers currently appear to be cadmium plated rather than painted and I'm not aware of cadmium paint.

 

[Jdm]

Well how about paint them all. I’ve done that plenty of times. Go ahead with all new gaskets while you’re at it.
It shouldn’t hurt resale to go with one different branding, but definitely will raise an eyebrow for some. Kinda like putting a Ford emblem on a Chevy. Might appear unprofessional to some. It would to me.