valve cover screw and torque

[TheTurtle]

Anybody know the size of of the valve cover bolts?  Slotted head.  Noticed a bolt stuck down in my cowl flap.  Little looking and found it fell out of the valve cover.  Started checking the tightness of all the rest and they were all barely tight.  Cant believe it wasnt leaking oil.   Found another one missing on the other side of the plane as well but couldnt find that screw...  Then I left the hangar and forgot to bring one with me.

So are they like car valve covers where its just tighten enough to not squeeze the gaskets out or some particular torque setting?

[Guest]

22 minutes ago, TheTurtle said:

Anybody know the size of of the valve cover bolts?  Slotted head.  Noticed a bolt stuck down in my cowl flap.  Little looking and found it fell out of the valve cover.  Started checking the tightness of all the rest and they were all barely tight.  Cant believe it wasnt leaking oil.   Found another one missing on the other side of the plane as well but couldnt find that screw...  Then I left the hangar and forgot to bring one with me.

So are they like car valve covers where its just tighten enough to not squeeze the gaskets out or some particular torque setting?

They are normally 1/4-20 NC threads.  Torque depends on gasket material, for normal Lycoming cork gaskets 50 inch pounds for silicone gaskets  about 30 inch pounds.

Clarence

[TheTurtle]

36 minutes ago, M20Doc said:

They are normally 1/4-20 NC threads.  Torque depends on gasket material, for normal Lycoming cork gaskets 50 inch pounds for silicone gaskets  about 30 inch pounds.

Clarence

these are orange and look to be silicon.  Now to find a slotted tip for my torque wrench.  thanks!!

[Hank]

Put a socket in your wrench, then slip in the slotted tip from a magnetic screwdriver. You can often get them at Harbor Freight, HD or Slowe's for a couple bucks.

[jetdriven]

The silicone gasket runs away from the torque and squishes out, then the screw gets loose and falls out. Over torquing the screw warps the valve cover then it leaks between the bolt holes. Cork gaskets coated in permatex aviation sealer fixes the problem, and it's cheaper also. 

Edited December 25, 2016 by jetdriven

[larryb]

Silicon works great but there is a way to install. First, get a set of hex cap screws to replace the slotted ones. Then get a hex driver for your torque wrench. The secret is the blue medium permatex on the screws. I torque in two rounds. One round at 10 in-lb and then a second round at 20 in-lb. Do not keep going around trying to get them all up to torque because you will wind up too tight and crushing the gaskets. Just two rounds and you are done.

[Bob_Belville]

Helpful info. I've made it a habit to snug up the screws with a large screwdriver whenever I have the cowl off. I can usually turn each screw 1/4 turn to "snug". 

[larryb]

One more thing. Guy Ginby sells nice reinforced silicon gaskets. He also sells the hex cap screws. One stop shopping. He was experimenting with a thicker version when I got mine. The thicker ones worked better for me.

[carusoam]

Nice Pirep, LarryB!

Best regards,

-a-

[Yetti]

I believe I torqued the silicone gaskets to spec something like 25" They did not leak for a year.  The mechanic was tightening them.... I was giving him a hard time about now they are going to leak.

[LANCECASPER]

If anyone who has a Continental IO-550 (Ovation or Eagle) would like a set of the GEE-BEE valve cover gaskets, I have a brand new set still in the package for the asking.

(I ordered a set for my TLS which has a Lycoming and he sent the wrong ones - he told me to give the Continental gaskets away. I really like the ones I just put on my Lycoming.)

 

They are spoken for - going to Jerry.