David Brown 990 Valve Cover Gasket

UP Oliver · Jun 24, 2016

I rebuilt my David Brown 990 about 8 years ago. I put the valve cover gasket in dry, and it started to leak on the right side of the engine soon after running it the first time. So I put some silicone on there, gave it plenty of time to set and put the cover on. No problems since. I am about to replace the head gasket and I just looked in my manual and saw where I am supposed to start the engine and let it run for half an hour when I am done and retighten the bolts holding on the head. I don't think I did that last time.

I don't have two gaskets, so I thought I would ask if putting silicone on this gasket is something people do or is there some other sealing material? I may just have to let it leak a little while it runs for that half hour before resetting the head bolts.

Thanks.

Steve@Advance · Jun 24, 2016

I normally don't silicone valve cover gaskets. If you didn't do it before, be sure to flatten the bottom side where the bolts come through (if it's sheetmetal, not cast). Some high tack spray adhesive works well to hold the gasket in place while positioning the cover. Cork gaskets are more forgiving of a little oil on the surface, rubber gaskets need to be completely dry, oil free, or they tend to "squirt" out from under the sealing area. Definitely don't put a rubber gasket on with wet silicone, or any other slick, non drying sealer.

I usually just sit the cover on while it warms up without the gasket. Unless it's a V engine that pumps up a lot of oil, then they can be gently tightened, just enough to slow the oil without compressing the gasket.

After retorquing the head, you'll need to recheck the valve clearance. That's always a good idea on any solid lift cam, reset the lifters after the initial run.

David Brown 990 Valve Cover Gasket

UP Oliver

Member

Steve@Advance

Well-known Member

Similar threads