Timing Cover: Washers for Screws

Good thread, thanks Slick.

Update to put a wrap on this:

Thanks to Rob (Robs SS) for the source on aluminum washers. I ordered AN960PD-416 from Aircraft Spruce (877-477-7823) and turned them down to 0.410 - 0.414. These are 0.5 x 1/4 x 1/16 inch flat washers. They are harder and thicker than the original aluminum washers and did not crush under the socket head cap screws (SHCS). They were also inexpensive, only 0.06 each, and shipping was reasonable.

Even if Galvanic corrosion is not an issue, the washer will prevent galling the timing cover. While Norton parts diagrams do not call for a washer under the cheese headed screws, I think anyone using socket head cap screws should use a washer. The bearing diameter under the screw cap is only 0.360" and the clearance hole in the timing cover is about 0.260", leaving a very small annular ring for the screw head to bear on the timing cover.

I also tried 3/8 x 1/4 x 1/16 inch black fiber washers. These proved adequate, but they do not give any improvement in bearing area. I would say go to the trouble of turning down the aluminum washers.

Slick

BTW ... use washers under SHCS on the Gearbox Cover as well.

just get these?

part-no: 00.0203

https://andover-norton.co.uk/en/shop-drawing/301/dommi-engine-650-750cc

texasSlick said:

Now, if I only had a lathe ... I'll be using the bolt method to turn them down.

Click to expand...

Slick
I just finished a batch and went very well - the only additional comments are:
1. Use a longer 1/4" bolt with spacers made from aluminium tube - they act as good "handles"
2. Took longer than I thought - need to take care to keep rotating to get even material removal.
3. I put the whole thing in a vice afterward and finished hand-linishing with fine grade emery cloth.

End result on the timing cover looks good
Cheers
Rob

To Rob:

Thanks again for the tip to source the aluminum washers.

To all:

I chucked an assembly similar to Robs in a drill press, and while it was rotating, sanded the group down to 0.410" dia. with a Dremel drum, finishing with a file and fine sandpaper. It went well, did not take too long, although it wore down 5 or 6 Dremel drum sanding sleeves.

I am using Jim Schmidt's fiberglass reinforced silicone timing gasket. With these washers under the heads of my socket head cap screws, and Jim's gasket, I am able to torque down the screws and I have finally eliminated that oil weep that has been ever present at the bottom edge of my timing cover for so many years!

I turned down enough to use on my gearbox cover, but as yet have not installed them.

Atlas Report: My Atlas has a Comnoz rebuilt head, new 9:1 flat top pistons (down from 10.5:1), newly rebuilt K2FC by Doug Wood, and I am in the process of converting to LED lights. I now need break in miles.

It runs good, no leaks, 'nuff said.

Slick

jimbo said:

just get these?

Click to expand...

Jimbo
I did not mean to ignore your suggestion - but I have had previous experience with red, fibre washers (that look like those) and found that they compress over time, leading to loss of tension.
Others may disagree, but that's why I'll stick to aluminium.
Cheers
Rob