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Camshaft bearing 'O' ring Mod
Morning all,

What size 'O' ring do i need to help prevent excessive oil / pressure loss on the front camshaft bearing on a pressure fed engine i am slowly building?
I have read most of the threads, but the actual size is never mentioned.
I have figured out that i need to reduce the size of the oil feed hole in the bearing, but the 'O' ring size and position on the bearing eludes me.

I realise this is a well trodden subject, for that i apologise  Blush

You can safely reduce the feed hole in the bush to about 3/32" or 2mm (n.b. assuming you will use an in-line filter).

I've run a pressure fed engine since the early 1980's with no o-ring and no oil pressure problems.

n.b. I should probably add that it likely depends on the rest of your set-up - there's more than one way to arrange an oil feed.
Graham use 1/8" or 3.5mm width O-rings each end of cam bush (see photo) use a 1/8bsp socket blank plug drilled with a 1/6"or 1.5mm hole in the cam oilway tap 1/8bsp through the side entry of the gallery into the oilway deep enough to take the plug locktite in place. The rear cam bush can be reversed and drilled 2mm add a chamfer to clear the gear. The rear main bearing drain hole drill out to1/4" and notch seal plate to match, use a metric viton seal. Increase the size of the relief valve drain hole to 5/16" to stop back pressure to the pump, and make the relief valve adjustable.
Thanks chaps, a lot of food for thought.
Worth mentioning that if you have a magneto engine the O rings need to be thinner.


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