oil feed to rockers alloy head single

[robert.clark]

I'm just looking at Ariel's design choices regarding lubrication of the rocker gear on the singles.

On the early 30's cast iron heads with exposed valve gear history shows that there was either no lubrication or later the switch to an oil mist just to the inlet valve and later to include the exhaust valve also.

The later enclosed cast iron heads introduced a rocker gear improvement with a direct oil pressure feed from the oil pump / pressure regulator / oil pressure gauge feed. As far as I know there was no oil restrictor fitted so lets say the pressure to the rockers was roughly + or - 15psi.

With the introduction of the alloy heads there is a change of design and instead of the direct pressure feed we have low pressure / low flow lubrication to the rockers via the oil return feed pipe. If there is flow there must be some pressure but what that is I don't know.

After 16 years or so of production and successful in-service use of cast iron heads it seems so unlike Ariel to switch their design philosophy in this area.

Just curious to get some feedback as I'm putting together the oil system on a new build alloy head 350 I'm building which includes a oil filter canister in the return line.

[Simon.Gardiner]

(With admin hat on - duplicate entry deleted. Please note that where an 'X' button can be seen in the line-up at upper right of a post this allows folk to delete the post themselves....)

Rocker feed change was made a few years before the general introduction of alloy heads. I'd suspect probably to simplify the drillings in the gear cover. Taking a rocker feed from the return pipe wasn't unique to Ariel singles, BSA A10s / A7s (and Ariel Huntmasters) have a similar arrangement. It seems to work OK, none of these machines has a reputation for excessive rocker wear.

(Sticking an oil filter in the return side isn't uncommon for any of these either and doesn't seem to cause a problem - speaking as someone who added a filter a couple of years ago....)

HTH

SG

[paul.jameson]

As has been stated in another recent similar topic you only need a few drops now and then to lubricate the rockers. Having run alloy head singles with the rocker feed from the return for many miles in the 1970s I can confirm that the system is totally adequate.

[Brian_Walker]

My VCH has the rocker oil feed from the timing chest, I try making up a 'T" to go into the return of the oil tank but was worried the amount is regulated by the relative diameters of the pipes and restriction of the return hole into the tank so I went back to the positive feed from the pump. This was a race bike and was running flat stick all the time, I even went to using an external gear driven pump but it flooded the top end too much.