Oil Feed to Rocker Arms

[Robin Fairservice]

How do you adjust the oil feed to the engine valve rocker arms?

[PJGD]

Robin,
There is no "adjustment" per se for volumetric oil flow to the rocker arms. The oil gets to the rockers up the center cylinder head bolt, then from a banjo around that bolt through a copper pipe up to the rocker shaft. The rocker shaft is hollow but with small lateral drillings that feed the rocker bearings. These lateral drillings are probably intended to control the flow to each rocker.

Normally the oil flow is plenty adequate, but if it is not, then you may have a blockage in the path up to the rocker. Check to see if the flow is roughly similar on both banks; if so, then blockage is unlikely. Is oil oozing from all rockers or is one or more relatively dry? If oil flow is thought to be too high, then assuming you are running an appropriate grade of oil, it may be that the rocker bearings are worn. Alternatively, it may be leaking from around the banjo due to defective sealing washers or inadequately tightened nut.

Let us know what you find out, or what the perceived problem is. . .

Philip

[Robin Fairservice]

I have noticed that there seems to be more oil within the rocker cover on one side compared with the other, and I wondered if the rates of flow were different, and then how would they be adjusted. I can't see any references to this in the Maintenance Manual.

[Forumadmin]

I did once have the return holes become blocked. This resulted in black smoke out of the exhaust as the oil from the full rocker cover was sucked down the valve stems. You should be able to pass a wire (coat hanger size) down each for about 6 inches.

As Philip says, make sure each of the eight rocker arms is receiving a drip of oil per minute. You do not have to count just make sure each is receiving oil! If not then you may be lucky and be able to remove the oil feed head bolt to make sure it is clear. If you cannot remove bolt then you might be able to clear with some compressed air by taking the tappet cover off and undoing one end of the oil delivery pipe. Otherwise the head will have to come off and the blockage removed.

The oil holes are only 1/16" so can easily become blocked.

[Robin Fairservice]

That was an interesting exercise. I used a stiff wire, thinner than a coat hanger, and it was quite struggle to get that through the seemingly tiny holes. I eventually managed it so I will see if it makes any difference.

[Forumadmin]

Robin,
That may be your problem if the holes are that thin then the viscosity of the oil may prevent return to the sump. You should be able to get a 3mm wire down as the holes are 6mm diameter with a slight bend on the outside face.