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MG MGB Technical - Rocker Arm Bushings

I just picked up the new rocker shaft and rocker arm bushings (from Moss)for my mid-seventies B engine.

In comparing the new bushings to the old, I noticed that the old bushings have two oil holes in them, where the new bushings do not. They have instead, a recessed groove, or "pocket" formed into half the inside diameter. These are the standard Moss bushings Moss P/N 330-150.

I question the ability of this "groove" to provide adequate lubrication to the rocker arm, but am hoping that others, with experience with these new bushings, can alleviate my concern.
JR Ross

I believe that the bushings are meant to be drilled for the oil passages, and reamed to size, too. I did this on an MGC but it's the same operation. You'll have to find the info on drill sizing, etc. in the Bentley manual (I think it's in there).

Paul Briggs
Paul Briggs

If you read the footnote in the Moss catalog it says:"Oil holes must be drilled in these bushings after installation in a rocker arm. Bushings must then be reamed to fit shaft, and plug replaced." RAY
rjm RAY

Thanks Ray. I guess that old adage about "looking before leaping", applies to me.
What is the best method of removing the plug in the end of the Rocker Arm, and if it's drilling it out, what is recommended as the best material to re-plug the hole when finished?
JR Ross

The plug is threaded into the end of the rocker shaft. A split pin prevents it from rotating out on its own. It can be removed with an ordinary flat edged screwdriver after the split pin has been extracted with a pair of pliers. RAY
rjm RAY

The procedure is in the WSM.
I suggest that people read same.
The groove is to distribute oil around the rocker shaft.
The holes have nothing to do with lubricating the shaft/bush; they are to spray oil around to lube the valve gear and feed oil to the pushrod cups. The spray hole is easily drilled after bush installation. If you are careful, you can drill the pushrod feed before pressing the bush in and carefully align the hole. You can make the hole a bit oversize. Or you can dispense with the passage completely as is done with solid rocker screws for racing - some people do this and claim there is plenty of oil floating around for adequate lubrication.

FRM
FR Millmore

Thanks FRM, I have a number of WSMs, and they are all well used. The page containing the Rocker Arm Bushing replacement is extremely well used, since it also has the Head Bolt Tightening sequence diagram on it. How I've never noted the Bushing Replacement procedure is unexplainable.

Ray,I think I didn't ask my question clearly enough. I was asking about the end plug in the rocker ARM not the rocker SHAFT.
The WSM proceedure however answers my question.

Once again, I am grateful for this site. Even after fourty-five years of owning, restoring, servicing, and playing with MGs, I learn something almost every time I visit here.

Thanks all.
JR Ross

The plugs need to be drilled out to facilitate the drilling of holes in the new bushings. Replacement plugs are readily available. I've had the same B for almost 39 years and am also still finding out new things. RAY
rjm RAY

I'm am to do the same with my worn rocker assembly. After reading all the above I reckon I will go for a complete Exchange reconditioned assembly! Happy New year to all. Mike
J.M. Doust

This thread was discussed between 05/01/2011 and 09/01/2011

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