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MG MGB Technical - Rocker bushes

I have bought a replacement rocker shaft and a set of bushes. The replacement bushes have no hole in them but have a groove that runs the width of the bush. Do they still need a hole drilled in them for the oilway?
Thanks.
Trevor Harvey

Trevor. I have not performed this task, having purchased rebuilt rocker arm assemblies for my past rebuilds. I do remember reading about this procedure over the years and there should be some good information in the archives covering it. The factory workshop manual, section A.5 in the early manuals and A.3 in the later manuals, covers the replacement of the bushings and indicate that two holes have to be drilled in the bushings if they are to work correctly. You might want to go through the archives and the manual, then ask about anything which is not clear.

Les
Les Bengtson

Once the bushings are pressed in and sized,a hole must be drilled through the rocker arm oil feed hole into the bushing. A special tool is normally required to press the bushings in and out due to the fact that they are very thin and will collapse if not properly supported. RAY
rjm RAY

Trevor,

I've done this job, and that means that anybody is capable of doing it. It was one of those 'things' I did with the advice and support of an experienced local club member.

Depending on your model year there will be one or two holes to be drilled in each rocker. I'm not sure of the year of change over but I understand later cars did not have the oil feed through the rocker arm. They relied on splash feed to lubricate the nipple to push rod contact. You will be able to tell by looking at the nipple which contacts the push rod. If it is drilled it should mean the earlier rocker arm feed is present. If not, the later reliance on splash feed system is in place. FWIW I understand that MG racing relied on the splash feed system for lubricating the rocker contact with the push rod cup.

As RJM mentioned, the bushes will need to be individually reamed to size for their location on the rocker shaft once fitted to the rockers. You will need to access the appropriate reamer diameter for this (I'm afraid I don't recall but a measure of the rocker arm will indicate the diameter range you will need in a reamer). Be prepared to do multiple fine shaving reams and frequent test fits of the bushed rocker to the shaft. What you are after is a snug fit with just the amount of freedom needed to allow a rotation of the rocker on the shaft.

If you need to drill the rocker arm oil feed hole in the bush you will first need to file of the 'plug' of seal which closes the line of the drilling on the outer face of the rocker arm. This is probably a brazed plug. You will know when you are through because the drilling hole will be exposed. This will need to be closed off again when the job is done. I did that by pressing in the point end of a woodwork nail (just far enough to close the hole, no further of you will interfere with the oil feed line), cutting it flush and brazing the end in place.

I pressed the old bushes out using an appropriate diameter of socked closed in a vice. I pressed the new bushes in using a bolt and two large diameter washes, one of which , by pure chance, had a circular groove which matched the diameter of the bush end, holding it flat against the pressing force). I held the bolt head in a ring spanner and turned the nut over grooved washer down against the bush with a ratchet socket wrench. Trick is to go slowly and keep everything aligned.

I used a hand drill for the job. The hole for the splash feed on the rocker shoulder is pretty well straight forward. Steady gentle pressure will minimise breakthrough roughage in finish on the inner bush surface and avoid 'leaping' the bit into the opposit bush wall. The rocker arm holes cost me a few drill bits as I was using a relatively fine drill bit and it is difficult avoiding scraping the bit along the inner of the oil feed hole line. Clean up the inner bush surface of any eruptions of material caused with drill breakthrough - fine wet/dry will do the job, avoiding sanding into the bush surface. Wash clean when done to remove any grit left behind.

It was a fiddly job, took a bit of time (of which I have a good deal) but very satisfying in the completion and assembly of a refurbished rocker/lifter system.

Be prepared for a bit of work but a lot of satisfaction.

Regards
Roger
Roger T

Thanks for the advice ,in particular Roger for the detailed information. You sound like a simlar type of mechanic to me. Using whatever you can to get the job done.
Trev
Trevor Harvey

It is a fiddly and time consuming task and probably cheaper to buy a rebuilt assembly.

Shafts are available 5 thou oversize and you only need to ream out the existing bushes and posts to suit - no need to buy or fit new bushes.
Chris at Octarine Services


Chris, Wish I had known that before I bought this one, it would have been much easier.
Trevor Harvey

And then you have destroyed another set of parts. This is a cheap repair of the sort done by mass market rebuilders, not at all suitable for cars we intend to keep and use for very many years beyond the general market "use it up and trash it" idea. I am appalled.

FRM
FR Millmore

Chris..
Can you tell me where I can purchase .005 oversize shafts.
Sandy
Hudson florida
SANDY SANDERS

Trevor, Yes and I get a lot of satisfaction from the fiddling. It helps to fill days and gives me a sense of better knowing my car as I add to the list of things I tackle.

Chris, you are probably right on a straight cost basis. Important to me though is the knowing how well (or otherwise) the task is done. Were I in full-time career though I would not have the time available to do things like this - purchased in would make all the sense in the world in that case.

Regards
Roger
Roger T

Sandy,

Investigate Moss US - they may stock them.

Fleming,

The end result is no worse, possibly marginally better due to the larger shaft & bearing surface. Only the posts are "trashed" but you can always use a 5 thou over shaft next time & fit new bushes - or buy brand new posts, they are still available! The rocker arms are not damaged in any way.

Bear in mind that "next time" would normally be 10 to 20 years time on average UK usage!!
Chris at Octarine Services

Apologies Fletcher - I had my friend Fleming on my brain - doh!
Chris at Octarine Services

Chris -
Not a problem, I can't even remember my own name!

There are no +.005 shafts in Moss (or anywhere else I've ever heard of), just standard ones @ $23, and "upgraded - Tufftrided" @ $74, and it's an old book. So you are certainly unlikely to ever find another +.005 replacement 10 or 20 years from now. Pillars are shown @ $13 for plain ones, and $20 or 23 for the tapped ones depending on year, and I doubt there will be any of those left either. Bushes are $2.60 ea, and when the time comes I can make them if need be.

And nobody should mess with reaming them when any competent automotive machine shop will fit them on a Sunnen hone for very little $$ and a far better job. The difference between a good reaming job with the exact right tool and a hone is considerable, and there is a much bigger step down to amateurs with expansion reamers.

FRM
FR Millmore

Why, Fletcher, If I didn't know you better I'd almost be offended (lol). Mine work and I'm happy with that, even if I do need to do them again in 10 years rather than 20.

Down here we have a 'can do'/'make do' culture. Works pretty well on average over time.

Regards
Roger
Roger T

Roger -
I am also very much a "do it all myself" type, and I do applaud anyone figuring out DIY ways of fixing as opposed to replacing/subletting, but I found that running a wheel cylinder hone through reamed bushes, frequently even factory reamed ones, showed ridges and valleys both circumferential and along the reamer flutes, that do not help durability or oil sealing. So I either send them out, or, bore or ream undersize and then hone or lap for things where I want best possible fit and least leakage.
I fit the crank bushes (no seals) on a model antique engine to .0001 clearance, and it will run all day without a drop of oil escaping, in contrast to others at shows which leave a 10 foot line of oil off the mains. And I also modified the engine from plan, so that it has internal collector grooves feeding oil to the centerpoint of those bushes, which nobody else does.

FRM
FR Millmore

"I am also very much a "do it all myself" type..."
"...it will run all day without a drop of oil escaping, in contrast to others at shows which leave a 10 foot line of oil off the mains."

That's the sort of stuff I have worked out about you Fletcher, which is why I am NOT offended.

PS I'm still rather chuffed with the quality of outcome I achieved. On an original bottom end with 130,000 miles on the clock, with my humble rocker bush reaming I'm running 63lb oil pressure hot (read Aussie summer hot) and 40-45 hot idle oil pressure. I will offer that I maintain and run my car as a day runner/tourer and not with any aspiration to sports performance - though she moves perfectly well in modern traffic flows.

Regards
Roger
Roger T

This thread was discussed between 13/01/2010 and 16/01/2010

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