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MG MGB Technical - Missing rocker pedestal shims.

I sent the head for my 1980 out for work to a reliable shop and had new valves & guides installed. I didn't remove the rocker gear before and now that I am ready to reinstall it on the head I can't find the shims for the center pedestals. He says he doesn't remember seeing any when he cleaned the head and rocker gear and that they were not in the cleaning tank etc. The head was rebuilt years ago and I suspect that they were probably left off at that point ( not as reputable a shop). The shaft looks so good that we decided not to replace the shaft or bushings. It has roughly 50,000 KM since the first time work was done.
What is the function of the shims for just the center pedestals and if they were "actually" left off at that point would I expect to see abnormal wear or is this guy just blowing smoke. TIA, Dave.
BTW, he says he can make some but I need the thickness. Does anyone know what that might be.
Dave Pearn

The shims go on the centre pedestals and put a slight stress on the shaft to relieve wear on the underside (of the shaft). If your shaft is still good after 50,000 clicks it must be the hardened variety. Quite often the shims are missing but are readily available from the likes of Moss.
Julian Wooldridge

I am amazed if the shaft is unworn at that mileage!

Not impossible, just very unusual.

The shims were added to stop the shaft fretting in the posts - the upside of the shaft wears where it goes through the four pillars.

The thickness of the shims is 5 thousandths of an inch.
Chris Betson

Chris; Not to plug a product, but in our area in the 80's, Slick 50 was the hot ticket, so I used it after the engine was rebuilt (for performance) and broken in at 30,000 km. I can still see the cross hatching in the bores 50k later so who knows, maybe the stuff has some merit after all.
Julian; I am moving to Calgary in late August so I might just see you at a show. I plan to run out to BC next year. Boy am I looking forward to crusing in the mountians.
Dave Pearn

I have never been convinced about oil additives - the secret of long lived engines is regular servicing - oil & filter changes.

Cheap oil changed every 3000 miles is better than expensive oil changed every 6000!
Chris Betson

Interesting reading here:
http://www.vtr.org/maintain/oil-additives.html

Wayne
Wayne Pearson

My oil changes were by time, not mileage, so thats more likely the reason.
Dave Pearn

I can vouch for what Chris says. Having changed the oil and filter in my V8 every 3k for 65k miles I did a top-end overhaul recently and it was as clean as a whistle inside. The engine has done at least 80k since the last rebuild but the tappets had less than 2 thou of wear, there were no wear ridges on the rocker shafts or rocker pads, and you could still see the honing marks over much of each bore.
Paul Hunt

Dave,
I just bought a rebuilt rocker arm assembly from Bob at Brittek. He said on the shims that they were added to stop shaft wear, but did not do the trick, therefore having them would make no difference.
Dave
David Steverson

Oh well, I ordered a set anyway. If nothing else, it would bug me knowing they were missing. Thanks for all the info.
Dave Pearn

This thread was discussed between 08/07/2003 and 11/07/2003

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.