rocker-shaft oil leak solution
Have you recently noticed a few drops of oil on the garage floor under your engine? Is your engine air-cooled - say a 3.2 or earlier?
It is not uncommon to find that oil is leaking from the valve rocker shafts.
What happens is this:
The twelve rockers in your engine are lubricated by oil spray bars, which run from the front to the rear of the cam carrier castings that sit on top of the cylinder heads. Each rocker runs on its own shaft.
These shafts are each firmly fixed into the alloy casting by a single bolt, which runs through the shaft. This shaft , when tightened, expands the ends of the shaft 'jamming' it tight in the bore and creating an oil seal. If this sealed surface starts to leak, the oil that comes past it is not collected within the rocker cover space, but exits into the open air down between your heads and cylinder barrels.
During maintenance or a rebuild, it's quite possible that the alloy bore will have been scored when the rocker shafts were removed and re-fitted.
The shafts unfortunately have two grooves that have sharp, unchamfered corners and it's scoring caused by these that allows an escape route for the oil. Until now, the only way to fix this problem was by fitting new cam-carrier castings at considerable cost.
Autofarm has now designed (and patented) a solution that will keep your engine oil-tight however leaky your rocker shafts are. The expander nuts that are fitted at each end of your rocker shaft have been re-designed with a small lip at their outside ends which compresses 'O'-rings against the end of the shaft. As the rings are squeezed by the tightening of the through-bolt, they expand to form the seal within the alloy casting. Their compliance will ensure that any oil path due to scoring is completely sealed.
A is the 'O'-ring and B the new design of expander nut
'It's a relatively small modification,' says Gary Cook, Autofarm Engine Technician, 'but the results speak for themselves. Even the otherwise driest of air-cooled motors usually weeps a little from this area, but we've routinely fitted this type of seal to most of the pre-3.2 engines we've built over the last few months, and so far not seen a single leak.'
We are now able to provide a kit of 24 expansion nuts - 12 threaded, 12 plain - and 24 'O'-rings for DIY fitment for just £213.19 including VAT, and can fit the system during a routine service for an additional £599.95 inclusive of VAT.
Email parts@autofarm.co.uk or engines@autofarm.co.uk for more information or to order yours now.