Improving The Breed

Bruce Smith of Sportsparts in Australia shares his thoughts on the B-series lubrication system, and how oil supply can be improved.

Some years ago, when I was racing a car powered by a BMC B-series engine, I had the misfortune to have an oil pump drive fail. This in turn destroyed the camshaft and put all the resultant metal through the engine, necessitating a full engine rebuild, not to mention needing a new oil cooler too.

To find out how I could stop this happening again, I decided to do some investigating. The first thing I discovered was that this is a common problem when more than about 6200rpm is used. Part of my research involved finding out the full intricacies of the B-series oil system. There are basically two different systems: bypass filtration and full flow. The manufacturers were very clever in the relatively minor modification to change from bypass to full flow – they basically did it by making a new union and a new bolt. What happens is that the oil in the sump enters a strainer, goes up through the pump and then diagonally up through the back of the block to a horizontal drilling that runs the full length that block on the right hand side, passing the pressure relief valve on the way.

In the blocks that have a bypass system, the oil enters this drilling which supplies oil to all the places where it is needed for lubrication. In addition, some of it enters the filter and then passes through a hollow bolt from which it drops back into the sump.

In the full flow system there is a union with an extended tube that comes up diagonally at the back of the block and which enters the horizontal drilling previously mentioned. This union prevents any of that oil entering the drilling. Instead it goes via a pipe or hose, depending on whether the engine has an oil cooler or not, to the filter. The bolt on this filter is solid, not hollow as previously. After passing through the filter, the oil then goes into the same horizontal drilling as before.