Matt Tomkins Smooth as silk

Matt’s Traveller experiences project creep

WORKSHOP ED

1969 Morris Minor Traveller

Engine 1098cc/4-cyl/ohv

Power 37bhp@4750rpm

Torque 50lbft@2500rpm

Gearbox 4-speed manual

0-60mph 32.6sec

Top speed 76mph

Fuel economy 45mpg

Work done Engine refreshed and bottom end balanced.

Last month I mentioned my decision to give the Traveller’s engine, which was rather oily and nasty after eight years of hard use, a freshen up with new gaskets and a coat of paint to bring the engine bay back up to show standard. Now, I could have done this in-situ, but it was raining and so I removed the lump from the car and put it on an engine stand in the shed.

Over the past couple of years, I’ve built several A-series engines both for myself and friends, including some highly strung 1275s, so the Traveller’s relatively standard 1098 lump, which I built some nine years ago on the kitchen table of my university accommodation, was bread and butter stuff. It never smoked, so I knew I could leave the pistons in their bores (which were minty fresh with honing marks still visible on inspection), but I felt it prudent, while it was out, to pull the crank, inspect the bearings and journals, and consider adding some newness to the bottom end while it was apart to replace gaskets.

The crank journals were perfect, and the bearings were in excellent condition, but seeing as I had a set of the required +0.020in mains and big ends in stock, I dropped them in, checking clearances first, of course, using Plastigauge.

New standard size thrust bearings and a fresh oil pump finished the job.

But it wasn’t finished, not really. Having experienced the benefits of a properly balanced engine on more than one occasion, I promised myself that I'd never build another without having the assemblies balanced properly. Removing imbalance from an engine, after all, not only improves drivability, reliability and comfort, but also aids bearing longevity; thanks to the reduced radial loadings on the soft bearing materials, (known as cyclic bearing loads).

But before I pulled the crankshaft out again, I called the exceptionally knowledgeable Wobbly Steve at Vibration Free Engineering in Bicester to glean some advice. Steve explained that by using a special free-moving surface plate mounted to a balancing machine, (he called it a dynamic table) they would be able to balance the engine as a complete short assembly, minus the timing chain, driving the crank via a belt on the flywheel. This would allow the engine to be balanced as perfectly

‘Cyclic bearing loads dropped from 10.4kgf at 4000 rpm to just 0.17kgf’