1937 Austin Seven Ruby (Special)
Matt ups the ante with an ambitious event booking
Why do I do it to myself? I seem to be unable to take on a project without giving myself a seemingly unachievable deadline. But this time, I might well have gone too far. As I write this, there are just weeks to go before my most local event, the Vintage Speed Trials at Grimsthorpe Castle in Lincolnshire on August 28. And I have an entry. In a fit of optimism, I’d booked the Seven in to the event months ago, but with the day of the event looming, I’m really starting to worry that it won’t be done in time. With just six weeks until the speed trials, and a wedding and honeymoon set to restrict shed time on the run up to the event, the engine was still in a million pieces, scattered across the workbench and, although the rolling chassis was together, nothing had been tested. I’d already resigned myself to the fact that if I do make the start line it will be without a body on the car, merely a bulkhead, floor, set of flitch plates and a brace from the top of the radiator cowl to the return flange onto which the scuttle will eventually fit. But that didn’t scare me in the slightest.
Not compared to the mammoth task of building the engine.
I’d assembled the cylinder block previously, and so set to work on the other key part of the build, the crankcase. This aluminium casting is the heart of the engine and soon, following the stepby-step engine build series completed within these very pages and then re-printed as a series in our ‘Guide to the Austin Seven’, I had the freshly balanced Phoenix crankshaft installed with its roller bearings, the outer race of the centre camshaft bearing driven home and numerous other fiddly jobs out of the way.
Another fine mesh…
At this point, I needed to select a pair of nicely meshing cam and crank gears. My engine hadn’t come with any, so I headed up the road to see A7
engine Yoda, Ian Bancroft, with whom I spent several hours of trial and error mixing and matching cam and crank gears from his massive stock until we found a pair that meshed just so. Ian then set about assisting me with establishing a satisfactory amount of end float between the cam bush and drive gear. What was initially present was enormous, far more than could have been resolved by simply lapping the tapered end of the cam into the gear. So Ian soldered a bronze washer to the back of the bush and carefully reduced the washer’s thickness in the lathe, removing it periodically and test fitting it, before skimming away more material until a clearance of three thou was achieved.
Back in my shed, I sat the oil pump in a tub of degreaser, plumbed the oil filter lines together to create a complete circuit, blanked the oil pressure gauge take-off and spun the oil pump with a drill. Degreaser gushed forth from the oil jets (it’s a splash feed engine), but missed the crankshaft’s lubrication apertures. Some incredibly gentle tweaking with a close-fitting drift inserted into the oil jet brought the flow to a more satisfactory location.
The final countdown
Now it really was a case of final assembly. I was nervous about the potentially catastrophic consequences of the slightest error at this critical stage so, once again, I employed the help of Ian Bancroft. Together we set to work, first carefully installing the camshaft for the final time with its centre roller bearings stuck in place with thick grease. Then on went the oil pump drive gear, and finally the oil pump blanking plate was glued into position with epoxy resin.
Modifying then fitting the oil baffles came next, slitting them to allow the big end of the con rods to pass through them allows the pistons and rods to be fitted with the block already bolted to the crankcase, allowing for a more thorough seal. Threebond is Ian’s goop of choice here, which he liberally applied to both sides of the crankcase to block gasket before
I lowered the block into place. Going around the fixings three times ensured that the block was seated firmly, then our attention could turn to the pistons and con rods. I’m using 58mm slipper pistons for my build, which we fitted to my re-metalled rods, taking note of the set A, B, C and D markings from the precise end to end balancing process at Vibration Free last month.
Sliding the pistons into the bores (having gapped and fitted the rings first, of course) was a momentous moment, but I couldn’t dwell on it for long. With the engine up-ended, the big end caps torqued and oil baffles carefully closed up, we fitted the gauze which serves to keep, in Ian’s words, ‘bits of straw and the odd mouse’ from entering the sump from the oil filler tube. Then, after dousing everything in sight and priming the oil pump with engine oil, on went the
‘With the gasket coated in Threebond, the block was lowered into place’
sump. Next, with the engine the right way up once more, we set the valve clearances (six thou) and tightened the flywheel (200lb ft) before fitting the driven clutch plate and nose cone that I’d previously shortened.
Feelin’ blue
Before fitting the cylinder head, it was necessary to test fit it to ensure that the larger than standard valves did not collide with the casting. Ian applied engineers blue (essentially a nondrying paint) to the valves before we fitted the ‘head without its gasket and turned the engine over two full revolutions by hand. On removing the ‘head, we noted two small areas where the blue had transferred onto the casting, so Ian broke out his die grinder and removed a tiny amount of material from these areas before we repeated the test. With no blue transferred onto the ‘head, we knew that we were in the clear. And the thickness of the gasket was our insurance policy. On, then, went the ‘head, which Ian torqued in sequence to 22.5lbft.
I’m hugely grateful for Ian’s assistance and expertise, and suddenly the looming deadline of the Vintage Speed Trials at Grimsthorpe doesn’t seem to daunting. Now it falls to me to fit the final components and get the engine running. There’s a parcel on its way from Oxfordshire Sevens with exhaust and inlet manifolds, silencer, a laser cut fuel pump blank and a billet aluminium valve chest cover, but I’ll tell you all about that, and whether I make my date with Grimsthorpe’s north front driveway, next time…
matt.tomkins@practicalclassics.co.uk