In an earlier article (Oselli and the MG Midget A-Series Engine) I discussed the history of Oselli and its links with the MG Midget. Since taking delivery of ABW, I've been able to do a lot more investigating into the tuning that had been carried out on the car.
ABW was tuned by Oselli in 1998. The engine was removed , reconditioned and rebuilt to 1293 Fast Road Stage 2 unleaded specification. But what does this mean?
The 1293 Fast Road Spec claims to gives 95 horsepower, but retaining good manners for town driving. Fuel consumption remains good at cruising speeds and there is lots of low speed torque (see previous article on towing with MG Midgets!). Oscelli strengthened the bottom end considerably to provide a reliable unit able to rev up to 7500 rpm and able to last over time.
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| Power curves from Oselli brochure, 1998 |
The work done by Oscelli:
- engine stripped out
- parts checked, tolerances measured, and prepared for machining
- engine rebuilt, clearances checked, cam timing set up
- engine bored out to 1293cc
- crank, flywheel, clutch, pistons and conrods all balanced
- tufftride treatment to crank, journals repolished, alignment checked
- heavy duty bottom end main and thrust bearings fitted
- flywheel lightened
- cylinder head modified to large valve OE62 Rally Spec
- A600 camshaft fitted, cam follows set
- high capacity oil pump
- miscellaneous new seals and gaskets
- performance distributor
According to the May 1990 catalogue, the specification of the Oselli A600 camshaft is: 37/71/71/37, 288° duration inlet/exhaust, 0.360" valve lift with std 1.25 rockers, 0.016" tappet clearance, 107° inlet valve full open for timing setting (data from Richard Wale, 2009). It was a slight de-tune on the 1293 'Rally' specification (for which the Kent 286 camshaft was standard).
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| Close-up of ABW's "Oselli tuned" engine |
Some months later Oscelli tuned the SU HS2 carburettors, fitting ‘AF’ needles – the standard specification being ‘AN’. The new needles offer better performance with the K&N filters, tuned exhaust, modified head, and fast camshaft fitted to ABW.
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| ABW's engine bay |
Standard Midget engines are quoted at 65 bhp. I'd be amazed if ABW is giving anything like 95 bhp – but she seems eager!
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