(11-29-2012, 04:33 AM)Rickabilly Wrote:

(11-26-2012, 05:53 PM)doubleboost Wrote: The 1500 was a triumph engine
Not the best
Had a crank shaft like a bent coat hanger
John

Actually John, the BMC 1500 as fitted to the MGA was a completely different engine to the Triumph unit, Quite often the confusion is born out of the whole British leyland corporation debacle and the fact that Nissan bought the rights to the BMC 1500 engine for use in it's small commercial vans and pickups, but based it's very successful A series engine on the lighter Triumph engines, albeit in a very much better engineered outcome to that of the Triumph version. Nissan didn't change anything at all with the BMC engine, even continuing to use UNC and UNF threads, where pretty much all components were interchangeable but with the A series nothing was interchangeable with the Triumph.

The MGA was still a three bearing model that remained almost unchanged except for capacity up until the early MGBs, where it gained two extra main bearings and was still being produced in the eighties, while one might expect that the change from three to five main bearings was in order for the engine to be able to handle more power, when in fact many of the high end historic sports car racers look high and low for the three main bearing models as the lower frictional losses and crankshaft of adequate strength means that they actually produce more power with the same specification of pistons, cam and top end.

The change to bearing specification was made for two reasons one was that it had become deeply unfashionable for a producer to build three main bearing engines and there was a belief that as the engine was being used in heavier and heavier saloon cars as well as the sports cars low RPM lugging might cause increased fatigue issues with the three bearing crank, as it happens the change from a solid crank pulley to a rubberflex harmonic balancer was the step that finally saved the crankshafts from fatigue failure in the heavier saloons.

As you can all tell, I spent way too much of my youth inside historic racing car engines

Best Regards
Rick