I have another stock 3 main with 125K on it which has only had rod bearings replaced in its life time as a maintenance item and it runs beautifully with great pressure. It drips 2 drops of oil when it is shut off. It revs quicker than any 5 main as it has also had the 'simple' mods done. Its current incarnation has just over 110K on it with 80 lbs oil pressure on the road and 70 at an idle. Granted it has had 2 rebuilds over its life, and is currently at 10 and 20 under on rods and mains respectively and. I have a 3 main with 247000 miles on it and it has been 'spiritedly' driven much of its life. For long life 5 main and you can make a five main spin guicker higher with simple mods,the simplest being a 16 lb flywheel.Then valve and cam improvements. With a 5-main engine you get a real rear main seal.Ħ3 for accuracy and concours should be a 3 main. With a 3-main engine you get to keep your mechanical tach. Also, on a 5-main engine, you can use the later straight-cut connecting rods that are much lighter than the angle-cut rods.Īnd, FWIW, the 3-main engine will incorporate a mechanical drive for the tachometer, which is absent from the 5-main engine.īottom line? For a street engine, it's a wash. Kenny makes a good point about the rear main seal on a 5-main engine. Others (including me.) feel that the extra crankshaft support in a 5-main makes for a stronger race engine, but this is really immaterial on a street engine. In fact, on a 5-main, bearings 1,3, and 5 are identical to those used in the 3-main, and some companies actually sell the 5-main bearing set for 3-main engines and tell you to throw away the extra four shells. I don't subscribe to that theory because there's so little friction in the two additional main bearings, which are narrower than mains number 1, 3, and 5 on a 5-main engine. One school of thought says that the 3-main has less friction. Some racers have a preference one way or another. I've never observed a perceptible difference in performance of a street 3-main vs. Should I be lusting after an early engine? Which finally brings me to the point, can you knowledgeable fellows wax poetic about the differences, advantages/disadvantages and sort of basically school me on the historical and practical reasons for the change. Neither was bruisingly powerful but both lent themselves to spirited, entertaining driving at less than supersonic speeds. Yet as I get sucked deeper into the MGB Matrix I also read and hear things like 'Free Revving' and 'Higher Redline' which brings to mind something more akin to the engine in my ill-fated Fiat 124 Sport Coupe of years past, or maybe the 3 cylinder 2 stroke that was in my '67 Saab Sonett. Over the years I have always heard,'stay away from the early engines' or 'They went to 5 mains for a reason'. So I never had a 3 main engine in any of my cars.

All of my other MGBs in the past were either '65s or '67s. It's a '63 but with the drivetrain (engine, rearend) from a '67. I'm working on my 5th (and probably last) MGB right now. Apr 27 Custom Brake Caliper Mount, Co.Jun 28 MOGreater Ozarks British Motori.

Jun 09 OHCincinnati Concours d’Elegance.

May 18 NYCanandaigua International Fes.

May 18 NCTriangle British Classic Car.

May 04 VAWilliamsburg British And Impo.

Redline racers for sale