While the main difference between the 1300 and 1500 engines is the stroke,
the bores are the same, but the piston pin height (also known as compression
height) is different because of the different strokes involved. Also, the
1300 head had a smaller combustion chamber than the 1500 head. The 73-74
1500 heads had larger diameter intake valves, while later 1500 heads used an
intake valve almost identical to the one in the 1300 engine. The exhaust
valves were identical between the 1300 and 1500 engines. Also if you bore a
1300 engine .040, you can install dome top pistons from the GT6+ as the two
engines have nearly identical piston pin heights. The best setup I ever built
using a 1300 engine, was using a 74 large valve 1500 head, dome top GT6
pistons, the 1300 block and crank, a reprofiled cam, and a sidedraft Dellorto
carb. This setup made for a real MGB killer. Well, that's my two cents worth.
John C. Smith
75 Spitfire
|