hi bought a engine last week it came out old c reg mgb 60s car engine no 18gb u-h 13939 im curious to what the difference is thanks
The main difference (no pun intended) is in the design of the lower end of the engine. The three main engine used three main bearings with the crank throws for two cylinders between each main bearing journal. The five main engine used five main bearings with each crank throw between two main journals. The basic engines are interchangeable using the right flywheels and front and rear engine plates and I beleive that the heads are interchangable as well. Some MGA owners update to the three main 1800cc engine as it is almost a direct replacement for their 1500 or 1600cc engines. You can get a lot more information from the guys that post on either the MG Enthusiasts board http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs or the MG experience board http://www.mgexperience.net/phorum/ .