The 8hp Briggs engines had a 3/4" threaded muffler port, while the 9hp engines on up have 1" muffler ports, except OHV models which do not have internal threads. If you buy an OHV engine to replace a L-Head engine, you will need to buy a muffler also. The throttle linkage on the new Briggs engines run horizontally instead of vertically, you may have to get a longer cable for this to work correctly.

Additional Info

An OHV engine may not fit in the place of a non OHV engine if your fuel tank in behind the seat.