Simplicity Regent Mower, Lawn and Garden Tractor

If your tractor had an OHV engine on it, you need to stick with an OHV engine. If your tractor had a non OHV engine on it, you need to stick with a non OHV engine. The mufflers are totally different between these two engines and it will cause you some problems to switch. Most of these tractors used a 28Q777 Briggs engine with an oil filter bracket that bolted onto the oil pan. If yours is this way, you will not be able to use another engine with an oil filter on it. At this time I would recommend that you install an engine that does not have an oil filter on it so you do not get into any problems with it fitting. If your tractor has an electric clutch on it you will need to buy and engine with a 9 amp or larger alternator to run it. If you tractor has a fuel pump on the engine, you will need to buy and engine with it already installed, or use the old one off of your engine and also the valve breather. If you purchase an AVS style Briggs engine, the fuel pump draws its vacuum from the dip stick tube. If the AVS style engine has no fuel pump, you would have to buy a new dipstick tube. You cannot change from one brand to another without major problems especially on the muffler. One of the Kohler models was a CV16S-43510.

Additional Info

The newer engines use a filter that screws directly onto the oil pan and will be in the way of the frame as shown in this picture.