I have a craftsman riding mower w/ a briggs 16hp ohv turbo cool I/c platinum engine #310707-0136E It was given to me used but in great shape. I have 3 acres to cut and it was doing the job just fine. After a few cuts it started to cut out. So I let it sit until I had more time to fix. Swapped out the gas and cleaned the carb. Also Changed the oil and cleaned the breather. Now it starts and runs but when you engage the blades and go down an incline it billows white smoke. When I disengage blades it stops smoking.Oil level is correct... do I have a blown head gasket? And or is it something else? Please help! Incline is anywhere from 22 degrees or less depending on where you are in the yard.

Pull the head and clean the head and valves--you will likely see substantial carbon build-up. The head gasket on Briggs are usually Teflon coated and reuseable. Do this every couple years. Ensure the aluminum head is not warped and the valves are not damaged. I would also remove and clean the air filter. Finally, start using full synthetic 10W-30 (e.g. Mobil 1) engine oil--turbo engines are tough on oil.