I am with the others. Sounds like a valve issue. Pull the valve cover and look at the rockers and the valves for No. 3. If the exhaust valve got stuck, you might just be able to squirt some penetrating oil around the guide and tap the valve with a block of wood and hammer and get it unstuck. If the exhaust valve does not seem stuck, then it might be the intake valve and that might be a speck more complicated. The exhaust valve is in the chamber and the design makes it impossible for the piston to hit it no matter what you do. On the intake side, its different because the intake is pretty close to the piston. So if it was a stuck valve and it kisssed the piston which unstuck the valve, you likely have a bent intake valve head which will never seat flat. That will require a little remedial work at the machine shop.
Could also be just a lot of crud and junk on the seat and valve preventing the valve from fully seating and sealing. If noting evident from a visual inspection, you may have to pull the head and take a look and see what is going on.
Last edited by Dragsix; 07/31/2023 3:07 PM.
