My Delta has a knock from the driver side of the engine and popping sound from the carburetor. With the engine running I pulled plug wires one at a time and the popping stopped on #3 cylinder which is on the driver's side.
I suspect an intake valve not closing properly. If it's a bad rocker arm or weak spring that would be an easy fix. I'm going to take the valve cover off in the next day or two. Will post again with findings and any suggestions are welcome.
Took off the valve cover today. Ran engine and noticed #3 exhaust rocker not rocking. That means the valve is not opening.
Took #3 rocker arms off and pulled pushrods. Discovered intake pushrod bent and rocker arm pivot broken in two. When I cranked the engine I observed the exhaust lifter not moving.
So I think this: The exhaust lifter froze causing the cam lobe to bang against the lifter causing the knock. Since the exhaust valve is not opening after the cylinder fires there is a lot of compression left so when the intake valve goes to open there is a lot of force against the valve and the pushrod, hence the bent pushrod and broken rocker pivot.
It looks like I need at least a new lifter, pushrod and rocker arm pivot. I have to take the intake manifold off to get at the lifter so I'm thinking, why not replace all the lifters, pushrods and rocker arms? It might cost more than just replacing the parts for #3 cylinder only but I don't want to put it all together and find another lifter going bad.