Hello everyone, I recently bought my first diesel oliver, it is a 56 super 88,  upon getting it started I noticed that it has a noticeable hollow sounding pop from the exhaust every second or so when it's idling, is this maybe a stuck exhaust valve or plugged injector? Or is this somewhat normal? The tractor did sit for a while before I bought it, just looking at where to start. Any ideas or suggestions would be appreciated! Thanks