Tell me this noise isn't what I'm afraid it is.

[bobH]

I'll offer a WAG... based on events as they happened on my own 47...
burned piston(s). I had problems with pre-ignition/pinging, and eventually found three pistons with holes on top, at edge, down into the ring-lands.
With heads off, easy to see on top of pistons.
Oh, the fun

[Old Henry]

Originally Posted by bobH

I'll offer a WAG... based on events as they happened on my own 47...
burned piston(s). I had problems with pre-ignition/pinging, and eventually found three pistons with holes on top, at edge, down into the ring-lands.
With heads off, easy to see on top of pistons.
Oh, the fun

That is certainly a possibility since, just a couple of weeks before the noise started, I put my old Stromberg 97 carb back on in place of the Holley 94 I'd been running. Then after the noise started I checked the spark plugs. They were a bit lighter than tan, more toward white, so I checked the jets in the carb and found that they were the .44's I'd put in to climb Pike's Peak and probably too lean. That's when I put larger ones in hoping it would stop what I thought was just premature detonation but it didn't. Maybe the damage was already done.

[JSeery]

Originally Posted by Old Henry

That is certainly a possibility since, just a couple of weeks before the noise started, I put my old Stromberg 97 carb back on in place of the Holley 94 I'd been running. Then after the noise started I checked the spark plugs. They were a bit lighter than tan, more toward white, so I checked the jets in the carb and found that they were the .44's I'd put in to climb Pike's Peak and probably too lean. That's when I put larger ones in hoping it would stop what I thought was just premature detonation but it didn't. Maybe the damage was already done.

Why did you pull the 94?

[Old Henry]

Originally Posted by JSeery

Why did you pull the 94?

I had rebuilt it myself because it was seeping gas when I parked it in the garage at night and stinking up the garage. I also thought it might be part of the missing problem I had. After I rebuilt it, including replacing the power valve, it wouldn't hold gas after parked at night and I had to fill it with my electric pump every morning and choke it to start it. The engine didn't run any better either. So, I decided to put the Stromberg back in and see if it did any better.

I had Uncle Max rebuild my 97 but he left the .44 jets in thinking they were OK at my elevation of 5,000 feet. Maybe they were and that has nothing to do with anything but the plugs looked a little lean to me so I put bigger ones in. Didn't help the noise.

[Old Henry]

I just tried removing a spark plug to see if that made any difference, planning on removing one at a time to try to identify the offending piston. Unfortunately, the noise from the air rushing in and out of the spark plug hole drowned out all other sounds and I couldn't hear anything else.

Other ideas to identify the bad piston?