To start off I had a small nut go down into the intake and ended up in one of the cylinders. So far I think I have narrowed it down to the #1 cylinder. I did a compression check on that one cylinder so far and the reading was about 75. I cant run the engine yet but will a cold reading be lower than a hot one? I have read the service manual and it says hot and the minimum should be 100. Thanks for the info. Oops, I have a 99 blazer 4.3

 

I checked all the cylinders on the passenger side and they were all around 120. I re-checked 2 on the drivers side and were at about 100 this time. I cant find the nut that I dropped in the intake but I know it went into the engine by the knocking. It looks like the number one piston has some slight scraping on it but doesn't look like anything major when I am using the scope. I don't see the nut in the other cylinders but and almost positive it is in #1. I was told to leave the plug out and floor it and it would probably come out the plug hole but this sounds insane to do. When turning the engine by hand I am not getting any resistance if the piston was hitting something or a valve. Besides pulling the head what else can I do?

 

It had to go through the valves to get to the piston. I'm sure you had fished around with a magnet. pull the intake manifold and you will probably find nicked up valves.

 

So far nothng with a scope looks bad with the valves. Im hoping it got shot out eh exhaust valve

 

SorryIf it is knocking (or has knocked) because of a nut dropped down the intake, then your engine is certainly not OK. Pistons are aluminum. Nuts are steel. Sorry to hear that happened.

 

Believe it or not it runs fine with no noise now and no issues. I guess the nut just passed through and out the exhaust. It ended up being a massive vacume leak which was causing a miss.