This is kinda long, sorry!!!
Okay so i picked up a 02 2500hd 6.0 4x4 from a guy who said it sucked in water needed a new motor. When i popped the hood it looked like it had been soaking in mud for a week, EVERYTHING is covered. turns out this guy was mudding and the truck has NO INNER FENDERS. Also the intake tube is missing and we had to tape mass air to the throttle boddy to start.

Anyways we started the truck and it fired right up but ran like poop, when he revved it it popped a little out the exhaust. it didnt smoke till he decided to hold the pedal to the floor to try nd load it on the trailer. it blew some blue/white smoke for a few min but only does it when gas pedal is held down. i never heard a knock or any bad internal sounds. it actually sounded stong and would idle.

my guess is the bottom end is fine and there might be some valve damage but slight since these no sound comming from motor. Im also thinking a lot of the reason it runs like crap is a bunch of sensors are messed up from the mud bath ( the oil pressure sending unit is sending bad signals) and would prolly run better if the mas air was actually hooked up right.
Also he said he changed oil and there was "only a little water in it"
it does not blow any kinda smoke at idle or when i ease on the gas.

so what do you guys think?? What should i do first?

Thanks

 

take the heads off and have a look...

 

I was thinink of starting with cleaning sensors and stuuf and then doing a compression test. if I pull the heads off they will be replaced along with lifters and possibly cam.

Which brings me to the question of which stock gm heads will add most power?

 

With an engine that has been through as much as you said that one has, I would pull the heads and have a look before doing anything else. Why do you have to replace them? Best factory heads to bolt on would be some LS3/L92 heads, but they are kind of expensive. The 317s on there now are perfectly fine.

Before you start replacing parts I would open it up and see what you are working with...

 

Well the was I looked at it was, if I pull the heads the should go to a machine shop to get tested which would cost money. I could try to find a set of decent stock heads off eBay and increase hp while I'm at it. What about ls1 heads?

 

If it was me.... And this is just me.... If this is a project truck, i would pull the heads as well... But to be honest, i would yank that 6.0 out of there, and take this opportunity to wash out the engine bay, and take a good. Look at everything!! A truck thats been run wet and hard and hung up to dry... I would take this opportunity and rebuild it like you want it!! Tear her down to the block and inspect everything!

 

Water in the crankcase... Never good! Dont take the sellers word for anything! Drain your diffs, see if they are contaminated, transfer case is in good shape? Cv axles leaking grease? Buying used 4wd always scare me... I have one...but it hasnt seen a dirt road...

 

I know this is old news bit I finally got around to picking up the truck today. Took a closer look and someone has already tried messing with the coil packs. Worse mews is there is oil coming out of the throttle body.... bad rings?? Tmrw I will pull plugs and see what's up. Looking like it might just go back up for sale.