I have rebuilt my 94 blazer's 4.3 engine and it was running great up until I had some lifters go bad. I have replaced the lifters and then found out that I had a blown head gasket on passenger side of engine. I no longer have water coming out of tail pipe and the engine was running great for a few min. I now have an even worse knock coming from the engine mixed with slight squealing. I did have water in my #6 cyclinger and fixed that issue. I can only imagine that bc I ran the motor for less than 5 min with water in the oil that it may have washed the lubrication off the bearings around the crank shaft. I have been working on this issue for over a week and the more I fix issues another one pops up. I'm quite frustrated at this point and am about to pull entire engine and start completely over with all new bearings and gaskets. The squealing is not coming from the belt at all. I only have 2,500 miles on motor. The tranny has been rebuilt as well as motor in last couple of months so I am not sure what to do at this point. I have adjusted timing as close as I can get it and the knocking is just continuing.

 

I have pulled the intake manifold 5 times and put it back together in a week and I cannot seem to get any positive results. I'm quite worried the noise is coming from the bottom end of the motor. What would be the best way to narrow down my issue?

 

Use a automotive stethascope and determin where your noise is coming from.By your description your engine sounds like it has a serious issues with crank and bearings.
Sometimes its better just to start over.Check all your clearances between the bearings and crank.Make sure the crank isnt out of round polish and regrind if neccesary and make sure you get the right size bearings.They also have some better bearings now that are better than the old tri metal kind.

 

I do have the stethoscope and I am ready to pull motor and completely start over. The engine has been board 30 over as well but I doubt that has anything to do with the bearings on the crank. I still have to drain the oil one more time to verify that oil has no water in it. I need to double check the timing but I believe you are right about the crank bearings. Would it be wise to just lift the truck and work underneath it after removing oil pan and front driveshaft or just pull the whole motor again?

 

I am working with a tight budget too, would better bearings be worth the cost? I didn't have any issues until the motor was ran with antifreeze in water so I shouldn't have to worry about that happening again as lesson was learned.

 

What would be the easiest way to find out exactly which rod is loose? Will it be noticable when I tear into the bottom end?

 

I'd say you spun the bearings, real easy to see when you take off the bearing caps they will be worn away.

 

Better bearings are worth it so get them.Make sure you get name brand quality parts and dont buy those trw bearings from autozone.Get this brand {clevite bearings} .They make a newer improved bearing thats not the old trimetal type.

 

Unfortunately I think just about every story i have heard about replacing the lower intake manifold gasket was followed by a knock story. Just happened to my neighbor. When replacing the LIM i guess its really easy to get crap into the engine and shortly after the replacement they start knocking. It sounds to me like you are pulling your engine sometime soon.

Depending on what way you decide to do that, it can be fairly easy or a big pain in the as$. taking the core support out along with the grille and everything will make your life 100x easier so you can pull the transmission with the engine and not worry about bell housing bolts, i just got done putting my neighbors engine back in his jimmy so trust me lol. Just a suggestion tho

 

Hey guys thank you for all the help. I have already pulled the engine. My number one piston rod cap bearing was razor thin. I will have to have everything micrometered and double check my spacing on that piston. I have already looked into the replacement parts and the clevite was my choice for bearings. I will need a new crank, the cam is fine. I was able to pull the engine with intake manifold and all within just a few hours. The more you work on your truck the more tricks and time saving tips you learn.