Engine Knock - I expect a spun bearing
 

Hello all,

Today when I pulled in at the gas station I noticed a loud knocking from the engine that speeds up as the engine revs. As said in the title, I expect its a spun bearing. Oil pressure hasn't changed at all. Does this sound like a rod bearing to the more experienced?

If it is a rod bearing, how difficult are these to replace? The bearing itself is pretty cheap but I really don't want to pay a mechanic several hundred bucks to replace a $20 part. Personally I've never dug into an engine, but I learn quickly.

A rod bearing is a rather inexpensive part, but the work to replace it is very labor intensive. And that is hoping that the bearing has not chewed up the crank journal it rides on...

Regardless, a knock is NOT good and should be remedied sooner rather than later!

A lot of times a cracked flywheel can be misdiagnosed as a rod knock. I had a spun baring in a k5 and when I finally got around to fixing it the crank was ovaled

Alright from what I've read about changing rod bearings it seems like something I can do. In the meantime I'm only driving it unless I absolutely have to, but will pulling the spark plug wire for whichever cylinder help keep it from messing up the crank?

I wouldn't drive it at all. once it knocks its better to just do a full rebuild or find a junkyard motor. Driving it will only make it worse, and you chance blowing it up.

I thought I had a rod knock.
 

Check the alternator and the A/C brackets if they are cracked or a bolt is missing you can hear a knock that sounds a lot like a bad rod bearing. It is worth checking before you go into engine removal.

Progress is slow. Got the engine out and the oil pan off, no play in any of the rods so rod bearing is out. I'll be checking wrist pins tomorrow but I'm leaning towards a collapsed lifter. What parts are needed for a valvetrain rebuild?

My little knock
 

My problem was not what I thought it was. My alternator bracket was cracked and missing a bolt so when I pushed the bracket back in place the knock subsided. Well it turns out I went looking to see if the flex plate was cracked and noticed where someone had worked on the transmission and used the wrong type of bolt. The upper bolt on the passenger side was the wrong type and the lower had just fallen out so I had a gap between the block and tranny. I got the correct bolts in place and the knock is gone. Good Luck with your project.

woooow, maybe i should check the bolts on my altenator bracket too before i spend the $$ on an engine replacement.....i have a knock too...

My 96 4.3L V6 is making a ticking sound. Started while driving at altitude (about 9,000 feet) and started to retard the engine. Got it towed home and my dad, a mechanic, has replaced numerous things. Thought it was the bearing on the balance shaft which was loose. The noise has changed. It is much quieter. The noise does not start until it's been running for about 15 minutes. It DOES NOT start right away. It comes on slow. It does speed up when you press the accelerator. Blazer only as 116,000 miles on it.
Got a code yesterday, which is over a month since the problem started, has not been driven since. Code 300, Multiple Misfire.
Any ideas?