engine knock

[jakedaniel]

OK, last night I was over at an ex's house and I went to the store to get some beer and when I came back out and started the truck I heard 3 or 4 loud knocks from the engine. Not knocking with engine rpm just random knocks. Ran OK otherwise, feels like it's lost some power but that might just be fear on my part. It always idles lopey and it's loud to begin with so I don't know if it's gotten any louder. I drove it home 15 miles on the freeway with no problems. Went out to check it this morning, started it and same thing. Sounds like it's coming from the passenger side valve cover but then again, who knows? Knocks 3 or 4 times loud then goes away. Plenty of oil and oil pressure, not overheating and I drove it around the block 3 or 4 times today to try and see what it would do. I don't have a compression gauge or the cash to buy one til Tuesday, I'm going to pull the valve covers tomorrow to check for anything broken, pull the spark plugs to see what they look like, and drain the oil to check for metal. What do you think it could be?

78 K5 w/350.

 

[Col_Sanders]

Check your oil for water. Have you been burning/losing coolant?

 

[jakedaniel]

No water in oil but have seen white smoke out the tailpipe on that side before, could be steam. It's too dark to check the radiator but I'll check it in the morning. Haven't had any overheating problems. Motor stays nice and cool. Think it's the head?

 

[jakedaniel]

oil looks good but black, coolant all the way to the top of the radiator, pressure is high and it stays cool but i found a piece of silicone or something on the dipstick. Plugs looked like ****, #8 was wet oil fouled, all the rest looked horrible too, one was finger tight and I saw #7 arcing off the block after I put it back together. I cleaned them up but didn't improve anything. I can't do anything about it now but I get paid on Tuesday and I'll throw plugs and wires on and change the oil. If that doesn't solve it I start my vacation on Thursday and if it makes it till then I'll pull the heads and replace them if they look bad, plus head gaskets, intake gaskets, and exhaust gaskets either way. Luckily I live close to work

Update: Made it to work. Knock wasn't loud today, 4 or 5 random knocks on startup, nothing else except the engine ran like crap. Maybe it's just plugs and wires. We'll know tomorrow afternoon

 

[Chevy305]

If you were messing with the plugs did you propperly gap them?

Also if this only happens on cold start ups, sounds like you have what I got - collapsed lifters. Mine is on the passeneger side too. On cold startups it knocks/ticks/ raps pretty good for a few secs until oil pressure is built up. Try adjusting your rocker arms see if it makes the ticking go away or change in tone.

Also if its progressively running worse and worse you could have wiped cam lobes, not likely but something to consider.

 

[jakedaniel]

The plugs were pretty trashed. I gapped them but they're garbage. I thought maybe lifters since after the first few seconds it won't knock no matter how hard I try to make it. I'm going to put on plugs and wires tomorrow and go from there. Lifters and a cam wouldn't be that hard, I could do that on Friday morning. It's running like crap but it's not getting any worse than it is now.

 

[jakedaniel]

Figured I'd let you guys know what ended up happening. Took it to the shop, motor had a blown head gasket. Didn't see the sense in replacing just one side so I had both heads pulled off, checked for cracks, valve job, new gaskets and 1200 bucks later the truck runs like new.

 

[Mike D]

My step son's truck used to knock when he would start it. The problem was a cracked/broken transmission flex plate. It sounded like a rod or bearing knock.