The Stovebolt Site Forums The Shop Area General Truck Talk whats that knock

hey guys disturbing news on my truck while out 4 wheelin yesterday i didnt realize my truck was 2 qaurts low on oil until i was commin home and saw the oil pressure drop to about 25 pounds and come back up i stopped right away and checked oil saw it was 2 quarts low filled oil started truck back up and made a sound like it was out of oil sounds like bottom end now when ever i rev the engine past 2000-2500 rpm i can hear somthing in the bottom end the truck still has 50 pnds-75 pounds oil pressure what do you think is wrong and can i fix this problem without completely taking the engine apart?

the engine does not knock or tick at an idle matter of fact i crawled underneith while running and she is quiet as can be but if i rev to 2200 rpm and hold i hear a knock comming from lower end again with oil pressure of about 55pnds

Not good!

does it sound like it might be a wrist-pin slapping?

what is a wrist pin. it sounds like a blunt knock like somthing is beating in the lower end kind

ok the reason im confused about this noise the engine is making is because i have heared this noise in other engines accept when you heard it the motor was junk imagine what a worn motor sounds like after you change the oil and start it up for the first time that quick rattle you get befor the oil filter gets filled with oil thats the noise now the thing thats baffleing me is that it doesnt do it at an idle doesnt do it under heavy throttle or under load when your driving but at an idle if you rev it to about 2200 rpm you can hear it maybe not as bad as at first start up. now the motor itselfe is not running any different than it has befor like i said befor im hoping this is somthing i can fix without a complete overhaul

Hareboy

Sounds like it could be rod bearing(s). They don't knock at an idle or under a load, but if you rev the engine, you will hear them (rattle). Better be pulling the pan and checking them with plastigage.

Good luck.

Doug

Your profile shows a 61 Chevy. Is the engine a 235? If so, rod bearing would be my guess.

wrist pin connects the piston to the connecting rod

I know this will most likely NOT be the problem with your truck, but I have to pass on this tale . I changed the front motor mount on my 261 last week. To lift the engine I put a 2x8 across the bottom of the oil pan (figuring that would distribute the weight to the sides of the pan and it did) and jacked it up. Changed the mount, no problem, dropped the jack and board. Then I noticed that I left the cover plate off. No biggie; jack the engine back up but this time I grabbed a smaller board that didn't quite reach to the oil pan edges. Replace the cover, drop the jack and start engine. I would have sworn that I broke a rod or pin or something. My knock was steady though and increased with RPM. It truly was a puzzle to me until I climbed under the truck to listen. OIL PAN NOISE! I put my hand on the pan and I could feel the knock. I had dented the pan just a hair. I took my hammer and smacked each side of the pan which popped the dent out and the noise was gone. These trucks are so easy to work on! (sometimes). Good Luck.

I also had a fly-wheel cover come lose ,it made a heck of a racket....let us know what you find out

it is speed limiter indicator. mine does the same thing a bout 2000rpm so i slow down. was hoping for an answer. just got home i drive it daily and it does it some times an not others especially when it is warm or it has warmed up. mineleaks and burns a little oil. i drove it on a 100 mile trip no problems a couple of weeks ago. will have it torn down and rebuilt but hope not this year. best of luck to you. ron

@ Blacksmithdon
HA HA! Oil Pan Noise - sounds familiar.

The guy I got my engine from used a forklift to hulk his engines around. So I run in the same situation.

The sound almost scared the s...ht out of me when I fired her up the first time.

Frank