Symptoms of a broken valve spring/bent pushrod?

[chevyburnout1]

So after a weekend of somewhat "aggressive" showing off, I have aquired a funky engine noise. When getting the rpms above roughly 1600 the engine starts to moderately "pop", and it gets more aggressive the higher in the rpms. The truck as a whole is louder when it happens and you can slightly feel it in the floorboards. Not a diesel fuel knock but more so like a deadblow hammer beating on the engine. The noise is still there even on deceleration, truck idles perfect and doesn't smoke or misfire at all even when making the noise so I kinda am ruling out injectors. Balance rates are relatively ok. The aggressive showing off involved a few 4400+rpm rolling burnouts and some 130mph drag races. So with the characteristics of the noise and what I was doing when it happened I'm wondering if it's valvetrain related? Curious who here has experienced bent pushrods/broken valve springs, and what were their symptoms? Only thing done to the heads are SoCal valve springs, everything else is stock. Any other suggestions is greatly appreciated! Thanks guys!

 

[Chevy1925]

sure its not a broke crank? your symptoms are not far off from what i see others have happen

 

[chevyburnout1]

Man I didn't even think about that. The only two broken cranks I've heard sounded like ten Clydesdales trying to kick their way out from inside the engine so it didn't cross my mind. Especially how great it idles, starts, drives, etc.

 

[Hot COCOAL]

Man I didn't even think about that. The only two broken cranks I've heard sounded like ten Clydesdales trying to kick their way out from inside the engine so it didn't cross my mind. Especially how great it idles, starts, drives, etc.

Maybe you shortened a rod?

 

[Chevy1925]

Man I didn't even think about that. The only two broken cranks I've heard sounded like ten Clydesdales trying to kick their way out from inside the engine so it didn't cross my mind. Especially how great it idles, starts, drives, etc.

it may just be fractured and not completely done yet or hopefully im dead wrong cause you sure as hell dont need that on your plate with all the bs you have gone through on this truck

Maybe you shortened a rod?

i hope not. he has a built motor

 

[malibu795]

it may just be fractured and not completely done yet or hopefully im dead wrong cause you sure as hell dont need that on your plate with all the bs you have gone through on this truck

First broken crank I had I ripped the throw web.. Sounded like a rod bearing had gone... At all rpms. 2nd one sounded like bunch of horses trying to get out

 

[hondarider552]

I bent 3 pushrods at 4500rpm. Sounded like what you are describing.

 

[chevyburnout1]

it may just be fractured and not completely done yet or hopefully im dead wrong cause you sure as hell dont need that on your plate with all the bs you have gone through on this truck

First broken crank I had I ripped the throw web.. Sounded like a rod bearing had gone... At all rpms. 2nd one sounded like bunch of horses trying to get out

I guess most signs point to that. Idle sounds perfect and quiet, and frankly normal daily cruising you wouldn't even notice it. I would assume any valvetrain issues would cause smoke. Adam it literally sounds like your truck did after the first passenger side valve lash adjustment. Except it seems poppy out of the exhaust instead of the intake.

 

[malibu795]

I guess most signs point to that. Idle sounds perfect and quiet, and frankly normal daily cruising you wouldn't even notice it. I would assume any valvetrain issues would cause smoke. Adam it literally sounds like your truck did after the first passenger side valve lash adjustment. Except it seems poppy out of the exhaust instead of the intake.

Bent push rod would keep the valve partially closed just like backing valve lash off

 

[chevyburnout1]

Bent push rod would keep the valve partially closed just like backing valve lash off

That's what I've been thinking, which wouldn't effect the low airflow at idle.

I bent 3 pushrods at 4500rpm. Sounded like what you are describing.

That gives me a little glimmer of hope!

 

[chevyburnout1]

Well I've done a little more research into this and I'm pretty sure the ol crankshaft has had enough. Stumbled upon a video a member ScreaminDuramax posted up of his snapped crank. Basically dead on the same noise its making. Looks like I have a winter build to start!

[YOUTUBE]lvFkg5hnrSA[/YOUTUBE]



Luckily I got the final moments of the beatdown on video Racing my buddy in his bone stock LB7 with a 5 second head start. Good old fashioned expensive fun

[YOUTUBE]HLCxvFywnX0&feature[/YOUTUBE]

 

[hondarider552]

Lol

hold my dog

 

[Bustedknuckles]

Run it and watch the crank pulley. It should wobble. Sucks to see for sure if it is!

 

[DMAXchris]

Doesn't sound like a broke crank. Does the balancer wobble?

 

[bmc1025]

Bent valve(s)?

 

[Utahski]

So after a weekend of somewhat "aggressive" showing off, I have aquired a funky engine noise. When getting the rpms above roughly 1600 the engine starts to moderately "pop", and it gets more aggressive the higher in the rpms. The truck as a whole is louder when it happens and you can slightly feel it in the floorboards. Not a diesel fuel knock but more so like a deadblow hammer beating on the engine. The noise is still there even on deceleration, truck idles perfect and doesn't smoke or misfire at all even when making the noise so I kinda am ruling out injectors. Balance rates are relatively ok. The aggressive showing off involved a few 4400+rpm rolling burnouts and some 130mph drag races. So with the characteristics of the noise and what I was doing when it happened I'm wondering if it's valvetrain related? Curious who here has experienced bent pushrods/broken valve springs, and what were their symptoms? Only thing done to the heads are SoCal valve springs, everything else is stock. Any other suggestions is greatly appreciated! Thanks guys!

Broken valvespring is not good. When one of my high dollar aftermarket valvesprings broke, what began as a slapping noise escalated quickly to a very loud knock that sounded like hammer blows. The valvehead had broken off and riveted itself into the piston crown. The hammer blows were that valvehead peening the injector tip. At idle the whole truck shook and the engine barely ran. It was ugly.

The broken crank started as lost power when accelerating. The thing ran, but not well. It escalated to a bad misfire.

With a broken exhaust pushrod, very loud noise came back through the atmosphere turbo intakes. Don't know how a bad intake pushrod would sound.

 

[chevyburnout1]

I've looked at the balancer and truthfully it was too hard to tell. The part where the belt runs moves back and forth a bit but the bolt and the part of the rear of the socal balancer I can see seem to stay in one spot. My eyes like to play tricks on me though lol.

The truck has been parked since as I haven't had time to look at it. But besides that noise it literally runs and drives perfectly. I'm hoping tomorrow I'll be able to devote some diagnosis towards it.

 

[NC-smokinlmm]

Hope its just a bent valve buddy.

 

[ripmf666]

Well I've done a little more research into this and I'm pretty sure the ol crankshaft has had enough. Stumbled upon a video a member ScreaminDuramax posted up of his snapped crank. Basically dead on the same noise its making. Looks like I have a winter build to start!

[YOUTUBE]lvFkg5hnrSA[/YOUTUBE]

Sounds like mine did.
[YOUTUBE]ROkdlAuu6yg[/YOUTUBE]

 

[chevyburnout1]

Partially tore into it today. Definitely a snapped crankshaft. Hoping I didn't tear up the block as I probably put about 200 miles on it after it snapped :roflmao: Will have it completely torn apart Monday

Winter build here I come! :woott: