Loud Knock

[fbilly420]

Started yesterday, ran fine stopped at a stop light. Truck stumbled a little (like a slight miss) and cleared back up in just a few seconds. Did the same thing about 10 min later. The truck sat through the day, picked my daughter up from school everything seemed fine. Slowing for a stop light had a sound like the belt was coming apart so I pulled over popped the the hood still running. Everything looked ok had a thumping sound near the intake so I thought maybe a rocker arm or something. I get home pull both valve covers everything looks ok. Running the truck with valve covers off the knock is VERY loud (sounds like it is coming from bottom end). Getting a lot of blow by coming through push rod holes at #4(quite a bit more than any of the others). I have 2 spare motors for my project truck so I think I am going to pull this motor today unless anyone has an idea that will save me a couple of days labor. Original forged rod motor with 225K on it.

Forgot to add knock is following RPM.

 

[ghohouston]

Maybe post up a video? It sounds to me like you have a failed lifter or bent pushrod, something along those lines

 

[fbilly420]

Well I am having a hell of a time trying to get this video loaded on youtube (forgot account info). I decided to just pull it and throw my other forged rod motor in as this is my DD. I will let everyone know what I find when I pull this motor down and find the culprit.