Rebuilt engine need help diagnosing

[afree92]

Evening everyone I need your help. I just bought a rebuilt engine for my 94 idi got her all put in the truck and fired her up. She ran great for the first 15 minutes after startup. Oil pressure is perfect and everything seemed to be working just fine. But about 15 minutes in I started to get air blowing back thru the intake. It’s hard to explain. I’ve posted a video to help me diagnose it. Below is the link to Youtube for a short video I made this evening.

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[IDIBRONCO]

It sounds to me like you have an exhaust valve/lifter/rocker arm issue. It sounds like compression coming back through the intake when the intake valve opens.

 

[hacked89]

Did you also take the driver side valve cover off and did all the lifters and rockers look to be operating normally?

 

[afree92]

I have not taken the drivers side off yet due it it sounding like the noise was comi g from the passenger side. I will check that out tomorrow afternoon and see if I can find anything. Thanks

 

[Booyah45828]

Bummer.

I hear a definite thump, which could be a valve hitting the piston. Something is definitely off, so pull the covers and see if anything isn't right compared to the others. If you don't see anything, a compression test is what I would do next, as that might also reveal which cylinder is making the noise.

 

[Black dawg]

really sounds like exhaust valve not opening, so compression comes back out the intake.

 

[Olds64]

x2 on checking the rocker arm movement on the driver's side AND running a compression test. If one of your cylinders has low compression you can do a leak down test to see if it's losing compression through the rings/valves/gasket.

 

[afree92]

Pulled the cover off drivers side this evening had a Rocker assembly that worked its way loose. Got everything back together and give it another try tomorrow. Thanks for the feed back everyone.