Loud banging coming from intake area

Tiny
VORDIMYRE
  • MEMBER
  • 1999 CHEVROLET MONTE CARLO
  • 3.1L
  • V6
  • FWD
  • AUTOMATIC
  • 270,000 MILES
Replacing head gaskets in my mother in law's car. I put the car all back together and then realized I hadn't tightened the rocker arms on the rear head after I had started the engine. I know I heard a really loud banging sound coming from the upper intake plenum. I shut the car off removed everything got to the rocker arms pulled them out took out the pushrods check the pushrods and they were all straight, so I put it all back together and started the engine again and still heard the same loud banging. I really need to know what this could be what I could have damaged and how to fix it. Also I cleaned out what I thought was a port to the egr valve in the upper plenum. It looked as though it had become plugged with old oil and carbon. This port comes just behind the opening to the throttle body to where the egr is mounted. Could this be causing causing the hammer on metal sound I can hear and feel?
Monday, March 23rd, 2015 AT 3:12 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,443 POSTS
Have you checked for a damaged cam lobe? Is the engine misfiring? And no, cleaning the EGR port wouldn't cause a knock.
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Tuesday, March 24th, 2015 AT 5:00 AM
Tiny
VORDIMYRE
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  • 2 POSTS
No I haven't checked the cam lobe yet. It is misfiring a little. After talking with my Father and a friend, I am now thinking that I could have punched a hole in a lifter or two or more. Is that possible?
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Tuesday, March 24th, 2015 AT 5:53 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,443 POSTS
I don't think you could punch a hole in one, but anything is possible. Since there is a misfire, check the cam lobes to make sure nothing was damaged.
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Tuesday, March 24th, 2015 AT 6:10 PM

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