2007 ls3 valvetrain noise

cash talks · May 13, 2011

bought an 07 half ton crew 4x4 yesterday with 125K. its throwing a PO304 Cylinder 4 misfire code. it has a horrible knock noise coming from the head/ valvecover. increases with rpm. 89%sure its not bottom end. holds 45psi of oil pressure at stop signs. gonna open it up this weekend. couldnt find any help on several sites. accepting guesses on what it is. it has no vibration/ balance issues like you would think. lucky one wins a special prize. i figured i would just put a low mileage motor in it but gonna open it up first. guy i bought it from said the chevy dealer told him it was a lifter and its common. if it was common it would be ALL over the web. besides, how do you know its a lifter without opening it up. would like it to be something simple and cheap and i will throw in a cam and springs while im in there.

whiskeymakin · May 14, 2011

i say lifter...throw a cam, lifters and springs in there and let er rip. not sure, but a compression test might tell.....leak down test

Elliott · May 14, 2011

I've got a buddy that had same problem and it was a lifter.Probably not to common but my lifters in my 5.3 have always sounded awful on startup since I bought the truck, so I could see where there is a potential problem, with that being said my motor has 234k on it now and still going

cash talks · May 15, 2011

tore it down last night. lifter collapsed

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cash talks · May 19, 2011

got it together last night. fired it up and it was quite. let it run for a couple minutes, put it up on the lift and changed the oil just to be safe that i didnt get anything down in it. started it back up, let it run for about 5 minutes and the same noise came from the same place. it was 1 am. i was ready to throw a hammer through the shop wall, or even drive the truck through it

cash talks · Jun 14, 2011

tore it back apart last night. on the dod motors, as seen in the pics, there are ports casted into the block that flow oil post lifter. the oil leaves the ports and goes through veins casted into the valley pan(the cam cover uner the intake). there are o-rings in the gasket that seal the oil under pressure. one shop guessed it was a blown seal. tore it apart, and that is what i found. ordered the new gasket today and get it tomorrow. will put it on and cross my fingers. hopefully the lifter builds pressure back up. will give an update