ctowns77

Bought this car with 160000 miles and put 700 miles on it then it started to knock. 2nd gear is out and had to get up to speed to shift to third, this was when the knock got really loud. Hoping someone can help determine maybe what my knock is. It is between cylinders #4 & #6 on the passenger side. If I tighten the two closest valves between these two cylinders the knock will go away for a second. Also it isn't as loud under load. It sounded like pushrod was hitting the valve cover before taking it off but doesn't appear to be anything wrong with valves or rockers that I can tell. Any and all opinions will be helpful in determining what it may be. I have been told the camshafts are notorious for breaking also. Could this be the camshaft with a loud high pitch knock?

Thanks everyone!!!

raroz28

Hows your oil pressure, and is it a knock or a tick?

ctowns77

Oil pressure is normal and its definitely a knock and not a tick. It started off as a really quiet knock that went away after 900 rpms but now its much louder and need help determining what it is. It sounds like it could be a piston wrist pin but whats throwing me off is that its between the two cylinders and not isolated at one cylinder. Could this just be pushrods beings its loud its really got me worried.

ctowns77

Any ideas anyone? I was going to try pulling spark plug wires tomorrow one at a time and see if the noise gets quiet. If so its probably a rod knocking right? Maybe pull out pushrods and see if they aren't bent. Compression test on the cylinders to check for warped head or bad head gasket. Anyone think maybe a worn cam would cause such a noise?? PLEASE PLEASE HELP all comments are appreciated and welcome!!

charliediss

You may have a bad lifter. I have had personal experience with a knocking noise that turned out to be a collapsed lifter, does this knock when cold AND hot? Remember that the cam turns at 2X crank RPM, this is directly translated to the lifters, which make a noticeably faster knock (almost a rattle at times) than something in the rotating assembly...On the other hand...she does have 160 + miles the clock, my 97 TA (rest her soul) spun the #4 rod bearing at 150,000...but it WRAPPED.

Good luck.

Charlie

LilJayV10

It sounds like the lifter is collapsing or the roller on the cam is bad and it eating into the cam.

Who told you these cams break often?

bw_hunter

Trying to diagnose sounds without hearing them is pretty tough...

A main knock is a heavy sound, like hitting a heavy hammer on a heavy block of metal. Very deep tone

A rod knock is a lighter sound but still a solid knocking noise.

A valve related tap is a light sound like a drum stick hitting a wooden block.

Bearing knock sounds change with load.....and they don't get 'better'.

If you suspected the pushrods hitting the valve cover you have a tap not a knock. If tightening the rockers eliminated the problem, even momentarily, it's not a rod or main knock.

With so many miles I'd recommend you inspect the rockers very closely and if you don't find anything look at the lifters

ctowns77

Well was able to take spark plug wire off but could'nt get plug out due to chevrolet innovations. The noise was still apparent but not quite as loud. 2 others opinions are it probably a lifter. I will try posting before and after plug disconnected videos. Again no change in pattern of knock just not as loud. Distortion on videos was close to same and the noise is rapid.

ctowns77

Before unplugging spark plug
[autostream]http://autostream.com/camaroz28/?page_type=firebirdplayerthumbnail&framepage=1633& transactionid=1314396543-17311862115&posted_by=ctowns77_www.camaroz28.com&y outube_video_id=nJsEHk3bUJ0[/autostream]

After unplugging spark plug, plug is still in. How do you get plugs out easily?
http://www.youtube.com/watch?v=qe_c7-VvAFk

ctowns77

No pushrods still there but sound is faster correct me if I am wrong this is my first time. Is that lifters bouncing around now or is it a rod? I'm hoping lifters. Someone please help my baby no comment since uploads!
[autostream]http://autostream.com/camaroz28/?page_type=firebirdplayerthumbnail&framepage=1634& transactionid=1314464603-70530128&posted_by=ctowns77_www.camaroz28.com&yout ube_video_id=AV_TqpJjk40[/autostream]

moparman

Here's a bump for ya.

charliediss

The backround noise you hear is the rockers (the very fast paced, soft taps that sound like you are pedaling a ten speed bicycle backwards while coasting) To me, this sounds too rapid and too soft to be a connecting rod bearing...this leads me one of THREE directions. The first is a possible spun cam bearing, the second is a collapsed lifter (my personal bet). A hydraulic roller lifter is a small piston that relies on fluid and an internal spring to maintain positive contact with the camshaft and the pushrod. If the lifter is collapsed, it is not maintaining consistent contact with the cam or pushrod and is thus being bounced off the cam and the pushrod as the cam rotates. The third possibility is a damaged oil pump pushrod (or somewhere else in that assembly). Remember these oil pumps have a pushrod that is in contact with an eccentric on the cam to drive the pump. What were you doing when this noise started?

Disclaimer:
I am a shadetree mechanic employed by the USN, by no means an expert.

ctowns77

I was running about 25-30 mph in 1st gear so I can hit 3rd in my ****(T56 because it acts like its in neutral in second any ideas on this also be great!)*****. Was lil high in rpms but not extreme or near redline at all when it came on. The sound was faint and could barely hear it before this occurred. After removing pushrods on #6 cylinders it does sound to me like the lifters are bouncing faster in there. My two mechanics suggested rod. Any more input anyone?

Psycho

The oil pump is gear driven off of the rear of the cam. So that's not it.
The lifters will rattle without the pushrods to hold them down.

bw_hunter

I would think that's correct on flat tappet lifters but these roller rockers have a dog-bone holder to keep them in place...

That said I sure wouldn't run ANY engine without the pushrods in place.

To the OP, you have so many conflicting opinions you might as well start tearing it down. With so many miles on the car it sure wouldn't hurt to have it gone through.....