My camaro has always knocked when it was cold and it would eventually go away when the engine warmed up. You couldn't really hear it at idle, you'd hear it from 2k rpm and up. On the way to work yesterday, the knock wouldn't go away.

When I got home, I took the valve covers off to check the valve train. None of the rockers had play in'em and none of the lifters felt weak. I also jacked the car up and checked the flywheel for cracks, but it looked fine. I ran a compression check and every cylinder was from 185-205ps. This morning I pulled it into my dad's shop and took the oil pan off and then the windage tray off so I could see the entire crank, and I couldn't find anything out of the ordinary. There was no metal in the pan or in the oil pump pickup.

I also replaced the belt tensioner last week after the pulley started making a rattling noise.

I did notice one of my cam lobes had a groove wore in it, I plan on getting a picture of it later today. I'll post it here when I do.

It's a deep sounding knock that gets faster and louder as the RPM's go up. The car still pulls great, even at high rpm's and oil pressure hasn't changed, its about 18-20psi @ 700rpm and 35-45psi at 2000+ rpm. I ran it down the road logging with datamaster and it pulls 2-5 degrees of timing for a split second after 4000rpm. Also, the car has been idling irratically ever since I put a different fuel rail on, it sounds like it has a slight miss at idle.

Any ideas where this noise could be coming from? Did I miss anything? I guess it could be a wrist pin too, but how would ya diagnose that?

 

if there was a groove in one of the cam lobes theres a good chance a lifter roller is flattened - recheck all of them for flat spots. also, if a rod is knocking and you dont know which one it is... generally the rod with the problems will be discolored or a different color from the other rods. your oil pressure is good, not great, 50 psi at cruising speed is about perfect

 

thanks for the response

Would it be a bad idea just to replace all the rod bearings? The car has 125k miles on it so it could use a new motor, but I just dont have the cash to completely rebuild it. Though I've never put new rod bearings on a crank without polishing it first.

 

i had 2 rods knocking in mine and replaced just the bearings with the engine still in the car and didnt have any problems for at least 20,000 miles and when i rebuilt the motor the bearings looked brand new.

If you have patience, you CAN polish the rod journals with the engine still in the car, but it must be done 1 rod at a time and be clean clean clean clean clean

 

also, if the rod bearings are wore more than just to the copper then i wouldnt waste my time because it will just start knocking again. also step the oil weight up ro 10w40

 

thanks again for the help

I couldn't feel any play in the rods at all, but I can't think of any other cause. I'm gonna wait till Monday and get a micrometer from work and check all of the journals since I don't intend to polish them.

I'm also probably gonna end up replacing the cam, lifters and springs, and maybe the rockers too since the LT4 hot cam kit comes with'em and looks like a good deal.

I hope its not a main bearing, it would suck to go through all this trouble and completely miss the problem.

btw, if this noise was bad piston slap, would that show up in a compression check? might sound like a dumb question but I had to ask.

Thanks again

 

piston slap will not show up, and the slap usually goes away as the engine heats up. if the cam bearings look bad, replace them. you will know if a rod was knocking when you pull the rod cap and look at the bearing itsself. it will be wore to the copper. if this is the case dont be suprised to see more than one wore to the copper.

 

For a long time, this noise would go away at startup. On Friday it wouldn't go away, which lead me to believe it was a rod bearing.

At least replacing the rod bearings would eliminate one possiblity, and with the k-member out of the car, replacing them should be fairly easy. If it still knocks I'll just put in some thicker oil and hope it quiets down the pistons.

Thanks again

 

I replaced the rod bearings, here are the pics of 1-7, my camera batteries ran out before I could take a picture of #8

Even though some of those bearings look like crap, the journals didn't look scored up, so I just gobbed some assembly lube on'em and installed'em. Hopefully this fixes the knock I was hearing.

http://s6.photobucket.com/albums/y21...=Cylinder1.jpg
http://s6.photobucket.com/albums/y21...=Cylinder2.jpg
http://s6.photobucket.com/albums/y21...=Cylinder3.jpg
http://s6.photobucket.com/albums/y21...=Cylinder4.jpg
http://s6.photobucket.com/albums/y21...=Cylinder5.jpg
http://s6.photobucket.com/albums/y21...=Cylinder6.jpg
http://s6.photobucket.com/albums/y21...=Cylinder7.jpg