Help diagnosing a noise

[SilverXJ]

New sound.. need help diagnosing it... I'll give you the back story... short

Put on my polished and ported head. It ran perfect.. smooth idle, plenty of power quiet. 300 miles later one of the Comp Cam lifters takes a dump because it was assembled wrong. Bent a push rod and damaged a roller rocker, Pull the head, replace the lifters with some Crower Cam savers and push rods and the damaged rocker. Start her up, break the new lifters in. Runs fine but after like 2 weeks I start hearing a sound again.

When started from cold the sound is not there. The vehicle has to be warmed up and driven for the sound to come around. Once it comes it can be heard at idle, acceleration, basically every where. Its a metallic rattle kind of sound. It seems that if I really push it and get it around 4000 RPM it starts to sound really bad.. almost like pinging (but its not pinging), just starts to sound almost random at higher RPMs. It definitely has a rhythm until it gets to higher RPMs.. I didn't hold it there long enough to really listen to it. It must be driven for it to come about. I pulled the valve cover this evening and let it idle for 30 minutes and the sound never came about, even though I unplugged the electric fan and it got hotter than it usually does.. a bit past 210*. Before I pulled the valve cover the engine was already driven and the sound was there. Pulled it in to the garage, pulled the valve cover and idled it for 30 minutes and the sound never came about. The sound has gotten worse over the course of a few weeks. And it seems to be the loudest just after I come off the accelerator.

At first the sound wasn't that noticeable and sounded like an exhaust leak.. so I had a few small leaks welded up, but the sound was still there. This weekend I replaced the manifold gasket and the donut gasket from the header to the down pipe. Sound was still there and it is getting worse. I also checked the flex plate to torque converter bolts and they were all tight. Didn't see any cracks in the flex plate either. It sounds like it is coming from the back of the engine. And it does seem to be loudest around the bell housing or the passenger side near the rear. I thought that it may just be echoing in the torque converter. Sounds like it might be from inside the block, but can't narrow it down that well. I also checked the preload on the lifters and it is exactly where I set it. 1/2 a turn past 0 lash. I backed it off 1/2 a turn then found 0 lash again and it was right where I set it weeks ago.I thought maybe the cam is fried, but preload hasn't changed one bit.

So I don't know... something with the torque converter? lifter bleeding down? Something else? All fluids are good. Temp stays around 210*, oil pressure is good (20 psi of better)... any ideas?

[FrankZ]

What brand pistons did you use? Based on your discription a collapased piston might be the culprit. I'd drop the pan first and plasti-gauge the bearings first to eliminate the rod and main bearings as the source of the sound. If they check out okay,,,pop the head and stast yanking pistons.

[SilverXJ]

Ha... piston guess is as good as mine. Remember Titan built this pile. And I would have better luck getting blood form a stone than a build sheet from them. I've asked at least 50 times (not joking) for a build sheet and that was one of my speculations prior to purchase. At one point they said they are P3071 Pistons.. which would be a 14.1 cc, but when I cc'd them it came to 13.4.

What would cause a collapsed piston? Also, why would it do it only when hot and driven? Could it have happened when the comp cam lifter collapsed?

The sound getting worse when I let off the throttle when the engine is floating makes me think it is a rod issue. However, being that it gets progressively worse when the rpms makes me think its a lifter bleeding down.

[FrankZ]

When I started my original stroker project my machinest measured the pistons I spec'd and flat refused to touch them (677cp). He had measured the dome thicknes and found that milling them would cause them to be very thin. He said that even a minimal amount of detonation would cause them to collapse. If you do pull the pistons make sure you measure the diameter of the piston at multiple points around the skirt. The tangs may be collapsed allowing piston slap.

Yes it's along shot, but still not out of the realm of possibility. Again, I would start by pulling the pan and plasti-gauge all of the bearings.

[Comanche91]

A friend had a noise at high RPM like - turned out the harmonic balancer was coming apart. Any telltale marks on the timing cover?

[SilverXJ]

I doubt its the balance as it is new and the sound does seem like it is coming from the rear. However, anything is possible and I will check that.

[Comanche91]

His noise sounded like it was coming from the rear also. In fact he thought it was his cat coming apart at first.

[SilverXJ]

Its not the harmonic balabcer. Oil is dripping down tonight and I will see if I can locate some plastigauge tomorrow.

[SilverXJ]

I pulled the oil pan today and there was a bit of metal particles in it. Some magnetic, some non magnetic. Not a whole lot.... but how much is acceptable? When I put the new lifters in about 400 miles ago I cleaned the pan and there was no metal in it when I put it back together. I didn't see any obvious signs of wear on the cam though. It has been through an oil change and filter since then. I only had time today to take off one rod cap and the bearing looked good and came out to .0015 clearance. But that is only one.

I can understand the metallic/magnetic particles coming from the cam and lifters if they failed, but where would the non magnetic silver particles come from? Pistons or bearings?

At this point I am not really sure what to do

[FrankZ]

Cam bearings maybe? How's the oil pressure been?

honestly i can't think of any non-metallic parts inside a 4.0 other than the snubber in the timing chain cover, and that's rubber.

[SilverXJ]

Oil pressure is great.. no less than 20 psi

Oh.. crap.. i meant non magnetic, not metallic.. ugh

[FrankZ]

Pistons, bearings, and possibly rings.

[SilverXJ]

Would any amount of either metal be considered normal?

[FrankZ]

I'm going to say no. Any small metal particulates should be held in suspension in the oil and removed be the filter. Larger pieces of material that end up at the bottom of an oil pan are symptomatic of a failed component(s). The only way to know exactly what the pieces are is to start removing and inspecting parts. Probably not what you wanted to read.

[Mgardiner1]

Frank is right. The any material visible after engine break in is most likely a sign of a failing component