pinging/clatter in m130 engine

[pch2021]

Hello all,
OI recently finished installing a rebuilt m130 engine in a 1969 280SL with 1st oversize pistons. My engine builder is very good at what he does- thus being said, we all make mistakes.

This car pings, clatters, etc. under the following conditions:
1. Only when it reaches 80 degrees.
2. When it reaches 3,000 rpms.
3. When I barely touch the throttle. If I push hard, it goes away.
4. it sounds like machine gun clatter, although not that loud.
5. The only thing that elicits it is throttle position. Nothing else.
6. It starts in 4 th gear[ automatic] at 45 mph, and continues all the way to 80. I haven not been faster.
7. Engine runs fine otherwise.
I have seen a number of posts about a similar noise.

To make this even more fun, adjustments to timing, mixture, linkage, etc. make no difference. Could it a torque converter or transmission issue? Need some ideas!
Thanks,
Pierre

[ja17]

Sorry to say this Pierre, but it sounds like a connecting rod bearing. Drain the oil and remove the oil filter. Check for metal specs in the oil. Tear apart the oil filter and closely inspect in the folds of the paper filter and if you see copper specs.If you do, you have a problem. Hopefully I am wrong this time.

For diagnostic purposes, temporarily removing spark plug wire on the bad cylinder, might make the noise change or go away.

[GGR]

I had play in a piston pin once. Noise was similar to a failed rod bearing, but within a certain rpm range only. Not lower, not higher than the given range. I'm drawing your attention on this as your problem starts at 3000 rpm.

[pch2021]

Joe,
the filter was clean. I didn't see anything. However, that doesn't mean it is ok. I think it makes sense to keep looking, however.