911 3.0 - Engine sound ?

[JLN]

We are rebuilding our 911 3.0 motor. (1979)
We are going to replace several rocker arms and the camshafts, these are damaged.
The block is line drilled and there will be new bearings.

It was an metallic screeching sound, increasing with revs.
Same sound without fan belt, i.e. not from alternator or fan.

What could this noise be coming from? Please, can anyone help us?
Watch the video clip :

https://www.youtube.com/shorts/ao6guBBVBvs

[porschedude996]

What did the oil look like upon disassembly?

[JLN]

Originally Posted by porschedude996

What did the oil look like upon disassembly?

There was some metal in the oil. The engine builder says it probably came from damaged rocker arms and the camshafts . . ? ? But he has not found a good reason for the terrible sound. The motor have normal oil pressure. He also says the oil pump is ok, but haven't opened it. Could it be faulty oil pump or something else ?

[Dpmulvan]

If your mechanic can’t figure out why there’s metal in your oil or why it’s making a metal on metal screeching sound better find a new mechanic. Why line bore a 3.0 unless there’s damage? What’s the mileage/history?

[PeteKz]

Ditto Dpmulvan's comment. Other possible sources of noise are, the throwout bearing, timing chain and sprockets.

Your verb tense is confusing. You said the "block is line drilled." Do you mean you have already fully disassembled it, inspected it, and "line-bored" the "case"? If so, were there any signs of main bearing or rod bearing damage? How about damage or wear on the sprockets, chain, tensioners and guides?

[JLN]

Sorry. I'm from Europe and my English is bad The same mechanic previously rebuilt the engine.
He wants to get it right this time. . Block was inn for check. The bearings looked ok, no wear.
Some deviation in roundness, the plan is now 0.25 over-dim bearings.

[PeteKz]

No problem on the language. I just need to make sure what you are saying.

How many kilometers since that mechanic rebuilt your engine?

[JLN]

Originally Posted by PeteKz

No problem on the language. I just need to make sure what you are saying.

How many kilometers since that mechanic rebuilt your engine?

Only a few miles. 100?

[porschedude996]

You need to search it out. A good way is to take a a couple of feet of 10mm rubber hose and hold one end to your ear. The other end is used to locate the source of the noise. Also a good way, if the noise is internal is a mechanics stethoscope.

[Dpmulvan]

Originally Posted by JLN

Sorry. I'm from Europe and my English is bad The same mechanic previously rebuilt the engine.
He wants to get it right this time. . Block was inn for check. The bearings looked ok, no wear.
Some deviation in roundness, the plan is now 0.25 over-dim bearings.

I wouldn’t trust the same guy line boring your case who couldn’t assemble it properly in the first place. Oversized bearings aren’t cheap either.

[Dpmulvan]

So how did your rockers and cam get damaged? Screw up with timing right?

[JLN]

Originally Posted by Dpmulvan

I wouldn’t trust the same guy line boring your case who couldn’t assemble it properly in the first place. Oversized bearings aren’t cheap either.

Agree with that. But it was a specialist-company which checked and drilled my block. .

Why many of my rockers and camshafts were damaged is surely also a good question?