Does This Sound Like Rod or Main Bearing Knock?

[mikedsilva]

Someone asked me to look at this engine they rebuilt 25 years ago, but only just got round to starting. 2.2L.

The sound is pretty ugly.
My first thought was rod.

In an effort to try to find a simpler cause, I removed all rocker covers and checked clearances.
I found all rocker shafts incorrectly fitted: they were equally centred. However, rockers were moving freely.
Cylinder number 5 spark plug hasnt been firing. It has carbs, might be blocked jets? I wouldnt think a cylinder not firing would cause that noise?
The exhaust valve rocker had zero clearance. I centred this shaft and set all clearances. Some were a tad loose but no where enough to cause that clackety sound.

Fired up and it's somewhat quiet initially, but after 30 seconds the clack makes itself known then gets louder and louder till we get this.

Owner is reluctant to pull engine and disassemble at this stage; he is hoping for a quick/easy fix still...

[Dpmulvan]

Check the valves on number 5.

[Dpmulvan]

I wouldn’t run it anymore.

[Joesmallwood]

Broken valve spring?

[917_Langheck]

That sounds like a top end clack rather than a bottom end clunk, but that is via your vid on my phone. Broken spring is a good suggestion if all the valve clearances are in spec.

Run a stethoscope to the find the noisy one.

[917_Langheck]

Originally Posted by mikedsilva

Owner is reluctant to pull engine and disassemble at this stage; he is hoping for a quick/easy fix still...

BTW, the surest way to spend the most money.

[pocv0]

Broken valve spring on # 5 ? I'll bet you have zero compression on 5. Probably on the exhaust side. I've heard a clacking noise similar to that, but it was a broken rocker arm.

H

[mikedsilva]

Originally Posted by 917_Langheck

That sounds like a top end clack rather than a bottom end clunk, but that is via your vid on my phone. Broken spring is a good suggestion if all the valve clearances are in spec.

Run a stethoscope to the find the noisy one.

I'm probably showing my ignorance here: but there are 2 springs. Surely not both could be broken
A few years ago, I rebuilt my personal engine using new springs supplied from Pelican; when I removed the engine at a later time to change cams, I found a broken outer spring but it never made any noise nor had any running issues.
So my inference is that both would need to be broken for it to be the issue?

[mikedsilva]

Had another look today.
Springs aren't broken
Compression is around 135psi
Spark plug is firing but I suspect the jets are blocked on #5.


Using my stethescope again, the noise is heard on the rhs.
Chain boxes are equally noisy but they are not the source of the noise.

From undernead the car, probing each head through the fins, is VERY noisy. Made me think pistons were hitting the head. Using a borescope I didnt see any witness marks on the pistons.

Touching the stethescope on the bolts for the intake manifold for the right side, was noisy but #4 was by far the loudest.

It's compressiom was around 125 so not an issue I dont think.

Removing the spark plug lead from #4 while running, the loud clanking disappeared by 90%. Refitting it, and it clanked away again. Test is easily repeatable.

I would think this suggests #4 rod bearing?

Unfortunately I did not get this on video.. I felt sorry for the poor little engine.

[stownsen914]

That’s an interesting finding on #4. But why would a knock related to excessive con rod bore clearance go away even if that cylinder isn’t making power? I’d think the rod would still smack around and be noisy.

[Joesmallwood]

Lost wrist pin on #4? With a borescope, do you see any witness marks on the cylinder wall that look like the end of the wrist pin sliding out and rubbing the cylinder wall?

[917_Langheck]

Definitely valve train.

That's my bet based on vid #2

[AVI_8]

The frequency of the noise from the engine suggests valve train related, every second revolution.
Though if that was the case why the noise would subside by pulling the plug in the cylinder?

[pocv0]

It has to be the rod end cap/bolts, rod bearing, or wrist pin ? Seems like the piston is floating up and down, not going to be a cheap easy fix for your customer.
I wouldn't run it any more.

[mikedsilva]

Originally Posted by pocv0

It has to be the rod end cap/bolts, rod bearing, or wrist pin ? Seems like the piston is floating up and down, not going to be a cheap easy fix for your customer.
I wouldn't run it any more.

He still wants to get a second opinion.
But yes, I agree with your above suggestions.

Couldn't see any obvious cylinder wall markings with my camera but that doesnt mean it isn't the wrist pin.

Anyway, I'm not going to have any more updates to this unless he is prepared to rebuild.

[Jim2]

Cut the oil filter open and look for bearing trash.

[PeteKz]

Or send an oil sample for analysis.

[pocv0]

Drain the oil, take the sump plate off and look for debris with your scope. Probably pieces of rod bearing laying on the bottom.

[cgarr]

does it quiet up when it warms up? if so Piston slap?

[proporsche]

Mike do a little favor to the engine and do not run it any longer -more problem will happen.You hear valve hitting the piston plus very possibly not just one cylinder.Tel the client the engine has to come a part -end of story-

as the boys above said, wrist pin ,or bearings..Have you drain the oil yet--that should be the 1st...

Ivan