Need help: noisy engine after over-rev Options

[DC_neun_vierzehn]

First, it's a '73 2.0 (2056 rebuild with about 1,000 miles on it). 123 dizzy. Car was driving great. No issues.

Then, last November, I over-rev'd my engine twice. First time due to forgetting to put the throttle body spring back on after reinstalling a new gasket under the TB. The second over-rev was immediately after because unbeknownst to me the throttle cable was tangled in at the pedal cluster due to omission of spring. Both times, I pulled the key out IMMEDIATELY, but not before I saw the tach needle shoot WELL past the red line. Both times my heart sank. Still beating myself up for the gaffes. Also frustrated that the rev limiter in my 123 dizzy settings didn't prevent the over-revving. Ed at 123 (great guy) said that rev limiter does not prevent the RPMs from going above the threshold it's set at, rather it prevents sustained RPMs beyond the limit. Ugggg.

First thing I did was look for leaks under motor, in the engine bay, check for any funny smells. Didn't see or smell anything. Next thing I did was take it for a nice and easy drive around the block. Drove fine, but I thought it sounded a little noisy. Next thing I did was take it for a slightly longer drive and slightly less nice and easy. Did not notice any loss of power or any difference it how it drove - just a little noisy. The best I can describe the sound it "loose" (thumpy ... chattery ... a little like a diesel engine).

Then winter came (snow, salty roads, etc.) and I put the car away for the winter and planned to dive in when spring came. For last several weeks, I've been diving in trying to find the culprit.

Here's what I've done so far.

1. Compression tested each cylinder. 3 were at 130. C4 was at 120.

2. Removed both valve covers. Inspected all rocker arms and springs. Everything looked fine. Checked valve lash. C1 and C2 both were in spec (.008 exhaust and .006 intake). However, C3 had .004 for both exhaust and intake, and C4 had .002 for exhaust and .009 for intake. I removed those rocker arms to inspect closer. Everything looked fine. Reinstalled the rocker arms and adjusted the valve lash to spec (matching C1 and C2).

3. Changed oil. Inspected all of the oil visually in a glass jar. Did not see any debris. I ran a magnet through each jar, no metal shavings or pieces on the magnet. I'm going to cut the oil filter open with tin snips later today to see if I see anything in there. Topped her off with 3.5 quarts of fresh oil and new filter.

4. Took a 10 mile test drive. Noises are still there. Uggggg.

5. Removed valve covers. Checked the valve lash. Everything still in spec. Nothing moved.

What could be causing the noise?

The car definitely sounds different since the over-revs. I'll try to post links to a few short vids with audio.

[emerygt350]

Super easy. The cheap boroscopes have an app that goes down your phone. It's just a little camera on a flexible stalk. The stalk goes down the spark plug hole. If you put the car in 5th you can just gently push it to move the pistons up and down as needed.

Did Ian do the krusty method? That is where you turn the engine (again, fifth gear) until a valve is completely open (pushed in) and the you check the clearance on the opposite side of the engine.

[DC_neun_vierzehn]

Super easy. The cheap boroscopes have an app that goes down your phone. It's just a little camera on a flexible stalk. The stalk goes down the spark plug hole. If you put the car in 5th you can just gently push it to move the pistons up and down as needed.

Did Ian do the krusty method? That is where you turn the engine (again, fifth gear) until a valve is completely open (pushed in) and the you check the clearance on the opposite side of the engine.

Thanks for the explanation on the how to use a bore scope.

No, Ian did not use the Krusty method. He used the traditional method (find TDC for C1, measure and adjust valves as needed ... repeat at each cylinder in firing order). I tried to read about and understand the Krusty method, but my brain hurt.