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.

[bdstone914]

Bent pushrod(s) ?

Pull them and roll on a flat surface

Using a stehascope or hose held to one ear can you isolate the area the noise comes from ?

[DC_neun_vierzehn]

Bent pushrod(s) ?

Pull them and roll on a flat surface

Using a stehascope or hose held to one ear can you isolate the area the noise comes from ?

Thanks for the suggestion.

@bdstone914 when I was inspecting the rocker arms on C4, I was able to pull the push rod out below the exhaust valve to have a look (looked fine, but I didn't know about the rolling on a flat table trick). I wasn't able to pull the push rod out for the intake because it was hitting the HE. Seemed like the same challenge for C3.

Same to assume I need to remove the HE to pull all the push rods out for C3 & C4?

And what about C1 and C2 - does the HE need to come off to have room for the push rods to come all the way out?

[Dave_Darling]

... I was able to pull the push rod out below the exhaust valve to have a look (looked fine, but I didn't know about the rolling on a flat table trick). I wasn't able to pull the push rod out for the intake because it was hitting the HE.

The pushrods should not hit the heat exchangers at all. Ever. Are you talking about the pushrod tubes? Those are not what we're talking about; the pushrods are the rods that actually push the valves open.

You have to remove the rocker arms for a cylinder to get the pushrods for that cylinder out. Remove them and roll them on a clean table top to see if any are bent. Installation can be a bit annoying, but it's easiest to put that cylinder at TDC so the valve springs aren't exerting any force on the rocker arms when you bolt the arms back onto the head. (Because 11 lb-ft isn't enough to seat the rocker arm shaft against the head when working against an open valve's spring!!) Convincing the inner end of the pushrod to stay in the lifter cup can also be annoying; I have been able to push an L-shaped Allen wrench down the pushrod tube and use the short end of the L as a fulcrum to move the inboard end of the rod up into the cup. It fell out, so I had to re-do it a few times, but eventually I got it to stay...

--DD

[DC_neun_vierzehn]

... I was able to pull the push rod out below the exhaust valve to have a look (looked fine, but I didn't know about the rolling on a flat table trick). I wasn't able to pull the push rod out for the intake because it was hitting the HE.

The pushrods should not hit the heat exchangers at all. Ever. Are you talking about the pushrod tubes? Those are not what we're talking about; the pushrods are the rods that actually push the valves open.

You have to remove the rocker arms for a cylinder to get the pushrods for that cylinder out. Remove them and roll them on a clean table top to see if any are bent. Installation can be a bit annoying, but it's easiest to put that cylinder at TDC so the valve springs aren't exerting any force on the rocker arms when you bolt the arms back onto the head. (Because 11 lb-ft isn't enough to seat the rocker arm shaft against the head when working against an open valve's spring!!) Convincing the inner end of the pushrod to stay in the lifter cup can also be annoying; I have been able to push an L-shaped Allen wrench down the pushrod tube and use the short end of the L as a fulcrum to move the inboard end of the rod up into the cup. It fell out, so I had to re-do it a few times, but eventually I got it to stay...

--DD

Interesting. As I mentioned above, after I removed the rocker arm on C4 (the one that was the most out of spec). While I had the rocker arm off, I pulled out the exhaust valve push rod to visually inspect, but I couldn't seem to pull the intake push rod all the way out bc it was hitting the HE (as I recall) as it was almost out. I'll try again. I'll take a pic if the same thing happens.

Also interesting about the pushrod needing to sit in a cap on the inboard end. Not sure I achieved that when I reinstalled it. It felt like it was in place when I put everything back together, but maybe not. That could be contributing to the noise I suppose, but it was noisy before I removed it to inspect. I'll be sure to look for this when I pull them this time.