Need help with engine noise

[Winter911]

Originally Posted by 917_Langheck

This is what Tony had us looking for when setting the rocker shafts - just a hint of shaft at the thin side aperture.



Like Ivan, I dont see that in the upper photo of the #3 exh, so maybe it did "walk," or is it just missing the nut? In the lower photo the angle can be deceiving, so leaving that speculation until further evidence.

Mine are only flush of the right side (5mm) The 8mm is inside the bore


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[Winter911]

Originally Posted by pampadori

What year is the engine? Could one cyl head have lost it's air injection plug near the exhaust port?
Would make a similar sound. A loud tap that speeds up as engine speeds up
Just a thought.

It’s a 2.4 MFI from 1973

[917_Langheck]

Yes, that photo better shows where the 5mm nut is and looks spot on...

[Winter911]

UPDATE:
Okay… the noise continues and at this point it’s getting unbearable. I took the intake valve covers back apart and the rocker arm on #3 at TDC makes quite a loud metal sound when rocking it side to side. Here’s a video:

https://youtube.com/shorts/2kfM0LkDcSY?feature=share

Could this be the culprit? I checked the rocker bushing bolts and they are FREAKING TIGHT.. so I don’t think it’s loose. Valve clearance seems just right also.

Is this noise normal? Too loud?
If the bushing bolts are tight, how else can I tighten the rocker arm?

Here are few pictures:

[917_Langheck]

From that latest video it appears that the rocker arm bushing has failed, or the shaft has. There shouldn't be that much rotational movement.

There should be a detail in the spec book indicating the limit of side to side movement.

[proporsche]

at this point you should remove the no 3 rocker shaft and inspect it for crack.
ivan

[Winter911]

Update:
The search still continues... Noise is still there.
The side to side movement on the rocker has nothing to do with the noise I'm hearing.

Can a worn valve guide really make this kind of noise? Car doesn't really smoke and I'm unsure on how much oil it burns.

Someone suggested it could an exhaust leak but it sounds more like a metal to metal noise.
I will take it the valve covers off once again to see.
I did narrow it down to either cylinder 3 or cylinder 2.

[cmcfaul]

do the valve adjustment again. It's easy to screw up as you turn the engine looking for TDC on each cylinder.

[ant7]

A few things that have already been suggested First of all, go around and check all the valve gaps again, then I would pull each spark plug in order to determine whether the noise gets less, as for smoke on start up, this is often down to oil collecting in the crankcase from the oil tank over a period of time, seeping past the piston rings...Valve guides and valve stem oil seal issues usually show up on the over run, as oil from the rocker cases gets drawn past the worn valve guide seals and into the cylinders via the valves.
Someone else mentioned the noise could be coming from an exhaust manifold problem, or could be a broken head stud, its a possibility, but it does sound more like a mechanical noise, I also wonder if you may have a valve that is sticking, this could be caused by over revving the engine at some point, and a valve is slightly bent.
There are quite a few thoughts on this thread already, and you seem to have checked most of them, just a few thoughts of my own added.
A...

[ant7]

Any update on this ???

[Solamar]

Originally Posted by cmcfaul

do the valve adjustment again. It's easy to screw up as you turn the engine looking for TDC on each cylinder.

My thought as well. I've done dozens of valve adjustments on many types of engines and still managed to screw up my 911 adjustment once, must have been at the wrong TDC. Noise was exactly as your first video.

[917_Langheck]

I dont think it's the gap, its the side to side limit; either the rocker arm bushing is worn out, or the pin is, or both. In the video the click is most prominent when sliding back and forth, not up and down https://youtube.com/shorts/2kfM0LkDcSY?feature=share

[AUSTmike]

Just check the rocker arm by turning the engine to TDC take out the shaft and then the rocker! check to see inside the bushing to see what it looks like !..I checked mine and i had to replace a shaft!..

while you have the shaft and rocker off place the shaft inside the bushing and try and move it back and forth while holding the rocker and shaft!..if theirs play then that's your answer!

I have same issue with the side by side rocker movement!..But i'm pretty sure its the bushings!

I will be taking my rockers off and sending them to the shop soon but i just want to make sure first!

[Winter911]

Update:

Hi all, I appreciate all the recommendations.

I pulled the valve covers yesterday and adjusted the valves once again. Re-Adjusted them all with the backside method and with the .004 clearance.
The valves should be dialed in.

I also pulled each spark plug wire to isolate the noise to a cylinder and the noise did not go away.

Here are the unfortunate news. The noise is still there..
Car runs good and no smoke.
Can an injector make a noise like this? I’ve read several people talking about loud injectors.
I put my stethoscope to injector #3 and it’s definitely really loud… louder than the others.
It’s hard to tell if that’s the source of the problem

[Winter911]

Originally Posted by 917_Langheck

I dont think it's the gap, its the side to side limit; either the rocker arm bushing is worn out, or the pin is, or both. In the video the click is most prominent when sliding back and forth, not up and down https://youtube.com/shorts/2kfM0LkDcSY?feature=share

I’ve never heard of a rocker bushing shaft getting worn out, or making this noise.
It’s a really good possibility since I didn’t consider it.

I guess I’ll have to take out the valve covers once again (lol). These silicone gaskets are really not having a good time.

[Winter911]

Originally Posted by AUSTmike

Just check the rocker arm by turning the engine to TDC take out the shaft and then the rocker! check to see inside the bushing to see what it looks like !..I checked mine and i had to replace a shaft!..

while you have the shaft and rocker off place the shaft inside the bushing and try and move it back and forth while holding the rocker and shaft!..if theirs play then that's your answer!

I have same issue with the side by side rocker movement!..But i'm pretty sure its the bushings!

I will be taking my rockers off and sending them to the shop soon but i just want to make sure first!

Can this be done with the motor still in the car?
Noise is near cylinder number 3 and I’m not sure if the bushing can be removed without tapping it out with something.

Was yours making a similar noise before you took it apart?

[David Inc.]

Originally Posted by Winter911

Can this be done with the motor still in the car?
Noise is near cylinder number 3 and I’m not sure if the bushing can be removed without tapping it out with something.

Was yours making a similar noise before you took it apart?

The rocker and shaft can be removed with the engine in but clearance will be a headache. From the looks of it your biggest enemy might end up being corrosion in the shaft bores. The shaft might take some wallops for you to get it out and the angle will be difficult engine in.

[917_Langheck]

Originally Posted by Winter911

I’ve never heard of a rocker bushing shaft getting worn out

Yes, they do, which is why when folks rebuild their engines the rocker arms often get rebushed. There will be a Porsche spec on this for max. wear diameter before needing to be machined and bushed.

Originally Posted by Winter911

I guess I’ll have to take out the valve covers once again (lol). These silicone gaskets are really not having a good time.

One of the joys of our passion....

[LBEEMING]

@Winter911

Did it end up being the rocker bushing?

[Winter911]

Originally Posted by LBEEMING

@Winter911

Did it end up being the rocker bushing?

@LBEEMING I honestly never figured it out. I adjusted the valves once again and it did get just slightly quieter but that dreading noise was still there.

An porsche engine guru told me that side to side movements on the rocker arm is normal (up to a point) and would not cause that kind of sound.

I did a leak down test and i got less than 5% on all cylinders so no loose valves or broken rings.

I did put a stethoscope to each MFI fuel line and it almost sounds like it might be an injector getting old... and since these things are mechanical they're super clicky and loud. Car pulls super strong and doesn't smoke.