Need help with engine noise

[Winter911]

Hi. I have to apologize for the continuous engine noise threads but this is a little different than my last one.

Before I had a loud tick on bank 4,5,6 and found out the valve adjustment screw came loose. Fixed that and all was good.

Next day, bank 1,2,3 started making this awful knocking sound. (YouTube link below)

https://youtube.com/shorts/WjcJrKGx88s?feature=share

I have the valve covers off and I have to push really freaking hard with a piece of wood to push in the valve spring so I don’t think any is broken.

The rocker arm bushings are all good and none have walked. They’re all super tight.

All valves are adjusted properly (used SnapGap so I know the gaps are right).

Car smokes on start up, but not when decelerating from high RPMs

Question 1) if I had a broken valve spring, how hard would I have to push in to compress it?

Question 2) how can I check for worn valves guides without driving the car?

If you have any ideas please please let me know. The last shop never got back to me and I’m on a tight budget.
I just want to enjoy the car (lol)

[yelcab1]

Air-Cooled Porsche 911, slant nose modified no less, and a tight budget don't go together. That noise is bad. Check for exhaust leaks. You probably should localize the noise a little more using a hose or a stethoscope to see where the noise is coming from. Exhaust or intake. Which cylinder? Cam shaft, head, or cylinder. I think more diagnostic is needed.

[Winter911]

Originally Posted by yelcab1

Air-Cooled Porsche 911, slant nose modified no less, and a tight budget don't go together. That noise is bad. Check for exhaust leaks. You probably should localize the noise a little more using a hose or a stethoscope to see where the noise is coming from. Exhaust or intake. Which cylinder? Cam shaft, head, or cylinder. I think more diagnostic is needed.

Unfortunately, that’s how it is sometimes.
I used a long screw driver as a stethoscope and it really sounded like it was coming from either cylinder 2 or 3 exhaust side, but it’s really hard to narrow it down.

Is it a really bad idea to run the car for a few seconds with the valve covers off to narrow it down ?
I already have plastic on the heat exchangers to keep oil off them

[Zuffenwerker]

I would give all the rockers s good shake when they are on tdc fire. I know you said they are adjusted properly though. The noise certainly seems 1/2 engine speed pointing towards valve train. You could also pull one plug wire at a time while it’s running to see if the noise changes on a particular cyl.

Would not recommend running it without valve covers but hey I’ve never done it. Let us know what you find.

Daniel

[Winter911]

Originally Posted by Zuffenwerker

I would give all the rockers s good shake when they are on tdc fire. I know you said they are adjusted properly though. The noise certainly seems 1/2 engine speed pointing towards valve train. You could also pull one plug wire at a time while it’s running to see if the noise changes on a particular cyl.

Would not recommend running it without valve covers but hey I’ve never done it. Let us know what you find.

Daniel

Each rocker from each cylinder at tdc clack when moved side to side. It’s more of a click when pulled forwards and backwards which seems normal due to the valve gaps.
I’ve read on this forum that side to side play on the rocker arms usually have nothing to do with valve train noise unless they are super loose.

I’ll try the plug wire trick when I put it back together.

For now, I’m trying to do as much troubleshooting as I can with the valve covers off

[Winter911]

Check all head studs and they’re all tight.

I rocked the valve stem in a vertical motion on cylinder 3 and there is some movement.
Worn valve guide may be the problem.

I’ll continue troubleshooting

[proporsche]

i hear broken valve spring...i would not
drive it...i just posted what could happen to you ..driving with one broken spring in Bohemia and 911.
If the engine is smoking cold or morning that would your valve guides.You should do a leakdown test..

Ivan

[yelcab1]

I see an engine drop and valve job disassembly in your future.

[1982911SCTarga]

Are you absolutely 100 percent certain that you don't have one valve out of adjustment? In checking this, did you go around the firing order and make certain all of the valve clearances are correct?

[Winter911]

Originally Posted by proporsche

i hear broken valve spring...i would drive it...i just posted what could happen to you ..driving with one broken spring in Bohemia and 911.
If the engine is smoking cold or morning that would your valve guides.You should do a leakdown test..

Ivan

All the valve springs seem super stiff. I have to push down on the rocker really hard with a piece of wood to compress the them, so there’s definitely no signs of a broken spring. Is there any other way to check?

It definitely smokes on start up so guides it may be

[Winter911]

Originally Posted by 1982911SCTarga

Are you absolutely 100 percent certain that you don't have one valve out of adjustment? In checking this, did you go around the firing order and make certain all of the valve clearances are correct?

Yes. It’s really hard to get them wrong with the snapgap kit. To me, the noise is more clunky than a valve tap so I don’t think a loose valve would make this kind of noise

[proporsche]

on the pic number 3 i cannot see the end of the rocker shaft?? is it in the right position ??it has to be on all of them to the thinner bore

[proporsche]

if you certain about the springs, valve guides it is...
Ivan

[Winter911]

Originally Posted by proporsche

if you certain about the springs, valve guides it is...
Ivan

Here’s a better picture. They all are flush-ish on the right side of the bore

[proporsche]

ok good;-)
still be careful of high rpm if you drive it...
Ivan

[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.

[boyt911sc]

Winter,

You need to use the P7E and P7I tools to remove and inspect the valve springs with the motor installed in the car. It takes only a minute or two to remove the valve springs per valve. Inspect them and re-install them back. Go to the next valve. The procedure is like doing a valve adjustment @ TDC for each cylinder.

You can not guarantee that all your valve springs are good and intact without further inspection specially the smaller interior springs. PM me if you need to borrow the P7E/P7I tools.

Tony

[boyt911sc]

[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.

[Winter911]

Originally Posted by boyt911sc

Winter,

You need to use the P7E and P7I tools to remove and inspect the valve springs with the motor installed in the car. It takes only a minute or two to remove the valve springs per valve. Inspect them and re-install them back. Go to the next valve. The procedure is like doing a valve adjustment @ TDC for each cylinder.

You can not guarantee that all your valve springs are good and intact without further inspection specially the smaller interior springs. PM me f you need to borrow the P7E/P7I tools.

Tony

Thank you to Tony, I really appreciate that. I put the car back together for now, but I may reach out in the near future for those tools.
Definitely before I drop the motor and rebuild the heads
Thanks again.