Clank sound on re-assembly

Tori · 06-16-2018, 03:35 PM

Alright,...... now what have i done ? Long block assembled. Timed, rockers on, valve adjusted. When rotating it makes a noise that sounds to me like a piston changing direction in the bore, (if the bore were slightly too big) or if the rod was contacting the skirt.

See video for sound. https://www.youtube.com/watch?v=tj7if7yIwmA&feature=youtu.be

I cannot pinpoint which cylinder it is, even used a stethoscope on each cylinder. If i rotate slowly, the sound is almost non-existant. I have checked piston to valve clearance and i'm good there at 4mm+

Heads where rebuilt, new rings, and one new rod and piston. (used) Motor has been apart for a year and a half.

I'm about to pull out my last hair.....

JJ 911SC · JJ 911SC's Garage

Shot in the dark for pin pointing the problem...

Where is the Z mark when the noise happen?

Eagledriver · 06-16-2018, 04:08 PM

Most likely something to do with the cams. They go “overcenter “ and try to snap forward when a rocker goes over the lobe. Watch the tensioners while the noise happens. Maybe you’ll see something move. Could also be slop between the intermediate shaft gear and the crank shaft gear.

-Andy

mikedsilva · 06-17-2018, 03:09 AM

Quote:

Originally Posted by Eagledriver

Most likely something to do with the cams. They go “overcenter “ and try to snap forward when a rocker goes over the lobe. Watch the tensioners while the noise happens. Maybe you’ll see something move. Could also be slop between the intermediate shaft gear and the crank shaft gear.

-Andy

Yes, I had a similar thing when putting my 964 motor together.. I thought the tension in the change was changing but it was the valve springs pushing back on the cam lobes at different spots during the rotation.

In your video, are the tensioners engaged? are the pins pulled?

Maybe pull all your rockers out except 1 and 4 and check again...

356RS · 356RS's Garage

In the video you can see the tensioner for 1-2-3 side compress each time the noise appears.

Tori · 06-17-2018, 08:02 AM

Thanks for the suggestions guys. I just tried to pinpoint the sound using the stethoscope again while the GF rotated the engine. I heard a loud click on #2 but could tell it was also coming from other places. I backed all the rockers off and really no change. I guess I’ll remove the rockers now and see what happens.

Tori · 06-17-2018, 09:05 AM

Quote:

Originally Posted by 356RS

In the video you can see the tensioner for 1-2-3 side compress each time the noise appears.

Is there meaning to this ? Can you elaborate please.

Tori · 06-17-2018, 10:45 AM

Just pulled all all rockers off (except 1/4) and no real change. Could it be the crank walking back and forth ?

This motor made ZERO noises and had no symptoms before tear down. It only came apart to fix oil leaks and do the typical 100K valve guide love.

mikedsilva · 06-17-2018, 04:04 PM

bummer- sorry, I do not know.

lvporschepilot · 06-18-2018, 12:07 PM

Sounds like the chain could be hanging up on a sprocket tooth (like at oil pump shaft sprockets) in at least one place. Did you set up the parallelism to spec and were the sprockets in ok shape?

Tori · 06-18-2018, 12:29 PM

Thanks for the suggestion. Sprockets are spot on, and there is no visible movement of the chains (hanging up) The sound is internal.

Trackrash · Trackrash's Garage

Quote:

Originally Posted by Tori

Is there meaning to this ? Can you elaborate please.

The tensioner should not be compressing. If you can compress the tensioner piston easily with a screwdriver, probably the tensioner should be replaced.

If it is soft you could have piston to valve contact or the sprockets not engaging correctly with the chain.

Tori · 06-18-2018, 12:56 PM

I think the tensioners are soft because the oil has drained out of them. I've measured all P to V clearance and have 4 1/4 mm clearance.

If it were a chain issue, binding, or alignment issue, how would that create a noise, or an internal noise ? Not challenging your diagnosis, just want to understand as i'm new to Porsche engines.

Trackrash · Trackrash's Garage

I would not start a motor that had soft tensioners.

Are they new tensioners? Have they been bled?

Info here. Carrera tensioner questions

Tori · 06-18-2018, 01:12 PM

they are the used tensioners that came out of the motor. I have not bled them. Was following Waynes book, it was rather vague on weather this was needed or not.

faapgar · 06-18-2018, 01:59 PM

You can support the LS tensioner idler arm with a rocker shaft bolt and cap between the idler and chain cover housing so the tensioner does not compress then rotate the engine.Ciao

smokintr6 · 06-19-2018, 10:40 AM

The only thing I noticed from watching the video is that the noise seems to happen at a different point relative to TDC each time. This can be observed because the crank is being turned with a non ratcheting breaker bar. It looks like the noise is advancing 30* ish per revolution. Not exactly sure what that means, but it's the only thing that stood out. If the noise is advancing each revolution its certainly not piston to valve clearance, if it's happening on the same cylinder each time. Does it seem like the noise is moving around to different cylinders?

Tori · 06-19-2018, 12:00 PM

Quote:

Originally Posted by smokintr6

The only thing I noticed from watching the video is that the noise seems to happen at a different point relative to TDC each time. This can be observed because the crank is being turned with a non ratcheting breaker bar. It looks like the noise is advancing 30* ish per revolution. Not exactly sure what that means, but it's the only thing that stood out. If the noise is advancing each revolution its certainly not piston to valve clearance, if it's happening on the same cylinder each time. Does it seem like the noise is moving around to different cylinders?

Yes, that is EXACTLY what i've discerned as well. That's why it's been so difficult to narrow down. I hear it in one spot, go there to listen, and it seems to come from another spot. I'm all on my own with this so it's super hard to rotate the engine and chase the sound.

I don't want to continue with the build if there is a true problem, but i cannot see what could be the issue. The case was not split, the pistons came off, but went back on after fresh rings.

ed mayo · 06-19-2018, 08:29 PM

Go back to the one thing you changed, the connecting rod and piston. First the piston, if no dice then remove the rod . As you said nothing was changed,,,,,except for that.

Tori · 06-20-2018, 07:16 AM

I suppose i'll have to do that, was hoping to not have tear it down again. This will be the 3rd time, and the 5th time i've had to borrow the cam tools. At this point, i'm too embarrassed to ask again. Guess now if i spend the money to buy one, it'll be Murphy's Law that i'll never need it again. LOL