3.2 sounds like a diesel

[stubble88]

timing chain?
piston slapping?
cylinder not firing?

sound out of the exhaust is great. but it backfired that last time I tried to start it. No oil leaks. no smoke at all. change oil with no metal shavings at all.
seems like timing is off. but would that make this knocking noise? goes away with revs.

Cold start. Sounds normal. But idle is a bit higher when cooler.

https://youtube.com/shorts/xoCcPnAEDok?si=KRrkkt-5kqOdrV36

Warm. Knocking sound shows up. Idle lower when warm.

https://youtube.com/shorts/m-xKjY6AADo?si=Sk4BD-UZcyNchIK2

[Ian Comerford]

A bit of background detail might be useful. Has it recently had any work, parts changed etc or did it just start behaving like this one day?

[stubble88]

Originally Posted by Ian Comerford

A bit of background detail might be useful. Has it recently had any work, parts changed etc or did it just start behaving like this one day?

Yeah. Sorry.
Car was a dedicated race car
Lots of motor work done by AASE in 2018
New clutch (stock)
New lightweight flywheel
Had straight pipes now has Dansk 2/2
New oil and filter
New fuel lines
Simple race harness replaced with good used one.
DME harness not changed.
911 chips custom. (This ill seek more info on)
Headers with Dansk. No cat

[proporsche]

did you know you covered the lens with your finger?;-)
Sounds like rod bearings....
i`d suggest to drain the engine oil ,look at the drain plugs and what is inside the oil..

Ivan

[GaryR]

Originally Posted by proporsche

did you know you covered the lens with your finger?;-)
Sounds like rod bearings....
i`d suggest to drain the engine oil ,look at the drain plugs and what is inside the oil..

Ivan

He did - "change oil with no metal shavings at all". I would check timing, check valve adj and rockers. I don't think it's timing chain slap but not too hard to pull the covers to look in there for a collapsed tensioner.

[Bill Douglas]

Is it something as simple as an exhaust gasket having blown. The reason I say this is it sounds like my SC did when it blew out the air pump pipe next to where the exhaust joins the heads.

[proporsche]

Originally Posted by GaryR

He did - "change oil with no metal shavings at all". I would check timing, check valve adj and rockers. I don't think it's timing chain slap but not too hard to pull the covers to look in there for a collapsed tensioner.

thanx i`m blind;-) yah if the rod bearing goes kaput it would have been deeper sound plus particles on drain plug.
Ivan

to the op
is it there from cold start or only warm engine?When did it started? also possible wrist pin when the engine is warm-hot..

[stubble88]

It’s always there. Hot or cold. I noticed it after adding the muffler. But I’m sure that’s because I can now hear more of the engine. Seems to go away at any rev beyond idle. But there seems to be a vibration. Has solid motor and trans mounts.

[ant7]

Just a thought, does the engine still use the micro switches on the throttle body ?

[stownsen914]

Solid motor mounts can cause vibration. I'd dump those and try again.

Mechanic's stethoscope can be helpful to localize engine noises. If it's an exhaust leak, probing around under the car with a length of fuel hose with one end near your ear (not too close!) or a recording device can help find it.

[WMichelsen]

I can't quite tell from your clips.

On my 3.2, I've occasionally encountered somewhat that kind of sound. Mostly at low RPM, idle and a bit above. Really worrying, couldn't pin it down, then it went away. It has come and gone several times over the years.

The best I can think is the hydraulic timing chain tensioners are ratcheted. Maybe as they approach the next tooth, the chain is loose enough that it slaps a bit. Then tightens back up as the tensioner advances.

I dunno, does this make any sense for you? Or, can anyone chime in on my case?

[stubble88]

Originally Posted by WMichelsen

I can't quite tell from your clips.

On my 3.2, I've occasionally encountered somewhat that kind of sound. Mostly at low RPM, idle and a bit above. Really worrying, couldn't pin it down, then it went away. It has come and gone several times over the years.

The best I can think is the hydraulic timing chain tensioners are ratcheted. Maybe as they approach the next tooth, the chain is loose enough that it slaps a bit. Then tightens back up as the tensioner advances.

I dunno, does this make any sense for you? Or, can anyone chime in on my case?

Ok. I think it’s looking like a timing chain issue. Or at least for starters. Although it’s not a high pitch ticking. More like a gurgle. But both sounds are present. Then add in the backfire. Which I believe came from the intake.

[stubble88]

I did find this on the exit side of MAF. But I’m thinking it’s a result of the backfire and blew it off.

[pmax]

Adjust the valves first.

[stubble88]

I did spin the flywheel slightly while tightening the bolts. But I did not think it was enough to throw it out of timing.

[Jim2]

Sir, do you know how to use a screwdriver as a stethoscope? Long shaft screwdriver, place the tip against object like timing chain cover, valve covers etc. then with your thumb over the end of the handle press your ear against your thumb. If it's bottom end related it will probably resonate all over the engine, but if t-chain, top end, hardware in a single cylinder... you should be able to narrow it down.

Loose fit forged race pistons can rattle like that until load and heat are applied, maybe not quite that loud though.

[stubble88]

I did a cold leakdown test

You can hear air from intake and exhaust. But wouldn’t some air be normal?

Cylinder 6 had the most at 14%

But for a cold leak down I’m guessing these are really good numbers?

At 50psi. I did cylinder 5 at 100psi but it was the exact same % so I didn’t bother on the others.

[917_Langheck]

Have someone push in the clutch while idling to rule out the throw out bearing; they can get noisy like that. But it does sound like a big end bearing to me, based on the video.

[stubble88]

Originally Posted by 917_Langheck

Have someone push in the clutch while idling to rule out the throw out bearing; they can get noisy like that. But it does sound like a big end bearing to me, based on the video.

Ah. Interesting. I did replace the throwout bearing. It does sound like a bearing to me also. Scary. But there’s not a drop of metal on the drain plug.
I got a stethoscope. So after a valve adjustment and timing chain examination I’ll have to see how it sounds.
Motor was completely rebuilt in 2008 by ASSE. But it was a race car. So who knows.
No smoke no oil leaks at all. Records through the years show many oil changes and top end rebuilds.

[ant7]

Main bearings rumble, big end bearing knock, both noises would not go away when you accelerate the motor, small ends rattle, piston slap also rattle until loaded and expanded with heat, as previous poster explained, your issue sounds more like tappets too tight, and on low rpm the engine is losing too much compression to fire correctly, once above idle, all 6 cylinders kick in, just my ramblings, but as others have said, check valve gap first!!!
Hope this helps.
Ant.