Piston Slap?

[Alexander]

 ..

 

 

Edited June 14, 2023 by Alexander

[paulyg]

The motor consumes almost no oil- about 1,000 miles since the last change/top up and there's no change on the dipstick. Might be a bit higher than it was in the first place. No leaks either (from the engine). 

 

A bit more detail about why I suspect a top-end oiling issue:

- The noise is most present when the engine is cold, but returns when the warm engine has idled for more than ~5 minutes

- It completely goes away as RPM is raised above ~2500 and feels "reluctant" to return when the engine goes back to idle, regardless of engine temp

 

I did take a look at my oil spray bar and it seems to be fine, and there's no unusual wear on any of the cam lobes. It has a plug on the front and is crimped in the rear. I noticed the fuel pump drive cam is definitely the most worn. Is there a possibility that this would be causing the noise? 

 

[Markster]

On 8/2/2019 at 1:11 PM, Inka’d02 said:

They were a new set of max-sil pistons and cylinders were re-bored.

 

What about the timing chain tensioner can cause the knocking noise? I am really curious about this one.

 

I like the small end bushing as well but they were done, unless maybe one failed...

I have max-sill pistons too.  What rings did you use?  Do the have Teflon on the skirts?  Mine do. Just curious about the rings u chose. ?

[jimk]

Are the required sealing washers on the spray bar banjo bolt?

[TobyB]

Good Q, Jim.

 

That cam looks ok to me.  And yes, the pump rod can make noise. 

Easy to test- just take it out.  Use the pump to block the hole, 

and run a temporary electric pump.

 

There have been pump and rod and spacer and gasket variations over the years,

so by now, getting it wrong's easy!

 

As to piston slap itself, the stethoscope with a rod (yes, you can bend it to get around corners)

is invaluable for lower end noises...

 

t

 

[paulyg]

Yes, sealing washers in place. See photo. 

 

I'm still really curious if anyone out there can definitively diagnose this sound- it's very distinctive to those of us who have dealt with it, I definitely recognized it from the original video in this thread!

 

I'll add that I've noticed that this noise persists even after meticulous valve adjustments and oil changes... it kind of floats in and out, on top of the normal top-end clatter that is to be expected with the specified rocker clearances. 

 

Finally, more of a question- would you expect piston slap to be heard at engine RPM or half of the engine RPM, as would be the case for something in the head? This noise is for sure at 1/2 per rev. I am no expert in how piston slap would present itself, but my gut says it would be at 1/rev, like rod knock. 

 

It may be time to replace the exhaust gasket/studs too, as has been mentioned. On the flip side, it seems weird that an exhaust leak would go away as the engine warms up but then return after it has idled for a couple minutes. 

 

[paulyg]

Just noticed something too. The engine in the video on page 2 (cold) depicting the sound in question has no mechanical fuel pump. 

Edited April 9, 2023 by paulyg

[John76]

On 4/8/2023 at 11:52 PM, paulyg said:

I am no expert in how piston slap would present itself,

On the Oscar stage by Will Smith? 😬

[Lorin]

13 minutes ago, John76 said:

On the Oscar stage by Will Smith? 😬

That was more “Pissed and Slapped”

[Son of Marty]

Piston slap makes a hollow tapping noise like a cold diesel engine warming has piston slap due to the clearance needed for the heavier piston design to expand when hot. 

[TobyB]

How round are your eccentrics?

 

Flatspotted eccentrics can make a pretty clattery noise when adjusted 'to spec'.

 

t

 

[allen]

Hi, I’m chasing the same noise in my engine, has anyone found out what it’s from ?

thanks Allen.

[Tom Gilpin]

21 minutes ago, allen said:

Hi, I’m chasing the same noise in my engine, has anyone found out what it’s from ?

thanks Allen.

I put a stethoscope on mine the other day and it's either coming from the timing chain or cylinder no.1. Mine goes away when warm and or higher revs. I'm just going to run it and see if it gets worse.

[allen]

5 hours ago, Tom Gilpin said:

I put a stethoscope on mine the other day and it's either coming from the timing chain or cylinder no.1. Mine goes away when warm and or higher revs. I'm just going to run it and see if it gets worse.

Mine starts 1 minute after starting the car, when it’s cold and revs are low but if I keep the revs above 1000 it disappears and once it’s warms up it’s gone all together…2 weeks ago I did the timing chain/oil pump and chain…checked all the bearings and everything looked good…it’s got me stumped 

[Tom Gilpin]

4 minutes ago, allen said:

Mine starts 1 minute after starting the car, when it’s cold and revs are low but if I keep the revs above 1000 it disappears and once it’s warms up it’s gone all together…2 weeks ago I did the timing chain/oil pump and chain…checked all the bearings and everything looked good…it’s got me stumped 

Yep sounds exactly like mine. I did the same with new oil pump chain, sprocket and shimmed the pump chain correctly. I replaced the timing chain tensioner and piston and checked all the main bearings. I didn't check wrist pins and I haven't put a oil pressure gauge on it yet. I read another guy in a different post saying he had the same thing, had had it for years and just ignored it now. I think I might just channel that guy.