M30B35 Knock?

[Lucan 196]

Posted this on the BM Facebook page but looking for good advice too...

m30b35 - second engine now. (Took last out for exact same reason) -  have a rebuilt m30 spare now *sigh

runs perfect cold, ones warmed up a tick/knock appears. At crank speed. Can’t identify the source despite checking over and again up on the hoist? Sounds like the lower front cover area though! Now, finger pressure on clutch pedal, noise goes away progressively til clutch pedals in 10mm or so. Bare in mind same issue with last engine.

clutch noise traveling through crank?

clutch pushing crank forward enough for expanded x (unknown part) to miss whatever’s touching?

 

 

[Eagle 1662]

What clutch\flywheel setup are you running? 

[Lucan 196]

s14 flywheel, m20 clutch, g240 tranny

Was suggested it could be vibration damper - I did use the same part on both engines.

[dirtydoogle 383]

51 minutes ago, Lucan said:

s14 flywheel, m20 clutch, g240 tranny

Was suggested it could be vibration damper - I did use the same part on both engines.

If it is bad enough to knock you will see it wobble 

Have you only had this issue with that clutch/fly set up installed? I would be suspicious of your thrust bearing or the fork rattling. Otherwise it is entirely possible you have crank walk issues, but the chances of that with two engines

 

Also check for headers hitting and that kind of jumk

[Eagle 1662]

Yep id be expecting the clutch\flywheel setup based on what you say and that sound. Some of these aftermarket\custom setups run the risk of this sort of thing in my experience.

[Lucan 196]

1. Will do my best to check crank float with everything assembled, clutch in/out while someone measures vibration damper clearance the best way?

Reading forums are leading me to believe its potentially the clutch fork, may need to check what TO bearing I've got installed. 

2. Need to warm car up without the trans on to verify - which is easier than pulling whole engine to check the thrust bearing at least, which was my initial worrying thought.

3. Confirm TO bearing height, I have a spare E21 323 bearing for my M20 fly onto M52 conversion somewhere I'll compare with, otherwise will need to figure out how to space out everything out further ?

[325_driver 422]

Stethoscope time! Before you start ripping things apart lol

I would be trying to discern first whether the noise is coming clutch end or crank noise.

Anyway you can just pull the clutch fork out of the box? 

Edited August 18, 2019 by 325_driver

[Mad_Max 231]

Just a thought as I had it happen in my old 280ZX many years ago, it could also be the input shaft bearing on the gearbox, it had the same symptoms. Knocking rattle when in neutral that would go away when the clutch pedal was pressed in enough. Boss drained the gearbox, found metal chunks come out of it. We put new gear oil in it and I kept driving it lol, waiting for the day the gearbox blew up........ but it never did.......

Might be a simple check to drain the box and check the oil, see if it's something let go inside the gearbox?

[Lucan 196]

On 8/19/2019 at 11:51 AM, Mad_Max said:

Just a thought as I had it happen in my old 280ZX many years ago, it could also be the input shaft bearing on the gearbox, it had the same symptoms. Knocking rattle when in neutral that would go away when the clutch pedal was pressed in enough. Boss drained the gearbox, found metal chunks come out of it. We put new gear oil in it and I kept driving it lol, waiting for the day the gearbox blew up........ but it never did.......

Might be a simple check to drain the box and check the oil, see if it's something let go inside the gearbox?

Will look into this, been kept busy at work so haven’t had a chance to investigate further.