Crankshaft movement

[JohnBM]

Q: last time we altered the timing because the engine was running hot , a distinct ( clunck ) sound was heard . Yesterday while working on car it was noticed behind the harmonic balancer a distinct bright section of the crank showing . First thoughts were the H/B was not on far enough , but by using a long bar in that gap and pulling to the front of the car it moves the crank and creates that clunking sound . Same as when moving bar to rear . I think something is coming adrift although it still run sweet . It’s a grey motor  no mods   $$$$ any ideas  ? It was rebuilt about 4 years ago  thanks John BM

[Maco]

Can you measure crankshaft end float. I had a simular problem after a motor builder reconditioned my motor.

He mixed up the crankshaft main bearing caps this allowed the crank to float 0.080" instead of 0.004"-0.008".

I also had some unusual noises as well.

Hope this helps.

Cheers
John

[JohnBM]

Thanks for that , something i can put to them 🤔

[ardiesse]

John,

Let's deal with the unusual noises first.

Run the car in neutral with the clutch engaged, and then disengaged.  If the noises go away or get quieter with the clutch disengaged, that's your gearbox internals making (some of the) noise.

Is it something like a gentle "nackanacka" sound coming from the front of the engine at idle?  Take the fan belt off and start the motor.  If the noise has gone away, stop the motor, grab the harmonic balancer pulley, and rock back and forth.  If you can feel any looseness or hear any gentle knocking sounds, your harmonic balancer's rivets have come loose (NB: this is only for the original-style balancer).

Is it a once-off sound when you start to use the clutch?  The timing gears are cut so that the effort of driving the camshaft pushes the crankshaft forwards, and using the clutch pushes the crankshaft forward also, so I wouldn't expect to hear noises.

Or do you hear a single "clunk" when you turn the ignition off? This is apparently what a loose flywheel does.

Ideally you'd use a dial gauge to measure the crankshaft end float, but you can measure crankshaft end float with feeler gauges.  There's some mucking around under the car though:

Remove the clutch cover.  This probably isn't as easy as it sounds, since you'll have to jack the gearbox up and take off at least the left hand rear engine mount; and if you can't slide the clutch cover off, the right hand rear engine mount also.  Then put the rear engine mounts back.

You can (1) lever the crank and flywheel backwards with a screwdriver between the back of the block and the flywheel, and (2) to move the crank forwards, all you need is someone in the car to push the clutch pedal down an inch or so.

Put a steel rule across the bottom of the bellhousing (hopefully not fouling on the rear engine mount brackets) and measure the gap between the steel rule and the front face of the ring gear for conditions (1) and (2).  The difference in thickness of the feeler gauge stack is the crankshaft end float.

Bear in mind also that in all the grey motors I've played with, the crankshaft end float has been way more than 0.008", without any ill effects.  And this makes a distinct bright section of harmonic balancer hub visible immediately in front of the timing case oil seal.  More than 0.015" end float suggests trouble though.

Rob

[JohnBM]

Rob, thanks for your reply , & for your time in replying , the end paragraph is in my opinion the most relavant .to my problem . I might add the noise heard was noticed late last year , & for what ever reason I did not persue it further . We have just driven to & from the Canberra nats  from Perth  ; with no probs what so ever .I will check with the eng Recond people for their view , but it’s out of warranty now  . Cheers 🐌🍺

[JohnBM]

Crank end float going to be sorted , hopefully , taking engine out  plus replacing head gasket with the modified one . Engine rebuild co not convinced it will remedy heating prob ,hopefully the sun will come up tomorrow 🐌🍺

[Trevor_B]

Hi John,
Make sure they follow the instructions on opening up the back coolant ports in the block and head. They need to match the enlargements to the gasket not just bore out to the larger diameter as I found mine were not concentric.

I am also aware of someone who did not do the opening up of the ports and the revised gasket had less of an improvment.

For me it made a very noticeable difference with a temp gauge that now runs at 75-80 degrees (in 25 degree ambient conditions) so definitely a noticeable decrease in temp at the rear cylinders.

Cheers,
Trevor_B

[surferboy]

Why don't you just turn up the volume on the quadraphonic stereo system until the noise goes away John ?
(then call the RAC tow truck when it breaks down.... that's what I would do  )


You do have a quadraphonic stereo system don't you  ?




surferboy
 

[JohnBM]

Thanks Trevor ,yes it’s goinb in Wednesday  and I am armed with all the info , drill out sizes , warnings of correct fit . Mind you they are not convinced it  will make much difference , I know when the timing was set right it made a significant diff . Any way I’m willing to give it ago .driving across the Nullarbor at around. 90/95 Kph in warm weather does not make for a happy driver or car , There is around 8 deg difference between the sensor in the head (normal pos) & the other sensor located in the bottom of the top radiator tank . So even with the cooler weather , when it’s done I should notice one way or the other if it’s worked . Cheers 🐌🍺

[JohnBM]

Rob; if your tuned in , the end float is way in excess of acceptable limits , it’s only done 40.OOO km since the rebuild which they did ( where the car is now) do they use shims in getting the end float correct ? I feel they may omitted something on the rebuild  but doubt they would admit to it . Plus the car has had A very bad shudder when taking off in first ; do you think the end float prob would most likely be the cause     I think I’ve mentioned that before  . Cheers John 🍺🐌

[ardiesse]

John,

They don't use shims to get the crankshaft end float right.  What it may mean is that the thrust faces on the No.2 crankshaft journal were ground overwidth, but the replacement No.2 main bearing shells are standard width.  Normally, undersize main bearings come with overwidth thrust bearing shells.  Your engine reconditioner is supposed to measure the width of the No.2 main bearing shells, and regrind the crankshaft to suit the new bearings, in both diameter and width.

There are two ways out of the dilemma.

The first is to get a pair of custom overwidth and undersize No.2 main bearing shells made by ACL.  It won't be hugely expensive, but you will have to wait.
The second is to find a good replacement crankshaft.
There is a third option: get the thrust faces hard-chromed and reground back to standard size.  This would be quite expensive.

Give me some numbers:  What's your crankshaft end float at present?  And what undersize have the journals and crankpins been reground to?

I don't think your clutch shudder in first gear would be caused by excess crankshaft end float, but I could be wrong.  Now that the motor's out of the car, take a good look at the clutch plate to see whether the disc is loose on the hub.

Rob

[JohnBM]

I’ll get back to you , if the engine reconditioners will talk to me . Thanks Rob