Knock in bottom end at idle only, help with diagnosis

[Cubic_Cleveland]

What does the timing do?

Do you have a sample of oil you can have tested?

Does it happen in gear?

[Cubic_Cleveland]

Mate it's standard Holden gudgeon noise. Every 202 Holden does it. Motor can only be a few weeks or months old and it will start. Don't worry about it that's just how they all are. Cheers Tony

Don't know who builds your engines, but mine don't make that noise!

[pamotorman]

pull one plug wire at a time at idle to see if it goes away. this way you may find out if it is a single cylinder that is making the noise.

[fdicrasto]

Sounds like either a main bearing issue or loose flywheel if stick shift.

[mag2555]

He did the pull the plug wire check out with no change .

[Olefud]

A friend bought a GMC with 100k+ miles and a light knock only at idle. A bit more oil viscosity took care of it. That was two years ago.

[pamotorman]

He did the pull the plug wire check out with no change .

OPPS missed that guess I better read closer

[2seater]

Our Buick V6's do that when the balancer/damper is staring to go bad. If suspect, remove drive belts from accessories to remove load and run engine momentarily to see if it changes.

[automotive breath]

The first thing I would check is the fuel pump/push rod if the engine is fitted with one. They make the exact sounds you describe when worn.

[CharlieB53]

I had a cracked piston skirt that knocked only at an idle.

Found it by idling the motor with one spark plug removed at a time. When the plug was removed from that cyl the noise was gone.

[JoePorting]

One of my old motors had the same problem. Turned out to be a cracked front damper.

[lc-gtr-1969]

Thanks so much for all the valuable input!

So I will give a little more history and info which may help...

I have checked by removing one lead at a time and there is no real change to knock. I got my stethoscope out just now and listened to the bell housing area, and there does not appear to be any noise emanating from the bellhousing.

I while ago I did experience a flywheel working loose (fairly common problem with these engines when running standard bolt sizes of 3/8), this was easy to tell as I could grab the flywheel and there was play in it... so I had the flywheel doubled doweled to the crank flange and the bolts were upgraded to 7/16... At the moment there is no play in the fly, however, as it is doweled now, I imagine the bolts could still be loose but I would not have any play as the dowels locate the fly very tight. I dont want to discount loose flywheel bolts at this stage as it seems possible.

The car is running electric fuel pump (holley blue), so no mechanical pump used at the moment. Ignition timing doesnt really make any difference from what I have observered, the only thing that changes it is RPM from my observations.

The HB idea is very interesting... Today I will remove the drive belt and see if it changes anything... I will also try to watch the HB to see if it gets a bit of a wobble on at low rpm...

Mate it's standard Holden gudgeon noise. Every 202 Holden does it. Motor can only be a few weeks or months old and it will start. Don't worry about it that's just how they all are. Cheers Tony

Cheers bud... I love 202s mate but they can have the quirks hey! This engine is running triple webers in an LC. Lots of fun in the little car. However, these days I tend to spend more time fixing it than driving it.

[202ci EH]

Broken cam thrust plate?

[lc-gtr-1969]

Thanks again for all the replies.

I took off the drive pulley and checked the engine running... the noise was much less noticeable with the belt off. I only ran it for a minute or two though as no water pump with the pulley removed.

I then though I should check the end float again to see if there is any movement by hand, and it was tight, good.

However, low and behold, the HB has play on the crank. It is moving over the crank, back and forth a few degrees. I am confident its moving independant of the crank. This seems like it very well may be the issue- what do you think?

[benno318]

Mate it's standard Holden gudgeon noise. Every 202 Holden does it. Motor can only be a few weeks or months old and it will start. Don't worry about it that's just how they all are. Cheers Tony

Don't know who builds your engines, but mine don't make that noise!

gudgeon noise in a 202, what the??? these have press fit pins unless modified or aftermarket rods. agree with cubic here!!

sounds like the problem has been identified but other possible causes are the already mentioned cam retainer plate (thin cast iron, can break quite easily) also timing gears can wear and sound not unlike a big end knock at low rpm's especially so the straight cut steel gears.

if not already done, drill and tap the crank snout (i use 1/2"unc) and mechanically retain the balancer with a nice thick washer (preferably a custom machined job with a step to sit inside the balancer bore) once you sort the inteference fit out.