Thread: Need some help/ideas diagnosing engine noise

Thanks for that Dan.
I presume a compression test should show up leaky valves as I'm not sure what I'm looking for with a slow to close valve.

Is there a fuel additive that will dissolve carbon? Or is it a head off job?
I've decided that since it's only going to be doing less than 2-3000kms a year I'll run him on 98

For the moment the rear main seems ok, it was leaking from the front timing cover but since I swapped that out it only seems to be leaking from the rocker gasket.

Is there any way of telling when a knock goes from - 'you need to do something about that sometime' to 'shut it down and do not drive til fixed'
or put another way are worn bearings catastrophic or merely annoying?

If it is a big-end bearing knock, it should be quiet, or relatively quiet when the engine is cold and the oil thicker. On initial start-up it should knock for a few seconds and then stop but return when the oil thins as it gets warm. It is easy to listen to when you stand near the engine and blip the throttle.

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A compression test with sticking or burnt valves will show very low readings, which don't get better when oil is squirted into the cylinder. if the valve stays open it can be detected by squirting compressed air down the spark plug hole on TDC, whilst an assistant feels for airflow at the exhaust pipe.

As for nasty sounds, stop it if the noise is violent banging and investigate,

Cheers Charlie

OK managed to do the tappets, they weren't too out of adjustment, and a compression test over the weekend.

Compression results are:
1: 145
2: 140
3: 145
4: 120 - adding oil went to 135.

So it looks like piston rings, but its not blowing any blue smoke under load, so I'm thinking of just driving it for a while over summer then starting a rebuild next autumn (Mar/Apr).
Plugs look good, light tan with no deposits.

Now I've adjusted the timing to run at 6BTDC, its idling low and not so smooth, so I'm thinking of doing a static adjustment, then tune by ear.
I'm not sure I've got the correct procedure.
Set the crank to 6BTDC using the pointer on the crank pulley.
With the top of the dizzy off and rotor removed, twist the dizzy til the points are at the max opening (might be there already?)
check and adjust the points gap - it should be 0.015.
Reconnect everything, and start it up, twist the dizzy to get the fastest idle whilst still sounding smooth. (Is this to compensate for any stretch in the timing chain?)
Go for drive, reduce advance if pinking occurs.

Its a Ducelier distributor.

Hi Ozdunc,

I think you have it a little wrong, you don't look for the maximum opening of the points while at 6dbtdc, you are looking for the moment the points spark as that is the trigger for the coil to actually fire the plug. The only reason to go to maximum opening is to set the gap of the points, you seem to be mixing up setting the gap and setting the timing, they are different operations.

So set the gap properly then set the mark on the crank to the desired position then turn the ignition on and when you turn the distributor you will see a spark on the points as they first open, stop right there and you should be ok. It is much easier to do it with a timing light as you can move it around with the engine running but either way works just fine. After initial setting you can take it for a run and see how it goes and see if you have any pinging, then you can advance it further until it does ping, then back off a little.

Cheers,

TimJ.

Thanks Tim,

You are correct I was confused about points gap and timing. So I did a bit of reading (the internet is a wonderful thing). I'll set the points gap, then I'll set the timing.
I have a timing light, but when setting by ear do you disregard the timing light once its initially around 6BTDC and just go for the fastest idle speed?

I would NOT go for the fastest idling speed. That's a recipe for over advancement.

This is my Lucas Distributor technique as used over decades of BMC etc ownership. It's an IRL jobbie, ie done on the road.

1. Find a stretch of road with a slight incline.

2. Approach it in top gear at moderate speed & floor the "go" pedal.

3. If it doesn't ping, advance it a bit.

4. repeat till it pings then back off till it doesn't.

Early MG etc Lucas distributors had a vernier on the side to faciltate the really fine adjustments, but I'm not sure re LR's as mine has a Holden engine!