High speed pinking

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Nickol
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High speed pinking

Postby Nickol » Sat Aug 25, 2018 6:50 pm

Is this possible? I drove another Morris today which pinked severely at 70kmh. We tried afterwards retarding the ignition until it hardly could idle but still the pinking occurred. So we took off the upper plate, checked the vaccuum works and the spring loaded advance and tried again. Still the pinking. We even enrichend the carb mixture, no change.

Any ideas?
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simmitc
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Re: High speed pinking

Postby simmitc » Sat Aug 25, 2018 9:28 pm

Is it definitely linking? A head gasket that is starting to go can make that sound under load but sound normal when not heavily loaded.

Nickol
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Re: High speed pinking

Postby Nickol » Sat Aug 25, 2018 10:14 pm

That is a good question - I am never quite sure what pinking sounds like but the clanging sound we got , I describe as pinking.

Head gasket? How would that make such a sound?
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philthehill
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Re: High speed pinking

Postby philthehill » Sun Aug 26, 2018 8:52 am

How old is the timing chain and timing gears?
If the chain and gears are severely worn the chain can hit the inside of the timing cover and sound as if the engine is pinking.

The sound of if pinking is exactly that - a loud.........….'PINK'.


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Re: High speed pinking

Postby Nickol » Sun Aug 26, 2018 11:42 am

1970 vintage and most probably never renewed........

Describing a noise, very difficult. Certainly sounds like a tappet/rocker clang......I suppose it would not do any harm to change the timing chain after all this time, even if it is not the culprit.
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paul 300358
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Re: High speed pinking

Postby paul 300358 » Sun Aug 26, 2018 12:23 pm

It may also be worth checking the condition of the rocker shaft.

philthehill
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Re: High speed pinking

Postby philthehill » Sun Aug 26, 2018 12:37 pm

If replacing the timing chain I would replace with a duplex set up and use a timing chain cover with a lip type seal if not already fitted.


simmitc
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Re: High speed pinking

Postby simmitc » Sun Aug 26, 2018 7:25 pm

If it is a head gasket then the noise comes from the high pressure in the cylinder escaping through a small gap in the gasket, Because the high pressure lasts only a fraction of a second (think 4,000 rpm, how long does compression last?) the noise is a kind of staccato clicking. Your noise could be a number of other things, but I would check compression soon, as prolonged running with a head gasket beginning to fail could be very damaging.

Never mind the age of the engine, do you know how many miles it has covered?

Nickol
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Re: High speed pinking

Postby Nickol » Sun Aug 26, 2018 9:55 pm

philthehill wrote:
Sun Aug 26, 2018 8:52 am
How old is the timing chain and timing gears?
If the chain and gears are severely worn the chain can hit the inside of the timing cover and sound as if the engine is pinking.
would you not hear something from the timing chain at all speeds , not just at70kmh + ??
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philthehill
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Re: High speed pinking

Postby philthehill » Mon Aug 27, 2018 8:14 am

Not necessarily
The faster the chain is going the greater the arc on the slack side due to centrifugal force.
When changing the timing chain whether it be a simplex (with or without rubber ring tensioners) or duplex type it is of benefit to install the later 'A' Plus timing chain tensioner arrangement as any excess movement of the chain on the slack side is eliminated.
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Nickol
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Re: High speed pinking

Postby Nickol » Mon Aug 27, 2018 8:31 am

Wow Phil - you either have an extensive well organised library of pictures to refer to or you took off the guard and photographed it especiallly for me! Whatever, many thanks.
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philthehill
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Re: High speed pinking

Postby philthehill » Mon Aug 27, 2018 8:39 am

Nearly everything I do as regards the Minor I record with a picture and yes I do have lots of pictures but I do not know about organised.
The engine pictured is one I was dismantling so as to utilise the block.


Edward1949
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Re: High speed pinking

Postby Edward1949 » Mon Aug 27, 2018 12:47 pm

Noise could be so many other things, maybe even something dead simple.
Can you replicate the "pinking" by driving in 3rd gear under load at similar revs (just to prove it is indeed engine-related)?
Could be any number of loose metal bits in engine compartment area vibrating at certain speeds.
Exhaust "just" contacting body frame under certain loads?
I'd do lots of checks before drastically retarding the ignition.

Good luck!

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Re: High speed pinking

Postby Myrtles Man » Mon Aug 27, 2018 1:39 pm

Edward1949 wrote:
Mon Aug 27, 2018 12:47 pm
Noise could be so many other things, maybe even something dead simple.
Can you replicate the "pinking" by driving in 3rd gear under load at similar revs (just to prove it is indeed engine-related)?
Could be any number of loose metal bits in engine compartment area vibrating at certain speeds.
Exhaust "just" contacting body frame under certain loads?
I'd do lots of checks before drastically retarding the ignition.
Apropos of that, a couple of years ago I put new pistons into a Norton Dominator engine, reassembled carefully (the conrods are a beast to properly locate) and, with the plugs out, kicked it over a few times to circulate the oil. To my horror it made a horrible clank each time I kicked it, convincing me that at least one of the conrods was not properly seated. Despairing, I went indoors for a restorative cup of tea and decided to have a closer look at it before pulling the engine apart again. Just as well I did as it turned out to be nothing worse than the kickstarter arm fouling the silencer slightly on the downstroke. :oops:

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Re: High speed pinking

Postby Nickol » Mon Aug 27, 2018 5:23 pm

Yes the noise also happens in thrid gear ( I wont call it pinking any more in case Phil scolds me!)
We will remove the timing chain cover in the next few days and have a look.

The noise is a regular even clang related to engine speed. It does not seem to occur unless the engine is under load. You can give a little bit of throttle at 70km/hr + and it starts. Lay off the throttle it stops. I also gave short bursts of throttle ( 1 to 2 secs) before laying off and that sort of switches the noise on and off as well.
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Edward1949
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Re: High speed pinking

Postby Edward1949 » Mon Aug 27, 2018 11:00 pm

Nickol wrote:
Mon Aug 27, 2018 5:23 pm

We will remove the timing chain cover in the next few days and have a look.

The noise is a regular even clang related to engine speed. It does not seem to occur unless the engine is under load. You can give a little bit of throttle at 70km/hr + and it starts. Lay off the throttle it stops. I also gave short bursts of throttle ( 1 to 2 secs) before laying off and that sort of switches the noise on and off as well.

Can't see why engine load would affect timing chain noise, it's completely isolated from the combustion side of things and isn't stressed or de-stressed by acceleration or a trailing throttle.

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Re: High speed pinking

Postby amgrave » Tue Aug 28, 2018 1:27 am

Sounds like it could be a big end or main bearing on its way out if the noise sounds like a clanging.


philthehill
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Re: High speed pinking

Postby philthehill » Tue Aug 28, 2018 7:03 am

Does the engine have a 3 piece crankshaft pulley?
The 3 piece pulley is well known for it cracking and finally coming away from its centre.
Check also the dynamo/alternator pulley for serviceability.


Nickol
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Re: High speed pinking

Postby Nickol » Tue Aug 28, 2018 8:39 am

I need to inspect - it looks like a single unit from memory.

The "clang" noise ? How else to describe it, thump, bang, drummimg.......I had big end trouble once before on anothe rcar and it did not sound like this and indeed was more prevalent at lower revs.

It should not be too difficult a task just to take the cover off and check the timing chain. We quite like the idea actually of installing a duplex anyway.
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Edward1949
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Re: High speed pinking

Postby Edward1949 » Tue Aug 28, 2018 9:35 am

Edward1949 wrote:
Mon Aug 27, 2018 11:00 pm
Nickol wrote:
Mon Aug 27, 2018 5:23 pm

We will remove the timing chain cover in the next few days and have a look.

The noise is a regular even clang related to engine speed. It does not seem to occur unless the engine is under load. You can give a little bit of throttle at 70km/hr + and it starts. Lay off the throttle it stops. I also gave short bursts of throttle ( 1 to 2 secs) before laying off and that sort of switches the noise on and off as well.

Can't see why engine load would affect timing chain noise, it's completely isolated from the combustion side of things and isn't stressed or de-stressed by acceleration or a trailing throttle.

I repeat: the degree of engine loading under acceleration should not affect rotating parts which are not subjected to combustion pressures.
Therefore your "pinking only under load" is unlikely to be timing chain, rocker gear, dynamo,water pump etc.
It is more likely to be mechanical items in the combustion area (pistons, bearings etc or gasket leaks which are exaggerated by loading under acceleration), or maybe simply pre-ignition as you first suspected.
Alternatively it could be something vibrating in sympathy with engine revs when the engine unit twists against its mountings under acceleration loading (eg exhaust contacting the chassis frame, or just some loose bit of metal).
I wish you good luck!


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