Technical Flywheel position and vibrations

[OzNiki]

Hi everyone. First post here. My 126 AC has an annoying buzz that goes throughout the cabin. It's quite loud and rev related. The car doesn't have to be moving. It occurs during higher revs and just makes the car unpleasant to drive. I've tried disconnecting the alternator/fan, no joy. Still does it. There's no metal on metal with the mounts, they're all fine. I've noticed the timing mark on the flywheel is at 6 o'clock for TDC. Where should the mark line up on the flywheel? At 12?

I realise these are quite vibratey engines, does the entire crank conrods and flywheel assy have to be balanced together?

Thanks, would appreciate any suggestions

 

[bugsymike]

Hi everyone. First post here. My 126 AC has an annoying buzz that goes throughout the cabin. It's quite loud and rev related. The car doesn't have to be moving. It occurs during higher revs and just makes the car unpleasant to drive. I've tried disconnecting the alternator/fan, no joy. Still does it. There's no metal on metal with the mounts, they're all fine. I've noticed the timing mark on the flywheel is at 6 o'clock for TDC. Where should the mark line up on the flywheel? At 12?

I realise these are quite vibratey engines, does the entire crank conrods and flywheel assy have to be balanced together?

Thanks, would appreciate any suggestions

Difficult without being there, but is it possible to bring revs up gradually to the vibration point, whilst touching various parts to locate better.
Obviously not hot or moving parts.
I was thinking,heat shield, loose exhaust baffle internally, broken exhaust bracket or one touching where it shouldn't, I would have said cooling fan but you have already eliminated that.
Do you feel it is a mechanical internal engine issue rather than external like the exhaust baffle. I have had exhaust baffle noise that a light tap with a ball pein hammer in the silencer box cured.

 

[OzNiki]

Difficult without being there, but is it possible to bring revs up gradually to the vibration point, whilst touching various parts to locate better.
Obviously not hot or moving parts.
I was thinking,heat shield, loose exhaust baffle internally, broken exhaust bracket or one touching where it shouldn't, I would have said cooling fan but you have already eliminated that.
Do you feel it is a mechanical internal engine issue rather than external like the exhaust baffle. I have had exhaust baffle noise that a light tap with a ball pein hammer in the silencer box cured.

Definitely not external. There's some sort of imbalance causing the vibrations which are then transferred through the engine mounts.. all the exhaust brackets are in one piece, no damage. It's why I thought the flywheel might be suspect.

 

[bugsymike]

Definitely not external. There's some sort of imbalance causing the vibrations which are then transferred through the engine mounts.. all the exhaust brackets are in one piece, no damage. It's why I thought the flywheel might be suspect.

As far as I know on most vehicles the flywheel is either doweled in to one position or bolt holes are offset so flywheel only fits in one position.
Others on Forum may know more.
Do you know the history of engine, has it been rebuilt?

 

[OzNiki]

As far as I know on most vehicles the flywheel is either doweled in to one position or bolt holes are offset so flywheel only fits in one position.
Others on Forum may know more.
Do you know the history of engine, has it been rebuilt?

You can actually put the flywheel on in 1 of 6 positions. There's no dowell or key way. There is a timing mark on the flywheel and at TDC on my car this is in the 6 o'clock position. My question being where should that timing mark be at TDC? On classic fiat 500s someone mentioned it needs to be at 12 o' clock.
I replaced the crank rear oil seal years ago but thought I put the flywheel back correctly as I had marked it.

As for a rebuild, I'm not sure of the history.

 

[bugsymike]

Oh! Sorry. Every vehicle I have worked on since 1969 in motor trade has either a dowel or only one position where every bolt lines up in flywheel.
Found this online, don't know if relevant. :-https://club126uk.co.uk/forum/index.php?topic=8658.15.
Also the gearbox locating dowels if missing and the rear support spring overtightened are good points.
Reason I mentioned previous history was a friend had a BSA 650 A10 that the big end came adrift and went through the crankcase, it had never felt smooth since he bought it. Previous owner had engine rebuilt with new pistons etc. But gudgeon pin in piston was not central and free moving so when I sorted the engine out for him I found the big end shells on one cylinder all worn on one side due to the loading caused.

 

[OzNiki]

Oh! Sorry. Every vehicle I have worked on since 1969 in motor trade has either a dowel or only one position where every bolt lines up in flywheel.
Found this online, don't know if relevant. :-https://club126uk.co.uk/forum/index.php?topic=8658.15.
Also the gearbox locating dowels if missing and the rear support spring overtightened are good points.
Reason I mentioned previous history was a friend had a BSA 650 A10 that the big end came adrift and went through the crankcase, it had never felt smooth since he bought it. Previous owner had engine rebuilt with new pistons etc. But gudgeon pin in piston was not central and free moving so when I sorted the engine out for him I found the big end shells on one cylinder all worn on one side due to the loading caused.

Hey I saw that post about a week ago and it's for the BIS not the air-cooled. The flywheels are totally different on the BIS. But the symptoms are pretty much the same as mine - droning buzz throughout the cabin when the car accelerates.. ****, your engine shat a conrod? Can an engine recover from that?

On the plus side here in Australia I've found a local machine shop that'll look at the flywheel and crank and balance them.

 

[bugsymike]

Hey I saw that post about a week ago and it's for the BIS not the air-cooled. The flywheels are totally different on the BIS. But the symptoms are pretty much the same as mine - droning buzz throughout the cabin when the car accelerates.. ****, your engine shat a conrod? Can an engine recover from that?

On the plus side here in Australia I've found a local machine shop that'll look at the flywheel and crank and balance them.

At the time the two crankcase halves were still available for the BSA.
I had a customers Ford that the son drove hundreds of miles with low oil on a motorway and punched a hole out through the block. At the time that engine was fairly new and rare to find second hand, Ford took the old unit back on exchange even like that. In those days the bill came to £2000, I did point out that if the son had spent £20 on 5 litres of oil it wouldn't have happened, he was not popular.

 

[OzNiki]

At the time the two crankcase halves were still available for the BSA.
I had a customers Ford that the son drove hundreds of miles with low oil on a motorway and punched a hole out through the block. At the time that engine was fairly new and rare to find second hand, Ford took the old unit back on exchange even like that. In those days the bill came to £2000, I did point out that if the son had spent £20 on 5 litres of oil it wouldn't have happened, he was not popular.

How low is low?

 

[bugsymike]

How low is low?

Put it this way, he claimed to put in oil, there was a 500ml empty can in the boot, when I drained the engine to go back for exchange roughly 500ml came out!

 

[OzNiki]

Put it this way, he claimed to put in oil, there was a 500ml empty can in the boot, when I drained the engine to go back for exchange roughly 500ml came out!

Hundreds of miles on half a litre is going to cause problems methinks! One has to ask, if it was a new engine how did it get so low on the first place...

 

[bugsymike]

Hundreds of miles on half a litre is going to cause problems methinks! One has to ask, if it was a new engine how did it get so low on the first place...

The car was only a few years old and I don't know the previous history. The new engine was what I fitted after the son's negligence, of course that was brand new from Ford.
Re the oil, I suspect he tipped that in at the side of the motorway after engine blew up to make us think he had put oil in.