6 replies to this topic

[jakethepeg]

After many years of absence I bought a mini last year, and I now have a bakers dozen in various stages of condition. However I have also driven quite a number of others recently, and one thing that has struck me is the general level of engine vibration in the cars. From memory the A series engine does not vibrate like this in other applications, ie Morris 1000. Is it compounded by being transversely mounted? by the way most of the minis I have experienced  have been 1275, and as the block was intended as an 850 does this make a difference.. With  my own 1275 saloon and 1275 van I have renewed the engine mountings, steady bushes and had the flywheels balanced. During the restorations of my mokes, pick ups and other vans I intend to fit mostly 998 engines or even 850s for originality.  Any thought or suggestions as it really impacts on the driving experience. Maybe this topic has been covered elsewhere but I am too thick/lazy to find it.

 

 

 

 

[Carlos W]

There has been a lot of talk regarding flywheel balancing and some very interesting threads from the likes of AC Dodd.

[tiger99]

And the 1275 is definitely rougher than the 998 because it has, or should have, significantly more energy in each firing impulse.

The arrangement of mounts and steadies makes a fair difference too. The main mounts are the same in all Minis except automatics but some have an excessive number or inappropriately placed steadies, possibly with the wrong bushes. The exhaust also has a major influence.

Then there is the mounting arrangements for the front subframe...

Lots of things that can be changed without incurring huge costs to make it hopefully better...

[jakethepeg]

Whilst I understand where you are coming from with that, the same engine in ,shall we say, a Marina/Ital did not vibrate s badly as most minis I have been in lately. Almost all of them have had rebuilt engines, so maybe they have not been put together so well

[tiger99]

No, it is because they are mounted very differently. And, in a transverse application the mounts have to deal with final drive torque, which is a lot higher than engine torque, so they have to be stiffer. Therefore their noise and vibration filtering capability is greatly reduced.

If done by the same reconditioned it is most likely that both longitudinal and transverse variants of the engine itself will be closely similar.

[jakethepeg]

That sounds very logical the stiffness of the mountings. Is it possible to buy upgraded mountings that are more compliant, ie polyurethane or Teflon. Essentially I suppose it is down to the balancing of the components inside the engine, yes?

[tiger99]

No, you can not and must not fit more compliant engine mounts to a Mini. In fact they usually need to be stiffened, typically by fitting metal cones in the top and bottom steady bushes. The exhaust mounts also have an influence.

Balancing of the engine, clutch and flywheel does make a difference, but a 4 cylinder engine always has secondary unbalanced forces and can't be perfectly smooth. Perversely, a 3 cylinder engine with intentionally unbalanced flywheel at one end and pulley at the other can actually have true primary and secondary balance, as does a straight 6.

I think you may improve matters if you have it properly balanced, but it requires a full strip down and is therefore expensive. But a Mini will always be a Mini, and as I explained can't be quite as smooth as cars using the same engine in rear wheel drive configuration. Enjoy it for its good qualities such as handling.