998 Crank shaft Pulley
Turbo Mini Forums

evening lads


Sending my stuff in to be balanced and engineer said my pulley is dead the rubber has gone on it so its only good for a paper weight

Now Rang MED and they do the 'S' pulley will this be fine on the 998, will be using the supercharger pulley with it aswell and the mangerment ring

thanks
Stephen

I didn't think that you can use the supercharger pulley and damper at the same time on the med kit but i might be wrong.

I run the management pulley and supercharger add on

Edited by gr4h4m on 8th Apr, 2015.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Thats the one I wanna run Graham is it all good no crank issues?

I haven't had any but I've only done a couple of thousand miles. I in that time I have had the engine stripped and checked and the crank was fine. I run a wedged harderned and balanced crank. The engine spins up to 7-7.5k,

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

I did read somewhere I shall find the sorce again that the 998/850 engines didn't need a damper untill they hit 12k

when I brought new engine and old one they both had the old skool pulley no damper

Crank dampers

The crank damper is the 'heavy' crank pulley fitted to all 1275 engines and some 998 engines.

This is basically an iron ring on a rubber inner ring that has it's mass and rubber spring constants matched to the 1st resonant frequency of the 1275 crank. It cancels out the resonances and prolongs crank life.

This may be because the crank has cyl 2&3 big ends on the opposite side to cyls 1&4 and at high revs this 'longitudinal' mass imbalance coupled with the spring constant of the iron (yes, it will have one) causes the crank to vibrate slightly. This cannot be solved by crank balancing, but can be solved by 'damping' out these harmonic vibrations.

The 1275 crank has 2 resonant harmonics within the 'usable' frequency range at 5950 and 6250rpm. If you don't use the damper, the crank may fatigue and break.

998 engines don't need a damper as the crank weighes less and therefore the 1st harmonic is beyond the usable range at 12k rpm or something. That is why the 998 engines have a 'light' pulley, and the 1275's a 'heavy' one.

Putting the heavy pulley (the damper) on a 998 won't do any harm, except adding to the rotational inertia, but putting a 998 pulley on a 1275 is asking for trouble.


Source - http://www.dummett.net/ime/website/ime/c/cranks.html

how true is that?

If in doubt, add a damper pulley, it certainly can't do any harm, if it's not on a race car then really the damper pulley is the sensible option on a non standard engine. This is of course my own opinion, as I'm sure others have different, but you aren't going to notice the extra weight getting more torque out of forced induction.

I took the tin 998 pulley off the last time I had my engine out, and fitted a damped one as i figured it had to be better.

Got a strange grumbly rumble at ~3000 now, so I'm wondering if the damper pulley has introduced an odd harmonic at half frequency.
Next time it's out I'll swap pulley back and see if it goes away.

Metric is for people who can't do fractions.

I've only ever seen the "damper" pulley on very late 998s.

I've also seen lots of sites that state that a 998 will never reach the first harmonic so doesn't need one.

I'm sure Vizard mentions it somewhere, maybe worth a read ?

One of the guys I used to work with was a workshop manager for a Leyland franchise before it went bust and he came to join our company.

He said that towards the end of production of anything A series (particularly Metro) Leyland were just using up anything they had that would fit to clear stocks of parts.

He said half his life was spent phoning through VIN numbers to make sure the parts they ordered would actually fit the car they were about to service.

The E reg 998 Metro city I scrapped (just bought it for the engine) had the 1275 damper.
It also had vented front disks off the Metro turbo.
The D reg MG Metro I scrapped had the solid front disks...

Schrödinger's cat - so which one am I ???

The damped 998 pulleys that I've removed from late 80s onwards 998s are not the 1275 pulley, but slightly thinner.

Rover would not have fitted them if they were not beneficial as they would have been extra cost to them.

I've got the full MED 1275 'S' damper setup on my latest 998 and I think that I may have to lighten it a bit.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

RE discs, only the early MK1 metros had solid discs; all mk 2's were vented. looks like someone was swapping bits about on the D plate as it should have had vents

My Mk2 D had solid discs. There was a change over at some point but things are not as simple as mk1/mk2

when were changeovers ever simple with british Leyland?

Double-Blind experiment, N:
An experiment in which the Chief Researcher believes he is
Fooling both the subject and the lab assistant. Often accompanied by
a belief in the Tooth Fairy.

I thought it was the metro 998s that got the pulley with the thin damper ring and the mini no damper.

All Mk2s had vented discs from day 1. Anything different was most likely people using whatever they could get their hands on.

Your quite clearly wrong.

Metric is for people who can't do fractions.

Look British Leyland built the Mini and the Metro, No one can say one's true to factory spec because no one knows what a true factory spec is. depends on the brummies building them on the day

well we've gone off topic somewhat here! anyhow my 86 C plate MG had vented discs; I am lead to believe that all cars with the facelift front (lets call it mk2) had the vented setup; I only ever say solid discs on the early cars. It always made me chuckle when they were referred to Turbo brakes when in fact they all had them in the end

If you say so. All the marketing material,original Austin Rover maintenance manuals, and the Unipart parts catalogue I have must be wrong. I'll throw them all in the bin.

Getting way off topic but all I can say is my D reg MG (N/A) had solid and E reg 998 city had vented.

I bought the MG from another engineer where I worked and he bought if from a relative who had it from new and all servicing was done by garages so far as I could tell from the paperwork.

It only had 60k miles on the clock so unlikely the disks had been changed and, even if they had been, that would have been a lot of hassle to go for solid as it would mean swapping the calipers as well which isn't a 5 minute job with their unbelievably weird dual circuit idea and plumbing.

I tend to go with the "when were changeovers ever simple with british Leyland?" theory especially as (as I mentioned earlier) another engineer who I used to work with who was workshop manager at a Leyland franchise before it went bust said he was forever phoning HQ with VINs to find out what parts had actually been fitted to Metros at the end of the A series run.
Whatever was left in the parts bin is how he described it.

Anyway, back to the pulleys....
@ Paul, I have a couple of the thinner damped pulleys as well but they came of early 1275 engines.
I only have one damped one of a 998 and that was the E reg Metro City and that's the same as the D reg 1275 MG Metro.
The one off the 998 is what's on my turbo lump because it had the best rubber.

So I'm back to parts bin engineering plus bodges/swaps by previous owners.


EDIT - the other difference between the later dampers and the early ones is the later ones have the thin metal ring (with the two slots) rivetted to the back (aparently for setting ignition timing at the factory) but, I have to take back what I said above, I have now found a later one (ie, with the metal plate) that is thinner than the 1275 one in one of my many boxes of bits.

Haven't a clue where it came from, I'll go with previous owners swapping things around.

I now wonder if the addition of the damper to the 998 was something A plus rather than parts bin engineering, ie, something else they did to the engine for A plus lowered the first harmonic ?

Edited by Rod S on 10th Apr, 2015.

Schrödinger's cat - so which one am I ???