Balanced crank? - also 4:1 compression

Post by **Kevin** » Sun Apr 19, 2009 10:39 pm

OK I give up what is blading then, I tried a search and all it revealed was references to marine engines.
Agreed that the flywheel is has the greatest rotational force but if total balancing is being done the biggest culprit is the clutch assembly itself rather than the flywheel.

Post by **bmcecosse** » Sun Apr 19, 2009 10:46 pm

Blading - is where the blades of the crank webs are 'knife edged' to allow them to cut through the air as they whirl around. Personally - a great waste of time and effoirt! Wedging - is where the crank webs are machined away into a wedge shape, to reduce the rotating mass. Both can be done - but really this is only for ultra high power high revving engines ! Flywheel lightening and balancing would follow of course.
To get back to the engine in question - does it show ANY other signs of having been 'breathed on' ? Does it have a crankshaft damper fitted (this is the absolute FIRST priority to improve the crank's life expectancy!) - any sign of the flywheel having been lightend and/or balanced?

Post by **Kevin** » Sun Apr 19, 2009 10:58 pm

I know what Wedging is just didnt know what blading is but sounds the same thing to me and I cant find a balancing company that mentions it either so it must be an outdated practice I suppose.

Post by **bmcecosse** » Mon Apr 20, 2009 10:54 am

Used by some of the Mini lads - put's a sharp edge on the (possibly already wedged) crank balance blades. Personally - waste of time and effort!

Post by **PTL851M** » Mon Apr 20, 2009 1:23 pm

Thanks for all the comment. As far as flywheel lightening goes, I dropped a new clutch in when I fitted the engine but I didn't notice anything obvious. At that stage though, I hadn't checked out the bottom end.

It idles smoothly enough - maybe another reason to think the flywheel's not been lightened?

Post by **MarkyB** » Mon Apr 20, 2009 6:04 pm

I'm not sure how much effect lightening would have on tick over but that's where it should show up as the mass of the flywheel is there to smooth out the pulses of power from igntion.
The discussion seems to have move from crude balancing techniques to lightening now

Post by **MarkyB** » Sun Apr 26, 2009 7:24 pm

Mmmmm humble pie

Here is the crankshaft in my current car:<br>

<br>
I am horrified, but also hoping that it was done in the factory as I bought standard shells to replace these:<br>

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The big ends Look OK but the main is the copper coloured one

.
None of the shells have + anything on them so can I assume they are standard as I will only be able to measure the big ends?
I still think the metal removal was done for balance rather than clean up as it's in the right place albeit V crude.
This engine has plenty of miles on the clock ( I'd be interested to know if it's the original, can I find out?) and runs well with just a slight rattle when 1st started.

Post by **bmcecosse** » Sun Apr 26, 2009 7:48 pm

The mains are 'shafted' to say the least. But you may get away with new shells, since there's not much sign of scoring.
I would say the big-end shells have probably been changed, and not that long ago either!

Post by **bmcecosse** » Mon Apr 27, 2009 8:01 am

These bearings will be worth a 'punt' for you! Certainly cheap at the moment - http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 0410670482

Post by **MarkyB** » Mon Apr 27, 2009 8:59 am

Thanks for the link but I bought shells before I started the job.
From the look of the locking tabs nothing has been done to the bottom end at all.
Unless the tabs themselves were replace with the big end shells.
From the state of the locking tab on the main pulley it has had 3 or 4 timing chains. Now replaced with a duplex set.

Is there a way to find out if this is the original engine?

Post by **alex_holden** » Mon Apr 27, 2009 9:21 am

MarkyB wrote:From the state of the locking tab on the main pulley it has had 3 or 4 timing chains.

Or front oil seals.

Post by **MarkyB** » Mon Apr 27, 2009 5:58 pm

Good point, could be that too.
I've got a feeling that not all the main bearing caps are going to come off as things stand (just the sump off) is it the front or the rear that will be a problem and is there a way round it short of taking the engine out?

Post by **bmcecosse** » Mon Apr 27, 2009 11:01 pm

With mains worn like that - these are definitely replacement big-end shells! The mains are absolutely typical of an engine that has been run short of oil - probably due to owner neglect (pre your ownership of course!) or possibly due to surge on corners when the oil has been down at the MIN mark. Worth checking if the plate and spring are still in place in the oil filter case - or has the engine been running without any filtration ?

Post by **MarkyB** » Tue Apr 28, 2009 9:17 am

I got impression that servicing had been paid for but hardly done and that the oil used was of very poor quality.
I removed loads of sludge from the rocker cover when I did the tappets (which were all miles out).
Looking back through the MOTs it would seem it's been around the clock at least once which is why I'd like to see if it's the original lump.
I already replaced the filter with the spin on type so I can't say if the plate and spring were missing but it seems like a good theory.
The owner before me was an elderly lady so "surge on corners" seems an unlikely scenario

Post by **MarkyB** » Tue Apr 28, 2009 8:16 pm

Before the light faded and I got too cold I removed the top shell of the centre main.
It appears to have a micron or two of lead indium still attached ( don't think a picture would show it).
Also had a go at getting the rear main cap off without success

.
At the weekend I'll take off the timing cover etc. and remove the front main cap to see how it looks and if it allows enough slack to get the rear off.
Do the top thrust bearings have tabs on them?

Post by **bmcecosse** » Tue Apr 28, 2009 10:37 pm

Rear main cap is unfortunately blocked by the gearbox mounting plate. I see no reason not to cut it away locally until you can ease the cap off - but that cutting won't be easy! It's well worth renewing the rear bearing shells - because excess oil running out there (from worn shells) will overwhelm the rear 'seal' - and cause leakage into the bellhousing. I would say it's worth popping the engine out, changing all the bearings and fitting a new oil pump.

Post by **alex_holden** » Wed Apr 29, 2009 8:16 am

MarkyB wrote:Do the top thrust bearings have tabs on them?

Yes.

I think I would take the engine out if I were you. It would let you measure the crankshaft journals properly too. Maybe think about replacing the oil pump at the same time?

Post by **MarkyB** » Wed Apr 29, 2009 9:37 am

Curses, foiled again!
As the engine only had a little rattle on starting if left over night I thought I'd get away with replacing the shells.
If the rear plate had a chamfer instead of a straight edge around the cap it would wriggle out

At least I have the front panel off so it could be worse.

Given the state of the mains a new oil pump does seem like a good idea.
I predict a weekend of serious tinkering in the very near future.