GT3 Flywheel… is skimming an option?

[GordonMasson]

Woe is me!

Ok, so I have a hole in my exhaust manifold so that needs to be replaced.

I wanted to replace the clutch because it was very heavy… and I am changing the gearbox out to one of the later GT3 gearboxes with the ratios more suited to the 2.0 litre engine but more of that later….

(PM me if you are looking for an excellent 47,000 mile UN1-026 gearbox as fitted to all 4 cylinder Renault gearbox cars.)

Anyway…. The clutch was taken off and the flywheel is scorched….see pics.

Not sure how deep it is but what’s the view on having it skimmed?

After spending this much money so far..... new gearbox, new clutch, I certainly don’t want to have it put back together and have a crap gear change or judder when I pull away which is what worries me about having the flywheel skimmed.

Any good or bad experiences about skimming or reasons to go with skimming or not.

Also, any ideas of the cost of a new flywheel?

AND … while I am in this deep… what about seals / bearings on the engine output shaft….do I need to change anything here. The car has done 47,000 miles.

[internets]

I had mine skimmed when I fitted the new clutch as a matter of course. Although mine was quite bad so needed doing anyway. Have done around 4k since with no problems or judder

Make sure they put the right step back in, I know they had fun with mine as the high spots were effectively hardened through all the heat cycles over time. From memory price was around £30 or £40 plus VAT

[andydclements]

Skimming isn't an option for the s4s / Sport 300 due to the material used but for all other 4 pots it's fine, and the step should be 0.5 to 0.6mm.

[andydclements]

Very hard.

It's probably true that it can be machined but doing it (including cost of suitable tooling) would be more than a flywheel is worth. I have one if you want to have a look.

[lotus4s]

Andy,

Not sure what you're referring to but I've had several S4s flywheels ground, the last one just a few months ago. My machinist never had any problems and usually charges around $60.

Here's a pic:

Oh and the reason for the extra holes in it was that we lightened and balanced it.

Edited February 18, 2011 by lotus4s

[Vulcan Grey]

The flywheel should be Blanchard ground, not turned on a lathe with a cutting tool.

Jim's flywheels above shows the small circular marks from a Blanchard grinder.

I've also had this done, works fine, just as new. However, you must have both the friction surface AND the pressure plate surface machined, and there is a step of .020"-.024" between the two. This step height must be maintained! One more thing, as the flywheel is made thinner, it changes the relation ship to the clutch release fork. THis changes the freeplay and or total clutch throw.

here's mine before grinding

Here's mine after grinding

Be very careful when lightening a Lotus SE-S4s & GT3 flywheel!! Holes in the edge of the disk can interfere with the crank sensor signals... The crank sensor gets its signal from those notches on the rim.

Jim,

Have you run this flywheel yet? I'm concerned that it may not run at all, or cause timing issues...

[lotus4s]

Yeah Travis, it's been on my old S4s for about 5 years and no problem. I know what you're thinking though, you may remember Steve Smith who had a machinist lighten a flywheel and they ground out the timing notches and the car wouldn't start. Took them a while to figure that one out...

[Vulcan Grey]

Yeah Travis, it's been on my old S4s for about 5 years and no problem. I know what you're thinking though, you may remember Steve Smith who had a machinist lighten a flywheel and they ground out the timing notches and the car wouldn't start. Took them a while to figure that one out...

Yeah, I remember that one, I couldn't remember if that was you I was talking with at that time.

[GordonMasson]

Thanks for the info guys...

So it looks like it can be done if its Blanchard ground (whatever that is.... excuse my ignorance) rather than skimmed then.

Seems like a much cheaper option if i can get that done but its a case of whether i can get it done here or not... remember i live in Aberdeen!

I just want to be absolutely sure if i have gone this far that its not a disappointment once its back together again.

Any thoughts on the main engine seal or bearing ?

Thanks

Gordon

[lotus4s]

Yes, I would recommend replacing the rear crank seal and pilot bearing while you're there along with the output shaft seals on the gearbox.

Edited February 19, 2011 by lotus4s

[GordonMasson]

The gearbox is brand new so that should be ok.

Is it easy enough to change the bearing and oil seal?

Any idea of cost of these?

Thanks

[lucio1234]

was wondering is 12mm the thickness of the part of the clutch contact ring

[Loose Cannon]

Gordon, I would be very interested in your subjective opinions on the change in clutch action with the new gearbox

[GordonMasson]

Hi Mark I haven’t done that many miles in it to be honest but it seems ok. The clutch seems to have more play in it before it disengages but I could be wrong.... might be my imagination. One thing for sure is that you ended up with huge muscles on your left leg trying to operate the old clutch but the new one is so much lighter. Its not a Ford Fiesta but its a big improvement and manageable in traffic / town now. If I had the option again I would still go down the skimming route.

Edited February 8, 2012 by Bibs