LimeyZ

Upgrading the stock clutch to a SPEC stage 2+......

Just bolted on my flywheel being careful to torque the bolts in stages (15-37-74 ft.lb.) Thought I'd just check the disc contact face for circular runout with the dial test indicator. What I found was .006" FIR (full indicator reading) when measured towards the outer rim just inboard of the pressure plate threaded holes.

Does anyone think this is excessive?

This is a stock steel flywheel that has just been resurfaced.

1999 Z28

3rdCoastPowerSports

iTrader: (5)

i could be wrong but i don't think your getting a valid measurement due to other factors, i.e. crankshaft end play. I don't think you can accurately measure flywheel run out with it mounted to a crankshaft that has end play. I could be wrong, hopefully someone who is sure will chime in

LimeyZ

You're right, the crankshaft end play could potentially be a factor.

I turned the flywheel about 6 times by wrenching on the bolts that fasten it to the crankshaft after they had been torqued. I was pressing hard to keep the wrench on the bolt heads while overcoming the compression in the cylinders so I'm guessing I had the crank loaded forward in the bearings.

On each turn the DTI was consistently reading a gradual increase to .006" in the same area then falling steadily back to .000" at 180 degrees on the other side.

SPEC-01

iTrader: (2)

If you have an outage of more than .005" across the surface then you need to either re-machine or replace it. Flatness is key (surface and plane).

Tboh

If It were me, I'd get the flywheel on a surface plate and check it that way, similar to how one might tram a mill head to the table.

Mounting it to a face plate on a lathe would tell you if that runout is there or not also.

You might try indexing the wheel to the bolt holes/crank, rotate 180 deg, reinstall then recheck using your tried method to see if the runout follows the move or remains with the indexed start point.

Interesting issue though, might explain a lot of the shudder in these type systems.

LimeyZ

I've checked it on a granite kitchen work top and I'm quite sure the friction disk side, which was the only side resurfaced, is extemely flat.

The problem I think, is the crank shaft mounting face of the flywheel, which was not resurfaced, is not quite parallel to the friction disk face!

Tboh: You talk like a fellow toolmaker/machinist! Anyway, I agree with you, any of your inspection methods would confirm this theory.

Also, I think I can prove how this happens during the grinding operation... I've drawn up a couple of CAD pictures which I need to post. Stay tuned...

A question: Does anyone get both faces of a flywheel resurfaced?

SPEC-01

iTrader: (2)

It is not typical to resurface the crank-face, in fact I can't recall a single time that we have done this or that it has been required.

LimeyZ

Rather than using my resurfaced cast steel flywheel I decided to buy a new one and went with the SPEC steel billet SC75S, which, I thought was extremely well manufactured Thank you SPEC!

Anyway, after torquing down the flywheel I thought I'd just check the circular run-out again on the friction face of the flywheel and to my surprise the same .006", as I saw on the resurfaced flywheel, was still there. I have to assume the error is related to the crankshaft mating face. I did clean the crankshaft mating surface well and even rubbed over it with some steel wool.

This was my inspection set-up with the magnetic DTI clamped to the catalytic converter:



Zooming in a little and zeroing the DTI:


Rotated the flywheel numerous times in case the end play in the crankshaft bearings was affecting the reading but the .006" persisted at 180 degrees to the .000" reading:



I can't fix this condition so I will just have to continue on. Also, other issues with the new slave are now come to light!

BALLSS

I would suspect you need to measure runout of FW on a lathe or other "non installed" fashion as the crank end play and the inconsistant rotation of motor under compression is a factor distorting the measurements.

FASTFATBOY

iTrader: (23)

Lay the flywheel down, put a straight edge across it and shine a flashlight from the rear of the straight edge, what do you see?

And or

Pull the flywheel and do the same test with the dial indicator on the face of the crank.

Tboh

Hey LimeyZ, I missed your comment on my suggestion. I only play machinist and toolmaker but glad it shows! Made me smile.

PS. Did this flywheel turn out to be flat or was it a pringle potato chip?