90 ZR-1 #2273 - To be rescued

[S.hafsmo]

Expert opinion received from Bill Boudreau,

Hi Steffen,

The outer region of the clutch disc friction surface is considerably more worn compared to the inner, judging by the gassing groove depth tapering to outer . The gassing groove starts out even depth inner to outer when disc is new.

Good pictures by the way.

The pressure plate and flywheel I’ve seen look worse than yours and still operate just fine. Use maroon scotch-brite pads by hand only to remove surface glaze, replace the disc and install a fluted pilot bushing (GM P/N 10125896) inset 14 mm and absolutely do not apply grease in the pilot bushing. Doing so will cause the oil saturated pilot bushing to fail almost immediately. The throw-out bearing and pressure plate should be good for another 150K - 200K miles.

I have new Valeo solid hub clutch discs but they are too thick requiring 0.020” washers installed between the pressure plate and flywheel for compensation height to allow proper clutch modulation action. 0.320” disc thickness is ideal if you can find a new one at that thickness.

[Ccmano]

Your 6.5mm disc thickness translates to .255 inches. As Bill notes .320 is the standard for a new disc. As I understand it minimum thickness is .230. So your disc is about done.

Will you simply replace the disc or will you take the opportunity to install a light weight flywheel and sprung hub disc?
H

[S.hafsmo]

The disc seems to be due for replacement, yes. It seems Bill has faith in the pressure plate and TO bearing, but he dares not give an estimate on the remaining life span of the DM flywheel.

Light flywheel is not an option for me. I've gone that way before on another project, and I regretted it ever since. The rattle and loss of driveability is just not worth it. I see Jerry's has a couple DM flywheels left, and I must say it's tempting, but it's not a cheap option. Right now I'm just looking to see if I can find all the right parts and their price, to estimate a total cost.
The OEM clutch disc also seems hard to find.

[S.hafsmo]

Got the TB back from Haibeck this week, and it's obvious that there is just so much one can do when the blades are getting worn. You can still see right past the blades close to the shafts. Maybe I'll have to attack it with the Molycote D321-R as well, to Band-Aid the lost DAG. TPS had also gotten damaged during shipping back to me, so I'll need to replace and calibrate that one as well.
Too bad, really, as I was hoping for some kind of magical repair resulting in a perfect seal. Maybe one has to go for the 63mm blades?

[A26B]

Originally Posted by S.hafsmo

Got the TB back from Haibeck this week, and it's obvious that there is just so much one can do when the blades are getting worn. You can still see right past the blades close to the shafts. Maybe I'll have to attack it with the Molycote D321-R as well, to Band-Aid the lost DAG. TPS had also gotten damaged during shipping back to me, so I'll need to replace and calibrate that one as well.
Too bad, really, as I was hoping for some kind of magical repair resulting in a perfect seal. Maybe one has to go for the 63mm blades?

Greg VanDeventer can repair just about any problem on a throttle body, including making new blades ranging from stock to 63mm & any size in between, shaft bushings, boring the T-body itself, etc. Personally, I would do the repairs before going through the molycoat/DAG process. Your T-body likely needs more attention than that.

[S.hafsmo]

I am rather upset with myself for not knowing of this gentlemen you mention, before I spent over $600 (incl. $150 in shipping) to repair the TB. What a waste..

How can I get in touch with Mr. VanDeventer?

[A26B]

Originally Posted by S.hafsmo

I am rather upset with myself for not knowing of this gentlemen you mention, before I spent over $600 (incl. $150 in shipping) to repair the TB. What a waste..

How can I get in touch with Mr. VanDeventer?

Marc does excellent work & is highly respected in the ZR-1 community. Please do not take my suggestion wrong. I had no idea that you had Marc do a rebuild on your throttle body. You should contact Marc with your concerns. I have no doubt he will address them to your satisfaction.

[S.hafsmo]

There is absolutely nothing wrong with the work Marc did on the TB, and it may very well be that the blades seal enough for the IAC to control the idle, if no other leaks are present. I'm sure he would've told me if he actually thought further work was necessary.

I probably failed to inform him of the extent of repair I was looking for.
He has been vastly helpful throughout my restoration project, and I don't really wish to bother him any more with it.

[XfireZ51]

I doubt Marc considers it a bother.

[LGAFF]

I have some original throttle plates