Clutch Replacement

[Ralph P.]

Need some feedback on the best source of an original type( B&B ? ) clutch & pressure plate for a 427 . The kit I got from LIC 5-6 years ago( branded "Qualitee" ) had an iron pilot bearing...so I also suspect the disc & pressure plate .
And... what about a roller type pilot bearing ? When does the flywheel really need to be refaced?
And.... Clutch fork ball stud... how do I confirm the one installed is correct ?
Thanks for the help ! I'm constantly amazed at the wealth of priceless information provided here.....

[John H.]

Re: Clutch Replacement

1962 was the last year for the Borg & Beck 3-finger coil spring clutch pressure plate; all Corvettes from '63-up used diaphragm clutches. LuK, Valeo, Sachs, and others have direct-replacement clutches for your car.

Oilite bronze pilot bushings work just fine, and it's a good idea to have the flywheel resurfaced when you replace the clutch.

[Michael M.]

Re: Clutch Replacement

I used a Centerforce Dual Friction clutch and pressure plate when I replaced them on my '68 427. Engages smoothly, low pedal effort. I have it in for over 5 years (and my car is a driver).

You should check the clutch fork ball stud for wear while you have the tranny out. Also, you should check the clutch fork for wear also. The riveted clip that keeps it on the ball stud has been known to break and the surface of the clutch fork that rides on the ball stud can wear out.

Also, not a bad time to check the engine block ball stud that supports the clutch "z" bar. You didn't mention it but this is also a great time to replace (if needed) the foil backed tunnel insulation above the tranny.

As far as having the correct clutch fork ball stud, I think there were three sizes offered by GM. Too long and the tranny won't go all the into bellhousing (ask me how I know!), too short and you won't have enough adjustment at the cluch pedal (in the engine compartment). I would say that unless you have reason to doubt for either of the above reasons that your current clutch fork ball stud is incorrect, I would go with the same length (if it needs replacing).

Good luck.

[Ralph P.]

Re: Clutch Replacement

Thanks, Michael...and John..
The tunnel insulation will be replaced... for the second time since getting the transmission OUT over that crossmember evidently can't be done without destroying it...
The reason it had to come out ( again) was due to the inability to shift into any gear with engine running. I've reviewed all the archives on geometry as to fork, rods, Z-bar ( bought a new one just to be sure...it's identical to the old ) , shift linkage adjustment , etc. I always had very limited adjustment & thought the disc was probably worn... but, the old disc looks very good. I've only put about 3200 miles on this drivetrain since rebuilt in 1989 ; so, I suppose that's to be expected . Anyway, I'm real sorry not to have just left well enough alone ! The real reason for this project was to replace a wrong dated M20 .
The fork ball question was to try & obtain a measurement of the base circle fork ball mount ( inside bellhousing) to the top flat on ball. Mine measures 3/4 " ... just trying to eliminate one possible variable.

[Ridge K.]

Re: Clutch Replacement

Thanks, Michael...and John..
The tunnel insulation will be replaced... for the second time since getting the transmission OUT over that crossmember evidently can't be done without destroying it...
The reason it had to come out ( again) was due to the inability to shift into any gear with engine running. I've reviewed all the archives on geometry as to fork, rods, Z-bar ( bought a new one just to be sure...it's identical to the old ) , shift linkage adjustment , etc. I always had very limited adjustment & thought the disc was probably worn... but, the old disc looks very good. I've only put about 3200 miles on this drivetrain since rebuilt in 1989 ; so, I suppose that's to be expected . Anyway, I'm real sorry not to have just left well enough alone ! The real reason for this project was to replace a wrong dated M20 .
The fork ball question was to try & obtain a measurement of the base circle fork ball mount ( inside bellhousing) to the top flat on ball. Mine measures 3/4 " ... just trying to eliminate one possible variable.

Ralph, I think your 3/4" measurement on the clutch fork pivot ball stud is correct. Do you have a 3899621 bellhousing?
I am restoring a '67 L68 427, and found that my pivot ball had an excessive amount of wear, for the mere 47,000 miles on the car. Mine had spent at least a couple years on the dragstrip, and I think those slamming shifts, take their toll.
I found (after a very long search), a NOS #3887159 pivot ball stud to replace my worn unit. These have been out of production for a very long time. This is the 1 and 3/8ths inch long original version, as opposed to the current service replacement that measures 1 and 1/2 inch long.
I laid this correct pivot ball stud beside my bellhousing, and it looks like your 3/4 measurement is correct.
Hope this helps. Keep us posted. Ridge.

[Ralph P.]

Re: Clutch Replacement

Thanks, Ridge... Yes, BH is a 3899621... appreciate the confirmation.