| Author | Message | ||
| Peter
|
Yes, as it sits right now, I can barely get a .0015" feeler at the deepest gouge, so the wearing is very minimal. I'll have to see how much can be taken off. All of my timing marks are fully there (no cutting into the letters/numbers). I just want to be fully prepared before I go "oops!". | ||
| Steve Magnusson (91tr)
|
Hi Peter -- I had this same dilemma since my ex-308GTS also had a clutch job before my ownership. It's interesting to note that this seems to be an area where Ferrari tried to be more accommodating -- in the MAIN SPECIFICATION table at the start of Section D it shows: "Maximum wear of flywheel thickness mm. 0.8" while the text on page D8 reads: "Maximum reduction of thickness is mm. 1." But I wouldn't lose a lot of sleep over this either -- IMHO if you aren't 1/3 way into the stamped letters for the timing marks you're probably OK. Still, it makes sense to minimize the amount of material removed and there's no need remove the last vestige of every crack -- I'd be very surprised if removing .010" (or at the most .020") didn't produce a quite acceptable surface (if warpage is not an issue). | ||
| '75 308 GT4 (Peter)
|
After finding out both on this site and privately, that the situation is not as bad as I thought it was. Even the workshop manual states that cracks can happen. Just machine down till cracks disappear. The manual states not to exceed 1mm of material removed. What I'm disappointed with the manual is nowhere is stated the max and min thickness of what the flywheel should be. What happens if this flywheel was already turned down to the min thickness, I have no reference of what it should be. Does anybody know the thickness dimensions of the flywheel? | ||
| Anonymous |
You may be relieved to know that the 308 flywheel is not surface hardened. So, providing you are not already at the thickness limit (or runout limit, check for warpage), you may be able to resurface. The spotted pattern is very typical of heat checking - not a result of oil residue. After resurfacing (if the wheel can be turned) your next step would be to Magniflux in order to see if the cracks persist. If you cannot eliminate the cracks without exceeding the thickness limit, the plate is a gonner. A big concern maybe how it got that way after only 4600 miles. Either something was badly out of adjustment, the clutch was driven too hard, or the flywheel was never machined at 42200 as thought. | ||
| CraigFL
|
Very interesting pattern! Could it be that the oil burns off and you get a stick/slip of the friction material that tears the surface? I'm not sure how hard the flywheel surface is -- Is it a surface hardening type material -- high carbon? | ||
| '75 308 GT4 (Peter)
|
I was quite shocked to see the flywheel when I removed the whole clutch assembly this past weekend. It also appears on the pressure plate, but not as serious. As can be seen in the photo, there is radial cracking on the flywheel. The pictured area is the worst, as the rest of the flywheel only has minor cracking. For size reference the longest crack would be about 7/16". The previous owner had the clutch done in Dec 1990 at 42200mi. The car now has 46800mi. The work involved new pressure plate, disc and t/o bearing. The flywheel was also machined, which leads me to think that too much was taken off, which exposed the unhardened part of the flywheel. Am I looking at a new flywheel (ouch$$$)? The leopard spoting on the surface appears to me being little droplets of oil vapour being burned on from the friction of the disc (bellhousing had a thick layer of goo, a mixture of the clutch dust and leaky oil seal vapours).    |