"With the pp bolts finger tight, there should be no gap between the pp ring and the flywheel friction surface but there will be a gap between the pp cover flange and the flywheel clamp surface, clutch or no clutch. If this is not the case, I expect the issue is the pp not matching the flywheel. It appears you have a flywheel with a protruding pp cover contact surface for the pp that sticks out above the friction surface. The mustang pp is designed for a level surface between friction and pp cover contact."The relationship between clutch finger travel & pressure plate travel is not linear, but proportional (it's a lever-and-fulcrum system), where (at least, in this case) the relationship is a ratio of roughly 4:1. In other words, if there were no gap between the flywheel friction surface & the pressure plate friction surface (with no friction plate installed), the fingers would have to move inward 1.320" just to accommodate the thickness of the .3300"-thick friction plate when installed between the pressure plate & flywheel.
The fingers don't have anywhere near that total amount of travel so, without this gap, the pressure plate could never be installed. Unfortunately, the gap is only 0.1325". Owing to the aforementioned 4:1 relationship, even with this gap, just installing the friction plate is enough to force the clutch fingers to move inward nearly a full inch, almost into contact with the friction plate.
One issue seems to be that there are substantial dimensional differences among various manufacturer's clutch parts, and none of these are specified by the sellers/manufacturers. There's simply no way to know. Today I looked three different friction plates, for example, all for the identical application, and they are
very different in design, as well as in several of their dimensions (such as hub height/diameter, damper spring number & arrangement, etc.). The same seems to apply to pressure plates.
When I purchased my clutch parts, I used the same application-specific parts as all the others who have done this same combination, with success, in the past.
- My pressure plate is a Sachs unit, badged as a Ford Motorcraft item, specified for a 1999 Ford Focus Zetec 2.0 (that's what my engine is).
- The friction plate is a 9" Exedy unit, specified for a Mustang II, selected to match the input shaft of my Mustang II-sourced, T5 WC (V6 version) transmission.
- The flywheel is a Fidanza aluminum unit, specifically for this version of Zetec. I did have the opportunity, today, to confirm its dimensions vs. a stock, Zetec steel flywheel. Its friction surface height is identical to the OEM unit.
I've noticed that for everyone who's also done this, there seems to be perilously little travel available for the pressure plate's fingers to travel. The fingers on all the applications I've seen point fairly steeply inward, toward the friction plate hub, rather than being either parallel to the pressure plate's outer surface, or somewhat proud of it (which seems common in other installations on different engines).
It certainly seems to be a universal issue when mating a T-5 to a Zetec, although others have been "lucky" (one builder employed a used-but-serviceable friction disc, which probably saved him from this issue). In my case, fractional differences in available parts seems to have worked against me.
That's my luck, by the way - this picture exemplifies my luck, for which I am famous among all who know me -
Attachment:
my luck.jpg
In my case, when the pressure plate & friction plate were installed & torqued properly, the pressure plate's fingers moved inward to such an extent that they were facing very steeply inward, almost touching the friction disc's center, with only 0.286" of remaining finger travel remaining. In my opinion, that was insufficient to allow the clutch to release when the fingers were compressed the remaining 1/4". This small remaining amount of travel would only have permitted the pressure plate to release 0.0071"....nowhere near the 0.200" or so I calculated it needed to actually release the clutch.
I made up a test rig (essentially a manual, lever-activated clutch release bearing), and tested this.
I was correct - when the fingers were compressed to the point that they were hard up against the friction plate, the clutch did not release.
As an experiment, I made up some 0.095" shims of hardened T-6061 aluminum (the same material as the flywheel), and installed them between the pressure plate's 6 mounting pedestals and the flywheel. The shims duplicate the area of each of the pressure plate's clamping surface areas exactly, so the contact area between the pressure plate & flywheel is the same as it was before.
The hardened steel dowels are still in place, and are fully engaged in the pressure plate.
The shims were enough to cause the clutch fingers to move outward to where I thought they should be, roughly at the same level as the outer surface of the pressure plate. This increased the available clutch finger movement to over 1".
Another test with the manual test rig proved the clutch now releases properly & fully, yet clamps with full pressure when released. It gives a very reasonable amount of travel for the hyraulic throwout bearing (a RAM 78136) to work properly.
Without the shims, the RAM unit would have been forced to use the very last 1/8" of its 1" available travel to release the clutch, and the unit's "snout" was almost in contact with the friction plate hub (this must NOT be allowed to happen, for obvious reasons - only the RAM unit's bearing can be allowed to make contact).
With the shims, the clutch now releases at about the halfway point of the RAM's travel (from full engagement to full release only requires about 1/8"-1/4" of travel, but this now occurs halfway along its travel, rather than at the extreme end of it).
I know this seems like an over-simple (and unusual) solution but, as it stands, the only other option would be to buy several different brands of pressure plates, in the hopes that one of them would provide sufficient clearance for the clutch to work.
My buddy (another Locoster, and a very accomplished mechanic) and I examined my solution together. He was initially very skeptical, but on going through it in detail, we can't find a fault with it. There doesn't seem to be any compromise whatever in strength, parts alignment, or balance of the flywheel/clutch assembly, and the hydraulic RAM unit can now work as it's supposed to.
As a bonus, its installation now meets RAM's requirements, without the use of any adjustment shims, perfectly. RAM specifies a bearing surface-to-clutch finger clearance of 0.150" to 0.200". My setup, with the shims, provides a clearance of 0.170".
Can anyone see any real problems with this solution?