Aftermarket Clutches

The original clutch and flywheel in my 62 was raised rim style flywheel with a 9.5" long style clutch. At some point, Dad put a 10.5" Ford long style in it. This with a new flat flywheel that I think came from D&D. He got it sometime in the 70s. so it is a long time ago and there are no receipts for it that I can find to confirm the source of the flywheel but I do have the receipts for the PP and clutch. The throwout bearing (flat style) is a BCA 1625-12.

I got under it yesterday and measured what I have. The Pressure plate is a McLeod (pronounced 'mc loud', apparently and identical to Weber clutch cover as well according to D&D) model 360400 it has 3 legs with holes at 3 1/8" spacing on each leg (std ford 10 1/2"). These holes appear to be on a 11 1/2 BCD. The flywheel is also drilled for a 6 evenly spaced holes on (best I can measure it on the car) 11 5/8" BCD. Can anyone here confirm the BCD for a standard chevy 10.5 diaphragm clutch? Is it 6 on 11 5/8"? Is anyone here running a D&D flywheel? What clutch are you ruinning?

Keith

Followup:

Put a Sachs 1625-10, which is a standard GM 10.5" diaphragm style, in it. Turns out the transmission is a 10 tooth muncie. OMG so easy compared to the street/strip McLeod. Got z bar rebuild bits from 4speedconversions.com. Had to sleeve the Z bar on the engine side as it was so worn. Also sleeved both pivots with bronze bushings. I did make a drawing of the NLA z bar and will be making a spare out of 4140 and having it welded. Very easy and easily feathered, now.

Has an engine vibration, now. I had to take so much off the flywheel that it may have been taken out of balance. Buying a new one from D&D (ouch).

Keith

I finally have the clutch mostly resolved. I put the new flywheel in it and the vibration went away. THe vibration is either from the clutch bolt pattern being off center (very unlikely as the ford pattern was fine for 30 years) or that the 0.040" taken off was enough to throw off the balance. The design of the 2018 D&D flywheel is a bit different than the ~1978 version. It is 5lb lighter but probably the same inertia based on the fact that it is more of an I in section than the '78 version. The old one probably would be useful to someone if it was balanced. It is drilled for both the ford long and GM diaphragm style 10.5" clutches. If anyone is interested in it' let me know.

The only 'issue' I have with it is the fact that the clutch goes to almost 0 lbf at the floor. A bit disconcerting but fine once you get used to it. What feels weird is that it does not snap back to on your foot as quickly as I want it to if you push it all the way to the floor. This is even with a bit more free play than needed on the bearing to the clutch fingers. It is as if the diaphragm style requires less throw than the long style. The pedal assembly cannot be easily modified for less throw. I can put the pushrod in a hole closer to the pivot on the Z bar, but then the pushrod is n o longer horizontal and then pushes with a moment on the clutch fork. You cannot move the pivot on the pedal side as it goes through a hole in the firewall.

Keith

Just did a bit of digging on this pedal feel thing. It is the over center spring on the pedal that is causing the pedal to go to 0 lbf. This spring helps your foot to keep the OE style (borg and beck or ford long style) clutch dis-engaged *and* returns the pedal to the fully disengaged position when your foot is off of it. When you go to a diaphragm clutch, you do not need so much help to hold it dis-engaged. Many places suggest removing it completely. The problem with this is that then your throwout bearing can rest on the fingers in many cases. I think the weight of the pedal may do it and definitely if you rest your foot on it. I know my Saabs have a spring to do exactly this (keep the bearing riding on the fingers), but the GM design assumes that the bearing is not in contact with the fingers when the pedal is 'up'. I think I want to maintain this design and will see if I can reduce the force when all the way down or maybe replace this spring with a lighter one. This will allow me to attain the 1/16-1/8" play at the throwout bearing instead of the much larger gap I have now.

IMO, these little engines don't require any 'competition' type clutch as they don't make enough torque to require it. If you like the feel of a 3 finger style, that is one thing or if you are racing it and need a positive feel and high rpm shifting a B&B style may be fine., but if you want a lighter clutch which has more than enough torque carrying capability, a diaphragm style is the way to go. a full kit from Sachs (ZF) is ~100.00 and at 10.5", it can carry more torque than this thing can produce. Supposedly 230 ft-lbf with a 4bbl is what the 215 can produce. The 10.5" GM was for up to 350 cuin small blocks. The 396 had an 11". The 350 had 360 ft-lbf! I think it will be fine.

Update: Posted elsewhere as well, I removed the over center spring and it really improved the feel of the clutch. The way to remove it is to stand on your head, remove the rubber stop then pry the spring coils apart a bit and force in a washer between coils. Opposite sides one at a time until you can get enough length to get the spring out. Once it is out, replace the rubber stop.