'68 BB Clutch Bellcrank/Z-bar mount point and length ?

[KevinK]

I'm finally re-installing the BB into my '68, ...however I have a question on the clutch bellcrank/Z-bar.
  When the Z-bar is mounted on the block side pivot ball (with the pivot ball mounted in the block as compared to the bellhousing) it seems awful close to the steering shaft/rag-joint. The AIM I believe shows the pivot ball in the block, ...but it almost seems the Z-bar would clear the steering shaft better if it were mounted in the bellhousing. (?)
  I was temporarily running a small block in the car (until the BB was finished). The Z-bar used with the SB is about 1" longer than the one I believe is for the BB. Is the BB bar indeed shorter?

1.) Does the block side pivot ball mount in the block or the bellhousing?
2.) Is a BB Z-bar shorter than a SB Z-bar?
 
  ...just to note, ...I do have the correct '...621 bellhousing and the engine frame mounts are the (original) correct BB ones. (ie. driver side slightly taller, (PN '......7').

  Thanks in advance for any information,
 
            Kevin
 
 
  ...lets hope it stays this clean...
 (Note: clutch pivot ball mounted in block, ...should this be in the bellhousing?)


  ...Finally resting back home again.


  Hopefully I'll have time over the next couple weeks to get everything back together and finish this up.  Will keep you posted... 

[JohnZ]

1.) Does the block side pivot ball mount in the block or the bellhousing?
2.) Is a BB Z-bar shorter than a SB Z-bar?

It mounts in the block; the rear face of the block (the surface the bellhousing bolts to) is in exactly the same fore-aft position in the car for both SB and BB cars. The BB Z-bar is shorter than the SB Z-bar.

[KevinK]

..Thanks John

[william]

Sorry I have to disagree here.

As measured at the rear face of the block a bb is about .375" forward of the sb position-that's why bb '69s used a different shifter mounting plate. The bb z-bar is .625" longer than the sb as the engine is offset to the right.

All of this creates a subtle problem when swapping a bb into a manual trans application that was built with a sb. The holes for the z-bar bracket were drilled at the factory when the engine/trans was postioned into the frame. If you use the original holes the z-bar will be at a slight angle and can cause release/alignment problems.

[KevinK]

Bill,
   Thanks for the reply.
   Some notes:
   - My '68 is an original BB car, ...Z-bar bracket on the subframe is still in it's original location.
   - When temporarily running the SB (350) in the car, everything was lined up (and functioned) fine. (noting that the Z-bar I was using is the longer of the two that I have).
 
   I did, just last night hook up the (shorter) Z-bar (pivot on block) and it does line up fine. Again, Z-bar frame bracket still in same place it's always been. One concern I had/have, ...it does seem that the bar should be a bit longer to fully seat on the block-side pivot. It fits 'ok', ...but even last night I started wondering, ..."should I be using the LONGER bar?
    ...and then I see your post this morning.
  (the only other thing that crossed my mind... Bill, ...you specifically mentioned " '69s" in your reply, ...this isn't a subtle difference between '68 and '69 is it? ...I don't think so, ...but you never know)
 
   Is there any chance someone has a loose BB (or SB) Z-bar they could measure? (or if you feel like crawling under your car )
 
  Thanks again,
                       Kevin
   

Sorry I have to disagree here.

As measured at the rear face of the block a bb is about .375" forward of the sb position-that's why bb '69s used a different shifter mounting plate. The bb z-bar is .625" longer than the sb as the engine is offset to the right.

All of this creates a subtle problem when swapping a bb into a manual trans application that was built with a sb. The holes for the z-bar bracket were drilled at the factory when the engine/trans was postioned into the frame. If you use the original holes the z-bar will be at a slight angle and can cause release/alignment problems.

[Hatman]

.

 The holes for the z-bar bracket were drilled at the factory when the engine/trans was postioned into the frame. If you use the original holes the z-bar will be at a slight angle and can cause release/alignment problems.

Is this true if so wouldn't this be a good way to tell if a car was a big block car? A person could just measure from the back of the subframe to the mount holes and would know right now .

[JohnZ]

Sorry I have to disagree here.

As measured at the rear face of the block a bb is about .375" forward of the sb position-that's why bb '69s used a different shifter mounting plate. The bb z-bar is .625" longer than the sb as the engine is offset to the right.

All of this creates a subtle problem when swapping a bb into a manual trans application that was built with a sb. The holes for the z-bar bracket were drilled at the factory when the engine/trans was postioned into the frame. If you use the original holes the z-bar will be at a slight angle and can cause release/alignment problems.

Oops, forgot about the BB offset to the passenger side from centerline, which makes the Z-bar longer on a BB.

Surprised to hear about the .375" difference in rear face of case position with a BB; it was normal Chevrolet design practice to consider that surface as a standard fore-aft datum line on other car lines, and to adapt component packaging to it both forward and rearward. Apparently the Camaro was a departure from that practice.

Also wasn't aware of any hole-drilling in the subframe for the Z-bar frame bracket; those three holes are present in the subframe for the base car, and no drilling is called out in L35 - only a different part number for the Z-bar. The only subframe drilling I recall offhand was on Firebirds for the battery cable clips, as the Pontiac starter was on the driver's side.

[KevinK]

Again, Thanks for the input.
   I had already planned on swapping the longer Z-bar back in (it's easy to do now) ...and get it right before I put the exhaust system back in. I'll take some pics once the bar is in for good...
   

[william]

All of this stems from a very odd situation I had while involved with a '69 Z/28 resto about 10 years ago.

For some reason the car was built with a bb crossmember as are most 1970 Yenko Deuce LT-1 Novas. We of course obtained the correct crossmember, got it all back in the frame and the z-bar was way off, obviously crooked. I started doing some measuring: the distance from the rear block face to the motor mount holes is the same sb/bb. If you place a sb frame bracket next to a bb frame bracket you will see the .375" difference. Ergo the engine is that distance forward of the sb position. If the z-bar bracket holes were the same I do not know how they would ever line up. Maybe this was just one screwed up car.

While we on on this topic the z-bar bracket used in '67 is different than 68-69 and does not interchange.