Clutch return spring

[cwmcobra]

Anybody know if the return spring that surrounds the t/o bearing actuation rod in the bellhousing is available?  I can't find one and am not sure it was there when I disassembled the engine.  I'll keep looking, but suspect I'll need one.

Thanks,

Chuck

[WkillGS]

The question came up years ago on V8Buick. He found a decent match from Lee Spring. Pics and dimensions here:
http://www.v8buick.com/showthread.php?101791-GS-bell-housing-throwout-return-spring

You can try some industrial suppliers like Graingers:
https://www.grainger.com/category/torsion-springs/springs/hardware/ecatalog/N-mgg#nav=%2Fcategory%2Ftorsion-springs%2Fsprings%2Fhardware%2Fecatalog%2FN-mggZ1z0aklz

Or McMaster Carr:
http://www.mcmaster.com/#torsion-springs/=1480s4s

[cwmcobra]

Thanks Walt.  I've done some research on those springs and see that there are a couple that will probably work.  The problem I see is not knowing the spring force that is required and matching it to the stock springs that are available.  And Brian tells me that the force should be higher than from the factory since the clutch pedals seem to sag over time, indicating that there is not enough margin in the force to offset reducing spring force over time.

I've found that my bellhousing did not come with a torsion spring.  Not surprising since the 4-speed was swapped in many years ago, so I wouldn't necessarily expect all the factory parts to be there.  Instead, my car has a return spring attached to the top of the clutch pedal and to the underside of the dash.  I didn't notice any play in the pedal before disassembly, but wasn't particularly paying attention for it either.  Pictures attached.

Would you guys be comfortable leaving the torsion spring out and relying on the pedal return spring?  Or would by recommend doing both?  I'd like to avoid the engineering project of making a stock torsion spring work, but also don't want to create the potential for teardown required in the future.

Cheers!

Chuck

[Brian]

Chuck,
  I think you need the one in the flywheel housing even if you do put on an additional spring.  The one in the flywheel housing compresses the slack in the system and pulls the clutch release bearing completely off the pressure plate.  If you take up the slack from the pedal end, it expands everything and can leave the release bearing touching the pressure plate.  No matter how much you repair/replace joints in the linkage system, there is still going to be some slack in the system.   

[WkillGS]

Agreed, keep the bellhousing spring.

My stock spring specs are:
0.120" wire diameter (with paint?)
1.220" ID
1.462" OD
270 degree deflection
Right hand wind
approx 8 coils

The McMaster 9271k131 looks close:
0.135" wire diameter
1.112" ID
1.666" OD
9.75 coils
42.86 inch lbs of torque.

I'll guess this has a higher torque than stock due to the larger wire size. Most other springs are in the 28-42 in lb range.

Lee Spring has a wider selection and is a closer match to the original:
http://www.leespring.com/browse_catalog.asp?rbunitOfMeasure=Imperial&springType=T&partnum=&UnitOfMeasure=imperial&specsCriteria=&subType=&isMIL=&pageNumber=99

The LTR115R 05 M (or S for stainless) is 0.115" wire and has a torque rating of 28 in lbs...... may be closer to stock.

I don't see the torque rating being too critical... the spring has a simple job to do. You don't want less than stock, but I can't think of a downside to a stronger one.

[cwmcobra]

Thanks for the advice and the detailed specs.  I spent some time yesterday going over the specs on the Lee, McMaster and Grainger springs that are available.  If I go this route, I'd like to buy an assortment and check them out before making a final selection.

Meanwhile, my engine is patiently waiting for its mate.  I think Brian will like the color of the clutch housing.  Kind of brightens it up, don't you think?  :-)

Chuck

[gssizzler]

Your going to really like that center force clutch! So much smoother ,less effort, and grabs so hard! I have one in the post car , what a difference over stock!

[cwmcobra]

Well, today was my lucky day.  I talked with a good friend who is also a 65 GS fan and found that he has a bellhousing with the shaft, yoke and spring available.  I'll be taking that off his hands and will use at least the spring in my restoration build.  Before I do, I'd like to take some spring force measurements to add confidence to substituting one or more of the stock torsion springs available.  I'll post conclusions as they are made.

Chuck

[WkillGS]

That'll be good info to add to our database here..... for the next time someone needs a spring.

While we're kinda on the subject, Buick added a grease fitting to that yoke shaft to keep it from binding. There's a welch plug in the bell sealing the hole for the shaft. Add a grease fitting to that plug.
There was a service bulletin on it in 65 or 66.

[cwmcobra]

Great information, thanks Walt.  Also while on the subject, I see there is a seal that is to be installed on the large diameter "ball" on the end of the shaft where it mates with the Z-Bar actuator.  I haven't seen that anywhere.  What are you guys using for that?  My best DIY approach is to use a piece of rear main rope seal that looks like it might fit.  Or, is it simply an O-ring that needs to be properly sized to that diameter?

Chuck

[GS66]

X2 on the Centerforce clutch. We had one in a 4 speed cuda, huge difference.

[cwmcobra]

X3, I'm already a fan.  Also have one in my Cobra replica.  Absolutely no complaints!

[wildcat65]

 
I was thinking of using somebody like this to make a spring:

http://www.leespring.com/torsion_spec.asp?springType=T&forWhat=Search

[WkillGS]

^^^^^ Their LTR115R 05 M   looks real close to my original, but a 300 degree version (custom) would be a better match.
Lee Spring could form the correct ends for us too!

Might be worth seeing if they can make a small run of correct replacements.

[cwmcobra]

Before installing the torsion spring in my bellhousing, I did a lot of measuring and force testing.  I didn't find any stock springs that were super close in design, but I'm sure some would work.  Attached is a drawing done online at the Acxess Spring site that is as close as I can come to duplicating the original design, of course minus the hook and eye on the ends of the legs.  Pictures of the spring are also attached.  For those interested in the paint markings, it appears to have dark green paint on it.  Might be Verde Green, for all I know.  :-)

Cheers!

Chuck