The clutch overcenters on speedshifts over 5500RPM. PITA, and will probably change out to a HD unit. Any recommendations to upgrade my standard duty BORG disc/pressure plate assy.? Engine is a well tweaked 1965 327/365 which likes to run to redline and beyond.
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Re: Abusing A Midyear.....Intended Use
Joe-----
For your use and application, you might be better off with something like a CenterForce II. I don't recommend those for normal use, but for the kind of use you're talking about, it would probably be best.
By the way, with all of these runs to redline and beyond, I hope you don't have stock connecting rods in the engine.In Appreciation of John Hinckley -
Re: Abusing A Midyear.....Intended Use
i have a 68 z and have bought all of the clutch combos from the various makers---and have spent a bazillion dollars---i wish i would have started with a dual disc from the start but did'nt want to spend the xtra dough---there are mfg's out there that have them to fit in a stock bell housingComment
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a block of wood on the back of the pedal
If your current pressure plate has enough pressure to overcome the torque of your engine (it's not slipping) you don't need a stiffer pressure plate. You want the clutch to engage about 2 inches off the floor. Two ways to accomplish this - either adjust the clutch to the proper point or measure how far it is now and cut a block of wood to take up the additional clearance and strap it to the back of the pedal so it contacts the floor and blocks overcentering.
MarkComment
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Re: Abusing A Midyear.....Intended Use
Joe -
No midyear ever had a Borg & Beck 3-finger coil spring pressure plate; all had bent-finger diaphragm PP's. I've had good luck with LuK and Centerforce II clutches, with the correct 1-1/4" throwout bearing and stock 1-1/2" ball stud.Comment
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Re: a block of wood on the back of the pedal
The 1966-88 repair manuel states that clutch pedal should be 1/2" FROM FLOOR TO shift from 1st. to reverse. This indicates proper adjustment. I would think the 2" block would prevent this 1st. to reverse. DonComment
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what you're trying to do is
to get the extra travel out of the pedal system. The clutch "over centers" when at high RPM the pedal pushes too far. Many people adjust the clutch pedal relative to the pedal free play when the clutch is at it's resting position. This totally ignores the travel of the pedal at the other end of the stroke. If it travels too far, then you have a problem. The point of the wood block is to only let it travel just far enough to do the job and no further. It actually works .
MarkComment
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clarification
The clutch ends up totally releasing about 1/2" from the end of it's travel and is totally engaged at about 2" off the floor.Comment
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the correct way to adjust a diaphram clutch
jack up the rear of the car so both wheels are off the ground,put the trans in 1st gear. have some one try and turn the back wheels while you slowly push in the clutch pedal. when the back wheels can be turned this is a far as you need to push in the clutch. install a clutch pedal stop of your choosing. always use a cluch disk that has the lining bonded to a thin aluminum backing which is then riveted to the disk,L-88 type.we alway used 10-1/2" diameter disks on 11" pressures plates so the lining does not "fuzz" on the outside diameter and cause clutch drag and we ground down the disk OD when used with a 10-1/2" pressure plateComment
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Re: Abusing A Midyear.....Intended Use
Joe,
The "over center-stuck to the floor" condition that you describe is very common, and can be corrected by adjusting the clutch as others have mentioned. GM was also aware of the problem in the late 60's with the 67-69 Camaro Trans-Am car program that they were somewhat involved in. The problem is the diaphragm going over center on disengagement. Their fix was slightly different. Their recommendations were to cut a small 1" x 1.5" hole in the bottom of the clutch housing to gain access to the pressure plate attaching bolts. A pack of washer shaped shims of .010"-.015" were to be installed under each bolt, one at a time until the over center problem was cured. This condition was most pronounced with a new full thickness clutch disk. As the disk wore slightly, the over center problem became less and less and shims were to be removed as necessary. It worked very well.
Obviously, no one wants to chop a hole in their clutch housing on a restored car today so the clutch adjustment method mentioned in previous posts is the logical choice. It works almost as well.Comment
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Re: the correct way to adjust a diaphram clutch
Your outline sounds simple & reasonable Clem. But why does one have to push pedal 1/2" from floor to engage 1st. & reverse? 2" or more for 3rd & 4th.?Comment
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Re: the correct way to adjust a diaphram clutch
reverse i can under stand because it is non syncronized but 1st i can not answer that. i always put my manual 4 speed trans in one of the foward syncro gears before trying to engage reverse to stop the gears from turning. some 4 speeds had aluminum clutch gear bearing retainer which caused the TO bearing not to move freely and cause clutch engagement problems because the soft aluminum would get worn and gouged and have a rought surface.Comment
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Thanks All, For The Responses
All,
First, let me address specific points brought up by some of you.
Joe....I only occasionally drive the car in such a "spirited" manner, probably not more than a few times a season. Love and respect the old gal, but sometimes I just can't resist the thrill of all that top end power. The con rods are stock, but I'm on Boyan's order list for the Crowers. That will be done in the near future.
John....the clutch is a diaphragm type, not a Borg-and-Beck type. The manufacturer is Borg. Sorry for the confusion.
Mark.....I agree with you about keeping the standard clutch. The clutch holds tight when engaged, and so, all of those "high clamping force" gimmicks used by some manufacturers just don't convince me.
Right now, the freeplay is set to just over one inch, as per 1965 Shop Manual. According to Clem, Michael and Don, this is probably not enough. Also, it is set to "standard release". Will changing to "quick release" alleviate the problem? I will take your advice and set the engagement per Clem (closer to the floorboards).
JoeComment
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