Author Topic: M20 clutch adjustment  (Read 6002 times)

68rsssrag

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M20 clutch adjustment
« on: June 29, 2006, 03:32:42 PM »
I have just installed my L35 with M20 in my 68 convertible after 3 years of work. I have almost run out of thread on the adjuster rod with a new clutch . I noted the Z bar is on a slight angle to the front of the car on the motor (ball end). Seems to me that the repro rod is the same as my originals. The fork and throwout bearing are all new GM, clutch is aftermarket.

Any ideas on why I am out of adjustment range so soon with all new stuff?

Thanks

Arno

hotrod68

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Re: M20 clutch adjustment
« Reply #1 on: July 01, 2006, 04:06:55 AM »
Uh-oh...sounds like you may have some mismatched parts. There were basically 2 different pressure plate designs--a "flat" diaphragm and a "raised" diaphragm. The flat diaphragm used a longer throwout bearing than the raised one. You may have a raised diaphragm throwout bearing on a flat pressure plate. That would do it. The raised plate throwout bearing was very short--less than 3" long, while the flat plate bearing had a shoulder on it that increased the length. There were other variations, but this was the most common mismatch. The raised plate fingers will look like a "cone", while the other plate fingers would appear almost flat. I pulled this boner in my younger days and the lesson has never left me! That's all I can think of, unless somehow you got the wrong throwout fork. Good luck, and keep that '68 rolling!
HotRod'68  1968 SS350 coupe undergoing frame-off resto/rod. 386/350/4.11s
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68rsssrag

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Re: M20 clutch adjustment
« Reply #2 on: July 04, 2006, 04:43:50 AM »
Could be the throwout bearing alright but i noticed tonight in the workshop manual that Big Blocks used a different "two peice" pushrod design but the catalogs like Ricks show it for small blocks. Could i have the wrong pushrod?

Arno

68rsssrag

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Re: M20 clutch adjustment
« Reply #3 on: September 16, 2006, 03:05:01 AM »
I have checked the throw out bearing, motor mounts, motor mount horns and swivel rod and all are correct. Any other ideas?

Arno

68rsssrag

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Re: M20 clutch adjustment
« Reply #4 on: October 03, 2006, 04:34:08 AM »
Guys, I'm starting to go wonkers on this, we've checked out every component twice and all seems correct but i am at the end of the swivel rod with a new clutch, what can be wrong here?

Arno

RamAirDave

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Re: M20 clutch adjustment
« Reply #5 on: October 03, 2006, 05:00:18 AM »
The pushrods are different for BB and SB.

The SB will have an "elbowed sleeve" (best way I can think to describe it right now) with a threaded rod inserted into the sleeve.  The BB is a threaded rod with a swivel block.
"Build them how the designers and engineers envisioned them to be"

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68rsssrag

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Re: M20 clutch adjustment
« Reply #6 on: October 04, 2006, 03:26:27 AM »
I have the BB rod, not sleeved.

RamAirDave

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Re: M20 clutch adjustment
« Reply #7 on: October 04, 2006, 03:51:57 AM »
So can you get it to adjust right, or does it run out of threads before?

Im guessing youre using a BB Z bar?
"Build them how the designers and engineers envisioned them to be"

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68rsssrag

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Re: M20 clutch adjustment
« Reply #8 on: October 09, 2006, 10:47:50 PM »
I am at the end of the threads (just enough to adjust) with a new setup, only the Z bar is original and from my car.

All the parts seem to match BB needs, e.g.one peice threaded rod, V8 throwout bearing, correct fork, correct motor mounts and horns.

As the clutch wears I believe I need more threads on the rod, in other words the rod gets longer, correct?

Arno

JohnZ

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Re: M20 clutch adjustment
« Reply #9 on: October 10, 2006, 04:53:05 PM »
Nope - as the clutch wears (disc thickness is reduced), the effective length of the lower rod will be reduced - it will get shorter, not longer. As the disc wears, the outer end of the clutch fork moves forward as the ends of the diaphragm fingers move rearward.
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68rsssrag

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Re: M20 clutch adjustment
« Reply #10 on: October 12, 2006, 04:21:23 AM »
Hi John

Thanks for clearing this up. I will operate as is and sleep soundly again.

Arno