Clutch problem, Help please....

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scooper
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Joined: Sun Aug 12, 2018 6:01 am

Clutch problem, Help please....

Post by scooper »

Help....I have a problem with the clutch in my Corsa with a Crown conversion. The clutch won't disengage. I bought it with this problem, previous owner couldn't fiquire it out either. The car has a 3/4" Tilton master cylinder, a 7/8" slave cylinder. Chevy Camaro (60s) throw out arm, it had a Centerforce diaphragm plate and disc in it, I changed that out to a Corvette 11" plate and disc, thinking the plate was bad, or to heavy. The clutch pedal feels like a brake pedal, rather than a clutch. I set the pivot ball height at 4-3/4", like Chevy recommends. I'm confident the problem lies somewhere other than the clutch now. What are you guys running for a hydraulic clutch set up in your cars? How far should the throw out arm move? Cylinder sizes?

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bbodie52
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Re: Clutch problem, Help please....

Post by bbodie52 »

:helpsos: :think: I don't have experience in this area, but did do some nosing around on the Web. Perhaps one of these will help...

Image
How to Troubleshoot a Clutch That Won't Fully Disengage

:link: https://www.yourmechanic.com/article/ho ... sunderland

Symptoms of a Bad or Failing Clutch Master Cylinder

:link: https://www.autoblog.com/2016/01/06/sym ... -cylinder/


ImageNew clutch will not disengage

:link: https://community.cartalk.com/t/new-clu ... gage/77783


ImageCamaro and Firebird Forum Discussion

:link: https://ls1tech.com/forums/manual-trans ... e-all.html
If the clutch disc is put in backwards it won't disengage.

ImageMore...

:google: :search: :link: https://www.google.com/search?source=hp ... zxrgg-ZJyE
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

scooper
Posts: 37
Joined: Sun Aug 12, 2018 6:01 am

Re: Clutch problem, Help please....

Post by scooper »

Thanks for the links, pretty much covered all the basic stuff, this has me stumped. I'm going to start playing around with master cylinder attachment points on the pedal arm, see if that changes the feel of the pedal, I'd also like to try increasing the slave cylinder diameter, see what that does for me. If all else fails, I'll put a hydraulic throw out bearing in it, according to the previous owner that is the only set up that worked in the car, he claimed it was to slow, I'm thinking the air gap was not set close enough.

66vairguy
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Re: Clutch problem, Help please....

Post by 66vairguy »

Since a Crown is a custom setup it's hard to say what is wrong. You need to contact the Corvair V8 guys and see what works for them. A fellow in L.A. CA uses a hydraulic throw out bearing. A bear to change if it fails, but works for him.

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bbodie52
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Re: Clutch problem, Help please....

Post by bbodie52 »

Upon further research...

:google: :search: :link: https://www.google.com/search?source=hp ... sf1sURLLqw

Image
:link: http://corvaircenter.com/phorum/read.php?1,18539,18539

Re: Clutch not releasing?
Posted by: steve goodman
Date: November 06, 2005 11:48AM

Hello Bill: There seems to be a typical problem with the V8 cars and the hydraulic clutch parts involved. Sometimes the bracket that the slave is mounted onto is too flimsy and moves when the clutch is depressed, I saw one that the bulkhead under the dash was moving when the pedal was pushing on the master cylinder.

Most of the time however the problem will be easy: bleed the clutch system

OR more difficult: finding the proper match of master cylinder and slave cylinder diameters to properly push the release bearing fork.

I hope yours only needs bleeding, same process as the brake system. Good luck and enjoy your toy!!!!!


Best, Steve
Image
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

scooper
Posts: 37
Joined: Sun Aug 12, 2018 6:01 am

Re: Clutch problem, Help please....

Post by scooper »

I made some positive progress today. I replaced the 1" diameter master cylinder with a 3/4". This solved the hard pedal I had, nice and smooth now. While I was under the dash hooking the new cylinder up I noticed that the bracket that had been added, (poorly), to support the clutch bell crank moved away from the master cylinder when the clutch pedal was pushed, effectively shortening the master cylinder travel. So I mocked up a support to keep the shaft from moving. I finally have some clutch disengagement, not 100%, but at least I'm headed in the right direction. Tomorrow I'll fab a nicer support, adjust the master cylinder and slave linkages, and hopefully be able to drive this for the first time since I bought it. Thanks for the replies, they have helped me keep my sanity as well as pointing me in the right direction.

66vairguy
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Re: Clutch problem, Help please....

Post by 66vairguy »

Glad you are making progress. I've run into a few lousy brake modes due to mismatched master and secondary cylinder sizes. A number of considerations to deal with and it takes some number crunching. You have to determine how much volume you need to displace the secondary cylinder enough to actuate the clutch properly. Next you need a master cylinder that can supply enough volume at a suitable pressure. Going to a smaller master cylinder bore increases leverage over the secondary, but may not supply enough fluid volume to move the secondary piston enough. If this is the case you may have to find a "longer master cylinder" or go back to a bigger bore and use the a revised clutch pedal pivot point to improve leverage - but make sure you have enough pedal throw with out hitting the floor. Like I said - a lot of number crunching and this is why engineers make good money.

scooper
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Re: Clutch problem, Help please....

Post by scooper »

All straightened out, took it for my first drive today. I had a multitude of issues:
1.) Too big of a master cylinder,(1"), went down to a 3/4", much softer pedal.
2.) Too much free play between throw out bearing and clutch fingers because of wrong pivot ball depth. My car has a steel scatter shield on it with the back plate behind the flywheel, that back plate adds 1/8" depth to the pivot ball. I removed the back plate, I'm not racing, just street driving.
3.) Poor alignment of slave rod to throw out arm, pushing at an angle instead of straight on.
4.) This is a big one, probably 75% of my problem...there was deflection of the cross shaft under the dash. When the clutch was depressed, the shaft deflected back away from the master cylinder, I wasn't getting the travel of the rod into the master cylinder I thought I was getting. I came up with a support to keep that cross shaft from moving.
5.) The clutch pedal was bottoming on the floor before the master cylinder was at full travel. I reworked the arm.

The clutch feels good now, catches 1/3-1/2 of the way off the floor from full up.

I'm happy with the clutch, now I can move on to some other minor issues; front and rear alignment, brake bias tuning, a bushing on the shifter that won't stay in the tube, and some minor cosmetic stuff. I'm just excited to be able to drive it a little before the weather gets bad here in the NE. Thanks for all your replies!

66vairguy
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Re: Clutch problem, Help please....

Post by 66vairguy »

Glad it worked out. Not to rain on your parade, but get in touch with the Crown guys about bellhousing alignment and centering. IT IS CRITICAL on a Crown if you want the input shaft/clutch gear and bearing to last. A good Winter project.

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bbodie52
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Re: Clutch problem, Help please....

Post by bbodie52 »

scooper wrote:...now I can move on to some other minor issues... a bushing on the shifter that won't stay in the tube...
This video may be of help in fixing your shifter linkage problems...

I managed to find the referenced flange bushings on Amazon.com (pack of 4). You may be able to locate them at a hardware store locally, too.
Image
The Hillman Group 58105 Flange Bearing, Bronze 3/4 X 7/8 X 1-1/8 X 3/4-Inch, 4-Pack
Price: $13.60 + $6.95 shipping

Image

:link: https://www.amazon.com/Hillman-Group-58 ... ge+bearing

Here are a couple of other sources...
Image1-1/8" Flange X 3/4" Bronze Flange Bearing (3/4" I.D. X 1" O.D.)
$5.38 plus $3.99 shipping
Image
:link: https://www.walmart.com/ip/1-1-8-Flange ... akQAvD_BwE
SPECIFICATIONS Manufacturer P/N: HIL58107
  • I.D. Size: 3/4"
  • O.D. Size: 1"
  • Length: 3/4"
  • Flange Width: 1-1/8"
  • Material: Bronze

Image
THE HILLMAN GROUP
1-1/8" FLANGE X 3/4" BRONZE FLANGE BEARING (3/4" I.D. X 1" O.D.)
:link: http://www.greschlers.com/1-1-8-flange- ... d-x-1-o-d/
$5.38
SKU: HIL58107

See page 7-9 of the attached 1965 Corvair Chassis Shop Manual - SECTION 7 - TRANSMISSION, CLUTCH AND CONTROLS for material on the shift linkage system. The 3-speed transmission info also applies to the 4-speed.

:chevy:
Attachments
1965 Corvair Chassis Shop Manual - SECTION 7 - TRANSMISSION, CLUTCH AND CONTROLS.pdf
1965 Corvair Chassis Shop Manual - SECTION 7 - TRANSMISSION, CLUTCH AND CONTROLS
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Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

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thewolfe
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Re: Clutch problem, Help please....

Post by thewolfe »

When I installed a hydraulic clutch I also had a lot of flexing up under the dash where the clutch pedal cross shaft attaches. It actually ripped that flimsy spot welded bracket out. Even when I made a new one out of angle iron the sheet metal of the dash still flexes. Making that area solid improves the feel of the clutch pedal a lot. Goes from mushy and just okay to crisp and positive feeling like it should. I sandwiched that angle iron bracket with another on top of the sheet metal which is accessed under the wiper cowl. It bolts through the lower angle iron bracket and also has 2 bolts that attach through the front into the trunk. This makes that whole area solid. The sheet metal also flexes around the master cylinder if you don't have some sort of steel plate behind it to spread the load.
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bracket.jpg
topbracket.jpg
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master.jpg
Nate Wolfe
65 corsa 180

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