69 clutch release issue
Thread Starter
Pro
Joined: Sep 2018
Posts: 535
Likes: 104
From: Chicago, IL
69 clutch release issue
Hey Everyone,
I got a 69 427 nom with numbers matching muncie trans, Repo 621 bellhousing. I bought a flywheel and clutch/pressure plate kit from summit.diaphragm, stock replacement
im prepping to break in the cam however i cranked the engine with the clutch pressed in and the car moved forward.....
i adjusted the clutch rod to the end of the rod, same problem.
I read that the ball might be too short with repo flywheels, it was 1.5 long
i put a 3790556 in today, which is 1.78 long
i can now get the clutch pedal to feel good with threads left on the clutch rod and now the car does not move forward in gear.
however next issue i got alot of preload on the throwout bearing.
Clutch rod, z bar and fork are all GM
will shimming the flywheel help? do i have a bad pressure plate? looking for advice,already had this out once.
IF i adjust the clutch with no load on the throw out bearing the car moves forward again.....
I got a 69 427 nom with numbers matching muncie trans, Repo 621 bellhousing. I bought a flywheel and clutch/pressure plate kit from summit.diaphragm, stock replacement
im prepping to break in the cam however i cranked the engine with the clutch pressed in and the car moved forward.....
i adjusted the clutch rod to the end of the rod, same problem.
I read that the ball might be too short with repo flywheels, it was 1.5 long
i put a 3790556 in today, which is 1.78 long
i can now get the clutch pedal to feel good with threads left on the clutch rod and now the car does not move forward in gear.
however next issue i got alot of preload on the throwout bearing.
Clutch rod, z bar and fork are all GM
will shimming the flywheel help? do i have a bad pressure plate? looking for advice,already had this out once.
IF i adjust the clutch with no load on the throw out bearing the car moves forward again.....
Race Director
Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
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Cruise-In VIII Veteran
These cars are known for there relatively short stroke in the clutch release department.
Some aftermarket clutches play better than others with this short coming.
sounds to me like you just don't have enough stroke/travel to operate the clutch you have chosen.
Back to the drawing board as they say.
Look into the clutches that DO work. Plenty of threads, information on this forum in the past on this very subject.
just because it fits a Chevy does NOT mean it will work on your Corvette.
Some aftermarket clutches play better than others with this short coming.
sounds to me like you just don't have enough stroke/travel to operate the clutch you have chosen.
Back to the drawing board as they say.
Look into the clutches that DO work. Plenty of threads, information on this forum in the past on this very subject.
just because it fits a Chevy does NOT mean it will work on your Corvette.
Le Mans Master
Joined: Mar 2001
Posts: 6,240
Likes: 1,013
From: Watkinsville, GA and Glen Cove, NY
4-Vettes is right on. I had the same problem. We have about .580 inches of available travel. If the clutch doesn't release in that amount of travel, it won't work. You can put it in a press and check that your clutch releases in this range, otherwise it won't work.
Instructor
Joined: Jan 2019
Posts: 145
Likes: 98
From: Central Kentucky
This thread was an immense help:
https://www.corvetteforum.com/forums...vel-range.html
Not sure how a universal type of clutch would work out. I got one of those from Summit, but changed gears (ha) and, after some research, went with the McLeod Super Street Pro.
https://www.corvetteforum.com/forums...vel-range.html
Not sure how a universal type of clutch would work out. I got one of those from Summit, but changed gears (ha) and, after some research, went with the McLeod Super Street Pro.
Race Director
Joined: Nov 2006
Posts: 13,258
Likes: 7,848
From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
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Cruise-In VIII Veteran
Wasn't all that long ago one of our resident gurus posted a fair bit of information on this topic. Including measurements taken using a press. I think it was Lars. But I could be mistaken.
What I am certain of is if you do some research you can find the answers.
You simply stated that you purchased a clutch kit from Summit. But didn't mention which one.
I personally run a RAM and I know a few others do as well and it works perfectly with the stock Corvette linkages and even pivot ball and fork.
What I am certain of is if you do some research you can find the answers.
You simply stated that you purchased a clutch kit from Summit. But didn't mention which one.
I personally run a RAM and I know a few others do as well and it works perfectly with the stock Corvette linkages and even pivot ball and fork.
Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
I run a Centerforce II in my '79 and it works well. You also have to make sure you have exactly the right thickness flywheel, length of release bearing, and length of pivot ball. All that information is available from multiple sources, including this forum. I know because I did the research when I swapped in the 5 speed. Just don't have the details at my fingertips anymore.
Le Mans Master
Joined: Mar 2004
Posts: 7,502
Likes: 1,510
From: Little Rock AR
The McLeod pressure plate is the one that came out on top for proper release. Lars posted a thread about it.
LUK is great and inexpensive from my experience as long as you are not over 350 HP.
If your assembled clutch is not in the middle of the threaded rod when properly adjusted you have something off. Might be the linkage pieces. I bought a whole kit from SST and they sent me 1 wrong linkage piece. Drove me crazy for a whole day. It was for a C2 Vette but I have a C3. Swapped out that rod and it all fell into place.
Can you post a few pix of your linkage? How are you adjusting the free play? What spec?
LUK is great and inexpensive from my experience as long as you are not over 350 HP.
If your assembled clutch is not in the middle of the threaded rod when properly adjusted you have something off. Might be the linkage pieces. I bought a whole kit from SST and they sent me 1 wrong linkage piece. Drove me crazy for a whole day. It was for a C2 Vette but I have a C3. Swapped out that rod and it all fell into place.
Can you post a few pix of your linkage? How are you adjusting the free play? What spec?
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Thread Starter
Pro
Joined: Sep 2018
Posts: 535
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From: Chicago, IL
update everyone.pulled everything out, long story short i installed the clutch disc backwards, im surprised that i made this mistake even as the disc says flywheel side stamped on it......so i guess a clutch disc backwards would still disengage as long as you had the long ball stud and preloaded the throw out bearing.
i took this opportunity to replace the positive cable with a 1/0 that i made and i just installed the McLeod Super Street Pro kit that seems to be good. (clutch disc correct way)
i will hopefully get the trans back in this weekend and check back in. Thanks for everyone's replys.
ill never make this mistake again!!
i took this opportunity to replace the positive cable with a 1/0 that i made and i just installed the McLeod Super Street Pro kit that seems to be good. (clutch disc correct way)
i will hopefully get the trans back in this weekend and check back in. Thanks for everyone's replys.
ill never make this mistake again!!
Race Director
Joined: Nov 2006
Posts: 13,258
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From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
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Cruise-In VIII Veteran
Glad to hear you have it figured out. 
Team Owner
Joined: Mar 2002
Posts: 44,686
Likes: 1,833
From: Huntsville AL
Post # 79, 83 & 87 are the meat of the conversation and fix for this problem if anyone in the future has this problem after a clutch replacement.
https://www.corvetteforum.com/forums...leasing-4.html
Thread Starter
Pro
Joined: Sep 2018
Posts: 535
Likes: 104
From: Chicago, IL
I got the trans back in and clutch pedal adjusted, cranked engine and everything seems to be working properly. i did leave the 1.78 ball in and once i put trans up the gap on the fork was about 1/8 from pressure plate fingers, i felt that it was too close, being that spec i read was 1/4 away. so i pulled trans out again and changed ball back to my original 1.5 long. all is well
thanks for everyones help and replys.
thanks for everyones help and replys.