clutch disc size
Thread Starter
Instructor
Joined: Feb 2009
Posts: 178
Likes: 2
From: York UK
clutch disc size
I rebuild my engine a while ago but the clutch has never bedded in and still shudders when pulling away from stationary. I fitted a performance clutch but I'd rather go for a stock clutch and hope this cures the shuddering. The only problem is that apparently there are different sizes of disc and I don't know which one is on the car. If I knew the size I'd order a new one, but without knowing the size I'd have to take it apart just to check it and either leave it till I got a new disc or put it back together while waiting. Is there any way of knowing what size of clutch is fitted without having to go to that trouble? It's a manual '69 350 coupe.
Melting Slicks
Joined: Nov 2006
Posts: 3,379
Likes: 1,797
From: Apple Valley, MN
If your flywheel is stock, it should be 168 teeth.
What did you do to the flywheel when you rebuilt the engine? Before you spend a bunch of quid on a new clutch, take a close examination of the flywheel surface and look for tiny cracks in the disc contact face and also for evidence of thermal distress. If you pursue resurfacing, have it ground on a Blanchard grinder as opposed to having it cut on a lathe.
What did you do to the flywheel when you rebuilt the engine? Before you spend a bunch of quid on a new clutch, take a close examination of the flywheel surface and look for tiny cracks in the disc contact face and also for evidence of thermal distress. If you pursue resurfacing, have it ground on a Blanchard grinder as opposed to having it cut on a lathe.
Le Mans Master
Joined: Mar 2004
Posts: 7,449
Likes: 1,477
From: Little Rock AR
Bell housing casting number can be seen on the side.
403 bellhousing = 10.5" clutch
621 bellhousing = 11" clutch
starter bolts in line = 10.5" clutch
starter bolts diagonal = 11" clutch
How many splines do you have?
you may have a different problem. Your engine mounts can look fine but when you go to take off, a failed drivers side mount can separate allowing the engine to lift twards the passenger side and the clutch can chatter. You need to remove the drivers side motor mount to check it. If it comes apart, it is trashed. Much easier and cheaper to verify before replacing a brand new clutch.
403 bellhousing = 10.5" clutch
621 bellhousing = 11" clutch
starter bolts in line = 10.5" clutch
starter bolts diagonal = 11" clutch
How many splines do you have?
you may have a different problem. Your engine mounts can look fine but when you go to take off, a failed drivers side mount can separate allowing the engine to lift twards the passenger side and the clutch can chatter. You need to remove the drivers side motor mount to check it. If it comes apart, it is trashed. Much easier and cheaper to verify before replacing a brand new clutch.
Last edited by stingr69; Jan 14, 2021 at 08:22 AM.
Thread Starter
Instructor
Joined: Feb 2009
Posts: 178
Likes: 2
From: York UK
Thanks for your replies. I checked the number on the side as stingr69 suggested and sure enough it is 3899621 therefore an 11" plate. I couldn't see whether the starter had straight or diagonal bolts. Before the engine rebuilt there was no shudder on take-off but as soon as I'd finished the rebuild it shuddered so I assumed it was because I'd fitted a performance clutch, although there wasn't anything to say it was a fault of the clutch. I didn't do anything to the flywheel other than inspect it, so it must be a 168 tooth, and I didn't renew the engine mounts, but it's possible that when the engine was removed it damaged the mount in some way. The shuddering only happens on take off in first gear for a couple of seconds and is no trouble after that, but I'd like to get it right. Very useful info.
Le Mans Master
Joined: Mar 2004
Posts: 7,449
Likes: 1,477
From: Little Rock AR
First verify the drivers side motor mount AND verify you have 1" of free play travel at your clutch pedal. If you need to use more than light finger pressure to move the pedal 1" before it gets stiff, your clutch pedal adjustment is off. If the pedal is stiff from the beginning, your clutch will not grab fully and that can also cause slip and/or chatter at take off.
