Long or short Throwout bearing? - Team Camaro Tech
Transmission & Driveline Transmissions and Differentials

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post #1 of 15 (permalink) Old Feb 20th, 19, 05:46 AM Thread Starter
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Frank
 
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Long or short Throwout bearing?

Which is the proper one for a '78 454 w/ Muncie M20 in a 68 Camaro? What else would you need to to know to know the right one?

'68 Camaro 454, 4sp
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post #2 of 15 (permalink) Old Feb 20th, 19, 06:16 AM
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Re: Long or short Throwout bearing?

Picture of the pressure plate, and, what it came out of just for starters.

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post #3 of 15 (permalink) Old Feb 20th, 19, 06:18 AM Thread Starter
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Re: Long or short Throwout bearing?

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Originally Posted by dyno jonn View Post
Picture of the pressure plate, and, what it came out of just for starters.
I'll be going with all new PP, disc & bearing

'68 Camaro 454, 4sp
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post #4 of 15 (permalink) Old Feb 20th, 19, 06:52 AM Thread Starter
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Re: Long or short Throwout bearing?

Might be a stupid question but, since I don't know.. Does having a long or short TO bearing change the length of travel for the clutch fork?

'68 Camaro 454, 4sp
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post #5 of 15 (permalink) Old Feb 20th, 19, 06:55 AM
R66
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Re: Long or short Throwout bearing?

STOCK bent (raised) fingered diagram pressure plates normally used the short clutch release bearing (throw out bearing). I think this was most common on SB & BB Chevys in the mid to late 60s and up thru the 80s.

STOCK flat fingered pressure plates take the long release/throw out bearing. Used mostly in the 50s and in 6 cylinder applications.

Aftermarket Borg and Beck pressure plates generally use the short clutch release bearing. But the manufacturer should give you a recommendation.

My advice for a stock street car is to buy a LuK kit with clutch pressure plate, release bearing, clutch disc, and pilot bearing all in one. They are inexpensive and work well. Their tech department will help you in decisions - organic or metallic disc, release bearing, etc. Rock Auto has them for a reasonable price.

Ron
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post #6 of 15 (permalink) Old Feb 20th, 19, 06:55 AM
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Re: Long or short Throwout bearing?

You generally determine the right throwout bearing by the pressure plate you are running. If the fingers on the pressure plate are flat when it is installed, its the long bearing. If the fingers are raised up on the pressure plate when installed, it the short one. McLeod has an adjustable one that will work as a long or short throwout bearing.
https://www.summitracing.com/parts/mcl-16505

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post #7 of 15 (permalink) Old Feb 20th, 19, 07:10 AM
R66
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Re: Long or short Throwout bearing?

Quote:
Originally Posted by Just 1 More View Post
Might be a stupid question but, since I don't know.. Does having a long or short TO bearing change the length of travel for the clutch fork?
No, it doesn't change the length of travel (stroke), only the relationship and angle between the fork and the pressure plate are changed. Thus, the change from and long release bearing to a short release bearing can be made with adjustment of the fork pivot ball and the clutch linkage rod on the z-bar (bell crank) which actuate the fork - If there is adequate distance on the input bearing housing as well as distance to the pressure plate fingers, etc.

On the Camaro and other cars, the stoke of the clutch fork is limited by the fire wall. Also using the wrong release bearing without changing the geometry (pivot ball location) of the linkage can lead to binding on the input shaft and incorrect contact with the pressure plate, failure to release the clutch, and other problems.

If your car has stock flywheel bell housing, and transmission, the stock setup kits sold by many suppliers will generally provide what you need.
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post #8 of 15 (permalink) Old Feb 20th, 19, 07:32 AM
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Re: Long or short Throwout bearing?

Buy a kit. The right TO bearing should be in there.
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post #9 of 15 (permalink) Old Feb 20th, 19, 07:39 AM Thread Starter
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Re: Long or short Throwout bearing?

Quote:
Originally Posted by R66 View Post
No, it doesn't change the length of travel (stroke), only the relationship and angle between the fork and the pressure plate are changed. Thus, the change from and long release bearing to a short release bearing can be made with adjustment of the fork pivot ball and the clutch linkage rod on the z-bar (bell crank) which actuate the fork - If there is adequate distance on the input bearing housing as well as distance to the pressure plate fingers, etc.

On the Camaro and other cars, the stoke of the clutch fork is limited by the fire wall. Also using the wrong release bearing without changing the geometry (pivot ball location) of the linkage can lead to binding on the input shaft and incorrect contact with the pressure plate, failure to release the clutch, and other problems.

If your car has stock flywheel bell housing, and transmission, the stock setup kits sold by many suppliers will generally provide what you need.
Unfortunately, there is nothing "stock" about this car. I'm trying to set it up properly for what it is, a 1978 454 with a M20 4sp in a '68 Camaro. I'm working on fixing previous owners "bubba'd" stuff. The firewall was in-dented and had a gash in it where the top of the clutch fork would travel. I have repaired that area and want to avoid contact with the firewall but, now that i've placed the engine and trans back in the car to check for overall clearance issues with the headers, oil pan, crank pulleys etc.. i'm not liking the limited amount of room i'm seeing at the firewall/clutch fork area.
I have replaced the engine frame stands with the proper big block stands and am using the prothane short wide engine mounts. New trans crossmember has the trans and engine sitting in the proper geometry aka: level and not leaning back, tail low like it was.

'68 Camaro 454, 4sp
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post #10 of 15 (permalink) Old Feb 20th, 19, 07:43 AM Thread Starter
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Re: Long or short Throwout bearing?

Quote:
Originally Posted by dyno jonn View Post
Buy a kit. The right TO bearing should be in there.
I'll be purchasing a kit from Craig Wright at The Wright Connection. He has helped me with shifter issues as well as other things and i'm kind of loyal to those who help when I need it.

'68 Camaro 454, 4sp
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post #11 of 15 (permalink) Old Feb 20th, 19, 08:16 AM
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Re: Long or short Throwout bearing?

V8 = short length
L6 = long length.

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post #12 of 15 (permalink) Old Feb 21st, 19, 05:53 AM
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Re: Long or short Throwout bearing?

Look at the clutch fork and the pivot ball assemblies to assure they are correct for your Gen 1. The forks are different than most other Chevy models. Also the clutch bell crank seems to be unique to the Camaro. I put in a GM NOS replacement fork (stronger) and had to remove it as it contacted the firewall. Repaired and installed the original and all is fine.

I am not familiar with BB installations. I think I understand they are offset to the passenger's side for some reason. I don't know the reason other than maybe clearance to some other components.

Good luck
Ron

If the PO butchered the firewall to allow the fork to move, he may have used the wrong components and adjustments to cause the problem. Thus the firewall modification.

Installing a long (or adjustable) release bearing in lieu of the correct short bearing might help obtain a workable design or cause more configuration problems. You should find the cause of the problem and correct it without potentially creating more problems with your own redneck repairs. I see no reason the 454 installation is not the same as any other BB in a Gen 1.

Last edited by R66; Feb 21st, 19 at 06:05 AM.
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post #13 of 15 (permalink) Old Feb 21st, 19, 06:22 AM Thread Starter
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Re: Long or short Throwout bearing?

Quote:
Originally Posted by R66 View Post
Look at the clutch fork and the pivot ball assemblies to assure they are correct for your Gen 1. The forks are different than most other Chevy models. Also the clutch bell crank seems to be unique to the Camaro. I put in a GM NOS replacement fork (stronger) and had to remove it as it contacted the firewall. Repaired and installed the original and all is fine.

If the PO butchered the firewall to allow the fork to move, he may have used the wrong components and adjustments to cause the problem. Thus the firewall modification.

Installing a long (or adjustable) release bearing in lieu of the correct short bearing might help obtain a workable design or cause more configuration problems. You should find the cause of the problem and correct it without potentially creating more problems with your own redneck repairs. I see no reason the 454 installation is not the same as any other BB in a Gen 1.
Anyone have anything I can look at for reference? I have no way of knowing what's right and what's not without seeing what's right.

'68 Camaro 454, 4sp
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post #14 of 15 (permalink) Old Feb 21st, 19, 08:23 AM
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Re: Long or short Throwout bearing?

Download an AIM from Camaros.org and check. All bellhousings and forks are the same.
As mentioned earlier, the P/Plate diaphragm are different heights due to application.
L6's are flat fingers; V8's are curved fingers.

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post #15 of 15 (permalink) Old Feb 21st, 19, 11:13 AM Thread Starter
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Re: Long or short Throwout bearing?

Quote:
Originally Posted by Everett#2390 View Post
Download an AIM from Camaros.org and check. All bellhousings and forks are the same.
As mentioned earlier, the P/Plate diaphragm are different heights due to application.
L6's are flat fingers; V8's are curved fingers.
I'm finding info that they're not all the same https://www.4speedconversions.com/3892632.html

also found this;

The 67-72 Camaro clutch fork, GM # 3892632, measures about 10 1/4" in overall length. The measurement from "dimple to dimple" is about 6 1/2". The spring hole is at the end near the "dimple".
I have two used and one NOS 3892632 forks in my collection.

The 73 Camaro clutch fork, GM # 330809, and the 74-81 Camaro clutch fork, GM # 340278, measure about 11 1/8" in overall length. The measurement from "dimple to dimple" is about 7 1/4". The GM replacement is # 14066235.
I have a 330809 fork in my collection. It's basically the same as the 3892632 except for length and the spring hole is located on the top 1 1/4" from the "dimple". The 340278 forks appears to have "ears" on the wider end.

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