Help identifying clutch system (1 Viewer)

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If you'd like a little more thread length on the clutch adjustment rod you can always run a die to thread it a little longer. Make sure to use good cutting fluid while working on it.
 
I usually just shorten the rod and clean up the end if is to long.
 
I’ve been running a 3/4” ‘73 style master and a 3/4” ‘73 slave also. Technically July’74… but Aug’74 changed to a different slave and some listings don’t differentiate. ‘73 gets the correct parts.

In ‘96 I searched for the, “…standard 11” low diaphragm type clutch… “ that the instructions that came with my DOWNEY conversion kit specified. The older parts guy set me up with an 11” LUK clutch. I now gather I got lucky… the 3/4” master, 3/4” slave, and braided stainless steel line have been delivering more than enough travel for 26 years and 50k+ miles. Always lots of free play… always released fully. With one exception… when the 12 year old master wouldn’t maintain pressure, Even then, it still disengaged fully when first depressed and for about 5 seconds after.
 
If you'd like a little more thread length on the clutch adjustment rod you can always run a die to thread it a little longer. Make sure to use good cutting fluid while working on it.
It’s been welded right at the end of the threads, but I might be able to file it down and rethread it.

The rod is disconnected from the slave, so the slave piston just pushes it, is that how the OEM rod and slave are? Not one piece, I have a spring there attached to the fork to push it back.
 
I’ve been running a 3/4” ‘73 style master and a 3/4” ‘73 slave also. Technically July’74… but Aug’74 changed to a different slave and some listings don’t differentiate. ‘73 gets the correct parts.

In ‘96 I searched for the, “…standard 11” low diaphragm type clutch… “ that the instructions that came with my DOWNEY conversion kit specified. The older parts guy set me up with an 11” LUK clutch. I now gather I got lucky… the 3/4” master, 3/4” slave, and braided stainless steel line have been delivering more than enough travel for 26 years and 50k+ miles. Always lots of free play… always released fully. With one exception… when the 12 year old master wouldn’t maintain pressure, Even then, it still disengaged fully when first depressed and for about 5 seconds after.
Thanks. My hyraulics look pretty old and rusty so I am just thinking of later in the future (maybe sooner than I would want). Do the 73 master/slave just bolt up to a 65? How about say a later one like a 77?
 
It’s been welded right at the end of the threads, but I might be able to file it down and rethread it.

The rod is disconnected from the slave, so the slave piston just pushes it, is that how the OEM rod and slave are? Not one piece, I have a spring there attached to the fork to push it back.

If it's been welded then it would possibly be better to locate a solid one piece rod and then lengthen the threaded area.
 
I’ve been running a 3/4” ‘73 style master and a 3/4” ‘73 slave also. Technically July’74… but Aug’74 changed to a different slave and some listings don’t differentiate. ‘73 gets the correct parts.

In ‘96 I searched for the, “…standard 11” low diaphragm type clutch… “ that the instructions that came with my DOWNEY conversion kit specified. The older parts guy set me up with an 11” LUK clutch. I now gather I got lucky… the 3/4” master, 3/4” slave, and braided stainless steel line have been delivering more than enough travel for 26 years and 50k+ miles. Always lots of free play… always released fully. With one exception… when the 12 year old master wouldn’t maintain pressure, Even then, it still disengaged fully when first depressed and for about 5 seconds after.
Of course the slave cylinder started leaking shortly after. I took your advice and installed the 73 hydraulics with braided line, thanks for suggesting it. It was working very well with more room for adjustment than the original hydraulics. After a 40 min drive I was parking it in the garage and happened to pressed the clutch hard all the way to the floor, the piston out of the slave came out and got stuck, with fluids everywhere. It broke the seal in the process. I’m guessing either the floor adjustment was too high or the nut on the slave rod was too far in. The rod is adjusted quite well now, with the release bearing not touching the pp and still enough to engage the clutch so I’m hoping I can fix it with the pedal adjustment.
 
Of course the slave cylinder started leaking shortly after. I took your advice and installed the 73 hydraulics with braided line, thanks for suggesting it. It was working very well with more room for adjustment than the original hydraulics. After a 40 min drive I was parking it in the garage and happened to pressed the clutch hard all the way to the floor, the piston out of the slave came out and got stuck, with fluids everywhere. It broke the seal in the process. I’m guessing either the floor adjustment was too high or the nut on the slave rod was too far in. The rod is adjusted quite well now, with the release bearing not touching the pp and still enough to engage the clutch so I’m hoping I can fix it with the pedal adjustment.

It’s always recommended to replace slave and master at the same time. The slave will often rust beyond its range of motion… increased range then causes a problem with the rust.

Do you have a return spring on the fork at the clutch slave? (Probably do, but don’t want to not mention it)
 
It’s always recommended to replace slave and master at the same time. The slave will often rust beyond its range of motion… increased range then causes a problem with the rust.

Do you have a return spring on the fork at the clutch slave? (Probably do, but don’t want to not mention it)
I replaced the master and slave together, both from a 73 as you mentioned, with a new braided line. The master is Aisin, slave is some other brand, they were both bought from cityracer. Yes I have the return spring on the fork. Would not having it cause issues? I thought it was there so the release bearing wouldn’t touch pp when you lift your foot off the clutch pedal.

If the clutch is adjusted improperly, the piston in the slave can come out correct? For example if nothing is stopping the rod (e.g. the pressure plate), and you had too much pedal travel, the fluid would just push out the piston/rod. That’s the intuition I have right now of what the issue was.
 
Improper adjustment could cause the slave to come out. Since both are 3/4" the slave will move the same amount at the piston in the master. The Rod should push the slave cylinder all the way back in with the help of the return spring. The slave shouldn't be pushed apart with a 3/4" master... especially since others have run a 1" without issues.

That said, someone may have previously adjusted the clutch master or pedal travel which is now creating problems.
 
Improper adjustment could cause the slave to come out. Since both are 3/4" the slave will move the same amount at the piston in the master. The Rod should push the slave cylinder all the way back in with the help of the return spring. The slave shouldn't be pushed apart with a 3/4" master... especially since others have run a 1" without issues.

That said, someone may have previously adjusted the clutch master or pedal travel which is now creating problems.
Thanks, that’s helpful about the amount of expected travel. It makes sense.

I’m thinking that someone is me, since I just put the new master cylinder, and set the adjuster to approximately what it was before. I didn’t measure the height of the pedal again 🤦‍♂️ . Lesson learnt.
 
The low profile pressure plate works I’ve used it for years.
I use just the stock 1978 master and 1978 slave. Adjust out the slack at the master also and adjust the slave so it just doesn’t drag on the fingers of the pressure plate and make sure your slave cylinder mount doesn’t flex some flex and will sacrifice the travel required. and for some old school trivia info AA used to sell this same low profile pressure plate CA5473 as there economy clutch instead of the more expensive Centerforce unit

Sometime the slack up at the master is too much and your clutch pedal hits
The floor before it has used up all the travel at the master end of things check the pedal adjustment also up under the dash .

Also make sure you have a return spring on the slave and the clutch pedal inside under dash. There is a spot for a return spring on the salve and also the clutch pedal. Don’t want the pedal weight hanging down and riding or resting on the master either

PS I have never used the LUK clutch kit It looks different to the actual low profile remaufactured junk I use in Canada I use a remanded Fenco branded or boxed one

I would use a Sachs brand also before a LUK boxed clutch LUK has changed something in there pressure plate I haven’t figured out yet.
 
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Follow the instructions, beginning to end. I run a sbc, nv4500 & a sbc,sm420. Adjust pedal height. Pedal free play is when the slave initially moves, not resistance. Then adjust clutch fork. The slave piston needs to be fully seated in the cyldr and run a return spring. Put pressure on the slave rod and crack the bleeder to ensure it's seated. The t/o bearing should not be in contact with the pp.
If the slave piston is not initially fully seated to the back of the slave cylinder and go thru the adjustment process and you can force the piston out of the cylinder or force the throw out bearing/fork against an immovable object like the bellhousing or pp and blow the piston seal.
 
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I replaced the master and slave together, both from a 73 as you mentioned, with a new braided line. The master is Aisin, slave is some other brand, they were both bought from cityracer. Yes I have the return spring on the fork. Would not having it cause issues? I thought it was there so the release bearing wouldn’t touch pp when you lift your foot off the clutch pedal.

If the clutch is adjusted improperly, the piston in the slave can come out correct? For example if nothing is stopping the rod (e.g. the pressure plate), and you had too much pedal travel, the fluid would just push out the piston/rod. That’s the intuition I have right now of what the issue was.
The return spring keeps the t/o bearing off the pp and it also needs to be strong enuff to retract the slaves piston fully into the back of the slaves cylinder.
 
Thanks, that’s helpful about the amount of expected travel. It makes sense.

I’m thinking that someone is me, since I just put the new master cylinder, and set the adjuster to approximately what it was before. I didn’t measure the height of the pedal again 🤦‍♂️ . Lesson learnt.
You need to set the pedal height then adjust pedal freeplay so you get the maximum stroke out of the master. As I mentioned earlier, adjusting pedsl free play is when the slave starts to move. It's not when you feel resistance. You have to physically watch the slave while slight pressure is applied to the pedal.
 
If the slave piston is not initially fully seated to the back of the slave cylinder and go thru the adjustment process and you can force the piston out of the cylinder or force the throw out bearing/fork against an immovable object like the bellhousing or pp and blow the piston seal.
That makes sense, I am pretty sure I didn’t do this part, to make sure the slave rod was sitting all the way back. I guess I could set the initial rod length even before adding fluid and bleeding , so I’d know for sure the piston is in the back of slave.
 
If the slave piston is not initially fully seated to the back of the slave cylinder and go thru the adjustment process and you can force the piston out of the cylinder or force the throw out bearing/fork against an immovable object like the bellhousing or pp and blow the piston seal.
In the page of the manual it states the pedal height for two configs, with and without brake booster. I don’t think I’ve seen a clutch master with a booster, what year were these for? I’m assuming it’s not talking about the actual brake booster, don’t see how that would be related.
 
You can physically push the fork/adjustment rod back and crack open the bleeder to ensure the piston is seated. .
 
In the page of the manual it states the pedal height for two configs, with and without brake booster. I don’t think I’ve seen a clutch master with a booster, what year were these for? I’m assuming it’s not talking about the actual brake booster, don’t see how that would be related.
No it doesn't. Below is from the fsm.
20220711_211038.jpg
 
When I figured it all out in ‘96 I didn’t have a FSM, and I doubt I even looked at the Haynes manual (figured it would not apply to a Chevy clutch). 26 years later the same LUK clutch is working great. If it ain’t broke… don’t fix it.

One of these days I’ll check the pedal height… don’t remember changing it, but I don’t know it was right to begin with.

I did adjust the yoke to minimize play between the pedal and the clutch master. Not far enough to push the master cylinder just enough that it doesn’t move before it pushes on the master cylinder’s piston.
 

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