3V Clutch ToB Spacing

[Ken R]

Could someone please help me with my throwout bearing placement. I'll do my best to keep this concise but adequately detailed.

So I have a stock 3v with the original TR3650, after having my OEM clutch spectacularly explode at Road Atlanta I'm installing a new one. So I upped it to an exedy Mach 400 and Ford OEM slave cylinder.

Currently everything is installed but after some reading I opted to check the slave face to pressure plate finger distance and I am getting about 0.40625". That comes from bell housing face to slave face of 2.65" and a engine block to pressure plate fingers measurement of 3.063".

Where I'm slightly unsure of my measurement is my exedy pressure plate fingers are slightly recessed

versus the OEM pressure plate

So I made the measurement in two steps, with a straight edge across the pressure plate I measured from fingers to straight edge (0.1875") and from the back of the engine with the spacer plate on to straight edge (3.25") so pressure plate fingers to back of the engine is 3.25-0.1875 = 3.063"

So part of my confusion I think comes from how the slave works, once installed is it always compressed like below

And then when the pedal is pressed the slave extends and pushes on the pressure plate diaphragm spring fingers? If that's the case then I would need about a 0.5" spacer which is fine but then I also wonder why exedy offers the kit with an OEM slave since it seems to be due to their pressure plate. When I compress it I get just over 1" of travel which is where the 0.5" spacer comes in (This is the old slave)

Am I overthinking this or am I missing something? thanks in advance

 

[blacksheep-1]

Could someone please help me with my throwout bearing placement. I'll do my best to keep this concise but adequately detailed.

So I have a stock 3v with the original TR3650, after having my OEM clutch spectacularly explode at Road Atlanta I'm installing a new one. So I upped it to an exedy Mach 400 and Ford OEM slave cylinder.

Currently everything is installed but after some reading I opted to check the slave face to pressure plate finger distance and I am getting about 0.40625". That comes from bell housing face to slave face of 2.65" and a engine block to pressure plate fingers measurement of 3.063".

Where I'm slightly unsure of my measurement is my exedy pressure plate fingers are slightly recessed
View attachment 94713
versus the OEM pressure plate
View attachment 94714
So I made the measurement in two steps, with a straight edge across the pressure plate I measured from fingers to straight edge (0.1875") and from the back of the engine with the spacer plate on to straight edge (3.25") so pressure plate fingers to back of the engine is 3.25-0.1875 = 3.063"

So part of my confusion I think comes from how the slave works, once installed is it always compressed like below
View attachment 94715
And then when the pedal is pressed the slave extends and pushes on the pressure plate diaphragm spring fingers? If that's the case then I would need about a 0.5" spacer which is fine but then I also wonder why exedy offers the kit with an OEM slave since it seems to be due to their pressure plate. When I compress it I get just over 1" of travel which is where the 0.5" spacer comes in (This is the old slave)

Am I overthinking this or am I missing something? thanks in advance

Boy is this a can of worms, I replaced my stock clutch with a single disc Spec. The pedal was always low, I would occaisionally miss a shift. After a few years, along with wear, I had enough and went to an Evedy dual disc which has worked out well. This was in my Gt500 and it has an integral bellowing so there is no way to get a read on it. The guys at Spec told me no spacer.. and it was not right. Every said no spacer and it has been perfect. You can't even get a read between clutches because they have to be installed, so this was a big PITA.
The only way I had to do this was to swap it out and drive it. It worked out fine, the biggest problem I had was getting the clutch properly bled. It took a few days before it finally gave up the air bubbles after sitting overnight.
I know this is of little help, but I would call Exedy and go with their recomendation.

 

[Ken R]

Boy is this a can of worms, I replaced my stock clutch with a single disc Spec. The pedal was always low, I would occaisionally miss a shift. After a few years, along with wear, I had enough and went to an Evedy dual disc which has worked out well. This was in my Gt500 and it has an integral bellowing so there is no way to get a read on it. The guys at Spec told me no spacer.. and it was not right. Every said no spacer and it has been perfect. You can't even get a read between clutches because they have to be installed, so this was a big PITA.
The only way I had to do this was to swap it out and drive it. It worked out fine, the biggest problem I had was getting the clutch properly bled. It took a few days before it finally gave up the air bubbles after sitting overnight.
I know this is of little help, but I would call Exedy and go with their recomendation.

Thanks blacksheep, yeah I really got into the weeds on this ha

The main thing I am trying to avoid is the over extension of the ToB and having to replace it sooner than expected, I suspect that the design intent was to create less clutch pedal travel to make for faster shifting which could be assumed based on the spring design. In short I guess as long as the sping/ToB are designed to have that limited movement then I am good, yeah I was planning on calling Exedy actually yesterday but got busy.

 

[blacksheep-1]

Thanks blacksheep, yeah I really got into the weeds on this ha

The main thing I am trying to avoid is the over extension of the ToB and having to replace it sooner than expected, I suspect that the design intent was to create less clutch pedal travel to make for faster shifting which could be assumed based on the spring design. In short I guess as long as the sping/ToB are designed to have that limited movement then I am good, yeah I was planning on calling Exedy actually yesterday but got busy.

Someplace around here I have a set of shims, if you need any let me know, they are expensive if you have to buy them

 

[Ken R]

Someplace around here I have a set of shims, if you need any let me know, they are expensive if you have to buy them

Ah I ordered a set Monday afternoon that should be here today, but I appreciate the offer

 

[Mike_FL]

Maybe worth sending Kohr Motorsport an email.
They know exedy clutches

 

[Ken R]

Maybe worth sending Kohr Motorsport an email.
They know exedy clutches

That was a good idea Mike and I did reach out to Dean to get some insight. He suggested a different way to make the measurements, the downside with this is you need to make one measurement before you take the original clutch off which I had already done. But he said you can measure from the crank to the fingers on the pressure plate with the existing setup and then with the new setup after everything is torqued down and the difference between the two is your spacer. While I have already removed my clutch I do have a spare flywheel so I might try and do it on my work bench and see what I get. He did mention that it's been awhile since he has done this setup but he doesn't think a spacer is needed and for reference when they install Exedy HyperSingle they use a 6mm spacer I didn't ask if that was including the flywheel which I am not sure if it is thinner than OEM.

I decided to give Exedy a call as well and after rambling my numbers off to the guy on the phone had a little laugh and you could tell he was accustomed to this question, he stated that it sounds like I am about in the window that I need to be and that their clutches are designed to have about 0.5" of movement. So obviously over extending the ToB is a concern the other would be not having enough travel to fully disengage the friction disc. Exedy mentioned to not go over the 0.5" which I didn't fully understand to be honest but I have a 0.059" spacer that I think I am going to install bringing my measurement to 0.465", the middle spacer in the kit was 0.119" which takes me to 0.525"
After taking a look at the new pressure plate and thinking through the physics on it that kind of makes sense. Due to the pressure plate springs simply being levers the Exedy one just has shorter lever arms and the OEM ones are more linear while the Exedy ones have a raised center which I am guessing will make pedal travel less and might have a heavier pedal in general along with a more on/off feel but at this point I think I am going to go small spacer and put it back together and hope for the best.

 

[blacksheep-1]

I work for Dean and brought my gt500 over there to do the clutch, and he talked me into a dual disc clutch, and I've been very happy with it. The Tremec in the gt500 has an integral bellhousing so trying to come up with a gap was problematic. Also removing the old clutch ( spec) wasn't any help because it was aftermarket. Whatever you do, take notes and put it as a sticky so others don't have to go through the same misery.

 

[Ken R]

I work for Dean and brought my gt500 over there to do the clutch, and he talked me into a dual disc clutch, and I've been very happy with it. The Tremec in the gt500 has an integral bellhousing so trying to come up with a gap was problematic. Also removing the old clutch ( spec) wasn't any help because it was aftermarket. Whatever you do, take notes and put it as a sticky so others don't have to go through the same misery.

Ah very cool, I have talked to him a handful of times and he's always helpful.
Yeah I have some crude drawings and calculations that I will clean up and add along with some more pictures, if it helps anyone it'll be a success to me ha