I recieved my spec clutch and wanted to do some double checking of fitment. There seems to be an issue in my opinion. I started by taking some measurements


but we all know how much that sucks when you do all the math and still can't SEE anything. So I started with this instead






And this was the result


So I measured it and came up with 0.500" disc to input shaft spline engagement




I installed the disc right


And used the right tools


The disc splines reach 0.750", so 0.250" is missing. This is what it should be


This is what it is


Am I being too picky here, or does this seem wrong? They will probably tell me I don't make enough power to worry about it, but I would feel better with full spline engagement. I would think it would only help the clutch disc float better too when released. I would think the spline life has to be suffering here?

I don't think you are being picky. I think the disk should travel further up the spline. Why don't you PM Noah Brainard at clubgp. He has responded to my PMs and may have the answer. His build thread for the F40/3800 in a Grand Prix is at:

http://www.clubgp.com/newfo...ookieCheck=650892749

I am anxious to follow your thread as my build will come up this summer.

One thing that I am also curious about is the travel of the HTOB and if anything has to be limited at the master cylinder.
Jim

Judging by the thickness of the Firebird Flywheel, and the stubby nature of that spline on the disk, I'd say it's an engineering problem. It's going to drive just fine like that, but there is a risk of it stripping the splines right off the disk since it doesn't have much engagement area. Typically the input shaft spline is tougher then the disks. Obviously, you could safely double the engagement, and not even come close to touching the HTOB's sleeve. Contact Spec, they will probably be able to correct the issue for you and future customers. They need that type of feedback.

The hub spline on the clutch disk could probably be flipped and pointed towards the trans. That should give you want you need. Have any pictures of the flyhweel side of the clutch disk?

Call spec, they should be able to flip it around for you or use a different hub if you send it back.

Are you sure the HTOB is contacting pressure plate fingers at the right spot? Looks like its rubbing of the inside of the finger.

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Turbo 3800 E85 5spd spec5
11.53@126.7

[This message has been edited by Justinbart (edited 01-23-2011).]

You could always use a fly wheel spacer to make up some of the diffeance....I have used these before on fly wheels that where on there last leg but just needed that extra little bit.....

If he flipped it, it wouldn't contact at all. The splines are biased towards the transmission on this particular clutch kit.

The Firebird flywheel I have in my garage measures 1.120" thick.

In order to use a stock Fiero style pressure plate, the correct thickness for a flywheel on the G6 transmission needs to be 1.620" thick. They made up for the difference with a 1/2" taller pressure plate. This leaves the splines 1/2" short of where they should be. So you either need to use a REALLY thick flywheel, or get a clutch disk with an unusually long spline hub. It really appears to be an engineering error on their part.

Im willing to bet this guy has the same issue, but it could have easily been missed during the install. You can see his clutch plate about 3/4 way down the thread.
http://www.clubgp.com/newfo...e=1&tmode=1&smode=1#

The stock G6 Disk spline does have a bit of a bias towards the transmission already, WITH the 1.62" thick flywheel as well. It's about 1/4" more then a typical Fiero disk (picured to the left).

[This message has been edited by Fierobsessed (edited 01-23-2011).]

I am looking into the pressure plate to HTOB fitment as well. I have a sneaking suspicion that it is off too. This portion of the clutch opperation gets tricky to figure out when having a custom clutch made. One thing that I do not recall reading about was weather or not the factory prefilled HTOB was ever emptied prior to taking a collapsed measurement. From the factory, the HTOB is filled about half full and then capped. This limits the collapsed travel conciderably. This could be the very reason some have reported blowing out the HTOB instantly, while others say you need a different clutch master cylinder to prevent it. But if the master cylinder is doing a full volume push on a HTOB that is starting half way though its stroke, then yes, there will be blow outs. I need to take more measurements first, but I think when I call spec I might have double bad news for them?

On a plus side, this will hopefully allow me to upgrade to a 3+ disc instead of the 2+

Measurement numbers I got from my F40 for the HTOB.
From the engine mating surface to the bearing surface
Compressed height : 3.220"
Released height 2.665"

This was a tough measurement to get, the HTOB has a bit of play in it.

My HTOB never had any fluid in it as far as I can tell, it freely compresses to a mechanical stop. I pressed the disconnect check valve, and nothing changed. So If my measurements are consistent with yours, you can consider the measurements pretty accurate.

[This message has been edited by Fierobsessed (edited 01-23-2011).]

I may have missed it due to being tired and sleepy, but did you get your flywheel machined to 0.840" thick? Because with the Spec setup, you're not supposed to.

No, this is a brand new, never machined, stock flywheel for a 2000 Camaro 3.8L V6. Same as the Firebird 3.8L V6.

quote Originally posted by Fierobsessed: Measurement numbers I got from my F40 for the HTOB. From the engine mating surface to the bearing surface Compressed height : 3.220" Released height 2.665" This was a tough measurement to get, the HTOB has a bit of play in it. My HTOB never had any fluid in it as far as I can tell, it freely compresses to a mechanical stop. I pressed the disconnect check valve, and nothing changed. So If my measurements are consistent with yours, you can consider the measurements pretty accurate.

Thanks Fierobsessed, those measurements will be very usefull to me. I took apart my HTOB tonight, but have not made any measurements yet. But here are some pics for your viewing pleasure.


In these two, you can see part of the actual piston itself sitting deep down inside the housing, between the the two cylinders



The black piece on the back of the bearing is what the piston pushes against


This is where the bearing sits when the spring is pushing it out, durring normal opperation, it should never get this far out


This is fully collapsed, two with the spring removed and one with spring installed just to verify that the spring has no affect on collapsed travel




This is a shot of the check valve area with everything removed. Once removed and hydraulic lock opened, I was able to push the piston in a bit further (0.150"?) and a fair amount of brake fluid emptied out. I wish I would have recorded the extra collapsed travel amount, but I didn't think about it till it was too late. I was a little ticked at myself for this, because it was one of the main reasons I took it apart in the first place. Oh well, I can get by without that info, but it would have been nice to have.

I nearly made this same mistake in the process of having my clutch made, by taking into consideration the pressure plate release location and forgetting that the splines on the disc would need to be closer also (not that that is what you did)
.
The difference between the fiero disc and the G6 disc regarding the spline location is not "1/4, if you look at the picture above you'll see that the lower friction surface is also lower than that of the Fiero disc on that board meaning the G6 disc would have to be raised by the same amount, there's also the effect of the angle at which I took that picture. I don't recall whether I used the 4 or 5 speed disc in there but I believe I included all of the important measurements across the F40 and Getrag early in the swap thread.

With the disc hanging off the end of the input shaft like that it is possible the hub will wobble causing the springs to screw out of place like what has been observed with the Spec clutch on some V8 applications. I would fix it now. The guy that built my clutch reached under his counter and pulled out several clutch hubs that experienced the same kind of failure that we have seen with some of the Spec clutches and he stated that was the cause without me telling him anything more than that the springs were coming out. You've also over measured if you are including the tapered area of the splines on the input shaft as well as what's on the inside of the hub contact area.

I'm using the first design clutch master cylinder and it is now flush mounted. I imagine the safest thing to do is install it and leave the bleed screw open before depressing the clutch to avoid possible over extension. I was weary of this from the start so I did not bolt the mastercylinder flush against the firewall initially. After the new pressure plate and flywheel was installed I found I needed a little more pedal and everything worked fine after it was all tightened down.

[This message has been edited by Joseph Upson (edited 01-24-2011).]

So I have some measurements of the pressure plate to HTOB fittment. It's looking grim. I started by measuring the fully collapsed piston depth in the HTOB piston bore. I used the outside bore cylinder as the referance. I didn't show the caliper fully seated in the pic, just to show how the caliper slide reaches inside the bore to obtain this measurement. I came up with 0.725" fully collapsed




I then intentionally blew the piston out of the HTOB with gentle air pressure.



Then reinstalling the piston and setting it's depth to 'maximum allowable outward travel' This will be known as 0.000", or "Zero" as I am using the outer cylinder as a base for these measurements because the piston should never travel past this point in opperation.


Now reinstall HTOB to trans and trans to engine with the HTOB set to maximum allowable outward travel




And these are the results of the test to check how far the pressure plate is collapsing the HTOB at rest (simulating the piston travel of a released clutch pedal)




And a couple of comparison shots of the pistons actual start of travel point and it's capable start of travel point. Thats a big differance of 0.375"



I got a piston depth reading of 0.350". Meaning the HTOB piston is STARTING its outward travel 0.350" away from Zero. It could be starting at 0.650" safely. The total differance is 0.375" but there needs to be some cushion on each end, so I would say a 0.250" change needs to be made. The same distance as the clutch disc splines. But I will let Spec know the measurements and let them decide how this should be corrected and by how far.

Now I know I could space the flywheel out 0.250" and that will take care of both issues at once, but then I will create a problem with the starter to ring gear depth and end up chewing up ring gears and starters. I ordered this clutch set BECAUSE it was not supposed to require shimming. So I really don't want to shim anything to correct a design flaw in a $400 clutch set. I will be getting in touch with Spec soon and see what we can do about this. I'm not saying Spec is to blame, I think this may have been the result of them getting the wrong information somewhere along the line from the original order for this custom clutch set. I hope we can get this figured out for me and all you guys planning this swap soon, I know there's a few of you.

[This message has been edited by 1fatcat (edited 01-24-2011).]

Probably the easiest way for you to start correcting this problem is to measure your stack height total and by item.
flywheel flange to friction surface. G6 flywheel = 1.62"
flywheel flange to top of splined area of clutch disc hub. Didn't measure this but the input shaft splines start right at 1.47" below the bellhousing mounting surface.
flywheel flange to top of pressure plate release flanges with assembly bolted together sitting on a flat surface. For the G6 assembly 3.33" with .020" taken away if I understood what I meant correctly so probably 3.35" tall.

[This message has been edited by Joseph Upson (edited 01-24-2011).]

quote Originally posted by 1fatcat: Now I know I could space the flywheel out 0.250" and that will take care of both issues at once, but then I will create a problem with the starter to ring gear depth and end up chewing up ring gears and starters. I ordered this clutch set BECAUSE it was not supposed to require shimming. So I really don't want to shim anything to correct a design flaw in a $400 clutch set. I will be getting in touch with Spec soon and see what we can do about this. I'm not saying Spec is to blame, I think this may have been the result of them getting the wrong information somewhere along the line from the original order for this custom clutch set. I hope we can get this figured out for me and all you guys planning this swap soon, I know there's a few of you.

why would their be starter problems? the ring gear would be on the inner edge of the flywheel, the side facing the engine, it would be in the same location as ANY flywheel

anyways..

The difference is where the shim is placed. If you put it on the crankshaft, the starter will not engage, if you put it on the flywheel surface, you'll need a different pressure plate.

Jeremy at Spec is working on the issue as I type. He asked for a stacked measurement so I sent him the measurement (3.100") along with some pics. This was one of the pics...see anything wrong? LOL

Jeremy at spec found a solution. His solution is sound and I believe it would work just fine. The solution was a redesigned clutch disc that had a deeper spline reach into the trans. Basically, lengthen the spline portion of the disc.

The pressure plate depth was a little different. Instead of re designing the plate, a spacer on the throwout bearing was the solution.

[This message has been edited by 1fatcat (edited 02-16-2011).]

quote Originally posted by 1fatcat: Jeremy at spec came up with a solution. I, however, chose to go a different route. His solution is sound and I believe it would work just fine, however, it involved spacers. The solution was a redesigned clutch disc that had a deeper spline reach into the trans. Basically, lengthen the spline portion of the disc. The pressure plate depth was a little different. Instead of re designing the plate, a spacer on the throwout bearing was his answer. Now don't get me wrong, it should work fine, but if I need to add spacers I'm going to kill 2 birds with 1 stone. I will space the whole works towards the trans, flywheel and all. And in the process, I will also take care of any balance concernes with the flywheel. All of the clutch info from here on will be on my build thread here...https://www.fiero.nl/forum/Forum2/HTML/113506.html.

Just an FYI, the HTOB base houses the input shaft seal on its back side. The input shaft starts to taper quickly once it passes the seal, so you are greatly limited on the thickness of the spacer to under 1/8" so the seal will still work. You could get really creative and move the seal to the spacer and then you could go further.

I think you misunderstood what I'm going to do. I'm not moving the HTOB toward the engine, I'm moving the flywheel, clutch disc and pressure plate all toward the tranny.

quote Originally posted by 1fatcat: I think you misunderstood what I'm going to do. I'm not moving the HTOB toward the engine, I'm moving the flywheel, clutch disc and pressure plate all toward the tranny.

i thought you said that creates an issue with chewing up ring gears??

why not just increase the height of the flyheel to match the 1.62" height of the g6 flywheel?

Now I am a liittle confused. I thought that the PP was extra tall so that it would release properly. However, if I read Jeremy's response, the PP is too short without a spacer.

I thought the only problem you had was the splines on the disk did not engage far enough onto the transmission input shaft. If you space everything toward the transmission, that also spaces the PP fingers closer to the HTOB. Does that mean you have to go with a different (less tall) PP or was Jeremy correct and the PP is not tall enough?
Jim

[This message has been edited by bowrapennocks (edited 02-02-2011).]

Moving the flywheel out will change the ring gear location, so I will not be using that ring gear. I will be using a stock L67 flexplate for the ring gear and as a spacer. I will also be using it to retain the stock balance of the engine. The back side of the flywheel, and the drill holes in the front, will be machined to a neutral balance. The stock flexplate will now keep things balanced and act as a spacer to push everything toward the trans.

The pressure plate needs to be moved toward the trans too, in order to further collapse the HTOB piston. Right now, the HTOB needs to travel to the edge of blowout because it's starting it's outward travel over half way through it's stroke.

Clearly, Spec got the wrong measurements and build this clutch around those incorrect measurements. They are not willing to redesign it now. Not for me or anyone else. They are willing to supply a spacer to correct the operation of their clutch, but if a spacer is their answer, I can do that myself.

To me, their spacer was a slap in the face. It was spec admitting their was a problem and solving it with an extra moving part. I told him that I could add space myself, what I can't do is manufacture a clutch disc or pressure plate. If they want to continue to built it wrong, thats up to them. I will not do buisness with them again.

[This message has been edited by 1fatcat (edited 02-03-2011).]

For your interest, please see pictures of a Spec aluminum spacer (for SBC 1.4" thick) and the pp that came with it. It bolts to the friction surface of the flywheel with longer PP bolts. The spacer has a removeable steel friction surface that is only 9" in diameter.

1fatcat What is the diameter of your Spec clutch disk?





Jim

That would be another way to do it. Add a 9" insert and stack washers under the pressure plate bolt holes. This would move the disc and pressure plate towards the tranny by X amount. Or if you could get a larger diameter insert, you could use it without washers under the pressure plate as the insert would be large enough to space the disc and pressure plate all at once.

There are multiple ways to fix the problem, what really ticks me off about the whole thing is that this custom built clutch was not supposed to have any problems.

I could have used a Camaro pressure plate and a G6 or Ranger disc, and then shim things out accordingly. I bought the spec set because it was not SUPPOSED to need shims. I originally was going to use off the shelf clutch parts and shim it, but then was told the spec set was a plug & play deal. So I gave spec $400 for a disc and pressure plate that I now need to shim anyways

I could have gotten a used Ranger disc for next to nothing and have it relined with whatever friction matterial I wanted. Same deal with the pressure plate. I could have bought a used one and have it rebuilt with whatever clamp force I wanted. And I'm pretty sure I could have done it all for way less than $400.

This whole thing leaves me extreamly disappointed in Spec.

What problems has the guy with it installed in his GP had with it so far?

quote Originally posted by 1fatcat: I could have gotten a used Ranger disc for next to nothing and have it relined with whatever friction matterial I wanted. Same deal with the pressure plate. I could have bought a used one and have it rebuilt with whatever clamp force I wanted. And I'm pretty sure I could have done it all for way less than $400. This whole thing leaves me extreamly disappointed in Spec.

Not to suggest anything towards Spec, but yes you sure could have. I certainly did. This is one situation where I feel strongly custom parts from up the street for equal to or less, than across the state is a much wiser approach. The hometown clutch shop does pretty much custom work by trade as they fix whatever comes in the shop as opposed to having a production line that might be interrupted for a one off job. Production corporations tend to have strictor guidelines governing whether or not they can allocate man and machine hours toward low to no profit custom applications. My options were laid out in front of me on the counter and the order filled the same day.

I have never talked with him to know if he has experienced any problems. I do know he is running a stock n/a 3800, so a lot less power than my mildly modded s/c 3800.

quote Originally posted by 1fatcat: I have never talked with him to know if he has experienced any problems. I do know he is running a stock n/a 3800, so a lot less power than my mildly modded s/c 3800.

Less power but much heavier car......

But I agree with you that I would want everything just right....

Just when you think spec was getting better at customer service. I try to stick up for them but its hard to in these situations. They should not sell a product that doesn't deliver. Have you tried to get a refund?

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Turbo 3800 E85 5spd spec5
11.53@126.7

I did not try for a refund. I did ask about an upgrade to a higher stage disc, but Jeremy told me that it would not work due to a different stack height. The HTOB travel was a concern to me and I think I made that clear to him. He kept dismissing the issue by saying they have not had any complaints (I have to wonder just how many L67/F40's are out there). I have read it here on PFF about blowouts and the measurements seem to confirm why.

[This message has been edited by 1fatcat (edited 02-16-2011).]

Different clutch disks have different thicknesses. My first stage 5 that I installed, (that somewhat worked) the pressure plate was setup for the wrong thickness. The stage 5 disk is thicker so I didn't have the right clamping force I was supposed to, it wouldn't even hold 9lbs of boost. After over 1,000 miles it started to work properly. My transmission then broke because the pressure plate was rubbing, without me knowing, the case cracked on the weak spot and caused a lot of play in the trans. The one I currently have is set up right and it held full boost right after the break in period.

So don't just give up on them. Make them get it right. I know its frustrating but we are talking about custom stuff.

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Turbo 3800 E85 5spd spec5
11.53@126.7

Spec has a solution to the problem. They sent me a modified clutch disc with a spline/center hub that reaches deeper into the trans. They also sent a machined billet spacer hat that fits very nice over the factory HTOB.

I don't know if Spec will redesighn this clutch set or just keep building it the same with the corrected parts? It should work just fine either way.

How is this latest solution from Spec working for you?

I do not have this car done yet, but the new clutch parts should work fine. The measurements are now very saticfactory in my opinion. The disc splines enguage the shaft with a lot more contact, and the HTOB piston sits deeper in the bore which should prevent the piston from blowing out. I do not know if spec redesighned this clutch package, or if they are just selling it with the modified components, or just selling the same thing they sent me the first time? If you want to order one, just make sure to ask them about this and they should be able to get you the right parts. I know it would be a lot more comforting to hear me say that the car is done and the clutch is working fine, but I just can't say that for sure yet. Sorry.

quote Originally posted by 1fatcat: I do not know if spec redesighned this clutch package, or if they are just selling it with the modified components, or just selling the same thing they sent me the first time?

I figured I'd post this so others don't get confused like I did.



This is what they sent me when I ordered the SC883-4 (Stage 3 3800 -> F40). From what I gathered from my emails with Jeremy, you have to tell them you're using a 3800 flywheel in order to get the HTOB spacer (the thing on top of the pressure plate, in my picture).

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My project: 3800 Series III Supercharged + F40 6-speed into an 87 GT. Wish me luck!

That looks like what I got. The spacer, and I see the center hub of the disc has a longer reach like my corrected disc did. Thanks for adding a picture of the corrected parts. I forgot to do so. Sorry.

**Delete**

[This message has been edited by Gohabs93 (edited 08-26-2011).]

It's been a while, so let me ask again: Has Spec's "solution" worked for anyone?

- What final setup did you end up with?

Thanks!