Clutch not disengaging

[mblommel]

Thank you!

Many thanks for your help Bernice.

I found some interesting information about the flywheel. A call to Tilton's tech support pretty much confirmed it's a Tilton unit. Part number is 50-101-120 not 80-101-120 as I had previously misread from the stamping on it.

The very helpful gentleman there was able to tell me it should with a 66-001HORA pressure plate and a 64185-2-F-15 friction disk. However he also told me the step from the friction disk surface to the flywheel is supposed to be .100 inch. It measures .058 inch now, so it's quite worn.

They gave me the contact info for AASCO Motorsports in Anaheim who could replace the friction surface and set me up with a working PP and Disk for it.

This all seems pretty great on the surface, but I'm not sure if all this information is 100% good. First the friction disk they specified has 15 splines . I'm pretty sure the Fiat input shaft is 17 spline. Second, I'm going to be in for probably $750 to $1000 for all the Tilton parts and service of the friction surface. Third, the gentleman at Tilton said the HORA PP is pretty stiff. Too stiff in fact for street use. He told me the O in HORA stands for orange spring, which is rather stout.

At this point maybe a lightened stock flywheel is a better bet. I suppose I could try my spacer idea too. I know this flywheel worked well for street duty with a standard PP and disk before.

 

[Rupunzell]

More than one way to deal with this HP flywheel.

Call Robin at Superior clutch and inquire with him as to what can be made for this specific flywheel/pressure plate/friction disc/release bearing combo. Suggest using Kevlar friction disc over organic, sintered metal or others for HP street use. It is smooth engagement, last very, very well, heat resistant, can be cleaned if oiled and generally pretty tough clutch material. Total cost for a custom clutch should be well under your estimate of $700.

http://www.superiorclutch.com

These are the Fiat drawings from the service manual that give dimensions of clearance between clutch disc fingers and free travel. Set up to measure this with the transaxle out of the car to verify that it will function properly when installed.

Here are some images of the 1300cc flywheel sent to Tilton years ago as a model for this flywheel. Weight is 8.5 pounds.

Bernice

Many thanks for your help Bernice.

I found some interesting information about the flywheel. A call to Tilton's tech support pretty much confirmed it's a Tilton unit. Part number is 50-101-120 not 80-101-120 as I had previously misread from the stamping on it.

The very helpful gentleman there was able to tell me it should with a 66-001HORA pressure plate and a 64185-2-F-15 friction disk. However he also told me the step from the friction disk surface to the flywheel is supposed to be .100 inch. It measures .058 inch now, so it's quite worn.

They gave me the contact info for AASCO Motorsports in Anaheim who could replace the friction surface and set me up with a working PP and Disk for it.

This all seems pretty great on the surface, but I'm not sure if all this information is 100% good. First the friction disk they specified has 15 splines . I'm pretty sure the Fiat input shaft is 17 spline. Second, I'm going to be in for probably $750 to $1000 for all the Tilton parts and service of the friction surface. Third, the gentleman at Tilton said the HORA PP is pretty stiff. Too stiff in fact for street use. He told me the O in HORA stands for orange spring, which is rather stout.

At this point maybe a lightened stock flywheel is a better bet. I suppose I could try my spacer idea too. I know this flywheel worked well for street duty with a standard PP and disk before.

 

[JspeedKC]

Don't give up yet

Mike,
I think if you "artificially" wear the new clutch plate to reduce the thickness by the amount that the flywheel is thicker than stock, you will have this problem resolved on the cheap.

Best of luck,

Jeff

 

[mblommel]

spacers....

I can't really wear down the friction surface too much more or I'll be into the heads of the bolts holding said friction surface to the rest of the flywheel. However, it looks like I need to move the PP out by .038" so I've got some 1mm spacers (.039") on the way. We'll soon know if it works.

 

[Rupunzell]

Check/adjust the flywheel-pressure plate-spacer balance. Adding these spacers can significantly alter the dynamic balance of the flywheel-clutch pressure plate with these spacers.

Only takes a few grams to make it all go very wrong.


Bernice

I can't really wear down the friction surface too much more or I'll be into the heads of the bolts holding said friction surface to the rest of the flywheel. However, it looks like I need to move the PP out by .038" so I've got some 1mm spacers (.039") on the way. We'll soon know if it works.

 

[mblommel]

Tolerance?

Thanks for the information. The spacers are 6mm inner dia, 12mm outer dia., 1mm thick +/- .05mm. Material is steel. My solid model calculation (solidworks) says they will have a mass of approx. 0.6531 grams each. I will need 6 spacers to move the PP out. So about 3.92 grams total weight to be added. Mind you they will be equally distributed around the perimeter of the flywheel. All that being said do you have a tolerance for flywheel imbalance? I would guess there is at least a rule of thumb out there.

My previous measurement of the total mass of the just the flywheel was 2961 grams. So the addition of the spacers is a change of 0.132% in mass. I have no idea what the mass of the PP or the friction disk is, but they are at least equal in weight to the flywheel. Seems like a pretty small change in overall mass of the rotating assembly, but I don't have a point of reference.

Thanks for the help.

 

[fiatfactory]

I had a quick look thru the thread and no one has yet mentioned there are in fact two heights of PP. 38 and 45mm from memory... could you just have low PP when you need a high?

SteveC

 

[davevoss]

That's Right

You're right Steve, I mentioned this early on in this thread, but its gone in the direction of custom shims, which is okay I suppose, but probably not what the original designer of that custom flywheel had in mind, I suspect the previously installed pressure plate was different than the one in hand now.

 

[Rupunzell]

Basically a washer.

Was under the belief and idea that a spacer would have been a flat sheet of metal that incorporated all three holes for each of the three seating pads of the clutch cover-pressure plate or a large ring.

There could be a potential problem using washers here. Lifting the pressure plate/cover by using two 1mm, 0.040" or so means the dowel pins will have that much un-supported air space. It is very possible all fasteners will fail under shear loading when the entire assembly is accelerated under load.

The six hex head cap screws are intended to generate tension clamp load with the dowel pins locating the pressure plate. There would be less bending force put on the dowel pins as they are essentially flat against two well supported surfaces. Once the air gap is introduced, a lever on the dowel pin has been introduced into this joint. This could result in shearing off the dowel pins and hex head cap screws.

As a rule, threaded fasteners are intended to generate tension clamp load, while pins are intended to locate parts. Exception being bolts specifically designed for shear loading. This is why SAE spec bolts have such long threads as they are intended for tension, not shear. This is not to say they cannot be used in shear loading, as they can be modified for this type of joint.. They are just far from the ideal fastener for shear loading.

IMO, take the time, effort and such to get the proper pressure plate and friction disc. Trying to make something that semi-works often ends in tears... specially in a highly stressed area like the flywheel-clutch system and remember what recently happened to Matt when the flywheel failed.



Bernice

Thanks for the information. The spacers are 6mm inner dia, 12mm outer dia., 1mm thick +/- .05mm. Material is steel. My solid model calculation (solidworks) says they will have a mass of approx. 0.6531 grams each. I will need 6 spacers to move the PP out. So about 3.92 grams total weight to be added. Mind you they will be equally distributed around the perimeter of the flywheel. All that being said do you have a tolerance for flywheel imbalance? I would guess there is at least a rule of thumb out there.

My previous measurement of the total mass of the just the flywheel was 2961 grams. So the addition of the spacers is a change of 0.132% in mass. I have no idea what the mass of the PP or the friction disk is, but they are at least equal in weight to the flywheel. Seems like a pretty small change in overall mass of the rotating assembly, but I don't have a point of reference.

Thanks for the help.

 

[mblommel]

Possible...

I had a quick look thru the thread and no one has yet mentioned there are in fact two heights of PP. 38 and 45mm from memory... could you just have low PP when you need a high?

SteveC

Anything is possible. After speaking with Tilton they all but identified it as one of their parts. According to them the original step from PP mounting surface to friction surface was .100 inch and requires a specialized heavy Tilton race PP and metallic race friction disc. Not what I'm looking for in a weekend fun car.

The car came to me using what looks like an ordinary Sachs PP and Valeo disc. These are production car parts, not specialized race only stuff. I posted pictures earlier in the thread. Currently the distance from the friction surface to PP mounting surface is .058 inch.

From what I've been able to ascertain there are at least 3 1300 PP's out there; Early 72-74 style, thick style and thin style. I have no idea if the distance from the mounting surface to friction surface varies between these.

 

[mblommel]

IMO, take the time, effort and such to get the proper pressure plate and friction disc. Trying to make something that semi-works often ends in tears... specially in a highly stressed area like the flywheel-clutch system and remember what recently happened to Matt when the flywheel failed.
Bernice

Understood. Unfortunately according to Tilton the parts they recommend to go with this flywheel are race only. The guy at Tilton even said the recommended PP was too heavy for this application. Additionally, to work with their parts the flywheel would need to be sent out for new friction surface insert. This car came to me running a stock PP and disc with this flywheel and it ran great.

 

[Matt Brannon - Midwest Bayless]

I had a quick look thru the thread and no one has yet mentioned there are in fact two heights of PP. 38 and 45mm from memory... could you just have low PP when you need a high?

Yes, there are two different heights of 1300cc pressure plates, but I don't believe there is any difference in the step height on the flywheels, and the clutch discs are the same, so they are fundamentally interchangeable.

The only gotcha I know of on these two variations of clutch/flywheels (i.e. 1974 flywheel/with tall cover vs 1975-78 flywheel with short cover) involves overall stack-height from the crank to top of the clutch cover. A 74 set up will interfere with the bell housing of a 75 or later trans.

At this point, just have the friction surface machined to a .020 step height from pressure plate mounting surface, and bolt everything back together.

I can't explain why the Sachs pressure plate shown in your original pix allowed for such an excessive step height, but clearly the Valeo PPs won't.

-M

 

[Rupunzell]

OK, if the steel friction surface is thick enough to remove about 1mm (~0.040") and if the flat head screw countersink will allow this much material removal to be done. Cutting much past the flat head screw's head can result in a screw failure. Check this.

There still needs to be a check done to assure proper height of the clutch pressure plate disc fingers meeting the spec provided in the Fiat service manual.

Once all has been altered, checked and double inspected, then it could be safe to install again.


Bernice

At this point, just have the friction surface machined to a .020 step height from pressure plate mounting surface, and bolt everything back together.

I can't explain why the Sachs pressure plate shown in your original pix allowed for such an excessive step height, but clearly the Valeo PPs won't.

-M

 

[mblommel]

No Dice.

OK, if the steel friction surface is thick enough to remove about 1mm (~0.040") and if the flat head screw countersink will allow this much material removal to be done. Cutting much past the flat head screw's head can result in a screw failure. Check this.

There still needs to be a check done to assure proper height of the clutch pressure plate disc fingers meeting the spec provided in the Fiat service manual.

Once all has been altered, checked and double inspected, then it could be safe to install again.


Bernice

Yeah, I was afraid of this. I checked tonight unfortunately and there is no way to remove 1mm of material from the friction surface without being into the screw heads holding it onto the flywheel. I guess either I'm using spacers or buying a flywheel. :sigh:

I spoke to Robin at Superior Clutch today. He told me that with the friction disc in place and the PP sitting on the flywheel but NOT bolted down distance from the PP mounting surfaces to the mounting surface of the flywheel should be .135 inch. I have not checked this yet, but I will. Unfortunately he is too busy with work he already has to take on reworking my clutch setup. Thank you Bernice for getting me in touch with him though.

I was looking at the aluminum flywheel that Apple Motors sells. http://www.applemotors.com/racept.htm#flywheel I was wondering if anyone had experience with this unit.

Thanks,

Mike

 

[Black-Tooth]

Geez Mike... $550 bucks!!! I'll sell you a steel one for $499!

If you do go with that aluminum flywheel, you should get the entire clutch assembly from him as well.

7 pounds may just be too LITTLE for a street car though... Usually a lightened 1300 flywheel comes in around 11.5 pounds from about 15 to start with... and that makes a world of difference.

For that kinda money though... for much LESS than that kinda money you could purchase a complete matching set of stock components and be off and running. I dunno what's wrong with the set you have... but hopefully you can return it all.

 

[mblommel]

Resolution to my Flywheel Problems

I wanted to resurrect this thread for the benefit of those who had been following it and/or trying to help me.

I now have the problem resolved with the help of Dave Dutton of Apple Motors in Denver. Dave is semi retired, but still manufactures CNC cut aluminum flywheels (out of his garge!) on demand.

I had intended to purchase a new flywheel form him, but after speaking to him on the phone he said "why don't you just send me your flywheel and I can figure out what it needs to make it work". Awesome.

It turns out I had the wrong style pressure plate the entire time. This particular flywheel requires the "tall" style pressure plate used on 128's and X's up to '74, and on Yugos. Dave sourced a Sachs MF180 unit that is identical to the one I had taken out and sent it all back to me. While the transaxle was out again I had a chance to re-seal the case where it was leaking (hondabond is awesome BTW).

I finished off the reassembly with some Redline MTL. Now I'm happy to say the clutch works perfectly and I was able to get the car moving under it's own power for the first time in 6 years!

Thanks to all for your input and assistance.

 

[Black-Tooth]

WOW! SIX years! Almost as bad as my seven!

Glad ya got it all worked out. Hopefully he lightened your old flywheel or you got one of his aluminum ones as well. Makes a world of difference for very few bucks, especially when the trans is out!

In any case, glad you and he are back on the road!

 

[mblommel]

it's been a while....

Haha, yeah it's taken forever.

I'm using my original 6lb aluminum flywheel with the new disc and pressure plate.

 

[Black-Tooth]

WHOA... that's almost a record! I believe Alex...

Kovatch's Autocross Dallara that went to OZ had a 5 pound flywheel. Hopefully yours is not too light for the street. That whole thing was a real problem.

I ordered a twin fan controller for my Vette and they sent the wrong one which burned up in 5 minutes but was unknown to me for a week! The replacement came with TWO 40 amp relays, but I could not find anywhere on THEIR drawings where they wanted me to wire them in. So I tried to figure it all out myself and I kept thinking they were redundant, or a band-aid of sorts, but I pressed on. Finally I called their Tech Support guys and it takes about 20 minutes and another call to get their specialist. After another 20 minutes we both came to the conclusion that those two relays were NOT supposed to be in the circuit and should not have been included in the factory sealed box, either!

HA! Sometimes too much of a good thing just trips ya up even more!

Congrats again!

 

[fiatfactory]

I had a quick look thru the thread and no one has yet mentioned there are in fact two heights of PP. 38 and 45mm from memory... could you just have low PP when you need a high?

SteveC

So my guess about the tall and low pressure plates was correct... :woot:

SteveC