I have a recommendation for those of you with an F40 swap with the HTOB. This will probably also work for the F23 and HTOB Getrag also. The Fiero Clutch master cylinder/pedal setup has too much volume for operating the HTOB and will overextend it. When I did my Archie LS/F40 swap he recommend that washers be placed in between the CMC and the firewall. Although this was an adequate solution, it is definitely not elegant. So I googled Fiero CMC and found some info on a Miata forum. Miatas have a similar but smaller diameter(5/8") CMC so they use the larger Fiero (11/16") CMC to gain more fluid capacity for certain situations when their setups won't completely disengage. So I thought, why not the other way. I went to Autozone and bought a 1995 Miata Clutch master cylinder for $19.95. I would fit by slightly elongating the holes. Miata unit does not come with a push rod. I could have just ground down the end of the stock Fiero one, but instead bought a Rodney Dickman adjustable one. Be careful you get the correct one, as I got confused about Early vs Late and had to exchange for the correct one. There are Early and Late CMCs, and early and Late pedal assemblies, but the year changes for the two do not coincide. I ground down the end to fit in the Miata Piston and it bolted up and it worked. I then had to adapt the 10mm Japanese fitting on the MC to the 12mm bubble flare of the Fiero tube. I used a 12mm bubble flare connector, a 6" Tube with 3/8 on one end and 12mm bubble on the other, and finally a 10mm Japanese male to 3/8 female adapter. Perhaps it could have been done cleaner, but that was the easiest way for me.
Still, doesn't look too bad, and gets rid of the spacers. I fits well even with my S10 booster.
Benefits - No danger of overextending the HTOB, lower pedal pressure, smother engagement, cheaper and easier to find parts, no bleeding problems, and adjustable pedal height. It is now level with brake pedal.
Hopes this helps someone. Let me know if this works for someone else.
People are overextending the HTOB because their flywheel/clutch/pressure plate setup places the HTOB in the wrong position within its range of motion. Once you have that set right, you can use a bone stock clutch master with either the F40 or the F23 w/o any issues.
Agreed when you actually measure every thing out the F23 and F40 bell housing is 1/4 inch deeper and most clutch flywheel set ups do not make up for this allowing the HTOB to over extend and leak. Done many F23 and five F40 swaps now and all used an HTOB spacer and all are still running fine.
------------------
DARN Cars now open with Over 30 years wiring experience between cars and trade as an avionics technician in both Canadian Air Force and civilian aviation. Over 25 years experience building and modifying cars. Over 10 years of full Fiero engine swaps and harnesses building and still going.
People are overextending the HTOB because their flywheel/clutch/pressure plate setup places the HTOB in the wrong position within its range of motion. Once you have that set right, you can use a bone stock clutch master with either the F40 or the F23 w/o any issues.
agreed, but this also will reduce pedal effort, which may or may not be a good thing depending on how you look at it.
Not sure if you all have the same issue I have but I have never been truly happy with my F40 swap. I did it myself so I could have done something wrong, but in my setup I have two washers behind the bolts to push the MC out from the firewall per Archie direction. I have bled, bled and re-bled my system but in my setup the clutch pedal is at rest in the normal posit, but when I go to push it down to disengage the clutch I can push it down halfway before I get any pressure, then I have to push it to the floor, and i'm talking THE FLOOR before I get any disengagement. I assumed I still have air in the system, but I have bled it so many times I just can't believe its still air. It works fine but it is just not as smooth as I'd like. I have even had a few times where the pedal is on the floor and I can't get it in gear, I have to actually have to pump it once to get the pressure up. So should I just continue to bleed it, or would the Miata MC be a better idea?
I'm having a similar issue with my F23 swap but not nearly as severe, but i think it's just air still trapped. have you tried removing the washers to see is that makes a difference?
[This message has been edited by ericjon262 (edited 11-30-2014).]
Its still air in the system. Since they only have one inlet/outlet to the HTOB, it can take some time to bleed it properly... especially if it is a new replacement one that is empty.
What happens is when cold you have to compress the air bubble, so you lose travel. When it heats up, the bubble expands making it larger and you lose even more travel.
Going to a smaller clutch master will make this issue worse.
Not sure if you all have the same issue I have but I have never been truly happy with my F40 swap. I did it myself so I could have done something wrong, but in my setup I have two washers behind the bolts to push the MC out from the firewall per Archie direction. I have bled, bled and re-bled my system but in my setup the clutch pedal is at rest in the normal posit, but when I go to push it down to disengage the clutch I can push it down halfway before I get any pressure, then I have to push it to the floor, and i'm talking THE FLOOR before I get any disengagement. I assumed I still have air in the system, but I have bled it so many times I just can't believe its still air. It works fine but it is just not as smooth as I'd like. I have even had a few times where the pedal is on the floor and I can't get it in gear, I have to actually have to pump it once to get the pressure up. So should I just continue to bleed it, or would the Miata MC be a better idea?
Thanks
Rob
Did you use a spacer? Is perhaps the problem the throwout bearing retracting on it's own and the initial movement being the tob moving to the clutch disk?
[This message has been edited by phonedawgz (edited 11-30-2014).]
I disagree with those of you who claim that HTOB overextension is caused only by lack of a spacer. The G6 that the F40 came from has a different pedal setup and a shorter stroke CMC because of the more efficient setup. The lever action slave on a stock Fiero requires more fluid volume to work because of the greater travel required due to mechanical losses. The HTOB was a definite improvement as far as mechanical/hydraulic efficiency and needs less fluid volume from the CMC. This setup more closely matches the G6 volume. I am not trying to tell anyone that they are wrong for using a spacer. I am also not saying that this takes the place of a spacer. In fact, I am sure in hindsight that my car would be improved by having one. I am making a SUGGESTION that this improves several things. I was not having a real problem with the stock setup, I just wasn't happy with it. Clutch engaged/disengaged just fine. But, pedal effort was kind of high for a HTOB setup, and the clutch was more like a trigger than a clutch. I had to only push it about 1/3 of the way down, even with the MC spacers. Also, for some reason that I have never really heard a root cause for, Fiero clutch setups are notoriously hard to bleed. I had this problem initially also. These are all problems I referred to in my original post. Using this CMC lowered pedal effort, made engagement smoother, and bled out in 2 pumps. I agree that my bleeding experience was anecdotal, but it did work for me. I cannot guarantee that this will fix anyone's bleeding problems, but it is a distinct possibility. The Miata CMC design is a decade newer and, to me at least, appears to be an improvement.
So again, if this helps anyone, please let me know. I don't need another post telling me I am wrong because I did things differently than you. There is more than 1 way to skin a cat.
no need to get angry, just because we don't think this solves the problem of the hyper-extension doesn't mean we don't like to see the info, it's nice to see other options out there for the master cylinder. Options allow us to fine tune our setups for faster release, or less effort.
------------------ 1st class A**hole.
we're in desperate need of a little more religion to nurse your god-like point of view...
I've been experimenting with Fieros since 1996 and have dealt with all the mastercylinders installed on the Fiero. In my experience the very best design in terms of dependability is the first design with the outlet between the reservoir and firewall. I've had the best results from rebuilding that particular unit as well as with it coming strait out of the box as a remanufactured unit. The later tube and cast iron designs gave me nothing but trouble right out of the box, so much so that I went back to what I knew worked. I had to bend the line a little to accommodate it on the 86, but it is what I use without spacers with my F40 going on 3 years now.
Thanks for posting this. I am currently trying to mate an Ecotec LE5 with an F40. Using a SAAB front case half and HTOB, G6 sprung hub clutch disc from Clutchnet, Cobalt PP, and custom flywheel. Got the clutch bolted up to the flywhheel the other day, found that I only needed about .150" of travel to release the clutch, and lighter pedal is always good. I will give this a try.
