Project - Large Bore Master Cylinder

Is this a potential product you'd be interested in seeing developed further?

  • Yes!

    Votes: 8 100.0%
  • Not so much.

    Votes: 0 0.0%

  • Total voters
    8
  • Poll closed .

RJM's GT500

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Hey Guys,
Just thought I'd share what I'm currently working on. This is a project I've had in mind for over a year now and finally had some time this week to make it happen. I'm currently developing a fully adjustable big bore master cylinder for the S197. The first prototype in the photos will be going in my 08' GT500 once it completes stress testing.
If there is interest I may start producing more of these. The prototype is a 7/8" bore and adjustable from 0% to +30% more fluid then oem. I'll be complementing the new MC with adjustable bottom pedal stop and top stop. These can easily be made in 13/16" bore as well with no design changes other then changing the honed bore size. That would give an adjustable 0 to +15% addition fluid flow over stock.
As shown this setup is a fully custom built CMC body, clutch rod and adjustable steel clevis end with a pressed bronze bushing. The rest of the internals are from a Tilton 76 Series 7/8" master cylinder so rebuild kits are readily available off the shelf at Summit, Jegs, etc should they ever be needed down the road. The unit shown here was manually machined and only a rough prototype to start testing with.

The idea behind this is for years I've wanted an adjustable clutch pedal setup for the various S197 Mustangs I've owned as once an aftermarket clutch was installed there was always room for improvement in the disengagement department. Second I believe having a larger bore to push a higher fluid volume, faster with less pedal travel will greatly help with the hard shifting lock outs and notch shifting, just as the 7/8" Tick master cylinders do for the bowtie boys with the same transmission as our GT500's. I've always felt the oem master cylinders were weak and barely capable of fully disengaging the clutch, especially aftermarket setups where I see a lot of guys having clutch troubles. The 13/14 GT500 got a slightly bigger bore aluminum master cylinder as Ford recognised the regular plastic units flexed too much under heavy load and didn't have enough capacity to disengage their new clutch setup satisfactorily. However those 13/14 cmc's are still a fixed setup with less flow capacity then these, no adjustability and still have the terrible plastic end links that break off.

A little background, I've been manufacturing adjustable clutch products for Nissan/Infiniti vehicles for the past 6 years and manufacturing aftermarket master cylinders solutions for them for the past year. The equipment to manufacture these is already in place should this project move forward beyond this first prototype. Please note at this time I have nothing to sell here, just looking to see if there is any owner interest if I was to begin manufacturing these in small qty's. Should any kind of production move forward I would happily become a SVT Forum supporting vendor just as I currently am at other non Ford sites.

What do you guys think? Is this something you might be interested in seeing made commercially available in the aftermarket?
 

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RedVenom48

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Subscribing. The factory release point on my car is damn near at the top of the pedal.

Conversely my dads stock 2014 GT clutch is right off the floor. Somewhere in the middle would be amazing!

I agree, a weak master cylinder could be a culprit in 1-2 upshift grinding while racing.
 

RJM's GT500

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lexustech48, Sounds like maybe there needs to be a third option of an adjustable 3/4" bore CMC (OEM size) If your engagement is right at the top you'd likely want to keep OEM bore and simply adjust for less overall travel to bring the engagement down on your setup. That or possibly the 13/16" bore setup with about 1/3rd less pedal travel then factory to still move a decent volume of fluid quickly while seriously decreasing the overall engagement height and pedal stroke.

As for your dad's 14'GT it sounds like he could definitely benefit from a larger bore CMC to get his engagement up higher and it would disengage the clutch faster during shifts since it would be moving more fluid per inch of pedal travel.
 

RJM's GT500

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Alright! I got the prototype unit install in my 08' yesterday afternoon and figured out the install process which is a very straight forward swap. 6 Bolts hold the pedal assembly in place along with simply twisting the switches 1/4 turns to remove them and one clevis pin to disconnect the brake pedal. 2 bolts hold the AC accumulator in place which when removed allows the accumulator to be moved slightly out of the way on 07'-09' cars giving nice access to the back of the master cylinder to connect/disconnect the fluid line. 2 bolts + 1 e-clip hold the OEM master cylinder in place to swap it out. Then it’s simply reversing the process and bleeding the clutch. Using a -4AN at the outlet port of the master cylinder allows you crack the fitting and pump the pedal to evacuate air just like bleeding brakes which worked fantastically. Clutch bleed on this cylinder without having opened up the lines at the transmission only took 5 pumps to get a firm full pedal. For the -4AN line I had already installed a JHR clutch line years ago and to adapt to the new cylinder I simply unscrewed the Ford quick connect fitting from the line leaving me with a female -4AN line to directly connect. Looking around it appears the vast majority of aftermarket clutch lines use the same setup with a common -4AN line + adapter fitting on the ends so for most nothing needs to be changed. If you have a hard-line or a 1-piece crimped on Ford end then a swap to something like the JHR or any number of others using the same construction would be needed with the cylinder.

This brings me to the next problem I discovered along the way with this project is a great deal of flexing is happening in the plastic factory pedal assembly. When my wife was helping me bleed the new cylinder you could visibly see the whole master cylinder being pushed forwards and flexing towards the firewall under load when just gently depressing. This leads me to believe even the OEM master cylinders are flexing around a great deal anytime one punches the clutch for a fast shift and very likely causing a loss of full master cylinder stroke under hard driving. It's moving around about an 1/8 to 1/4" which is significant as if the master moves away from the pedal box as you push it then you directly loose 1/8 to 1/4" of master cylinder stroke + loss of fluid volume output from the cylinder leading to grinds. I'll be pulling the pedal unit back out this week and adding some custom bracing to the factory pedal unit in key places I've already identified looking at my spare pedal unit which should firm things up immensely.

Otherwise the new large bore master cylinder paired with my RXT feels amazing the little bit I've been able to drive it. The pedal gained a little firmness which was to be expected but its still lighter then the factory clutch setup that came on my 08' by a long shot. It has good clutch feedback with good modulation and before I adjusted it further it was fully disengaging the clutch to where going into 1st and reverse were like butter with only a 3" of total pedal stroke dialed in. I've since adjusted the pedal stroke up to about 4" total stroke and the clutch is now engaging right around mid-stroke, exactly where I wanted it. Now my foot never leaves the floor thru the entire stroke for great clutch control. For me there's nothing worse then a very high engagement point where your trying to modulate the release with your leg dangling in the air, you get far more control with your foot planted. I haven't had a chance to flog the car yet as it's still too cold and what little spirited driving I got in yesterday only resulted in lots of tire spin but I'll keep everyone posted. Right now with the exception of the plastic pedal unit flexing I couldn't be happier with the new cylinder :)
 

Catmonkey

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Is the bracket reaction a result of the beefier master cylinder or did it flex with the OEM master cylinder? This might serve to further firm things up without replacing the master cylinder.
 

RJM's GT500

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Is the bracket reaction a result of the beefier master cylinder or did it flex with the OEM master cylinder? This might serve to further firm things up without replacing the master cylinder.

Catmonkey, given my setup with the McLeod RXT + larger cylinder still has a pedal pressure less then the OEM clutch and OEM master cylinder I can say without a doubt the factory plastic pedal unit is definitely flexing with the OEM cylinder. This would be made worse for anyone with a heavier then stock clutch/pressure plate as well.
In addition to that my cylinder has a solid steel mounting block where it meets the factory plastic pedal assembly which in theory should be stiffening up the OEM bracket somewhat already when compared to the factory master cylinder which only has two (thin) molded plastic tabs where they bolt to the pedal unit. I can see how the oem master cylinders would be flexing more then mine when under heavy load at the track or in spirited driving. I was seeing up to a 1/4" in deflection of the master cylinder on the factory pedal unit by my wife simply pushing the clutch slowly sitting in the driveway, nowhere near how hard you'd slam the clutch down while racing or even regular driving for that matter.

Where the cylinder attaches to the side wall of the plastic bracket isn't very well supported and isn't tied into where the bracket physically bolts to the firewall. It's like Ford left the whole left side of the bracket where the cylinder mounts hanging in free space with only the rubber firewall gasket to limit the deflection towards the engine bay. Looking at my spare bracket I'm going to whip up an additional support that backs up the free hanging side of the bracket and ties the master cylinders mounting points directly into the beefier part of the bracket where it bolts to the brake booster. That should eliminate any flexing and make the plastic pedal unit stiffer as a whole.
 

Catmonkey

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I'm running an RXT too, but I upgraded to the 13/14 master cylinder. Your option looks even better. I'd like to see what you come up with for the bracket support.
 

RedVenom48

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Saw your posts on FB, but id definitely be interested in the MC and bracket. Id probably pick up the bracket first (broke lol)
 

RJM's GT500

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Here are some more pics of the prototype unit installed in the OEM pedal assembly before it was installed in my 08' over the weekend. These photos also show the top fluid inlet from the reservoir. Someone had asked where it was since it wasn't shown in my earlier photos.
 

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Catmonkey

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How would the tubing to the slave cylinder integrate with the master cylinder. Does anyone make an adapter that would mate the end in your pics and the OEM fitting?
 

RedVenom48

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Might need to require a braided clutch line. I know my McLeod came with Ford Specific fittings to work with their standard flare ends
 

RJM's GT500

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How would the tubing to the slave cylinder integrate with the master cylinder. Does anyone make an adapter that would mate the end in your pics and the OEM fitting?

Catmonkey, most of the common aftermarket lines use an industry standard -4AN Braided stainless line with special fittings to make them connect with the Ford quick connect ports. In my case I'd installed a JHR Clutch line upgrade a few years ago when I redid my clutch and the Ford end at the MC simply unscrewed allowing me to directly connect the -4AN female end of the braided SS line to the -4AN Male outlet port on my prototype master cylinder. Looking around at the most common clutch line upgrade options it appears about 75% of companies are selling lines with the same configuration as my JHR. See the pics I snapped during the install showing the line details.
For those with ends that can't be removed I can certainly offer a compatible braided SS line kit with these cylinders for a fairly nominal cost but I think most of us here already have upgraded lines and of those most will be compatible already.
 

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RJM's GT500

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Looks really good!

Have you had a chance to do any WOT 1-2 shifts?

lexustech48, unfortunately it's been too cold and wet to safely do any hard 1-2 shifts. I got on it a little the other day on a back road where it was dry but still ended up getting sideways going into 2nd on cold tires.
 

RJM's GT500

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Might need to require a braided clutch line. I know my McLeod came with Ford Specific fittings to work with their standard flare ends
lexustech48, I looked up your line and can confirm the McLeod upgrade line does indeed come with adapter fittings on each end of a standard -4AN braided SS line so you would be able to do just as I did in my photo with your current clutch line. Unthread the Ford adapter and be good to go.
 

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