Hydraulic Clutch Conversion (71-75 manual pedal assembly req

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Hydraulic Clutch Conversion (71-75 manual pedal assembly req

Postby monzaaddict » Sat Mar 17, 2018 11:24 pm

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This conversion is similar to what has been available for more popular cars for years. It adapts a Gm LT1/LS1 Camaro (F-Body) hydraulic clutch master to a Monza/Vega equipped with the early style manual pedal assembly. GM did this on one of their show cars in the 90's. Mark Stielow has done this on his Camaro builds. McLeod/Detroit Speed/Speedtech and others offer kits for popular car models. Grandam75 conceived the idea of adapting the hydraulics to an early H-Body pedal assembly (project journal page 4 bottom) viewtopic.php?f=20&t=26198&start=45 ,I simply refined his design. He has been using this setup for a few years on his ls1/t56 Vega. I have messaged him a few times and he has reported no issues with clutch pedal feel and function. There is no need to move the engine wire harness firewall plug with this design.
I am thinking of offering a kit that consists of the firewall bracket and small parts required and a list of additional parts to be sourced by buyer but may offer a complete kit. No price yet, just gauging interest, but a pedal to clutch complete hydraulics (I am offering just the pedal end of the hydraulics) is going to be $400 - $600 depending if using ls1/lt1 factory throwout bearing (slave cylinder) $80 or aftermarket $300+.
When I started researching what was required (pedal ratio, bore size), I came to the conclusion a 6 to 1 pedal ratio and a 3/4 bore master was best. Google "hydraulic clutch pedal ratio".
I bought a kit for a 55-57 Chevy from McLeod and determined that the master they use is from an lt1/t56 Camaro. It is the same 3/4" bore that is used on ls1 cars but has a shorter internal stop offering longer stroke and more volume. I imagine they choose this master over the ls1 master due to its increased volume allowing the hydraulics to be used with either an an external slave or internal hydraulic throwout bearing with a properly adjusted pedal stop and the fact that it includes the reservoir and hose. LMC127 is the LT1 clutch master which includes the reservoir and hose (LMC362 is the LS1 clutch master which does not include the reservoir or hose. The reservoir and hose can be purchased from hawk motorsports). http://www.manualtransmissionpart.com/m ... -16_us.pdf
The pedal is 12" from pivot to center of foot pad. Placing the clutch pivot pin 2" from the pedal pivot gives 6 to 1 ratio. The bend in the pedal presented a problem. A 5/16" clevis pin welded to the pedal was what I felt to be the best solution.
I determined that I could not modify the pushrod in the manner that McLeod does to convert to thread for a rod end but found that AP ( the factory clutch master manufacturer) used a pushrod with a pivot head design that was shared with Lockhead and Tilton. Tilton offers multiple length 5/16" threaded pushrods. Tilton (part # 74-400) pushrod was the perfect length allowing me to add a (QA1 CFR-5) 5/16" thread 5/16" bore rod end .
Next, I made a mockup out of MDF (medium density fiberboard) to determine the proper position and angle (20 degrees) to mount the master that would allow the pushrod to remain inline with the clutch master bore throughout the full range of motion. The clutch master attaches to the firewall bracket with 5/16" 18 x 3/4" bolts flat washers and lock washers (It would be a good idea to use anti seize on these bolts as they are going to be in a difficult location to reach when installed).
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Last edited by monzaaddict on Sat Mar 24, 2018 12:57 am, edited 9 times in total.
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Postby monzaaddict » Sat Mar 17, 2018 11:41 pm

Last edited by monzaaddict on Fri Mar 23, 2018 7:16 pm, edited 4 times in total.
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Re: Hydraulic Clutch Conversion (71-75 manual pedal assembly

Postby monzaaddict » Mon Mar 19, 2018 12:20 am

A paper template will be included to approximate where the firewall must be opened for the clutch master to pass through.You have to cut out the template with scissors and razor blade.
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The first couple of users are going to have to carefully enlarge the firewall opening until clutch master can be installed and removed easily. A seal will need to be installed. I feel this is best done on the interior side and will leave it to the end user to come up with a solution. If the stock insulating pad is in use just cut a slot for the clutch master to pass through.
I needed to come up with a pedal stop to prevent over extending the throwout bearing. I took a chance on a simple furniture leveler I found on Ebay, cut the foot of it, added 3/8" 16 by 1 1/8" long coupling nut (Everbilt Home Depot),locking nut and a rubber bumper again from Ebay. My pedal assembly had a predrilled hole that I aligned one screw of the pedal stop/furniture leveler with. I let the back end rest against one of the studs that go through the firewall and then drilled 3 holes for self tapping screws. It works great and is cheap.
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Last edited by monzaaddict on Fri Mar 23, 2018 5:36 pm, edited 7 times in total.
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Re: Hydraulic Clutch Conversion (71-75 manual pedal assembly

Postby monzaaddict » Mon Mar 19, 2018 12:23 am

An early 71-75 manual pedal assembly is required. The factory starter circuit switch on clutch pedal has to be removed and a jumper added between the purple starter circuit wires (or leave the switch hanging with a rubber band or tape around it to maintain contact between the purple wires).
The clutch pedal needs to be drilled, clearanced and a 5/16" clevis pin welded. A paper template is included indicating the exact centerline of where the clevis pin needs to be. You have to cut out the template with scissors and razor blade. The only portion that needs to be accurate is the center hole and the edge near where the clevis pin will be located. Center hole will be loose to fit over bulge in pedal. Add 4 pieces of cellophane tape to edges of hole in template. Align the template with edge of pedal and by looking through hole that starter safety switch would have connected to the pedal ensuring it is aligned with mark on template.
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Start with a small drill bit and work up to 5/16". I used cobalt drill bits. If the clevis pin is a little loose in the hole turn the pedal on its edge and with the clevis pin installed, hammer the area next to the clevis pin. In order for the clevis pin to clear the pedal assembly bracket the clevis pin has to be located with the head encroaching on the bend in the pedal. This is the area that needs to be slightly clearance so the clevis pin head sits flush. Use a dremel 932 3/8" grinding stone.
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Before welding the clevis pin on the head side, the clevis pin has to be oriented so that the hole the hitch/hair pin that holds the rod end to the clevis pin fits into is parallel to the bottom of the pedal assembly bracket when the pedal is in the up position. In addition, the hitch pin has to be installed with the flat part parallel to the pedal assembly bracket.
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Weld head of clevis pin to pedal.
Last edited by monzaaddict on Sat Mar 24, 2018 1:26 am, edited 10 times in total.
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Re: Hydraulic Clutch Conversion (71-75 manual pedal assembly

Postby monzaaddict » Mon Mar 19, 2018 12:26 am

The clutch master needs to be disassembled and replacement pushrod (Tilton 74-400) installed.
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The eyelet has to be cut off the stock pushrod. Then using Lisle (part # 31840) o ring and seal pick pull back rubber boot and remove the circlip that retains the pushrod.
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(Note: there is an internal spring that will push the piston out of the bore. I was convinced I would never get the assembly back together but within minutes it was done). Remove the factory pushrod from the plastic retainer and install the Tilton pushrod. Stretch out the circlip and once the leading edge is in the groove, hold it in position and use the Lisle o ring tool to push the circlip into the groove. reinstall rubber boot. Install jam nut and rod end. screw rod end on 8 turns and tighten jam nut.
Another diy option for modifying the original pushrod that does not require disassembly is cut it to length and add a clevis end that is attached with a set screw through the side. This part is available on Ebay as a fix for worn Ford clutch master pushrods. A 3/8" to 5/16" reducer again available on Ebay is also required. You only have one chance to get the length right and therefore I decided to go with the threaded pushrod instead.
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The triangular bracket that attaches steering column to firewall needs to be cut (more than shown in picture) and new bolt hole drilled.
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Last edited by monzaaddict on Fri Mar 23, 2018 7:37 pm, edited 6 times in total.
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Re: Hydraulic Clutch Conversion (71-75 manual pedal assembly

Postby monzaaddict » Mon Mar 19, 2018 1:32 am

The firewall bracket gets sandwiched between the brake master or the power brake booster on cars so equipped. The pushrod from either the brake master or power brake booster will need to be cut, threaded for a 3/8" 24 x 1 3/4" coupling nut (204606BG Rod Coupling Nut, Grade5, 3/8-24, Pk5) with locking nuts. The pushrod must be lengthened by 1/4" to compensate for the thickness of the firewall bracket and restore the brake pedal to its original height. Measure rod before cutting.
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One thing to add is that the added thickness of the firewall bracket will move the booster forward and do to the engine compartments tight confines the fender well will likely have to be slightly clearanced and a new hole drilled (1/4" forward of original) for the factory booster brace. .
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Early Vega's have a brake distribution block on firewall that will need to be relocated. Later Vega's and Monza's have the distribution block/proportioning valve moved to the fender and should not interfere with installation.
Russell makes adapter fittings for either -3an or-4an hose that fit the clutch master (and ls1 hydraulic bearing). These have a seal and are secured with a roll pin.
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I think an additional 90 degree steel (steel for high pressure hydraulics not aluminum) fitting should be used just after the fitting on the clutch master to direct the line away from the exhaust and steering and towards the firewall where the line can snake down to the bellhousing.
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It might be a good idea to install heat shield on the hydraulic clutch lines.
Last edited by monzaaddict on Wed Nov 07, 2018 7:36 pm, edited 6 times in total.
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Re: Hydraulic Clutch Conversion (71-75 manual pedal assembly

Postby hammerdown7 » Mon Mar 19, 2018 8:13 am

Thanks for putting all this together. My stock cable is still working fine but if I need to switch over sometime in the future I'll know where to come for the "how to and what with" thread you have made available, a great service to all h-body owners.

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1976 Chevrolet Vega Cosworth

Re: Hydraulic Clutch Conversion (71-75 manual pedal assembly

Postby monzaaddict » Mon Mar 19, 2018 7:40 pm

An LS1 throwout bearing or any internal hydraulic throwout bearing has a lower fitting which is the inlet. This fitting on the ls1 throwout bearing like at the clutch master has a seal and is secured with a roll pin. Lines with factory male/female quick disconnects are available from McLeod. When disconnected no fluid is lost. Standard 4an or 3an hose can be used but fluid will be lost when disconnected and bleeding after servicing may take longer.
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The upper fitting on the LS1 or any internal hydraulic throwout bearing is for the bleeder (air travels up). I would recommend a speed bleeder kit for the throwout bearing making bleeding the hydraulics a one man operation. When installing screw in fitting for speed bleeder note that some use a conical seal like a bleeder on a caliper. A special length fitting is required to reach the seat in the throwout bearing. For this reason some speed bleeder kits come with a cone fitting that is short (often the cone is cut off leaving just the threaded portion) and include a washer which instead forms the seal. Make sure the washer surface on the throwout bearing is smooth as it was never intended to be a sealing surface. As an extra measure use a hydraulic thread sealant such as loctite 545. Feed the speed bleeder line back up into the engine compartment. Picture is of fitting that would be in engine compartment. Bracket could be attached to brake master cylinder bolt and bleeder disconnected via clip when bleeding.
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Dorman and others make an aluminum bodied replacement for the LT1/LS1 clutch masters that are compatible. The aftermarket masters such as sold by McLeod based on a Wilwood master modified and fitted with an adapter and the Tick performance Tilton based master with adapter have an overall length that make them incompatible (not enough room between bracket and fender).
There are some excellent videos on Youtube specific to bleeding LS1 hydraulics (perfection clutch etc.). https://www.youtube.com/watch?v=OWAzZvOJpDs&t=55s
Make sure you prebleed the master and slave before installation. Rebleed after all parts are installed. If you are using a speed bleeder open bleeder and place into clear container with enough brake fluid to immerse bleeder (some people will put in reservoir if all fluid is new in system). With speed bleeder you should be able to just pump pedal to bleed system. With regular bleeder add clear plastic tubing to end of bleeder and place into clear container with brake fluid. Video above recommends OPENING BLEEDER FIRST, then push pedal down, close bleeder and release pedal. This is different than what you would do when bleeding brakes.
Last edited by monzaaddict on Fri Mar 30, 2018 4:23 pm, edited 7 times in total.
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Re: Hydraulic Clutch Conversion (71-75 manual pedal assembly

Postby monzaaddict » Mon Mar 19, 2018 7:42 pm

The total volume of the clutch master will likely exceed that required to release your clutch. A pedal stop must be installed and properly adjusted in order to prevent over centering pressure plate fingers and/or blowing out seals of throwout bearing. Initially set the stop so that there is 7/8" of pushrod travel at clutch master. The distance from the front of rubber bumper to front of bracket should be 2 5/8" at start of procedure.
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With the car stationary, ENGINE OFF, transmission in gear and rear wheel(s) (posi - both wheels off ground / non posi - one wheel on ground I think) progressively adjust pedal stop lower to allow clutch pedal to be depressed incrementally further while having another person check for clutch release by seeing if wheel(s) can be turned. Adjust pedal stop so that the pushrod travels 1/16" further than the point at which the clutch releases and wheels can be turned. https://www.youtube.com/watch?v=f4T2H3KDlAc
Last edited by monzaaddict on Mon May 28, 2018 12:56 pm, edited 3 times in total.
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Re: Hydraulic Clutch Conversion (71-75 manual pedal assembly

Postby monzaaddict » Fri Mar 23, 2018 7:14 pm

a simple bolt on clutch pedal stop can be fashioned using the following parts (threads 3/8" 16):

- an adjustable furniture leveling glide
https://www.ebay.com/itm/Universal-Adju ... 1989363833

- a threaded rubber foot
http://www.ebay.com/itm/262262785446?_t ... EBIDX%3AIT

- a jam nut
https://www.lowes.com/pd/The-Hillman-Gr ... ts/3012489

- A coupling nut
http://www.homedepot.com/p/Everbilt-3-8 ... /204337391

- 4 screws

The following parts are also needed:

- 5/16" x 1" clevis pin (I am going to weld pin to pedal)
http://www.ebay.com/itm/172064093104?_t ... EBIDX%3AIT

https://www.ebay.com/itm/Qty-250-5-16-I ... 2749.l2649

hitch/hair pin
https://www.ebay.com/itm/Bridge-Hitch-H ... 2749.l2649

-Russell 641001 Clutch Hose Fitting Clutch Fitting -4AN Male
http://www.ebay.com/itm/252313385182?_t ... EBIDX%3AIT

-Russell Clutch Hose Fitting Clutch Fitting -3AN Male
https://www.ebay.com/itm/Russell-640281 ... uR&vxp=mtr

LT1 camaro clutch master LMC127 is the same as LS1except the internal stop allows for a longer stroke and it includes the reservoir. With the adjustable pedal stop adjusted properly the lt1 master could be used.

- clutch master for an LS1 98-02 camaro LMC362 does not include reservoir
http://www.ebay.com/itm/170918203204?_t ... EBIDX%3AIT

https://www.ebay.com/itm/1982-1992-Cama ... 2749.l2649

- QA1 CFR5 rod end 5/16" 18 female thread 5/16" bore
https://www.ebay.com/itm/QA1-CFR5-Rod-E ... 7N&vxp=mtr

- 5/16" 18 jam nut
https://www.ebay.com/itm/Zinc-Plated-Fi ... SwstxVTkWk

Another solution to modify the clutch pushrod might be to use this repair kit
http://www.ebay.com/itm/261851765088?_t ... EBIDX%3AIT

and this spacer
http://www.ebay.com/itm/370915026348?_t ... EBIDX%3AIT

McLeod female quick disconnects
McLeod 139201

The plate causes the brake pedal to sit lower. cutting the pushrod and adding a coupling nut and two jam nuts will allow the pushrod to be extended restoring the pedal height.
3/8" 24 x 1 3/4" coupling nut
http://www.ebay.com/itm/222387321725?_t ... EBIDX%3AIT

3/8 24 jam nuts
https://www.ebay.com/itm/HEX-JAM-NUTS-Z ... SwkLhZ~ILr

I disassembled one of the masters and found the bore has a steel liner - I had assumed it was plastic. Also the pushrod used by AP/Lockheed/Tilton are basically the same. Therefore the stock rod can be replaced with a threaded 5/16 rod made by tilton. Three lengths are available. 74-400 is the one you want

https://www.summitracing.com/parts/til-75-030 (too short)
https://www.summitracing.com/parts/til-75-031 (longer than needed)
https://www.summitracing.com/parts/til-74-400 (correct length)

https://www.ebay.com/itm/1955-82-GM-Car ... 1714!US!-1

clutch pedal pads - verify fitment
14038638 mid 90s camaro
https://www.ebay.com/itm/Fits-GM-Pedal- ... RV&vxp=mtr
332515 pedal pad reproduction part # w-204 you can get stainless trim for this! (fitment verified most like original)
http://www.autometaldirect.com/chq-72-8 ... -7656.html
https://www.ebay.com/itm/GM-Camaro-Nova ... SwiuxaqCdh
dorman 207233 generic replacement (fitment verified)
https://www.ebay.com/itm/help-20733-clu ... L3&vxp=mtr

clutch fluid reservoir bracket ( may not clear windshield washer fluid bottle on pb cars) ( reservoir could likely be just mounted to firewall)
https://threepedals.com/products/clutch ... -mc-gen-2/

http://www.hawksmotorsports.com/82-92-c ... roduction/

LS1/LT1 Camaro clutch hydraulics bleeding procedure

setting pedal stop
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