Manual brake conversion

JSATX

Goblin Guru
I’ve been kicking the idea around of getting rid of the vacuum brake booster for some time. Finally getting around to installing the stainless braided brake lines which replace the 2 rubber GM lines and one intermidiate hard line from DF, and decided that if I was going to drain all the brake fluid anyway now was the time to make the switch.

It turns out it’s pretty straight forward. It’s more a problem of doing the research and figuring out the parts you need.

For several reasons I decided I wanted to keep the GM brake fluid reservoir. There’s really no good place to mount the smaller three individual tanks (front, rear, clutch) anyway.

Wilwood makes an out of the box solution. It’s a remote fed tandem master cylinder. 7/8” is the smallest size and that’s what you want for mechanical brakes as it increases the psi at the caliper. Part number 260-14241-BK

Next you’ll need a way to link the pedal to the master cylinder. The MC comes with a rod threaded 3/8-24. You’ll need a threaded coupler, 2 lock nuts, and a solid rod end. Now of course no one makes a direct fit rod end, I used McMaster-Carr PN 2434K51 which is the closest thing to the stock GM pushrod I could find. You’ll need to open the bore up from 3/8 to 7/16 to fit the pedal stud. Next you have to cut it down. My measurement was 2.00” from the inside edge of the bore and that’s for a stock configuration. After I make sure everything’s functioning I plan to cut it down significantly to bring the brake pedal next to the gas. But that involves modifying the brake potentiometer and I don’t want to deal with that just yet.
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Then it’s as simple as drilling two 3/8” holes in the brake pedal box, mounting the MC, and screwing it all together.
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The MC comes with standard 3/8-24 double flare fitting adapters. You’ll need to cut the old GM metric fittings off the front and rear hard lines and install standard 3/8-24 fittings. I got a dozen stainless fittings from amazon for about $8.

(To be continued....)
 

JSATX

Goblin Guru
I ended up trimming the rod end until the pedal just barely turned on the brake lights, and then backed it out a couple turns. Snugged up the lock nuts and everything is totally solid I’m pretty happy with how it turned out. I hit a slight delay as I couldn’t find any copper crush washers, so just waiting on those to arrive before filling it back up with fluid and bleeding everything.

I’m also kicking around a line lock, I’ve already bought one I just don’t know if I care enough about drag racing to install it. However lots of people use them as parking brakes so that may be worth it.
 

DCMoney

Well-Known Member

In case you or anyone needs some in the future, lots of harbor freights around.

I planned on installing a line lock as a quick and cheap parking brake.
 

Waterdriver

Goblin Guru
From a licensing inspection standpoint and at least in WA, hydraulic parking brakes will not pass. I was looking into adding a drift brake with integrated parking brake lock and dropped that idea when I came across that state regulation. Your mileage may vary.
 

IDRVSLO

Goblin Guru
From a licensing inspection standpoint and at least in WA, hydraulic parking brakes will not pass. I was looking into adding a drift brake with integrated parking brake lock and dropped that idea when I came across that state regulation. Your mileage may vary.
Remember no inspection! Do whatever you want!;)
 

Tim Moland

Well-Known Member
I have questions about line lock too. I wanted it to do sick burnouts! So I was asking lonny and Adam about it on one of my visits, and they eluded to it being not worth it. There reasoning being that the front of the car was so light, even with the tires locked up, it would just push them. I tend to agree. Your thoughts?
 

Ross

Goblin Guru
Somewhere here I read the weights being 600 pounds on the front wheels, and 1100 pounds on the rear wheels, with a 200 lb driver in the car.
So a little more than 1/3 of the total weight is on the front. Probably would push the front a little, but if you took the stock windshield washer bottle, pump, and squirters, and aimed them at the rear tires... probably make for some sick burnouts. :)
 

JSATX

Goblin Guru
I have questions about line lock too. I wanted it to do sick burnouts! So I was asking lonny and Adam about it on one of my visits, and they eluded to it being not worth it. There reasoning being that the front of the car was so light, even with the tires locked up, it would just push them. I tend to agree. Your thoughts?
On the road it would definitely push them. In a water box I doubt it.
 

JSATX

Goblin Guru
Brakes are bled and feel great. Haven’t been able to road test just yet as other aspects of the car are still disassembled.

I kinda went a little crazy ordering 3/8-24 fittings. I ended up going with the first thing I ordered too! Oh well they’ll probably sit in my extraneous hardware box for the next 10 years
682ED5E5-02D0-430E-AFB9-6B8880999A30.jpeg
 

KLMOTORSPORTS

Well-Known Member
Anyone that has done manual brakes, how is the pedal feel with a 7/8” bore master cylinder? I am putting in a Tilton 600 pedal box and trying to figure out master cylinder bore size to purchase.

Thanks for any info!

Ken
 

JSATX

Goblin Guru
I hope to have an answer for you this weekend. While the brakes have been finished for some time I have a lot of other things removed from the car and haven’t been able to test them.
 

KLMOTORSPORTS

Well-Known Member
I hope to have an answer for you this weekend. While the brakes have been finished for some time I have a lot of other things removed from the car and haven’t been able to test them.
Awesome, appreciate it and look forward to the information!
 

JSATX

Goblin Guru
Just a quick update. After driving the manual brakes around for a bit I must say the additional brake control is significantly better than expected, but the force required to operate them is also higher than expected. I can just barely get them to lock at full pressure, I suppose that’s a good thing but I am surprised at how much force it takes to lock the tires, before it was just barely too much and they smoked.

What I like the most is before with the oem brake booster it felt like you either were slightly braking or locked up, it was very difficult to slightly vary pressure on the pads. Now it is completely different. I have a much wider range of stopping power to play with. Also the feedback in the pedal is so much nicer, you actually feel how much brake pressure is applied instead of the disconnected feeling of the brake booster.

It will certainly take some getting used to, but so far I can say I would do it again.
 

George

Goblin Guru
I wish you were ot so far away so you could try my car with the brake booster vacuum regulator it lets you have it all and can be tailored to driver preference.

Brad
 

JSATX

Goblin Guru
I wish you were ot so far away so you could try my car with the brake booster vacuum regulator it lets you have it all and can be tailored to driver preference.

Brad
That’s probably a much easier route. Vac regulators can be quite expensive though, what did you use?
 

KLMOTORSPORTS

Well-Known Member
Just a quick update. After driving the manual brakes around for a bit I must say the additional brake control is significantly better than expected, but the force required to operate them is also higher than expected. I can just barely get them to lock at full pressure, I suppose that’s a good thing but I am surprised at how much force it takes to lock the tires, before it was just barely too much and they smoked.

What I like the most is before with the oem brake booster it felt like you either were slightly braking or locked up, it was very difficult to slightly vary pressure on the pads. Now it is completely different. I have a much wider range of stopping power to play with. Also the feedback in the pedal is so much nicer, you actually feel how much brake pressure is applied instead of the disconnected feeling of the brake booster.

It will certainly take some getting used to, but so far I can say I would do it again.
Awesome, really appreciate you posting the feedback!! Probably a slightly smaller bore master cylinder would help with the pedal pressure issue...do you want bore size the master cylinder is that you have? Trying to match this up myself with my Tilton pedal box...thanks again for posting!

Ken
 

JSATX

Goblin Guru
Awesome, really appreciate you posting the feedback!! Probably a slightly smaller bore master cylinder would help with the pedal pressure issue...do you want bore size the master cylinder is that you have? Trying to match this up myself with my Tilton pedal box...thanks again for posting!

Ken
I’m already getting more used to it. Of the three bore sizes offered with this MC I got the smallest. 7/8”
 
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