Removing Brake Booster Options

[Paulski]

Hello,

I have a 27 spirit frame kit under my bucket and I want to get rid of the power brakes. The bucket is "finished" (are they really ever!!) so I am looking for options that doesn't move the MC because of the cut out in the body floor for it and doesn't require welding to the frame since its already powder coated. So here are a few of my ideas/questions:

- Fab up a spacer that bolts up to where the power booster is now and extend the push rod

- Fab up a bracket that bolts to the frame and extend the push rod (harder option I think because space limitations in getting a drill/tap around the body/frame)

- Leave the booster in and cap off the vacuum line. Is this safe? I only semi understand how power boosters works and don't really know what the internals look like (7" dual diaphram). I have a few holes in my brake pedal arm that will let me adjust the pedal ratio. As of now with the engine off, I can comfortable press the pedal so I dont think I will really need to change ratios.

- Of all the options, should I switch over to a "manual" master cyclinder? The one thats in there now is a steel corvette style, I think its a 1" bore and both reservoirs are equal size. I have disc on the front and drums on the rear.

Thanks,
Paul

 

[fletcherson]

Disconnecting it is a bad idea, power brakes without vacuum are not very effective, very hard pedal, not much stopping power. Take the car to a safe area (empty parking lot, etc), unhook it and try it, if you want, but allow pleanty of room to stop. Why do you want to eliminate the booster?

 

[Paulski]

Disconnecting it is a bad idea, power brakes without vacuum are not very effective, very hard pedal, not much stopping power. Take the car to a safe area (empty parking lot, etc), unhook it and try it, if you want, but allow pleanty of room to stop. Why do you want to eliminate the booster?

Somethings going on where the brake pedal won't fully return when I let off the brakes (only with the engine running) so the brake lights stay on, I have to manual pull the pedal all the way up ~1/4" or so. I'v checked to make sure the rod isn't binding on anything and greased it at the MC and heim joint at the pedal, but can't figure it out. I'm leaning towards the power booster because its probably right at edge of having enough vacuum (10-12 in hgs). If its not the booster, than I'm guessing its the something inside the MC, like the a nic in the bore or something. Also, as little as these cars are, I dont think it really needs a booster, but this was my first build so I have lots more to learn and experiment with still!

 

[fletcherson]

Somethings going on where the brake pedal won't fully return when I let off the brakes (only with the engine running) so the brake lights stay on, I have to manual pull the pedal all the way up ~1/4" or so. I'v checked to make sure the rod isn't binding on anything and greased it at the MC and heim joint at the pedal, but can't figure it out. I'm leaning towards the power booster because its probably right at edge of having enough vacuum (10-12 in hgs). If its not the booster, than I'm guessing its the something inside the MC, like the a nic in the bore or something. Also, as little as these cars are, I dont think it really needs a booster, but this was my first build so I have lots more to learn and experiment with still!

Ok, I've worked on vehicles for a looong time, replaced numerous failed boosters, but I've not personally seen one fail in this way. Normally, they simply leak vacuum, you can usually hear them hiss, then as it gets worse, you notice less mechanical advantage and possibly engine performance reduction. I would be more inclined to suspect something mechanical with the pedal, linkage, or lastly, the m.c. The thing about a booster is it really reduces the pedal pressure required, so it wouldn't take much to allow the pedal to stick. Can you adjust or shorten the rod from the pedal to the m.c. a little? Perhaps a return spring, or a stronger one? Just a thought. It would be simpler than reworking the entire system and less expensive. You could install a office to reduce the vacuum or simply unhook it to see if it makes a difference, but allow safe space to test your stopping distance because it will change or require more effort. Be safe!

 

[old round fart]

Is the brake switch in the brake line? If not it could be an adjustment or bad switch. Spirit stuff is well thought out so I would look for a mechanical issue.

 

[Paulski]

The brake pedal/MC rod is adjustable, I do have a return spring, and the brake light switch is a NC push button the pedal pushes against when not stepping on the pedal. What makes me think its the booster is when I shut the engine off, the brake lights stay on and I can pull up on the pedal to turn them off, I think it does it sometimes while driving too, but if its just parked without the engine running, the pedal freely returns all the way up. I guess I need to get someone to follow me and let me know if the brake lights are staying on and find an open parking lot and disconnect the booster. Is there any concerns with the engine only pulling 10-12 hg of vac at idle as far as thats being enough for the booster, i thought boosters wanted more like 18+?

 

[tfeverfred]

Have you called Spirit? They seem to be a good company to deal with and may have some valuable info? Also, have you always had the problem or did it just develop over time?

 

[409T]

I had problems with low manifold vacuum and vacuum booster brakes. A Crane Cams vacuum bottle fixed it.

 

[old round fart]

Easy fix! Adjust the switch to put a little more distance between the pedal and the end of the switch and go for a ride!

 

[rubicon]

I had to add a return spring to solve the same problem on my car. Your spring does not look like it has enough tension on it. Lightly push on the pedal and see if it returns all the way. Also adjust the switch if the pedal is returning all the way back.

 

[HenrysT]

I'm wondering if that booster is working and pulling on the linkage and taking up the free play... it only happens when it's running, right? You can try moving the pedal to see how much free play you have and see if the brake lights come on in that free play then start it up and if you have the same free play.
Like it was said before, adjust the brake switch or get a little "heavier" spring.

 

[choppedtop]

Sounds like you may just need a return spring on the pedal, or a stronger one.

 

[AusBucket]

I would drill another hole for the spring as far out towards the end of that lever as possible. I agree with the other posters that it does look a little light on. Easiest way to check would be to add a second spring and see if it cures the problem.
Regards,
Mike.

 

[Gerry]

Best to solve the problem, not work around it.

 

[Paulski]

I haven't had a chance to drive it (dead battery and a bunch of clutter blocking the driveway!) but I did pull off the spring to see how much free play is in the push rod, I can move it freely back and forth about 3/16" in and out of the power booster before I felt resistance pushing into the booster. It did like to sit naturally all the way against the resistant and when I reinstalled the spring, it pulled the brake arm/pushrod all the way back that 3/16". The spring pulls it all the back pretty easily, but I'll look into a 2nd spring. I also noticed the push rod can twist a little bit because of the heim joint that connects it to the brake pedal arm, maybe its twisting and misaligning just enough to cause friction? Maybe ill remove the heim joint and try a clevis or something with less play in it.

 

[fletcherson]

I haven't had a chance to drive it (dead battery and a bunch of clutter blocking the driveway!) but I did pull off the spring to see how much free play is in the push rod, I can move it freely back and forth about 3/16" in and out of the power booster before I felt resistance pushing into the booster. It did like to sit naturally all the way against the resistant and when I reinstalled the spring, it pulled the brake arm/pushrod all the way back that 3/16". The spring pulls it all the back pretty easily, but I'll look into a 2nd spring. I also noticed the push rod can twist a little bit because of the heim joint that connects it to the brake pedal arm, maybe its twisting and misaligning just enough to cause friction? Maybe ill remove the heim joint and try a clevis or something with less play in it.

That idea with the heim joint is very possibly the issue, or part of it. I had to make all of my linkage and used a bell crank setup. I initially ordered heims, but had to switch to a clevis on the mc rod for that exact issue. A stronger or shorter spring may not be a bad idea as well.