Technical Under floor brake pedal instal?

That all depends on where you put it.
If you just added it under the foot pedal pad, it wouldn't change very much.
If you cut at or near the bend and adjust the angle it will change it just a little
If you cut and add between the pivots it will change a bunch.


The tab for the master, has a certain relationship to the angle of the pedal.
Just for shits and giggles let's say the legs are 2 and 12 giving a 6:1 ratio.
IF I wanted to, I could get this placement and relationship in such a way with those same legs that with 6" of travel the master moves next to zero. All of a sudden the 6:1 ratio changed to 6: 0.0001 I used an extreme to highlight the importance of the tab for the master's location and how easy to change it due to placements.

 

the pedal height that pontiac used on the Underflooors was 4-3/8 from the toe board to the back of the pedal on manual brakes , which is the same depth of the MC bore with the 1" master and a 4.75 :1 ratio

 

I went and measured the pedals in my 1997 Ram, and the brake pedal is 7 3/4" off of the floor. The clutch is about the same, but about a inch forward of the brake. In my 37 it just seems like there is a lot of room above the pedals. 31Vickey, I think that I am going move my foot pad up to get the height I am looking for, without changing ratio to much. Is there more pedal travel in power brakes, compared to manual?

 

Manual brakes should be increased foot pad travel for about the same master stroke compared to power brakes.
Since the manual doesn't have power assist, in order to decrease leg effort while maintaining the same pressure at the brake pads the lever is longer and rides higher .
Think about a pipe on your breaker bar, you can apply more force but your hand moves a lot more. Take the pipe off, you move less but need more effort- now have your buddy pull in the bar too. There's less travel but you both travel to move the bolt.

I hope that makes sense - coffee

 

The pipe on the breaker bar makes sense. So if I had manual brakes my pedal would be higher, and in my eyes would look normal. Now to find a m/c and booster. I know the factory Jag one is 15/16 bore, but not sure of stroke. I have read that I wouldn't notice a difference with a 7/8 bore, witch are easier to find. A 1977 Malibu has one but I would like one with a screw on cap. Are there different strokes on power boosters, do they all have the same bolt pattern? Thanks again 31Vickey. coffee is good

 

Boosters are just an effort or force adder. The stroke going in equals the stroke coming out.

There's different mounting patterns and bracket angles. Minor fab work gets you any thing you want. The biggest limiting factor in an under floor mounted booster is its diameter. There's only a few in the 7" range.


All things equal and set up properly, the only advantage to power brakes or difference is how far you'll need to pick up your foot to apply the brakes. It's ergonomics. With power brakes you can pretty much keep your heal on the floor, pivot your foot and the movement is small. With manual brakes you'll need to get your foot up and involve the thigh and hip some, the movement is larger.

 

I am getting closer, to narrowing this down. I believe that I am looking for a m/c for a 4 wheel disc. When I get under the truck an measure, from the bottom of the cab I have 7.5 inches. I am also looking for a 8 inch booster. This will stick below the frame, but not the lowest part on the truck. Does the m/c, booster, and pedal have to be in a straight line? Can I have the pedal rod angled down a bit?

 

Since that pedal can be up to 20" away you can have some misalignment without causing you troubles. But it's got to be within reason. Your "just a bit" might be different than the next guy's

 

You have gotten some good advice here.

Based on the thread title I would say that if the brake pedal was under the floor then you would have a very difficult time trying to apply the brakes and slow down

 

I'm not sure I agree with the bottoming the cylinder thing Every car I've bled the brakes on the pedal has hit the floor.

 

here is a set i made up for mine.. manual brakes and hydro clutch... pedal ratio is about 6.5-1 i have the clutch hooked up temporarily and the pedal push is easy.. pedals bottom out about 1\2" from the floor. i ran into trouble getting them to clear the corner of the block.. if i remember right power brakes on need about 5-1 ratio.. best to have the master cyl and all before making anything final..

 

Twenty8tudor, I like your setup, where did you get your hydro clutch? There has been a lot of good info for me in this thread, and thanks to everyone that chimed in. I am going to but a m/c and a clutch master, before I finalize anything. If I want to keep everything in a straight line, I am going to have to modify my pedal. There is no way I can get a 8" booster under there, without doing so. Somewhere I saw a picture of how to measure pedal ratio, so I will look fro that and go from there. I will be back with a what I have later.

 

Thanks! It's just store bought stuff.. Master is an 88 jeep Cherokee and the slave is a 62 chevy.. The bore sizes don't match like everyone said they had to but it has enough travel to release the clutch..

Easiest way I figured out to do it was take a square and draw a line on a piece of cardboard.. Use that to center your pivot hole of your pedal.. Then you can draw parallel lines above and below the pivot line to get the distance ya need and make your pedals hit the lines. Makes it a lot easier to measure that way. If ya need I can draw it out later today.. Just divide how far ya go up by how far ya go down. I went up about 10.5" from center of pivot pint to center of the pedal pad and 1 5/8" down so 10.5" divided by 1.625" ends up at 6.4-1 ratio

 

The m/c that I found is a mid 80,s disc/disc corvette. You can put lines on either side, and they have a 15/16 bore. I have looked at so many please correct me if I am wrong. My tranny came out of a Dakota, but the clutch m/c and clutch slave, have a pin to hold the lines in. I already have both, from the truck. I really want a threaded one, but I need a 7/8 bore, so if anyone can point me in that direction thanks

 

Try Novak conversions for hydraulic clutch parts.
I know they have that fitting with the pin to change over to inverted flair threaded hard line into the jeep/mopar cylinders, if that's what you need.

I think you could use any clutch master you wanted, you just need to make the line.

 

If you are running discs then that corvette mc will work. There is another one for corvette for drum/drum too.

I would second Novak too. I have bought parts from them going back 10 years.

 

I went from nine and a half inches by 2 inches to 11 and a half inches by two and a half inches. It still gives me a 4.5 :1 pedal does this look right for the pedal. I can then lower it and put it where I want it. The one on the left is a welder series and on the right I drew. Anyone got a water jet.

 

Looks good

Water jet!?!
We don't need no stinking water jet.

Hand torch and drill press.

 

31Vickey, you are a very talented man, I have read your threads and I appreciate your in put. That is a pretty nice piece. Time to get some 3/8 plate and fire up the plasma. Do you have a part # on the corvette m/c. I keep finding them from jegs, summit, and every else, but I know I can get one from NAPA.

 

Great site to buy from or use as a good parts number reference. Take a look at this master and see if its what you are looking for. I tried an 86 one, but it has the plastic reservoirs on top.

https://www.rockauto.com/

1980 CHEVROLET CORVETTE 5.7L 350cid V8 : Brake/Wheel Hub : Master Cylinder

 

JFYI, there was never a drum/drum Corvette. They went from single system 4-wheel drum to disc in '65, then to dual disc in '66.

 

What would make you not sure this is correct?

 

Completely stacking the return spring might not be a good thing. I'm just saying I don't think the factory did it because when bleeding nonpower brakes the pedal always hits the floor.

 

The fact is master cylinders are designed to be able to full stroke without damage. Some test procedures required very high pedal effort with an open system to verify no pedal contact with the floor, checking firewall, pedal and bracket integrity.
All production power and non-power cars/truck had to have the pedal checked for bottoming out the master first, or modifications were made to correct the problem before any testing could begin, again fact, not opinion.
What vehicles were you bleeding that had pedals hitting the floor?

 

Bob, we've been over this several times on different threads. I've been at this for a long time and every replacement master cylinder's instruction sheet says in big bold print Do not stroke the master full depth, or past a specific depth. With Most bleed jobs the pedal does go to the carpet.

 

It's possible that the residual valve at the end of the bore on some OE single system masters could be damaged while full stroking, and maybe is why some re-builders may carry over older info with dual masters. Several new dual masters I've purchased do state to fully stroke while bleeding, so these "instructions" do vary.
All my testing experience is with '67 and newer dual system vehicles, and if the master cannot be fully stroked, the advantage of a dual system may not be achievable because of limited displacement capability. Fact, not opinion.
With a single system, full travel is not as important, because you're going to loose all braking anyway with a leak, rupture or failure!
We have been over this subject before, and while you may not agree with me on the proper way to set up a dual master, others may hopefully learn something from our postings, or at least think more clearly about it.

 

It's not that I don't agree or don't disagree.
I'm bringing info that's contrary, however it's contrary by dozens of sources, 100s of personal sightings, and 100s of experiences of my own ( if I can see this then millions of others can too) that differ from what you say and vehemently tout is fact. Seems as though it's your "one" against millions. I've not been involved with OEM testing so I can't intelligently dispute, prove, or counter what you say that you've done or seen. However I can tell you that the things V8 Bob brings as fact only has 1 source that I've seen and that source is V8 Bob.

During bleeding, brake pedals bottom out on the carpet, now that's a fact that can be easily be proven. Did the design team not take the carpet into account? Should the carpet be removed to see if the pedal bottoms on the floor or the pushrod bottoms? I don't know the correct answer but that doesn't change the empirical and self evident.


The warrant paperwork states stroking the master fully to bottom will damage the master and void the warranty. So what's an intelligent person to do? Follow the advice of one single source who's statements are contrary or follow the supplier of the parts and upholder of the warranty?

 

I got mcmopar covered. Although I started building cars with an arc and oxy/acc torch too, 31Vicky, sometimes its just a lot easier to get bigger things cut/made than going to get steel, draw it out, cut it out, and then grind down the hand cut parts till they completely match (since they will be side to side with each other). That time can often be better off spent elsewhere on the car

 

Cool beans glad you could help.

I'm just old school I guess. I needed great parts when computers were big as box cars. The way to get them was by flame cutting because plasmas weren't around then either. Grinding just flat out sucks, eventually you figure out that if the torch gets handled better there's much less grinding and the world is a happy place full of nice one off parts. Also knowing how to grind makes a big BIG difference.

The CNC stuff is very impressive and maybe I'll have you quote me some stuff one day. About all I can get you is a paper template though. If I had an electric eye plasma I'd make good use of that almost everyday. Maybe you can quote me a set of those spring hangers, I made a similar set in the last few days, and will probably make another. With my patterns, I can easily change the axle tube size on the fly in a matter of seconds. Is it that easy in the CNC programs?

Speaking from my own preconceived notions here, I think one off parts would be expensive, but high repetition multiples would be cheap compared to old school hand methods.