Manual brake conversion? [Archive]

ShelGame

01-16-2006, 04:49 PM

Has anyone ever done a manual brake conversion to a TD? My Daytona C/S is race only, and I'd like to get that rusty old POS of a booster out of there. Is it just a matter of making an adapter plate, like the older RWD cars? How about the linkage?

gasketmaster

01-19-2006, 01:17 AM

I'm curious as well :bump2:

Bardo

01-19-2006, 02:36 AM

why do it your only going to save a 1/2 of a pound

Murphy

01-19-2006, 09:12 AM

i would think you would WANT power brakes for racing...but thats just me.....

ShelGame

01-19-2006, 09:28 AM

Why? Reduced engine bay clutter, eliminate a possible source for vacuum leaks, and especially less weight. The vacuum booster weighs considerably more than 1/2lb. More like 5lbs. I've got it out, I'll weigh it if you want to know for sure. I'm trying to get the Daytona down to ~2700lbs (minimum legal weight for the class) and it's at ~2800 now. 5lbs makes a difference.

EDIT: Actually, I checked again, min weight for the car (minus driver) is closer to 2600lbs considering the "ballast" this particular driver is carrying around. Car + driver needs to be 2810lbs, min.

Terry - I went ahead and pulled the parts and sketched up an adaptor plate. I can send you the sketch, if you want. Feel like producing a kit for sale? I'd be more than willing to test it for you ;) It looks like the MP master cyl pushrod kit for the RWD cars will work (might have to cut it down), so I bought one of those, as well as the 15/16" MP aluminum mater cylinder (it appears to have the same bolt pattern as the TD master cyl). Although, 15/16" is very close to the 24mm we already have. So, there's probably no advantage to using the MP master cyl. But, it was in a kit for about half the price from Mopar. I figure my father-in-law can use it in his Dart, worst case...

Bardo

01-19-2006, 09:48 AM

im so sorry i was so drunk last night i didnt even know i typed anything

ShelGame

01-19-2006, 10:25 AM

I just saw a pictures of a GLH engine bay...

Do Omni's have manual brakes as standard? I didn't see a booster...

Clay

01-19-2006, 10:40 AM

they have a booster, its almost all tucked under the cowl.

ShelGame

01-19-2006, 11:03 AM

they have a booster, its almost all tucked under the cowl.

That would explain why I couldn't see it...

Clay

01-19-2006, 11:17 AM

I think you will need to make an adapter plate for the master cylinder.

Then you will need to have the correct length rod as well. There are adjustable ones available for older cars from places like Master Power Brakes (http://www.mpbrakes.com/chryacc.htm)

The issue will be selecting the right master cylinder for the right amount of pressure and fluid flow for the application.

Bigger bore, less pressure, more pedal travel.

smaller bore, more pressure, less pedal travel.

A lot of people do this. There are many advantages when running big HP engines that dont make lots of vacuum. The guys who are doing it are usually running BIG cars with BIGGER engines, and they dont have any issues. We run small cars with small BIG HP engines (sometimes) so it should be easier for us.

Basically, someone needs to make the adapter, and try some of these different master cylinders out and find which one works best for them.

Bigger disc brakes (SLH, etc) will probalby help a good bit as well with this conversion.

clay

ShelGame

01-19-2006, 11:26 AM

The adaptor plate and pushrod - I have figured out. The MC size - not so sure yet. I think I'm going with the stock 24mm for now.

I think you have it backwards, though. A smaller bore MC will have a lower pedal force, and longer travel, than a bigger bore MC. What's the smallest MC ever used on a TD? 20mm? I might need to get one of those...

I was also reading that it's recommended to move the brake pushrod up on the pedal 1/2 - 1" to improve the force ratio. That doesn't look like a simple task on our pedals due to the location of the brake switch. So, I probably won't be changing that right away either.

gasketmaster

01-19-2006, 01:04 PM

Thanks for the info guys :)

gasketmaster

01-19-2006, 01:15 PM

Terry - I went ahead and pulled the parts and sketched up an adaptor plate. I can send you the sketch, if you want. Feel like producing a kit for sale? I'd be more than willing to test it for you ;)

Sure......you could send me a copy of your sketch :thumb:

I might be able to have somebody knock a few adaptor plates out :)

Thanks!

ShelGame

01-19-2006, 02:26 PM

Sure......you could send me a copy of your sketch :thumb:

I might be able to have somebody knock a few adaptor plates out :)

Thanks!

Here's the sketch Terry...

I've got a 1/2" ally plate in my garage. I'm going to make a prototype with the drill press. I'm just not sure how I'm going to cut the 1-1/2" hole, though. Like I said earlier, I think the MP pushrod for the V8 cars will work. I guess I'll find out when it gets here.

These measurements are based on my '89 Daytona. I'm not sure if different years/models would need different plates. L-bodies in particular...

Clay

01-19-2006, 02:34 PM

hey Rob,

why are you drill/tapping the outside 4 holes on the adapter?

clay

altered7151

01-19-2006, 02:56 PM

ShelGame

01-19-2006, 03:02 PM

hey Rob,

why are you drill/tapping the outside 4 holes on the adapter?

clay

The 4 outer holes are studs on the original booster (at least on my Daytona). I was going to put M6 studs into them and just use the original nuts on the inside of the car (brake pedal brkt). I guess they don't have to be tapped, but then you'd have to have a buddy hold the wrench in the engine bay while you crawl under the dash to tighten the nuts.

Is the Omni booster mounted different?

ShelGame

01-19-2006, 03:05 PM

I'd be interested in seeing how this turns out, and how well it brakes. I had considered doing the same thing when my daytona drag car was still a reality. I had did a little research and the honda guys have a pretty slick setup. The were using an aftermarket master cylinder, but if we can just find what size it is we could use a comparable stock unit.

I thought I had read somewhere that the smallest MC the TD's used was 20mm. But I don't know for sure. I think a 20mm would work good. A 24mm (what most TD's came with stock) will give a pretty hard pedal, I think. If we could move the pushrod pin on the pedal up 1/2 or more, then the 24mm would be OK. But I don't see how that's possible. At least on my Daytona brake pedal...

altered7151

01-19-2006, 04:25 PM

The honda guys seem to be using a stock manual brake master from the civics and some integras. Might be an option to look into, but like your talking about Rob they are also using the manual brake pedal assembly, which I'm assuming moved the fulcrum point on the pedal. This would be an awesome change on an l-body, especially with the header I have in mind.

Darkwolf

01-19-2006, 06:24 PM

My 81 horizan had manual brakes.

Clay

01-19-2006, 07:56 PM

The 4 outer holes are studs on the original booster (at least on my Daytona). I was going to put M6 studs into them and just use the original nuts on the inside of the car (brake pedal brkt). I guess they don't have to be tapped, but then you'd have to have a buddy hold the wrench in the engine bay while you crawl under the dash to tighten the nuts.

Is the Omni booster mounted different?

ahh, I got ya, makes sence now!! I just figured you would use bolts.

thanks,

clay

ShelGame

01-24-2006, 02:09 PM

Progress report:

OK, so I just cut out my adapter plate at lunch here at work in our machine shop. Took about 1/2 hour on the drill press/bandsaw/belt sander. I'll post pics later tonight when I get home and get the studs in place.

I'm hoping that my master cyl and pushrod kit will be waiting for me at the doorstep when I get home.

Oh yeah - my sketch is wrong, the threads are M8 X 1.25mm (not M6 X 1.25)...

ShelGame

01-25-2006, 09:13 AM

OK, here's the nearly finished pics. The adaptor plate is done, it fits nicely. The studs I found (at the local Ace hardware) aren't exactly what I wanted. They're to long to bottom out on the adapter plate. So, I locktite'd them in place.

The Mopar Perf manual pushrod fits the Daytona brake pedal pivot perfectly, but it's way too long (~7"). So, I ran a die the rest of the way down the pedal end (it was only threaded about halfway) and cut 1-1/2" off of it. But, it's still ~1/2" too long. So, I have to figure out how to shorten the master cylinder end of the pushrod by that much. I'll add another update once I figure that out...

glhs399

01-25-2006, 10:06 PM

I'm doing this to m GLH Omni rally car right now. Thanks for the info. I'll post some pictures when I get it finished up.

D.Folsom

gasketmaster

01-26-2006, 02:29 AM

Looks nice Rob :thumb:

ShelGame

01-26-2006, 04:48 PM

Looks nice Rob :thumb:
Thanks. ( I assume you mean the adapter plate and not my engine bay :) )

I think for the pushrod, I'm going to take 1/2" off, then put it in the lathe here at work to try and re-make the spherical end. And also add a groove for an o-ring to keep the pushrod in the MC. Originally, the MP pushrod/MC kit came with a rubber ring that fits into the wide, deep groove on the pusrod (the groove can be seen in the pics above), that's meant to keep the pushrod from pulling out of the MC and causing, well a very bad situation. I think a simple o-ring will work just as well, though. And much easier to cut into the pushrod. More pics to come.

Turbodave

01-30-2006, 10:51 PM

Good info, I moved this thread into the new fabrication section.

ShelGame

01-31-2006, 11:19 PM

OK, so I finished the pushrod and assembled the adaptor plate, master cylinder and pushrod to the car.

I ended up cutting ~3/4" off the pusrod to get to 4-3/4" overall length. But then I adjusted it back up to ~5" overall. Which is fine, there's about 1" of adjustment available in the pushrod. I had to re-make the spherical end on the belt sander. I put the o-ring in the MC piston to help keep the pushrod in the bore. I don't think it's necessary actually, but it is a little bit of insurance.

The brake pedal seems to fall a little further back now (closer to the driver), but it's not uncomfortable at all.

Still need to plumb up the lines, and figure out what to do about a proportioning valve. I broke a couple of ends off in the stock valve getting it apart. Plus, I doubt it's the right ratio for manual brakes. I'll probably just get the Mopar prop valve or some other aftermarket adjustable valve.

I'll post a follow up on the brake pedal effort and stroke once I've driven the car. Which should be in the next month or so. Since the first race is April 7 in Indy...

Captain Chaos

02-04-2006, 01:12 PM

I just saw this post and have been wondering about this very thing because my booster is bad. The adapter is exactly like what MP sells for using late model M/C like these on my 66 Plymouth which had a 4 bolt M/C. Then all you do is buy the adjustable pushrod and your set. If you decide to make these I'd be interested in one.

ShelGame

02-04-2006, 03:05 PM

Just weighed the booster - 8lbs...

DodgeZ

02-04-2006, 04:37 PM

im so sorry i was so drunk last night i didnt even know i typed anything
:lol: :lol:

I've done that once...... ok maybe more....

Bardo

02-06-2006, 06:48 PM

:lol: :lol:

I've done that once...... ok maybe more....
good im not the only idiot then:D

finallall

03-08-2006, 02:59 AM

Just wondering why you guys don't use the manual brakes off the old Omnis? They would be a direct bolt on. I'm about to put on a manual setup on my Omni and I have rear disks too. Was wondering which prop valve to use? The one from the 4 disk setup or the one that came with the manual brakes?

Thanks.

ShelGame

03-08-2006, 09:37 AM

What year Omni's came with manual brakes? If you have pictures or part numbers for all of the parts, please post them.

It was simply easier for me to get the parts I did and modify as needed.

finallall

03-08-2006, 01:13 PM

What year Omni's came with manual brakes?

85 and prior years had them. By the way if you're converting to a manual brake system you must use a manual brake pedal! Otherwise it will require much more force to press the non-manual brake pedal. This was told to me by a Mopar Guru who did several of these conversions. As for pictures, I can make some and post them latrer.

GLHS60

03-08-2006, 03:42 PM

Interesting thing about the factory L body manual brakes is the firewall plate can be mounted in one of two ways. One way the rod mounts to the power brake pedal but requires more pressure. Great brakes but much harder to press. The other way requires the manual pedal as the rod attaches at a different point and requires less pressure. Perhaps not as good pedal feel but easier to press. Either way reacts much faster than with a booster.

Thanks

85 and prior years had them. By the way if you're converting to a manual brake system you must use a manual brake pedal! Otherwise it will require much more force to press the non-manual brake pedal. This was told to me by a Mopar Guru who did several of these conversions. As for pictures, I can make some and post them latrer.

ShelGame

07-17-2006, 09:18 AM

OK, here's some more lessons learned from this swap.

1. Manual brakes with the power brake pedal suck. Way too hard of a pedal. Eve nwith the samller master cylinder (21mm). I can't actually stall my convertor. The car starts to creep at about 2500rpm (my convertor is supposed to be a 3500rpm stall). So, launching in my race car is not optimal at this point. I brake torque it to 2200rpm and floor it when the lights come down. But, my R/T is not consistent this way.

2. The cross linked braking system that came stock on the '89 Daytona is not fun to bleed. It's impossible to tell where the air is in the system. When the pedal feels soft, you just have to bleed every single wheel.

So, I'm going to modify a brake pedal to move the M/C pickup point about 1/2" higher up on the pedal. Also, I'm going to switch to an older style full front/rear proportioning valve. Hopefully, I can brake torque the car that way...

Anonymous_User

07-17-2006, 06:19 PM

Hey, I don't know if any of this will help or not:

My street/strip car is a '69 Ford. I have 4-wheel disc brakes on it - front are Ford, rear are Chevy. I use a stock master cylinder out of a '87 Shelby Z bolted directly to the firewall and custom made a rod to attach to the brake pedal. I had to experiment with the proper fulcrum point on the brake pedal to get the right feel and proper braking. This has been working great.

Oh, and I also do not run any prop valve. Straight from the m/c to the rear brakes. From the m/c to a line lock solenoid, to the front brakes. Basically I have 100% braking front and rear. I never have any issues with too much front brake. Even with the 3.5" wide front tires.

I guess the point is that the stock m/c works good in a manual brake car when you figure out the proper leverage for the brake pedal.

ShelGame

07-17-2006, 10:14 PM

I guess the point is that the stock m/c works good in a manual brake car when you figure out the proper leverage for the brake pedal.

That's my biggest problem. I thought I'd be OK just using the samller of the available TD master cylinders (21mm), but it's still not enough. I need to move the brake rod higher up on the pedal...

glhs875

07-18-2006, 07:57 AM

glhs875

07-18-2006, 08:06 AM

That's my biggest problem. I thought I'd be OK just using the samller of the available TD master cylinders (21mm), but it's still not enough. I need to move the brake rod higher up on the pedal...

Moving that rod up makes a big improvement. I moved mine up about 1 inch on the 88 Daytona auto trans power brake pedal that I put in my Charger. Brakes are way better with less effort then when it was in the stock position. I used an Omni manual brake master cylinder on my conversion. The brakes stop as good as when they were power if not a little better. Iam still going to upgrade the front with a Kelsey Hayes 88 Daytona setup, but with the bigger Caravan calipers.

capev86

07-20-2006, 01:15 PM

manual steering?...maybe on race only

manual brakes?....no way on a performance car with 4 wheel disc!!!

Clay

07-20-2006, 03:02 PM

manual brakes?....no way on a performance car with 4 wheel disc!!!

whats wrong with a performance car with 4 wheel discs and manual brakes?

all power brakes do is assist.

I bet you would be suprised how many performance cars have manual brakes.

Una

07-20-2006, 10:45 PM

Here's the sketch Terry...

I've got a 1/2" ally plate in my garage. I'm going to make a prototype with the drill press. I'm just not sure how I'm going to cut the 1-1/2" hole, though.
They make 1.5" holesaws.. Should be able to cut through aluminum just fine, I cut through sheet metal with them at work over and over. Take it slow, and use tapping/cutting fluid. :)

ShelGame

07-21-2006, 07:52 AM

I have a 1-1/2" hole saw, but I didn't think it would go through 1/2" thick plate.

I put it in the drill press in our prototype shop, and chucked up a 1-1/2" drill they had. That bored through it just fine...

ShelGame

07-21-2006, 07:54 AM

manual steering?...maybe on race only

manual brakes?....no way on a performance car with 4 wheel disc!!!

It's a drag-only car.

1. Manual brakes release faster than power brakes. Makes for more consistent launches. Consistency is everything in bracket racing.

2. The booster weighs ~12lbs.

3. No booster = less chance for a vac/boost leak.