manual brakes for 85.5 n/a car

so ive just got my ecotec swapped 944 driving under its own power and ive realized in a short time that my braking setup is not going to cut it. just driving it around the parking lot at my shop it just doesnt have anywhere near enough braking power. granted the rotors are rusty from sitting for over a year, but i just dont get a confident feeling.

so here is my braking setup
-1985.5 n/a car, stock calipers
-wilwood 1" bore tandem master cylinder, 260-7563
-adjustable proportioning valve
-pushrod moved 3/4" up the pedal

the brake pedal is rock solid, and i dont have much pedal travel. i chose that master cylinder because thats what it said in the old ls swap faq i read.

so i know the first thing everyone will say is go hydroboost, and trust me, id love to


for one there isnt room for the booster, and there is no way for me to run a power steering pump. the only place for it is either driven off back of the intake cam, or the bottom drivers side, but there is a steering rack in the way. so im stuck with manual brakes.

i thought about going back to the stock master cylinder, however ive read that its not a great option for manual brakes. i know a smaller bore master cylinder should help, im just unsure what a better option is.

i do have some plans for future brake upgrades, i have started collecting parts (ls430 fronts, 12.19" rotors, rx7 rears), and i have tossed around doing a floor mounted wilwood pedal box, the room id save from removing the master cylinder from the firewall would allow me to build a nice intake manifold. however i wasnt really planning on doing any of that till next winter, id like to drive and enjoy the car this summer before i pile into another round of mods.

so what do you guys think? smaller master cylinder? should i just dive in and get the caliper/rotor upgrades done? will that 1" bore master ive got be a decent match for those calipers?

I had that exact set up. Wilwood 1" master, front ls430 calipers and rear rx7 calipers. And no, that 1" master is just scary and will not work. Your best bet would probably be the floor mounted pedal setup. You could probably get creative with an electric hydraulic pump too.

the pedal box idea is something down the road i may do. its not something i really want to do at this time, just an idea i thought of (one day i want to put down 650whp, but thats year away). and the electric booster setups seem to add considerable size to the master cylinder, i dont know if i have enough room for it.

was hoping to find a tandem master cylinder that will work well for a manual brake setup.

I have a DMC, running 3/4 front, 13/16 rear MCs.  You might be able to get away with 3/4 on both ends with a proportioning valve.  Also, don't overlook brake pads, go for something with some bite.

How much room is between the bottom of the wilwood tandem m/c and your intake manifold?

http://www.ebay.com/itm/BUICK-GRAND-NATIONAL-POWERMASTER-POWER-MASTER-CYLINDER-BRAKE-UNIT-OEM-PARTS-/262303236406

http://www.geocities.ws/diels12000/Booster/PowermasterSetup.JPG

Maybe you could fit one of these in there and mount the pump somewhere else.

Lemming wrote:I have a DMC, running 5/8 front, 3/4 rear MCs.  You might be able to get away with 3/4 on both ends with a proportioning valve.

what brakes are you running?

spence wrote:How much room is between the bottom of the wilwood tandem m/c and your intake manifold?

very little. the lines actually come straight down beside the manifold, but everything is real close.

i has doing some digging trying to find a smaller bore tandem master cylinder. the smallest i can find in the aftermarket is the wilwood 7/8". i stumbled across some datsun/nissan stuff, and they are the identical design to the 1" wilwood that i have. from what ive read that master cylinder was actually designed as a bolt on for 260z and 280z cars with aftermarket brakes as their 7/8 and 15/16 (depending on year) master cylinders were too small. not sure on the truth of that, however its a bolt on for the z cars, and the 510 guys use z car masters for their upgrades as they are bolt ons for their smaller 3/4 bore.

so i might give the 3/4 bore 510 master a shot. rock auto has them for a whopping $38 canadian, and its a bolt on.

spence wrote:http://www.ebay.com/itm/BUICK-GRAND-NATIONAL-POWERMASTER-POWER-MASTER-CYLINDER-BRAKE-UNIT-OEM-PARTS-/262303236406

http://www.geocities.ws/diels12000/Booster/PowermasterSetup.JPG

Maybe you could fit one of these in there and mount the pump somewhere else.

hadnt really though much about those. i may be able to do something with that setup, however i seem to remember all the grand national guys remove them and go back to vacuum booster because the electric assist unit is terrible.

I don’t have much info on the single piston N/A calipers but most Porsche calipers have similar total piston area and 23mm/19mm master cylinder bores.  Non power assisted brake systems run smaller MC bores and larger diameter brake lines than power assisted. Yes, 1” MC is going the wrong direction, 3/4 would be better.

Edit: This assumes original master cylinder bores are 23mm/19mm.

yes the factory master is 19mm/23mm

This electric booster looks even slimmer

http://www.ebay.com/itm/10-LEXUS-RX450H-BRAKE-MASTER-CYL-579943-/390835254376?fits=Make%3ALexus|Model%3ARX450h&hash=item5aff98b468:g:M1wAAOxyx0JTjmSY&vxp=mtr

http://www.ebay.com/itm/LEFT-ELECTRIC-BRAKE-BOOSTER-w-MASTER-CYLINDER-138110-10510-A18944-/252103839525?fits=Make%3ALexus|Model%3ARX450h&hash=item3ab28f4f25:g:9pMAAOSwiLdWBaKf&vxp=mtr

thats interesting. im going to have a better look into how that works. looks like it has one outlet going from the master through the booster and one just leaves the master. im a little unsure how that works. or does is it even a true booster?

hmmm

Honestly, I'm not sure... I think I have an idea on how it works but I'm just a dumb millwright

Looks like when you step on the pedal fluid flows into the pump and gets pressurized and then pressurizes the whole master. The other line in the pump must be for the front brakes? It's probably all controlled by a computer, so you'd have to figure all that out too. I'm not sure if it would work by a simple on/off relay.

There's a couple engineers on here and I bet they can explain it better.

My brakes are Wildwood Integra 6r fronts and 968/951 rear.

just a little update, ive got a datsun 510 master cylinder on order. should have had it by now, huge storm up here kinda screwed everything up. looking like i wont have it till tuesday

ended up getting the master today, got it installed. i think i still have air in the system, at least im hoping. after fighting with the pushrod, assembling everything and bleeding it the first time i found the fittings on the bottom of the new master werent tight enough and leaking. i had to pull it all back apart to be able to tighten them. got it back together, went around and bled the whole thing twice and the pedal still didnt feel that great, but at that point i ended up having to get the car moved off the hoist for tomorrow so i put it back together.

the car does stop, and it is a hell of a lot better than it was, but the pedal feels like crap. im going to try bleeding it again, might see if i can get my hands on a pressure bleeder.

Thats too bad the 510 master didnt help. I think any manual tandem m/c is gonna feel like crap though.

Here's some more idea's that I had saved on my PC when I was thinking of ways to ditch my manual master. This one would give you a ton of room for your custom intake your planning on building.

ive seen that setup before, didnt really think much about it, starting to consider it now. really want to get the brakes better with the manual setup, there is no reason i shouldnt be able to make a manual brake setup with a tandem master to work correctly.

right now i think its just still got air in the system. i had this sort of pedal feel when i first bled it with the wilwood 1" master, after more bleeding it got better. i was hoping to get it bled some more tonight but i wrecked my back working today.

I forgot to attach this one too... Manual master cylinder with brake servos from a MGB

There's also a dual brake servo available --------> http://www.vwjim.co.uk/ourshop/prod_2110864-Brake-Servo.html

thats another interesting way to do it.

i think if i had to i could fit a hydroboost setup in the car. did some more looking today, and after looking at some pics of the hydroboost unit i think i could fit it around the motor. the problem would be the power steering pump, my options are a solstice setup (which is rare as only some of the n/a solstice/sky had a hydraulic power steering pump) or run the cavalier style pump off the intake cam, however id have to notch the firewall out to fit it. that would also drasticly change the future plans of my custom intake manifold design.

good news is a borrowed a friends motive power bleeder and i think i have all the air out now. brakes feel a lot better now. only moved the car back and forth in the shop, but the initial bite feels pretty good now. hopefully it feels good on the road.

the saga continues.....

had to move the car out of the shop today so i took it for a spin around the parking lot, brakes still dont stop the car. there seems to be a lot of pedal travel before anything happens. i do have some firewall flex to contend with, but its not that bad. had a look at the calipers, thought they might be retracting causing the long pedal stroke, but all looks good. it is making 1300 psi at the front calipers, but thats hard as you can push and the pedal is almost to the floor.

unsure what my next move is. starting to wonder if i went too far the other way with the master cylinder bore size and i dont have enough fluid volume now. if its going to mean another master cylinder i may just do my brake upgrade now and match the master cylinder with those calipers.

At this point I usually toss out the link to Jake Latham's brake calculator.

Getting all of the numbers might take a bit of work, but if you can get into the ballpark, his calculator should be able to provide some useful feedback for designing your new setup. You could also start out by inputting all the information on your present setup, and seeing if the values it returns fit what you're seeing.

http://www.jakelatham.com/radical/info/brake_calculators.shtml

Note: Jake's link to the Longacre website instructions for finding a car's CG height is broken. Here is an an online calculator that can tell you how to get the information:

https://robrobinette.com/cg_height_calc.htm

ive been playing with that calculator for a while now. i question the line pressure calculation it gives, for my setup it shows around 580psi and on my gauge it shows 1300. a disc brake systems needs 900-1200psi to work effectively. aside from that it seems to work ok.

If you do the brake upgrade now, the stock mustang master cylinder size feels great with the lexus / rx7 calipers. I think it's bore is 1 1/16" to give you an idea

If you've got 1300 psi at the calipers, you should be going through the windshield regardless of where the pedal is. Are you sure you have good pads/rotors?
Also, 85.5 na brakes weren't that great compared with what you might be use to today.