I have an 84 Camaro that has a disc brake rear end from an 89 Trans Am GTA. I am using the master cylinder from an 85 IROC that had 4 wheel disc brakes. Ever since I did the swap, the brakes have just sucked. There are new pads and rotors up front that I just put on, and it actually seemed to stop a lot better for a few days, then it went back to crap. The rear has new calipers, pads, and rotors. Now I know the 89 rear disc brakes have much larger rotors than 85 rear brakes. Could it be that my 85 master is not providing enough line pressure to power those 89 brakes? Or are the calipers the same anyways? I think it's the rear brakes because the car stopped a hell of a lot better with the stock rear drums. Any help would be greatly appreciated. Thanks in advance.

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1984 Camaro Sport Coupe - Rebuilt 355 S/D TPI L98, Crane 2032 CompuCam, Crane adjustable fuel pressure regulator, MSD Blaster coil, custom burned PROM, stock TPI intake, Accel 24# injectors, gutted air box with K&N filters
F41 Suspension Package, 700R4 Tranny, TCI Breakaway torque converter, 3.27 Posi Rear
Hooker Shorty Headers, Catco High-Flow 3" Cat, Flowmaster 3" American Thunder Cat-Back

Best 1/4 Mile Run:
13.847 @ 95.91 MPH

1992 1LE B4C Police Camaro RS - 305 TPI 5-Speed

 

did you change the porpotioning valve to match the disk rear? if not i'd guess that maybe your problem. as far as i know i'd think the master cylinders are the same.

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ICON Motorsports
1st & 3rd
MM Black Diamond 538 F&AM

 

just got to the parts store and get the correct master, also you MUST use the 4WD proportioning valve and i think the 4WD system used a smaller more powerfull brake booster also you must have a disk parking brake cable installed (thats how they keep the calipers set) its alot of stuff to do, but it all has to be done,...

 

I have the 85 proportioning valve and the 85 master. So do 85 and 89 brakes use different proportioning valves? Thanks for the replies.

 

It has been awhile, but here goes. The master cylinder is the same between drum cars,and 89 and up rear disc. The old style disc ran a diffrent master. The p vavle is the same between the old disc brakes and teh new,from 86 on up I know for sure can't say if they where the same before that. The p vavle did change in 89 or 90. If you are going to buy a new one pick up the one for the first design. I went from drums to a 9 bolt rear with the old style calipers, and which time I changed just the p vavle, i did not change the master evne though they where diffrent, But I wanted to go with the new brakes anyway so i just left it alone. The old style worked good when they where adjusted. I now have the 89 up ones on myu car and they work good.

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86Z28, GM 350, Jet perf Q-jet & chip Dual snorkel air cleaner, Edelbrock performer intake, Edelbrock headers, Edelbrock cat-back, Off road pipe, MSD 6AL, Accel Super Coil, Taylor Spiro-pro wires, Rapid fire plugs, Jet fan switch, World class t-5, Hurst Short Throw Shifter, Ram Flywheel, Center force dual friction clutch,Aluminum drive shaft, BW disc rear 3.45's & a posi, PBR calipers, Earls braided brake lines, Polygrapite bushings all the way around, poly tranny mount & torque arm mount, Hotchkis lower control arms & panhard rod, Rancho limiter straps, KYB struts & shocks, Gm Wonderbar, Edelbrock strut tower brace, SSM sub frame connectors, Jamex lowering springs, Carbon metallic brake pads, Crossed drilled rotors, Mobil 1 Tranny fluid & motor oil, GM syntheic rear end oil, K&N, Grant stering wheel, 1,200 watt system, Jet Black Paint, 91 Z28 rims, 92 wing, Tinted windows.

 

the year doenst really mean anything, as long as you have a 4WD master and p-valve, also the parking brake will need to be coverter to the rear disk for them to work right.

 

the year does matter the master cyl, is diffrent between the old style and the new style disc brakes, the drum cars and the new style disc brakes use the same one. And yes you alos will need diffrent e- brake cables.

 

The 85 master is one for the older smaller disc brakes, not drum brakes. So do I need the 89 master? Yeah, I know I need new e-brake cables, I'm driving around without an e-brake right now. Thanks.

 

Forget all the other ancillary stuff, the question should be whether you bench bled the MC correctly.

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