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Old 12-16-2010, 10:30 AM
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drum to disc question

I bought this disc brake conversion kit thru Summit, made by Stainless Steel Brakes, Summit guy picked out this 'kit' made just for my '69 Cutlass . well , he was wrong, now I got the wrong (incomplete ) kit comming..... SSB guy said I need to replace the master cyl and add an ajustable pressure distibution (?) valve to the rear ..... Now....ressidual pressure......is that what is needed for the drum bakes ? , (to keep them from draining too far back ) ? I am convert ing from power drums to power disc in the front.... so my question therefore is ......... why can't I just remove the restriction fitting from the master cylinder the goes to the front brakes ( which will be discs ) ???????????????

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Old 12-16-2010, 01:56 PM
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You need to think about Reservoir & Piston size also. The Front Disc needs a larger Reservoir, The Power assist needs larger Piston Dia.
You could just get a Master Cyl. for a newer Cutlass say 72 for Power Disc/Drum brakes.

http://www.rockauto.com/catalog/moreinfo.php?pk=965507
http://www.rockauto.com/catalog/moreinfo.php?pk=309081
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Old 12-16-2010, 02:06 PM
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I realize the problem with the smaller reservor....would be pain in the butt, keeping it full.........probabley should put new MC on anyway, don't know how it's been on ........ thank you
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Old 12-16-2010, 02:14 PM
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You have to have the right Master cyl.. The disc and drum MC will have a bigger Reservoir for the disc brakes... You will have a MC with one small and one big Reservoir.. Just like SSedan64 said.. You shouldn't need residual valves on it.. You only have to use them if the MC is lower then the bottom of the car..
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Old 12-16-2010, 02:20 PM
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I'm sorry but I don't understand why this is so hard. These cars came with disc brakes from the factory. You can get exact replacement master cylinder, calipers, hoses, and rotors from any auto parts store. The 1969 cars used a metering valve that bolted below the master cylinder. These are reproduced and available from just about any GM repro parts house. The caliper brackets bolt to the spindles and are available repro, as are the hose to frame brackets. The disc spindles are also available repro, but with simple machining your drum spindles become disc spindles. Add some new hard line and that's all it takes. Also, these factory discs clear 14" wheels. This whole setup can be put together for about half of the SSBC kit cost.
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Old 12-16-2010, 05:25 PM
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well, I thought it would be simple also, thought it would be simplier yet just to by a kit and be done, but, then if I knew before, what you just said,it'd be differnt. How am I to know this til I ask ?...anyway.......thanks
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Old 12-16-2010, 06:41 PM
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I didn't know either until I did lots of digging.
The 65-72 A-Bodies (Skylark, Cutlass, Chevelle, LeMans and 1970-72 Monte Carlo & Grand Prix) share the same basic Brakes.

Here's a few more tidbits:
http://www.buickperformance.com/discbrak.htm

Hotrodders Knowledge Cluster: Disc Brake Conversions
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Old 12-17-2010, 09:01 AM
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Quote:
Originally Posted by SSedan64
I didn't know either until I did lots of digging.
The 65-72 A-Bodies (Skylark, Cutlass, Chevelle, LeMans and 1970-72 Monte Carlo & Grand Prix) share the same basic Brakes.
Actually, 64-72 A-body, 67-69 F-body, and 68-74 X-body all share the same spindles and brakes.
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Old 12-17-2010, 09:10 AM
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disc bks

as far as i'm concerned school is still out on this.. i have disc/drum and the m/c is at frame level and below the bks. i don't have anything in line and have NO problems with bleed back....
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Old 12-17-2010, 10:00 AM
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the '69 manual says; ''the F85 or A body series use 14''wheels and the disc is 1'' thick and 11.3'' dia. All other series use 15'' wheels with a disc that is 1-1/4 '' thick and 11 -7/8 dia. on B-C body and 11'' dia on E body. ...A body caliper mounts with 2 special allen head bolts, other series use two special hex head bolts....''..........so.............maybe they are not ALL the same ?
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Old 12-17-2010, 10:50 AM
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Quote:
Originally Posted by delawarebill
as far as i'm concerned school is still out on this.. i have disc/drum and the m/c is at frame level and below the bks. i don't have anything in line and have NO problems with bleed back....

A lot of people run without them..And get away with it.. It doesn't make it right.. This isn't a paint job or your interior, It's his brakes..You can smoke dope all your life, And never get caught, But it don't make it right, does it....They make residual valves for a reason.. And it isn't just to make money.. When it comes to your brakes.. I will post what's ''NEEDED'' to make it right.. You may not have any trouble, But I wouldn't want to be the one telling someone not to use them, And maybe get someone killed Not doing it the right way..Good day Sir..
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Old 12-17-2010, 01:33 PM
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Quote:
Originally Posted by knighthawk
the '69 manual says; ''the F85 or A body series use 14''wheels and the disc is 1'' thick and 11.3'' dia. All other series use 15'' wheels with a disc that is 1-1/4 '' thick and 11 -7/8 dia. on B-C body and 11'' dia on E body. ...A body caliper mounts with 2 special allen head bolts, other series use two special hex head bolts....''..........so.............maybe they are not ALL the same ?
Not sure where you're reading this, but here is the stock A-body rotor:



The rotors on the full size cars are thicker, as you note, so the calipers are correspondingly different. The brakes on the FWD Toronado are also completely different.
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Old 12-18-2010, 03:44 AM
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Quote:
Originally Posted by joe_padavano
Actually, 64-72 A-body, 67-69 F-body, and 68-74 X-body all share the same spindles and brakes.
I always forget the F & X Bodies.
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Old 12-18-2010, 07:03 AM
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brakes

I didn't say he should NOT do it.. I said this is what "I" do..
i've heard both sides for yrs, I do know what is working on my cars. if i felt the need for the valve i'd put one in. I know a fella running rear bks only.. not a chance i'd do that, but if i flet my brks were an issue i'd be changing something...
but your point is well taken... information is good..

Quote:
Originally Posted by NEW INTERIORS
A lot of people run without them..And get away with it.. It doesn't make it right.. This isn't a paint job or your interior, It's his brakes..You can smoke dope all your life, And never get caught, But it don't make it right, does it....They make residual valves for a reason.. And it isn't just to make money.. When it comes to your brakes.. I will post what's ''NEEDED'' to make it right.. You may not have any trouble, But I wouldn't want to be the one telling someone not to use them, And maybe get someone killed Not doing it the right way..Good day Sir..
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Old 12-18-2010, 10:50 AM
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Quote:
Originally Posted by delawarebill
I didn't say he should NOT do it.. I said this is what "I" do..
i've heard both sides for yrs, I do know what is working on my cars. if i felt the need for the valve i'd put one in. I know a fella running rear bks only.. not a chance i'd do that, but if i flet my brks were an issue i'd be changing something...
but your point is well taken... information is good..

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