Hi All,

This may have already been answered, and I apologize for re-posting if it has...

I have a 1971 Chevelle with stock drum brakes (not power). I was looking to convert it to disc brakes (front first), but have heard that the booster is unnecessary, almost overkill. Is there any validity to this statement?

I was also wondering if I could use the stock master cylinder to complete this task? Is there anything I'll need to watch out for?

As far as which kit to buy, I was looking at the following (http://www.performanceonline.com/1964-72-CHEVY-PONTIAC-BUICK-OLDSMOBILE-GM-A-BODY-CAR-FRONT-STOCK-SPINDLE-DISC-BRAKE-CONVERSION-KIT-19110/). Any thoughts on the quality of this kit? Any other recommendations?

Thanks,
Jay

Good question. I'd like to know as well. If I set mine up with disks I'll still change the master cylinder to a dual chamber unit because mine has the old round one that goes to all 4 wheels. I see this is your first post. Welcome Jay!

Itis best to update the master cylinder to get one with the larger fluid volume required by the disk brakes. If I recall, the 1973 non-power cylinder has been used by some. You might try a search in the two forums here for the specifics. The brakes will be a bit stiff compared to a power system, but they will still be pretty good. I bought a new car in the mid 70's with non-power disk brakes and it was fine.

We have an old '87 S10 truck with standard disc brakes. Feels about the same as standard drum brakes for pressure that you have to exert. I really don't even notice it when driving along and stopping. I've never seen the need to switch.

I updated my 66 from single pot manual master four wheel drum to dual master front disc.

I used a front disc conversion from Ground Up, without the booster. Apparently the same master cylinder as would come with a booster. It fit perfectly, and works fine. It included a prop valve, bracket, etc. I bought all new lines and hoses. They all fit fine. It did take some line shortening and reflaring to fit the prop valve without the booster, but that was minor and easy. It drives and stops fine to me, although a bit more pedal pressure is needed vice, say, my 08 Pony.

Highly recommended.

I updated my 66 from single pot manual master four wheel drum to dual master front disc.

I used a front disc conversion from Ground Up, without the booster. Apparently the same master cylinder. It fit perfectly, and works fine. It included a prop valve, bracket, etc. I bought all new lines and hoses. They all fit fine. It did take some line shortening and reflaring to fit the prop valve without the booster, but that was minor and easy. It drives and stops fine to me, although a bit more pedal pressure is needed vice, say, my 08 Pony.

Highly recommended.

What kit did you use from Ground Up? I can't seem to find one without the booster.

Thanks,
Jay

Good info!:thumbsup:

I have a 1971 Chevelle with stock drum brakes (not power). I was looking to convert it to disc brakes (front first), but have heard that the booster is unnecessary, almost overkill. Is there any validity to this statement?

I was also wondering if I could use the stock master cylinder to complete this task? Is there anything I'll need to watch out for?

The OEM m/c bore for drum/drum is 1" and for disc/drum it is 1-1/8". Keeping your m/c for disc/drum means that you're «reducing» the m/c bore which means less pedal force required at the expense of longer pedal travel. So the pedal will probably feel «softer» than it does now (hence the «booster unnecessary» statement), but the brakes will feel less responsive (because of the longer travel). The longer travel might be a problem if you reach the end of the m/c stroke before the brakes are fully applied (although, I don't think it is a problem with Chevelle drum/drum m/c).

You will also have to make sure there is no residual pressure valve in your m/c port for disc. You can check with a small wire and look for a rubber check valve in the port. more info in this post (http://www.chevelles.com/forums/showthread.php?t=349339).

Although you might enjoy your brakes without them, OEM disc/drum set-up always had a metering valve (http://www.inlinetube.com/Prop%20Valves/PR-105.htm) on the front brake line. In 1970, they added a proportioning valve (http://www.inlinetube.com/Prop%20Valves/PR104d.htm) on the rear brake line. Since 1971, both of these valves were incorporated in the combination valve (http://www.inlinetube.com/Prop%20Valves/VCH106.htm), replacing the distribution block (http://www.inlinetube.com/Prop%20Valves/PR-107.htm).

have a '77 pickup truck with front disc/rear drum brakes with no power booster. works well. think your proportioning valve may be different than the one that came on your car but not sure.

The OEM m/c bore for drum/drum is 1" and for disc/drum it is 1-1/8". Keeping your m/c for disc/drum means that you're «reducing» the m/c bore which means less pedal force required at the expense of longer pedal travel. So the pedal will probably feel «softer» than it does now (hence the «booster unnecessary» statement), but the brakes will feel less responsive (because of the longer travel). The longer travel might be a problem if you reach the end of the m/c stroke before the brakes are fully applied (although, I don't think it is a problem with Chevelle drum/drum m/c).

You will also have to make sure there is no residual pressure valve in your m/c port for disc. You can check with a small wire and look for a rubber check valve in the port. more info in this post (http://www.chevelles.com/forums/showthread.php?t=349339).

Although you might enjoy your brakes without them, OEM disc/drum set-up always had a metering valve (http://www.inlinetube.com/Prop%20Valves/PR-105.htm) on the front brake line. In 1970, they added a proportioning valve (http://www.inlinetube.com/Prop%20Valves/PR104d.htm) on the rear brake line. Since 1971, both of these valves were incorporated in the combination valve (http://www.inlinetube.com/Prop%20Valves/VCH106.htm), replacing the distribution block (http://www.inlinetube.com/Prop%20Valves/PR-107.htm).

Denny,

Thank you for the detailed response. That's what I was looking for!

Thanks,
Jay

I called Ground Up and discussed the kits with them. The sales guy quickly said he could provide the kit w/o the booster. The rest was the same. I was impressed at how well it all fit and worked.

I ordered a set of prebent brakelines for the conversion to disc. W/o the booster the prop valve is closer to the firewall, so the lines to it needed adjusting.

My car has too much cam in a no compression motor, with 12 in vacuum, so I did not want power brakes. Also don't have power steering, and I like it that way. To me, it drives just fine.

I called Ground Up and discussed the kits with them. The sales guy quickly said he could provide the kit w/o the booster. The rest was the same. I was impressed at how well it all fit and worked.

I ordered a set of prebent brakelines for the conversion to disc. W/o the booster the prop valve is closer to the firewall, so the lines to it needed adjusting.

My car has too much cam in a no compression motor, with 12 in vacuum, so I did not want power brakes. Also don't have power steering, and I like it that way. To me, it drives just fine.

Thanks Ron. I'll give them a shout!

Thanks,
Jay