What Did You Do To Your G-Body Today? [2023]

[Supercharged111]

Did a job I've been dreading, swapped the stock style distribution valve to a disc/disc unit. I found an aluminum one that seemed stronger than the brass ones I've had prior issues with. I followed the video that Texas82GP linked in my build thread for proper seating of the lines. Seemed to have worked mint!
However, I think the right rear caliper is bad maybe. Once I changed the crush washers (yep I forgot to install new ones at first) I tightened the banjo bolt to what seems a proper torque. Can't get a socket on it due to interference with shock, but that bolt is tiiiiight and its leaking like a sieve!!!! I called it a night and plan to look again at some point today. Might pull the caliper and try to torque it. Weird cause the other side is dry and did the same procedure.View attachment 214267View attachment 214268

What are the consequences of running a disc/drum prop valve on a disc/disc setup? Will you experience issues bleeding the brakes?

 

[Injectedcutty]

What are the consequences of running a disc/drum prop valve on a disc/disc setup? Will you experience issues bleeding the brakes?

The pressure for the drum vs the disc caliper is different. You can get away with a stock valve, but have to add a residual pressure valve inline to the rear to offset the difference. Typically easy with steel lines, but with stainless lines that are impossible to reflare, especially under the car I wasn't gonna take that chance!

 

[Supercharged111]

The pressure for the drum vs the disc caliper is different. You can get away with a stock valve, but have to add a residual pressure valve inline to the rear to offset the difference. Typically easy with steel lines, but with stainless lines that are impossible to reflare, especially under the car I wasn't gonna take that chance!

This is along the lines of what I was thinking and if that's the extent of it, I can live with that until the car is ready for more serious use.

 

[oldsmobile joe]

You can get away with a stock valve, but have to add a residual pressure valve inline to the rear to offset the difference.

what are you talking about? who says? why would you need to add RPVs to a system that didn't have them and wasn't designed for them. the factory never did this on this era of disc brakes. And none of the third gen f bodies did this with 4wheel disc.
and what are the RPVs offsetting? the difference in what?
i have researched this WIVES TALE before. none of the factory service manuals show an RSV for our cars, it is not incorporated in the proportioning valve.

residual pressure valves are used for two reasons:
first is to keep the excessive brake fluid from traveling back to the master cylinder. this causes the fluid to drain back and is caused when the master is level or below the height of the wheel cylinders. ie, my 57 olds has a factory mounted master cylinder mounted on the frame. our gbodies have their master mounted relatively high on the firewall in comparison.
second is to keep the wheel cylinder cups from leaking when there is no pressure on them. our gbody wheel cylinders have metal springs and cups inside to support the wheel cylinder cups.

What are the consequences of running a disc/drum prop valve on a disc/disc setup? Will you experience issues bleeding the brakes?

switching from a disc/drum proportioning valve to a disc/disc version unit should have benefits because it changes the proportion of brake fluid going to the rear disc brakes.

 

[Supercharged111]

what are you talking about? who says? why would you need to add RPVs to a system that didn't have them and wasn't designed for them. the factory never did this on this era of disc brakes. And none of the third gen f bodies did this with 4wheel disc.
and what are the RPVs offsetting? the difference in what?
i have researched this WIVES TALE before. none of the factory service manuals show an RSV for our cars, it is not incorporated in the proportioning valve.

residual pressure valves are used for two reasons:
first is to keep the excessive brake fluid from traveling back to the master cylinder. this causes the fluid to drain back and is caused when the master is level or below the height of the wheel cylinders. ie, my 57 olds has a factory mounted master cylinder mounted on the frame. our gbodies have their master mounted relatively high on the firewall in comparison.
second is to keep the wheel cylinder cups from leaking when there is no pressure on them. our gbody wheel cylinders have metal springs and cups inside to support the wheel cylinder cups.



switching from a disc/drum proportioning valve to a disc/disc version unit should have benefits because it changes the proportion of brake fluid going to the rear disc brakes.

I believe in the trucks that the residual pressure valves reside in the master cylinder itself but don't quote me and they are different disc to drum. I understand that the drums and discs have different requirements for fluid volume and pressure, but in another thread the poster mentioned needing to swap brake lines around on the prop valve to be able to bleed properly. I became unsure if the cars separated front from rear or if they tied the corners together instead which, from what I understand, is something the fwd cars do. Just wanted to make sure there wasn't more to it that I was missing as the motive power bleeder wasn't able to bleed my fronts and I also had no luck with a gravity bleed. I must have something else going on with mine.

 

[Built6spdMCSS]

What are the consequences of running a disc/drum prop valve on a disc/disc setup? Will you experience issues bleeding the brakes?

Rears won't work correctly but at ~25% of the braking forces in the setup, probably wouldn't even notice unless on track or something where you can test it.

I installed a brass Disc/Disc Valve when I put my C5Z06 Front Brakes on so I couldn't say from experience but I had the Disc/Drum Valve on my SS with 2wd Blazer Front Disc and LT1 Fbody Rear Disc Brakes for a solid 8 years..

 

[Texas82GP]

Did a job I've been dreading, swapped the stock style distribution valve to a disc/disc unit. I found an aluminum one that seemed stronger than the brass ones I've had prior issues with. I followed the video that Texas82GP linked in my build thread for proper seating of the lines. Seemed to have worked mint!
However, I think the right rear caliper is bad maybe. Once I changed the crush washers (yep I forgot to install new ones at first) I tightened the banjo bolt to what seems a proper torque. Can't get a socket on it due to interference with shock, but that bolt is tiiiiight and its leaking like a sieve!!!! I called it a night and plan to look again at some point today. Might pull the caliper and try to torque it. Weird cause the other side is dry and did the same procedure.View attachment 214267View attachment 214268

When I torqued the banjo bolts on the Blazer front calipers on the Grand Prix they seemed fantastically tight before the torque wrench clicked. I thought it was going to strip out or twist off for sure. If you're sure it's tight enough, you might check for a burr on the shoulder of the bolt, on either side of the brake hose or on the machined surface of the caliper.

 

[Injectedcutty]

When I torqued the banjo bolts on the Blazer front calipers on the Grand Prix they seemed fantastically tight before the torque wrench clicked. I thought it was going to strip out or twist off for sure. If you're sure it's tight enough, you might check for a burr on the shoulder of the bolt, on either side of the brake hose or on the machined surface of the caliper.

Jared, I actually just checked torque and it was fine. I'm a dummy, the bleeder valve (speed bleeder) is leaking the fluid down onto the banjo which made it look like the bolt doing it sheesh. I'm glad its not the bolt, but now trying to figure out why the bleeder is leaking is concerning considering they're correct for the application. Its always something.

 

[Texas82GP]

Jared, I actually just checked torque and it was fine. I'm a dummy, the bleeder valve (speed bleeder) is leaking the fluid down onto the banjo which made it look like the bolt doing it sheesh. I'm glad its not the bolt, but now trying to figure out why the bleeder is leaking is concerning considering they're correct for the application. Its always something.

Just keep swimming. You'll get there. The work looks great, as always.

 

[bruisedbanana79]

Started unboxing and drooling over all the new UMI parts! Here’s a little teaser of some parts. Goal is to get the rear done this week and start on the front end shortly after