73stroked duster
Well-Known Member
Looking to improve braking power on my 73 duster. Will changing the stock single piston caliper to a wilwood 4 piston caliper setup help?
Upgrade front brakes
- Thread starter 73stroked duster
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72Dart6pack
Harder Better Faster Stronger.
Nope.
goldduster318
Overzealous Car Modifier
It would be good to know a couple of things:
Do you have a power booster?
What size master cylinder?
What brake pads?
What size wheels do you run?
How much performance do you want?
Typically #1 is to get some higher friction coefficient pads
#2 is to increase brake pressure by either going down a size on master cylinder or adding a booster if you don't have one
#3 would be to upsize the rotors and possibly change calipers.
Do you have a power booster?
What size master cylinder?
What brake pads?
What size wheels do you run?
How much performance do you want?
Typically #1 is to get some higher friction coefficient pads
#2 is to increase brake pressure by either going down a size on master cylinder or adding a booster if you don't have one
#3 would be to upsize the rotors and possibly change calipers.
I agree. Only thing I'd add would be to insure the system is working well. Check that the pistons and calipers move smoothly, fluid isn't too old, and the drums are also adjusted and working well. If the fluid comes out the bleed all brownish, then bleed all four corners good.
As far as pads (and shoes) go. If they were produced by a participating member of the friction manufacturer's association, there will be a lining code on the pad. You can use the last two letters as a rough guide to effectiveness of the material. (or they will be positioned as shown in the link for the newest revision of the edge lining code).
Of the big companies, Centric did not particpate, but you can e-mail them. Smaller specialty companies generally don't mark them either.
As far as pads (and shoes) go. If they were produced by a participating member of the friction manufacturer's association, there will be a lining code on the pad. You can use the last two letters as a rough guide to effectiveness of the material. (or they will be positioned as shown in the link for the newest revision of the edge lining code).
Of the big companies, Centric did not particpate, but you can e-mail them. Smaller specialty companies generally don't mark them either.
73stroked duster
Well-Known Member
Have disk up front drums in back no power buster. Just installed new master cylinder with a 1.031 bore. Have a 360 stroked motor. Car does stop but ok with a Good amount of pedal pressure.
goldduster318
Overzealous Car Modifier
going down to a 15/16" bore would reduce the pedal pressure needed for a stop but increase the travel on the brake pedal.
Depending on your vacuum a standard booster won't work well.
In my case, I have a hydratech hydroboost (and a matching 1 1/8 master cylinder since it boosts so much), which runs off the power steering pump. That alone makes a huge difference.
Depending on your vacuum a standard booster won't work well.
In my case, I have a hydratech hydroboost (and a matching 1 1/8 master cylinder since it boosts so much), which runs off the power steering pump. That alone makes a huge difference.
73stroked duster
Well-Known Member
Do you think larger rotors and calipers will make a difference
goldduster318
Overzealous Car Modifier
It does but not as much as you'd think. The bigger stuff helps with brake torque but its only a percentage with all else being the same.
I went from what you have to 11.75 fronts with the stock calipers, manual 15/16 master cylinder, it was better but incremental
This spring I switched to the Dr Diff 13" Mustang Cobra Fronts and 11.75 Mustang cobra rears. Same master cylinder, and it did stop great, but with a lot of pressure on the pedal.
Once I installed the hydratech, the brakes are basically insanely good, I wasn't used to it and had all 4 locked at 55mph. And I have 275-35-18 Max performance summer tires.
If pedal pressure is the only issue a 15/16” master cylinder is the way to go for manual brakes. Otherwise some kind of booster is in order, depending on your vacuum levels.
If stopping power is an issue, you probably have something wrong with your brakes. The stock 73+ disks and drums actually work pretty well if they’re in good shape. Make sure the pads/shoes aren’t contaminated, the drums are properly adjusted, and the factory combination valve is balancing the braking front to rear (it can get out of whack if the brakes are bled improperly).
I would make sure everything is working properly first. If you have 15” rims, you can buy a set of 11.75” caliper brackets and run the later Mopar 11.75” rotors, they came on some of the 77-81 B/R bodies. You can order the brackets from DoctorDiff. Also, if you actually have A-body calipers, you can use the later FJM body calipers. Externally they’re the same, but they have a larger piston bore than the A body calipers. Both those and the A body calipers will work with the 11.75 caliper brackets.
If you’ve got 14” rims you’re stuck without a rim upgrade. And if you’ve got 15” rims the 11.75’s are about as big as you can go.
If stopping power is an issue, you probably have something wrong with your brakes. The stock 73+ disks and drums actually work pretty well if they’re in good shape. Make sure the pads/shoes aren’t contaminated, the drums are properly adjusted, and the factory combination valve is balancing the braking front to rear (it can get out of whack if the brakes are bled improperly).
I would make sure everything is working properly first. If you have 15” rims, you can buy a set of 11.75” caliper brackets and run the later Mopar 11.75” rotors, they came on some of the 77-81 B/R bodies. You can order the brackets from DoctorDiff. Also, if you actually have A-body calipers, you can use the later FJM body calipers. Externally they’re the same, but they have a larger piston bore than the A body calipers. Both those and the A body calipers will work with the 11.75 caliper brackets.
If you’ve got 14” rims you’re stuck without a rim upgrade. And if you’ve got 15” rims the 11.75’s are about as big as you can go.
73stroked duster
Well-Known Member
I will check the banacing valve. Since I installed the new master cylinder and bleed the brakes I can’t get the luminated brake light to go off unles I remove the wire from the valve.
That would definitely indicate an issue with the valve.
The procedure to recenter the valve is to bleed the brakes in this order- passenger rear, drivers rear, passenger front, drivers front. There’s a valve with a spring inside the factory combination valve that sets the front/rear bias, if it gets out of whack it messes with the balance and that could mean you’re doing most of your braking with the rear drums and not the front. The light indicates there is an issue there.
Got to sort that out before you make any other changes. The light should go out when the valve is working properly.
The indicator light, if it the switch is working correctly, is a warning that either the front or rear hydraulics is not developing pressure. In other words, there's a leak, air, or similar problem on either the front or the rear.
1970 Chrysler Imperial Hydraulic Brake Service Guide Safety Switch
It is located before the proportioning valve. This remains true even with the later combination tee, switch and proportioning valve. The only difference is that its all internal. Your '73 would have come with a combo valve.
Since you haven't mentioned extra movement, then its probably air or not getting fluid and pressure from either the front or rear of the M/C.
This is '73 also explains the switch and valves.
1973 Chrysler Brake Reconditioning Guide Safety Switch Cutaway
Proportioning valve needs nothing special. Not sure if your 73 has a metering valve. But if it does, it is better to open it while bleeding. If your bleeding the traditional way with a helper, one wheel at a time, the metering valve is pressure opened anyway.
1970 Bleeding advice
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C130 Chief
Mechanical Genius
Another thing to consider is the front caliper pistons on 73-75 A-bodies are smaller (2.6") than pretty much every other Mopar single piston calipers (2.75").
73stroked duster
Well-Known Member
Here are pics of what I have
73stroked duster
Well-Known Member
I’m assuming so this is the way I got it.
Ok. Well, thing is we don't even know what brakes you have on there now. Because that's not a stock valve.
I was assuming, and based on the comments I would say most of us have been assuming, that you had stock 73+ disk brakes because you asked about stock brakes. Since that isn't a stock valve, we really don't have any idea what you have. So, until you know what brakes you actually have, I don't know how much help anyone can really be.
The light would still indicate an issue with your current system though, and that still needs to be sorted out before you go any further.
73stroked duster
Well-Known Member
Thanks for all the reply’s. I just bleed all the brakes again and all brakes seem to be locking up good. I have a pretty firm pedal but the light is still on. Thinking about replacing the valve and see what that does. Getting tired of bleeding though.
I don't recognize the valve either, but I'm most familiar with the earlier fixed caliper systems.
Would the previous owner know? If you have some additional photos, maybe someone will recognize it. Might also look at Master Power Brake, SSBC and other aftermarket places.
If the PO doesn't know, and there is no markings, knowing where the connections from the m/c go, and what lines go in and out of that valve we can figure out what is going on.
My suggestion is to make a simple drawing of where the tubing from the cylinder goes, noting all the junctions and devices on the way to each brake. That's just me, I can understand things better with diagrams.
To learn about the braking hydraulics, the 1967 pamphlet is good start. In this they introduce the tandem master cylinders. All routing from then on is just minor variations on that. (for chrysler and most american cars that is). The newer booklets I linked to assumed that background was familiar.
1967 Imperial & Chrysler Dual Hydraulic Brake Repair Book - Session 232
Would the previous owner know? If you have some additional photos, maybe someone will recognize it. Might also look at Master Power Brake, SSBC and other aftermarket places.
If the PO doesn't know, and there is no markings, knowing where the connections from the m/c go, and what lines go in and out of that valve we can figure out what is going on.
My suggestion is to make a simple drawing of where the tubing from the cylinder goes, noting all the junctions and devices on the way to each brake. That's just me, I can understand things better with diagrams.
To learn about the braking hydraulics, the 1967 pamphlet is good start. In this they introduce the tandem master cylinders. All routing from then on is just minor variations on that. (for chrysler and most american cars that is). The newer booklets I linked to assumed that background was familiar.
1967 Imperial & Chrysler Dual Hydraulic Brake Repair Book - Session 232
73stroked duster
Well-Known Member
73stroked duster
Well-Known Member
Looks like a valve that summit racing sells called right stuff pv71.
OK. So that confirms its a distribution block combination safety switch with proportioning valve.
It looks like they have some mopar options, in fact the ones for a '73 a-body. I don't know what the difference is, if any, in the proportioning or the light. Might ask them tommorrow.
https://www.getdiscbrakes.com/brakes/proportioning-valves-and-blocks?product_list_limit=52
If you're getting full pressure on the front calipers (and the rears) then I'd try pads with more initial bite. I'm not sure what is available for the brake. I know for my Wagoneer, Raybestos had a pad "Profession Grade" semi-metalic (M at the end pad number) that I found very grippy. Lining has FF friction rating too, which is decent for street pad.
It looks like they have some mopar options, in fact the ones for a '73 a-body. I don't know what the difference is, if any, in the proportioning or the light. Might ask them tommorrow.
https://www.getdiscbrakes.com/brakes/proportioning-valves-and-blocks?product_list_limit=52
If you're getting full pressure on the front calipers (and the rears) then I'd try pads with more initial bite. I'm not sure what is available for the brake. I know for my Wagoneer, Raybestos had a pad "Profession Grade" semi-metalic (M at the end pad number) that I found very grippy. Lining has FF friction rating too, which is decent for street pad.
Realize I should clarify that its unlikely the proportioning relates to your pedal feel issue as you've described it. If its working right, it won't start proportioning until something like 500 psi is reached. So when you start to push on the pedal, all four corners will get the same pressure.
The rears help most when you first apply the brakes, so do make sure they are adjusted etc.
One last thought, the brake warning light is also wired to a switch on the hand brake. Its possible there's a wiring or switch issue. The only thing that has me wondering about all of this is that it sounds like the problems started with the installation of the new m/c.
The rears help most when you first apply the brakes, so do make sure they are adjusted etc.
One last thought, the brake warning light is also wired to a switch on the hand brake. Its possible there's a wiring or switch issue. The only thing that has me wondering about all of this is that it sounds like the problems started with the installation of the new m/c.
73stroked duster
Well-Known Member
Correct light problem after I installed m/c. I have read that I should have used a proportional valve centering tool when bleeding brakes.Im not sure how to recenter the valve after the fact even if you can. Maybe I need to just install a new one
What!?
Not sure where you read that but it makes no sense. The Chrysler FSMs and tech pamphlets (like those I linked to) will gave you straight scoop.
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