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GM Disc/Drum Proportioning Valve for 1/2-20, 9/16-18 Outlets

SAME DAY SHIPPING! Order within the next 8 hours 29 minutes and receive same day shipping

Specs
Centerline of Holes:
2.68
Material Type:
Brass
Overall Height:
1.95
Overall Width:
1.08
Overall Length:
5.15
Sold in Quantity:
Each
Overall Thickness:
1.08
Outlet Fitting:
Bottom front/Top front are 3/8"-24 IFF (to font brakes), Rearmost port is 9/16"-18 IFF (to rear brakes).
Garage Sale:
No
Notes
Includes hard lines with fittings, hardware, bracket, and brake light switch. This is a combo valve (metering for front/proportioning for rear) into one valve. Residual valves NOT built in.
GM Disc/Drum Proportioning Valve for 1/2-20, 9/16-18 Outlets
Product Video
GM Disc/Drum Proportioning Valve for 1/2-20, 9/16-18 Outlets

Click image to enlarge

Watch the video below to learn more about the differences in brake lines, flare types and fittings you may want to consider before plumbing away on your current chassis project.

Details

Reviews

Q & A

What's in the Box

These proportioning valves are similar to what GM used on many cars in the 70's. They are non-adjustable and may require an adjustable valve in the rear brakes (if needed). Block incorporates metering (for front brakes) and proportioning (for rear brakes) into one unit. For use with front disc, rear drum brake systems.

Includes hard lines to connect to a master cylinder with 1/2"-20 and 9/16"-18 outlets.

GM Proportioning Valve Plumbing Instructions (PDF)

Notes

Bottom Front Port: 3/8"-24 IFF threads - goes to one front brake
Top Front Port: 3/8"-24 IFF threads - goes to one front brake
Middle Top Port: 1/2"-20 IFF threads - comes from master cylinder
Rear Top Port: 7/16"-24 IFF threads - comes from the master cylinder
Rear Most Port: 9/16"-18 IFF threads - goes to rear brakes

Specs


Item Details

For M/C with 1/2"-20 and 9/16"-18 outlets.

Customer Reviews

Rated 4.8 out of 5 by 9 reviewers.
RATING BREAKDOWN
9 reviews
5 Stars
7
4 Stars
2
3 Stars
0
2 Stars
0
1 Star
0
RECOMMEND THIS PRODUCT:

carnut300
Verified Purchaser
Quincy, IL, USA

product was as described and worked fine

October 06, 2014
produck worked unlike the cheap ones you get with disc brake kits
Yes, I recommend this product.
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rubberrodder
Tacoma WA.

Worked as it should. Excellent part

September 30, 2013
I did a custom mounting bracket for my install. So I did not use the bracket and lines. But the actual part is on and performing flawlessly. I will definitely buy one for the next project.
Yes, I recommend this product.
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oldawg
Verified Purchaser
wichita ks

fix those pesky brakes

April 06, 2012
looks great when installed
Pros:
  • Easy To Install
Yes, I recommend this product.
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30sedan
Verified Purchaser
pa

it's got to stop!

October 15, 2011
have it plumbed in, but have not tested at this time
Yes, I recommend this product.
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Doughboy
Andalusia,Illinois

Would buy again

August 28, 2010
I used this on my 1957 Chevy, worked great and no problems.
Yes, I recommend this product.
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DODGETHIS59
Verified Purchaser
SKYLINE, AL

COULDN'T BELIEVE I FINALY FOUND IT!

August 23, 2010
NONE OF MY PARTS SUPPLIERS CARRY A REGULAR DISC/DRUM VALVE ANYMORE. BUT SPEEDWAY NOT ONLY HAD IT BUT HAD IT IN A KIT WITH EVERYTHING I NEEDED. GOOD JOB! I WILL LOOK HERE 1ST IN THE FUTURE.
Yes, I recommend this product.
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sal
Verified Purchaser
brick nj

worked great

August 05, 2010
used it on my 34 ford with a gm master cylinder and worked fine.
Yes, I recommend this product.
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jim
wny

a must for disc/drum brakes

February 22, 2010
worked just fine
Yes, I recommend this product.
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Backyard Bob
Illinois

Conveinient Kit

February 06, 2010
Quick and easy way to plumb a cowl mounted booster. Includes all fittings needed
Yes, I recommend this product.
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Page 1 of 1

Product Q&A

11 questions : 11 answers

1 answers

What size line and adapter do I use for the rear brakes port? Nothing I've tried seems to work. Part numbers would be great.

Gabe
August 10, 2014

What size line and adapter do I use for the rear brakes port? Nothing I've tried seems to work. Part numbers would be great.

Answers

August 11, 2014
EricM
The outlet for the rear brakes is 9/16"-18 IFF. You can use adapter number 9103183-9/16 to adapt it to 3/16-24 IFF which will allow you to connect a 3/16" steel brake line such as 91031800.
1 answers

do i have to use both port for the front brakes or can i block one off and it still work for me? my father and I rebuilt a 1956 dodge pickup and we are using a chevy manual dual master cylinder. front disk and rear stock drum brakes. can I use this part and block off one of the front ports and it still work the same or do you carry something that will work better for me.

Levasseur2
August 04, 2014

do i have to use both port for the front brakes or can i block one off and it still work for me? my father and I rebuilt a 1956 dodge pickup and we are using a chevy manual dual master cylinder. front disk and rear stock drum brakes. can I use this part and block off one of the front ports and it still work the same or do you carry something that will work better for me.

Answers

August 05, 2014
EricM
Yes you can plug off one of the front line connections and use a T fitting instead.
1 answers

Master Cylinder to valve line size The instructions for this valve say line size to be 1/4 inch. The lines that came with my valve are smaller than 1/4 inch. They do attach ok to my master cylinder with 1/2 and 9/16 fittings but tube is small. Is this a problem?

txstude
Texas
January 28, 2014

Master Cylinder to valve line size The instructions for this valve say line size to be 1/4 inch. The lines that came with my valve are smaller than 1/4 inch. They do attach ok to my master cylinder with 1/2 and 9/16 fittings but tube is small. Is this a problem?

Answers

January 28, 2014
EricM
The 3/16" lines that are provided with this valve are just fine. The original GM applications used 3/16" front and 1/4" rear but most of the time hot rodders use 3/16" for both to simplify the system and fittings required.
1 answers

Where do I get the 1/4" line 3/8-24 thread fitting? I read the instructions, which direct you to use 1/4" lines. I can't for the life of me find a 3/8-24 fitting of any kind for use with 1/4" line, though. 7-16 all day long, 9/16 sometimes, 1/2 yeah that too... 3/8? In 1/4? Doesn't seem to exist. So, where do I get the fittings for this beast - or are the instructions in error?

yossarian19
April 22, 2013

Where do I get the 1/4" line 3/8-24 thread fitting? I read the instructions, which direct you to use 1/4" lines. I can't for the life of me find a 3/8-24 fitting of any kind for use with 1/4" line, though. 7-16 all day long, 9/16 sometimes, 1/2 yeah that too... 3/8? In 1/4? Doesn't seem to exist. So, where do I get the fittings for this beast - or are the instructions in error?

Answers

April 23, 2013
Jason
We apologize for the confusion and an error on the plumbing instructions for part number 91031351 proportioning valve. The lines to the front brakes should be 3/16” lines using standard 3/8 x 24 thread nuts. This will give more pressure to the front disc brakes to match the caliper requirements.
1 answers

Will this part work on my 1997 chevy k1500? I want to do away with the kelsey hayes system.

July 26, 2011

Will this part work on my 1997 chevy k1500? I want to do away with the kelsey hayes system.

Answers

July 28, 2011
John
This valve was engineered for GM cars of the 70’s where the engineers knew the weight of the car in the front and in the rear, caliper bore size and wheel cylinder bore size, and also the same size tire front and rear. To use on an application without comparable specifications it is doubtful you will achieve exact front to rear braking and may also require an adjustable valve in the line to the brakes receiving too much pressure. Simplest solution would be to plumb the front brakes direct from the big reservoir on the master cylinder and in the line going to the rear plumb in an adjustable proportioning valve such as our part number 91031353. Once plumbed in place simply adjust as needed to achieve equal front to rear braking.
1 answers

will this valve work on an 83 cadillac that had power steering assist and now has vacuum booster

mo
chicago
April 19, 2011

will this valve work on an 83 cadillac that had power steering assist and now has vacuum booster

Answers

April 21, 2011
Bill
If you have converted the brake system over from the Hydro-Boost system to a conventional brake system using a firewall mounted style vacuum booster and a standard style brake master cylinder and have disc brakes in the front and drum brakes in the rear then this Non Adjustable Brake Proportioning valve will work for you. These proportioning valves are what GM used on many cars in the 70's. They are non-adjustable and may require an adjustable valve in the rear brakes if needed. This is a combination valve which incorporates metering for the front brakes and proportioning for the rear brakes into one valve.
1 answers

does this proportioning valve have a stop taillight hook_up ?

chevy
March 27, 2011

does this proportioning valve have a stop taillight hook_up ?

Answers

March 30, 2011
Craig
That proportioning valve part # 91031351 does not have a brake light switch built into it. It has a brake warning switch in it that would hook to a light to tell you of a brake failure. We do have an adjustable proportioning valve with a built in brake light switch part # 83526011179.
1 answers

Can I use brake light switch item # 91031303 in one of the 3/8-24 front line for a brake light switch?

Rob
southern MN
June 27, 2011

Can I use brake light switch item # 91031303 in one of the 3/8-24 front line for a brake light switch?

Answers

June 29, 2011
John
This GM style proportioning block has two 3/8 x 24 ports for the front brakes. One can be plugged and the other line T’d if desired. Or instead of plugging the one port it could be used for a brake light switch such as number 91031303.
1 answers

Will this work on a 77 Chevy pickup?

Modesto, Ca
June 15, 2011

Will this work on a 77 Chevy pickup?

Answers

June 16, 2011
John
This is a non adjustable proportioning valve and originally came from the mid 70’s GM mid size vehicles. The engineers knew the weight of the car in the rear and the weight in the front and also the bias during hard braking. Also the cars came with the same size tires front and rear. To use on an application other than originally intended may require the addition of an adjustable proportioning valve to the rear to limit premature lock up during panic stops. This is especially true if used on pickups where the weight variance front to rear is greater and the rear is lighter to start with. In this scenario I would suggest the addition of part number 91031353 or the equivalent in the line to the rear brakes.
1 answers

will this vale work on 1988 s10 pickup

nonk
New Iberia LA.
June 14, 2011

will this vale work on 1988 s10 pickup

Answers

June 16, 2011
John
This is a non adjustable proportioning valve and originally came from the mid 70’s GM mid size vehicles. The engineers knew the weight of the car in the rear and the weight in the front and also the bias during hard braking. Also the cars came with the same size tires front and rear. To use on an application other than originally intended may require the addition of an adjustable proportioning valve to the rear to limit premature lock up during panic stops. This is especially true if used on pickups where the weight variance front to rear is greater and the rear is lighter to start with. In this scenario I would suggest the addition of part number 91031353 or the equivalent in the line to the rear brakes.
Page 1 of 2

You may also be interested in:

Adjustable Proportioning Blocks With Brake Light Switch
(Part #91031358)
                        

This adjustable proportioning block allows you to run lines from the master cylinder to the block and then to the appropriate wheels. What is neat about it is that it also contains the proportioning valve and brake light switch. This dramatically reduces the amount of fittings needed and potential leaks.

The adjustable proportioning valve regulates rear brake pressure, helping to maintain correct brake bias between front and rear brakes. It is designed for dual bowl master cylinders. The distribution block connects to the master cylinder and distributes brake fluid to all four wheels. An easy to turn handle with directional arrows makes it simple to either increase or decrease rear brake pressure.

The block accepts 3/16" brake lines and the inlets and outlets on this unit are 3/8"-24 inverted flare females.  It has two inlets from the master cylinder, two outlets to the front brakes and one outlet to the rear brakes.  It includes five stainless steel 3/16" fittings and wiring pigtail for rear brake light switch. Mounts to any convenient location. This is not a direct factory replacement for original blocks. Some line modifications may be necessary.

910-31358 Instructions (PDF)

Learn more about how adjustable proportioning valves work by reading our tech article. Brake System Selection.  

Speedway Purple Proportioning Valve
(Part #91031353)
                        

Allows easy adjustment of front-to-rear brake bias. Universal design works on all race cars. Has a 100 to 1500 psi range with up to 57 percent pressure reduction.

Includes two 1/8"-27 NPT to 3/8"-24 inverted flare fittings.

Brake System Builder's Tip (Link) 

Wilwood 260-11179 Adjustable Proportioning Block
(Part #83526011179)
                        

This block has the proportioning valve built-in to the rear brake ports and a stop light switch built into the front brake ports. All ports are 3/8"-24 inverted flare female.

  • Compact design simplifies mounting, plumbing, & wiring
  • Maintains full isolation between front and rear fluid circuits
  • Rear circuit has a single inlet and single outlet with the adjustable proportioning valve
  • Front circuit has a single inlet with two outlets

Proportioning Valve Installation Instructions (PDF)

Brake System Builder's Tip (Link)

Detailed Schematic of Proportioning Block 

Learn more about how adjustable proportioning valves work by reading our tech article. Brake System Selection.   

GM Disc/Drum Proportioning Valve for 3/8-24 Outlets
(Part #91031364)
                        

These proportioning valves are similar to what GM used on many cars in the 70's. They are non-adjustable and may require an adjustable valve in the rear brakes (if needed). Block incorporates metering (for front brakes) and proportioning (for rear brakes) into one unit. For use with front disc, rear drum brake systems.

Includes hard lines to connect to a master cylinder with 3/8"-24 outlets.

910-31364 Instructions (PDF)

9/16-18 IFM to 3/8-24 IFF Adapter
(Part #9103183-9/16)
                        

Brass adapters. Select from:

  • 3/8"-24 IFM to 7/16" - 24 IFF
  • 7/16"-24 IFM to 3/8" - 24 IFF
  • 1/2"-20 IFM to 3/8" - 24 IFF
  • 9/16"-18 IFM to 3/8" - 24 IFF