Location of brake Proportion valve: Does it matter? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

WyattTX · 07-02-2019, 12:01 PM

I notice many aftermarket master cylinders have the P valve directly under the master cylinder. But most OE P valves are long distance away from the master cylinder (like near the front bumper, or the center of the frame). Why is this? Is there a benefit of the P valve being further from the master cylinder, or are manufacturers just being mean and making it difficult to reach for nothing?

sweetk30 · 07-02-2019, 01:22 PM

my mid 80's truck i swapped to disc / disc and used a adjustable rear bias aftermarket valve and its next to the master now since i replumbed the hard lines and no problems.

GASoline71 · 07-02-2019, 01:23 PM

The "valve" on these old trucks is merely a junction block and not a proportioning valve. Not sure if the block needs to be so close to the master cylinder. But a proportioning valve can be anywhere as long as it can control the amount of fluid to proportion the front and rear brakes accordingly.

Gary

WyattTX · 07-02-2019, 02:30 PM

Interesting. I just remember replacing a P valve on an 82 Jeep CJ8 (front disc, rear drum). It was bolted in the worst possible place, IMO. It was inside the C channel frame under the vehicle. I figured AMC engineers put it there for a reason, but maybe they were just jerks, afterall.

**mongocanfly** · 07-02-2019, 03:35 PM

.I've gottem mounted on front crossmember and at mc on different trucks...all it is is a junction/dividing point...doesn't matter where it is...I prefer it down low just from a visual standpoint...

**The Rocknrod** · 07-03-2019, 07:33 PM

No if it's bled properly it is a hydraulic connection, so no problem with the distance.

D13 · 07-12-2019, 10:33 AM

GM ran the single front line feeding the valve as far as possible before splitting for each front line. Least amount of tube = lowest cost. Uses the prop valve as a L/R front line splitter too, thus saving another T. Plus it allowed the same location for all the brake combinations including the hydroboost mess, which doesn't play well with prop valve on MC.

WyattTX · 07-14-2019, 06:46 AM

Ah, so the bad location is just cost cutting. That makes sense. Thanks for the info, everyone.

Dead Parrot · 07-14-2019, 07:01 PM

Had a 79 Camaro with the P-valve bolted to the MC-Booster assembly.

kipps · 07-14-2019, 07:36 PM

Quote:

Originally Posted by D13

...Plus it allowed the same location for all the brake combinations including the hydroboost mess, which doesn't play well with prop valve on MC.

I assume you mean the physical interaction between the steering hoses and the P-valve? -- two objects trying to occupy the same space?

Or is there something else that I'm not getting here?

07-02-2019, 12:01 PM	#1
WyattTX Registered User Join Date: Nov 2015 Location: Down south Posts: 518	Location of brake Proportion valve: Does it matter? I notice many aftermarket master cylinders have the P valve directly under the master cylinder. But most OE P valves are long distance away from the master cylinder (like near the front bumper, or the center of the frame). Why is this? Is there a benefit of the P valve being further from the master cylinder, or are manufacturers just being mean and making it difficult to reach for nothing?

07-02-2019, 01:22 PM	#2
sweetk30 Registered User Join Date: May 2012 Location: horseheads,ny rust belt Posts: 2,794	Re: Location of brake Proportion valve: Does it matter? my mid 80's truck i swapped to disc / disc and used a adjustable rear bias aftermarket valve and its next to the master now since i replumbed the hard lines and no problems. __________________ 77-k30lb BIG truck build . 87-k30lb budget beater build . 85-k30lb the plow machine build . 85-c10sb summer fun toy . ----------------------------- HOLLEY SNIPER efi = worst case of p.i.t.a i ever had . EDELBROCK pro flo 4 = best deal going so far . love my setup works great.

07-02-2019, 02:30 PM	#4
WyattTX Registered User Join Date: Nov 2015 Location: Down south Posts: 518	Re: Location of brake Proportion valve: Does it matter? Interesting. I just remember replacing a P valve on an 82 Jeep CJ8 (front disc, rear drum). It was bolted in the worst possible place, IMO. It was inside the C channel frame under the vehicle. I figured AMC engineers put it there for a reason, but maybe they were just jerks, afterall.

07-02-2019, 03:35 PM	#5
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,582	Re: Location of brake Proportion valve: Does it matter? .I've gottem mounted on front crossmember and at mc on different trucks...all it is is a junction/dividing point...doesn't matter where it is...I prefer it down low just from a visual standpoint... __________________ Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver

07-03-2019, 07:33 PM	#6
The Rocknrod Moderator Join Date: Aug 2011 Location: China Spring, TX Posts: 7,280	Re: Location of brake Proportion valve: Does it matter? No if it's bled properly it is a hydraulic connection, so no problem with the distance. __________________ Master Chief, US Navy, Retired 1964 C10 Step-side Short Bed - In Progress 2009 2500HD Duramax LTZ 1948 GMC Panel 1956 Big Window Stepside 1953 5 Window Chevy Stepside 1932 Coupe New Seat Foam for Bench Seats?

07-12-2019, 10:33 AM	#7
D13 Registered User Join Date: Feb 2007 Location: Memphis MI Posts: 1,851	Re: Location of brake Proportion valve: Does it matter? GM ran the single front line feeding the valve as far as possible before splitting for each front line. Least amount of tube = lowest cost. Uses the prop valve as a L/R front line splitter too, thus saving another T. Plus it allowed the same location for all the brake combinations including the hydroboost mess, which doesn't play well with prop valve on MC. __________________ 1987 2 ton 1982 250/TH350 beater in progress Dad's 1981 3/4 L6 3 on tree posi and no options, awaiting restoration or scrapping Plus a mess o' tractors

07-14-2019, 06:46 AM	#8
WyattTX Registered User Join Date: Nov 2015 Location: Down south Posts: 518	Re: Location of brake Proportion valve: Does it matter? Ah, so the bad location is just cost cutting. That makes sense. Thanks for the info, everyone.

07-14-2019, 07:01 PM	#9
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,474	Re: Location of brake Proportion valve: Does it matter? Had a 79 Camaro with the P-valve bolted to the MC-Booster assembly.



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