master cyl/prop valve - The 1947 - Present Chevrolet & GMC Truck Message Board Network

special70gmc · 11-18-2003, 10:42 PM

what wqould happen if i was to use my drum drum 3/4 ton MC and prop valve with my new disc brakes? im kinda no really tight on money and i cant quite cough up the cash to pay for the last pecies. aso i have a late model MC but no prop valve could i use that? thank you -kyle

Glen · 11-18-2003, 10:49 PM

Your drum setup requires a 10lb residual pressure valve to keep the shoes out near the drum.

disc setups only require 2lb rpv valves.

the brakes would drag.

Longhorn Man · 11-19-2003, 12:04 AM

Plus, on top of that,t eh reivour needs to be bigger on discs since there is no mechanical adjustment...the hyd make up the adjustments on them.

cableguy0 · 11-19-2003, 12:25 AM

plus ur truck wont stop worth a sh!t because disks require more pressure to operate than drums do. brakes are a very bad place to cut corners but im not gonna lecture u its your life and ur truck both in your hands. just wait till u can afford it and get a new master and prop valve

SEVEND2 · 11-19-2003, 04:25 AM

I agree, DONT RUSH IT!
Remember its your Truck, Life, your passengers and others around you....

save up a bit longer and get little by little

SEVEND2 · 11-19-2003, 04:27 AM

b t w - post you are looking for those parts on the parts board, you never know a Board member might just have a great deal for you......

jose · 11-19-2003, 04:37 AM

Is there a difference between disk 1/2 ton prop valve and disk 3/4 ton prop valve ?

72MARIO · 11-19-2003, 11:00 AM

Can you get a Adj. porp valve ? Summit selles them for like 50 bucks I think you need thoed tings that hold presssure in the lines though ... I don't know

Glen · 11-20-2003, 12:55 AM

I just wanted to clarify, Im talking about the "residual pressure valves" not Proportioning valves.

P. valves maintain the balance between front and rear braking.

RPV's retain 2lbs of pressure on the caliper pads and are usually mounted internally inside the master cylinder.
Drums again require 10lbs. of pressure to keep the shoe extended slightly touching the drum.

**Smitty** · 11-20-2003, 08:52 PM

And the pressure difference between the two means that using the drum brake M/C you will have constant pressure on the calipers. Causing unnecessary wear to pads, glazed rotors, and lost gas milage.

11-18-2003, 10:42 PM	#1
special70gmc Registered User Join Date: Sep 2002 Location: long island, new york Posts: 1,333	master cyl/prop valve what wqould happen if i was to use my drum drum 3/4 ton MC and prop valve with my new disc brakes? im kinda no really tight on money and i cant quite cough up the cash to pay for the last pecies. aso i have a late model MC but no prop valve could i use that? thank you -kyle __________________ 1986 c-10 swb 5/7 drop 20'' coys 1958 belair 2door

11-19-2003, 12:25 AM	#4
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	plus ur truck wont stop worth a sh!t because disks require more pressure to operate than drums do. brakes are a very bad place to cut corners but im not gonna lecture u its your life and ur truck both in your hands. just wait till u can afford it and get a new master and prop valve __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

11-19-2003, 04:25 AM	#5
SEVEND2 Registered User Join Date: Aug 2001 Location: Menifee, Calif, USA Posts: 2,145	I agree, DONT RUSH IT! Remember its your Truck, Life, your passengers and others around you.... save up a bit longer and get little by little __________________ With a 1972 Chevy Custom-10 Long bed w/350cid th350, (under-construction). Progress on truck so far (follow link): http://67-72chevytrucks.com/vboard/s...ad.php?t=51051 and stage 2 http://67-72chevytrucks.com/vboard/s...ad.php?t=58132 ~ "Why couldn't you have just put the bunny back in the box?" ~

11-19-2003, 04:27 AM	#6
SEVEND2 Registered User Join Date: Aug 2001 Location: Menifee, Calif, USA Posts: 2,145	b t w - post you are looking for those parts on the parts board, you never know a Board member might just have a great deal for you...... __________________ With a 1972 Chevy Custom-10 Long bed w/350cid th350, (under-construction). Progress on truck so far (follow link): http://67-72chevytrucks.com/vboard/s...ad.php?t=51051 and stage 2 http://67-72chevytrucks.com/vboard/s...ad.php?t=58132 ~ "Why couldn't you have just put the bunny back in the box?" ~

11-19-2003, 04:37 AM	#7
jose Registered User Join Date: Feb 2001 Location: Salem , Oregon 97301 Posts: 1,796	Is there a difference between disk 1/2 ton prop valve and disk 3/4 ton prop valve ? __________________ 68 GMC 4x4 SWB jose6772@yahoo.com Last edited by jose; 11-19-2003 at 04:39 AM.

11-18-2003, 10:49 PM	#2
Glen Registered User Join Date: Jan 2003 Location: Chandler, AZ Posts: 189	Your drum setup requires a 10lb residual pressure valve to keep the shoes out near the drum. disc setups only require 2lb rpv valves. the brakes would drag.

11-19-2003, 12:04 AM	#3
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Plus, on top of that,t eh reivour needs to be bigger on discs since there is no mechanical adjustment...the hyd make up the adjustments on them.

11-19-2003, 11:00 AM	#8
72MARIO Registered User Join Date: Nov 2000 Location: Huntsville Ontario Canada Posts: 4,052	Can you get a Adj. porp valve ? Summit selles them for like 50 bucks I think you need thoed tings that hold presssure in the lines though ... I don't know __________________ 1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD

11-20-2003, 12:55 AM	#9
Glen Registered User Join Date: Jan 2003 Location: Chandler, AZ Posts: 189	I just wanted to clarify, Im talking about the "residual pressure valves" not Proportioning valves. P. valves maintain the balance between front and rear braking. RPV's retain 2lbs of pressure on the caliper pads and are usually mounted internally inside the master cylinder. Drums again require 10lbs. of pressure to keep the shoe extended slightly touching the drum.

11-20-2003, 08:52 PM	#10
Smitty Senior Member Join Date: Dec 1999 Location: Spring Valley, Ca. Posts: 1,109	And the pressure difference between the two means that using the drum brake M/C you will have constant pressure on the calipers. Causing unnecessary wear to pads, glazed rotors, and lost gas milage. __________________ Smitty '71 Short Fleetside Spring Valley, Ca.

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