Proportioning valve question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dracko · 03-07-2019, 12:02 AM

I am planning to run a manual disc/drum setup on my ‘64. I have a MC for a 71/72 non power truck and have a proportioning valve from my crossmember donor truck; it was an ‘83, and had power brakes to the best of my knowledge.

Can I use a prop valve from a power brake truck in my manual brake system?

dracko · 03-07-2019, 12:53 AM

I am planning to run a non-power disc/drum setup on my ‘64. I have a MC for a 71/72 non power truck and have a proportioning valve from my crossmember donor truck; it was an ‘83, and had power brakes to the best of my knowledge.

Can I use a prop valve from a power brake truck in my non power brake system?

Short 3/4 · 03-07-2019, 01:18 AM

When I did the same setup on my old 66 2wd I got a generic adjustable prop valve and plumbed it into the rear brake line. Worked great for several decades, and was nice to be able to dial in rear brakes depending on load.

dracko · 03-07-2019, 01:25 AM

Quote:

Originally Posted by Short 3/4

When I did the same setup on my old 66 2wd I got a generic adjustable prop valve and plumbed it into the rear brake line. Worked great for several decades, and was nice to be able to dial in rear brakes depending on load.

Thanks man I definitely considered that, but tough to not use this OE one I got for free. If it won’t work I’ll end up buying a new one. Off-hand, do you know if there’s any rubber seals or parts in prop valves that could dry up or deteriorate over years of sitting?

**Captainfab** · 03-07-2019, 01:38 AM

Yes you can. The proportioning valve does not care if the line pressure is manual or boosted.

Short 3/4 · 03-07-2019, 01:48 AM

Ya, free is always good. No, I have no idea what's inside those things.

dracko · 03-07-2019, 09:25 AM

Quote:

Originally Posted by Captainfab

Yes you can. The proportioning valve does not care if the line pressure is manual or boosted.

Thanks for the info! Is there anything in these valves that dries out or deteriorates over time?

64shortbox · 03-07-2019, 10:44 PM

Nothing inside the proportioning valve (combination valve as GM calls them) that will decay other than a few O rings & maybe one cup. When you are ready to bleed your brakes make sure to remove the brake light warning switch and install the little tool that holds the shuttle valve centered. I've attached a couple of pics of a cutaway proportioning valve and the little tool that holds the valve centered when bleeding your brakes. The holding tool is made of plastic and is only like $5.00 if I remember correctly.

64shortbox · 03-07-2019, 10:56 PM

Food for thought - did you keep ALL the brake lines from your donor truck? the reason I ask is believe it or not the brake lines from a 73 - 87 C-10 will fit our trucks like they were made for them. I did have to make a bracket to mount the proportioning valve in the 73 - 85 location but other than that it all came together perfectly.

dracko · 03-07-2019, 11:35 PM

Wow thanks for all the info on prop valves and that tool for bleeding, never heard of one before.

I didn’t take any of the brake lines from the donor truck, but after seeing those pics and some of others trucks that have done the same that looks like the way to go. I wonder how brake lines from a power brake truck would work with my manual setup?

Thanks again!

AcampoDave · 03-08-2019, 08:54 PM

They'll work too. Brake lines don't care about boosters either.

dracko · 03-08-2019, 10:30 PM

Quote:

Originally Posted by AcampoDave

They'll work too. Brake lines don't care about boosters either.

Ha, that’s funny but my main concern was how they’d fit because they’d be starting 4-6” closer to the firewall with no booster. But I’ll try to find some cheap and make it work. Thanks

AcampoDave · 03-08-2019, 10:55 PM

They fit, check it out. http://67-72chevytrucks.com/vboard/s...d.php?t=782830

dracko · 03-08-2019, 11:03 PM

Quote:

Originally Posted by AcampoDave

They fit, check it out.http://67-72chevytrucks.com/vboard/s...24#post8482224

Well damn I did not notice you’re running a manual setup in that pic. Thanks again!

Idaho64GMC · 03-09-2019, 10:41 AM

your system should work fine. I recently did a disc/drum swap from an 86 into my 64. I used everything from the 86 but went with a manual master cylinder rather than a power MC. Everything works great

dracko · 03-09-2019, 10:51 AM

Quote:

Originally Posted by Idaho64GMC

your system should work fine. I recently did a disc/drum swap from an 86 into my 64. I used everything from the 86 but went with a manual master cylinder rather than a power MC. Everything works great

Right on! Thanks for the info man.

dracko · 03-09-2019, 12:20 PM

Quote:

Originally Posted by Idaho64GMC

your system should work fine. I recently did a disc/drum swap from an 86 into my 64. I used everything from the 86 but went with a manual master cylinder rather than a power MC. Everything works great

Right on! Thanks for the info man.

03-07-2019, 12:02 AM	#1
dracko Registered User Join Date: Jan 2010 Location: Regina, SK Posts: 809	Proportioning valve question I am planning to run a manual disc/drum setup on my ‘64. I have a MC for a 71/72 non power truck and have a proportioning valve from my crossmember donor truck; it was an ‘83, and had power brakes to the best of my knowledge. Can I use a prop valve from a power brake truck in my manual brake system? Last edited by dracko; 03-07-2019 at 12:35 AM.

03-07-2019, 12:53 AM	#2
dracko Registered User Join Date: Jan 2010 Location: Regina, SK Posts: 809	Proportioning valve question I am planning to run a non-power disc/drum setup on my ‘64. I have a MC for a 71/72 non power truck and have a proportioning valve from my crossmember donor truck; it was an ‘83, and had power brakes to the best of my knowledge. Can I use a prop valve from a power brake truck in my non power brake system?

03-07-2019, 01:18 AM	#3
Short 3/4 Registered User Join Date: Jan 2017 Location: Los Osos Ca Posts: 560	Re: Proportioning valve question When I did the same setup on my old 66 2wd I got a generic adjustable prop valve and plumbed it into the rear brake line. Worked great for several decades, and was nice to be able to dial in rear brakes depending on load. __________________ 65 short stepside K10 292-SM420-T221 8 lug closed D44 front NoSpin HO72 4.10 rear

03-07-2019, 01:38 AM	#5
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,252	Re: Proportioning valve question Yes you can. The proportioning valve does not care if the line pressure is manual or boosted. __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

03-07-2019, 01:48 AM	#6
Short 3/4 Registered User Join Date: Jan 2017 Location: Los Osos Ca Posts: 560	Re: Proportioning valve question Ya, free is always good. No, I have no idea what's inside those things. __________________ 65 short stepside K10 292-SM420-T221 8 lug closed D44 front NoSpin HO72 4.10 rear

03-07-2019, 10:44 PM	#8
64shortbox Registered User Join Date: Jan 2011 Location: Tulare, CA Posts: 734	Re: Proportioning valve question Nothing inside the proportioning valve (combination valve as GM calls them) that will decay other than a few O rings & maybe one cup. When you are ready to bleed your brakes make sure to remove the brake light warning switch and install the little tool that holds the shuttle valve centered. I've attached a couple of pics of a cutaway proportioning valve and the little tool that holds the valve centered when bleeding your brakes. The holding tool is made of plastic and is only like $5.00 if I remember correctly. Attached Images

03-07-2019, 10:56 PM	#9
64shortbox Registered User Join Date: Jan 2011 Location: Tulare, CA Posts: 734	Re: Proportioning valve question Food for thought - did you keep ALL the brake lines from your donor truck? the reason I ask is believe it or not the brake lines from a 73 - 87 C-10 will fit our trucks like they were made for them. I did have to make a bracket to mount the proportioning valve in the 73 - 85 location but other than that it all came together perfectly. Attached Images

03-07-2019, 11:35 PM	#10
dracko Registered User Join Date: Jan 2010 Location: Regina, SK Posts: 809	Re: Proportioning valve question Wow thanks for all the info on prop valves and that tool for bleeding, never heard of one before. I didn’t take any of the brake lines from the donor truck, but after seeing those pics and some of others trucks that have done the same that looks like the way to go. I wonder how brake lines from a power brake truck would work with my manual setup? Thanks again! Last edited by dracko; 03-07-2019 at 11:42 PM.

03-08-2019, 08:54 PM	#11
AcampoDave Registered User Join Date: Feb 2013 Location: central California Posts: 2,780	Re: Proportioning valve question They'll work too. Brake lines don't care about boosters either.

03-08-2019, 10:55 PM	#13
AcampoDave Registered User Join Date: Feb 2013 Location: central California Posts: 2,780	Re: Proportioning valve question They fit, check it out. http://67-72chevytrucks.com/vboard/s...d.php?t=782830 Last edited by AcampoDave; 03-08-2019 at 11:01 PM.

03-09-2019, 10:41 AM	#15
Idaho64GMC Registered User Join Date: Feb 2013 Location: Twin Falls, Idaho Posts: 70	Re: Proportioning valve question your system should work fine. I recently did a disc/drum swap from an 86 into my 64. I used everything from the 86 but went with a manual master cylinder rather than a power MC. Everything works great



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