[74buick]

Hello everyone, I have a 1974 Buick Apollo, I have the kit to replace the drums with disc/rotors. My question is, my car comes with a proportioning valve already [see pic of what I currently have] do I need to replace it? does anyone have the correct item number if need to replace it? any tips will help me a lot. I appreciate your time and your help; thank you

 

[SouthBay2s]

I believe on '74 drum / drum cars that is still a distribution block, not a true prop valve, so it has to be replaced. It is not designed for disc brakes.

"By the book" you want a prop valve designed for your brake setup - disc / drum, disc / disc, etc. So from that standpoint you need to buy an aftermarket one to get the proper pressure balance between the front and rear brakes. We use the generic GM Inline Tube one that can be found on their website when the disc brake conversion is generally stock style (not Brembo giant rotors and calipers). If you have some crazy brake upgrade, find an adjustable one.

And does the maker of the conversion kit have a prop valve they recommend?

 

[WaterDog]

Here is a link to a previous post on the issue. Drum Brakes to Disc Break Conversion

 

[Nova 71]

Yes it does need to be replaced, as SouthBay2 said you'll need a disc/drum prop valve. To bleed the system properly you will also need a Brake Proportioning valve bleeding tool. This tool will go in the port where the pressure switch is located. When installed it will keep the valve centered allowing you to bleed front and rear brakes.

I hope this helps

Kevin

 

[74buick]

I believe on '74 drum / drum cars that is still a distribution block, not a true prop valve, so it has to be replaced. It is not designed for disc brakes.

"By the book" you want a prop valve designed for your brake setup - disc / drum, disc / disc, etc. So from that standpoint you need to buy an aftermarket one to get the proper pressure balance between the front and rear brakes. We use the generic GM Inline Tube one that can be found on their website when the disc brake conversion is generally stock style (not Brembo giant rotors and calipers). If you have some crazy brake upgrade, find an adjustable one.

And does the maker of the conversion kit have a prop valve they recommend?

very good information, I will ask the place where I bought the kit for the prop valve, THANK YOU God bless

 

[74buick]

Yes it does need to be replaced, as SouthBay2 said you'll need a disc/drum prop valve. To bleed the system properly you will also need a Brake Proportioning valve bleeding tool. This tool will go in the port where the pressure switch is located. When installed it will keep the valve centered allowing you to bleed front and rear brakes.

I hope this helps

Kevin
View attachment 438472

I appreciate your time and knowledge, thanks for the link and info. ! God bless

 

[Twinshadows]

yes - you need too replace that unit (in u'r picture) ; as Adam says - - that IS NOT a :

Proportioning Valve !

It's called a "distribution block" - - which was added when GM started using the 'Dual M/C's ' to split
the front brakes from the rear brakes .............. and , have two seperate brake syetems (for safety) .
That's where that (distribution) block comes into play . (early years ,you didn't have 'That Valve' , using a
single style M / C ) .

I also bought the = more modern "Combination Valve" , from " INLINE TUBE " = with the M/C SS short
(pre-bent) lines .
info : Inline Tube - the 'Combo Valves' = are all the same (for different brands) mostly .
........... just the (pre-bent) lines are the difference . They sent me the wrong type lines
(different bends) ......... a simple phone call ........
and they took care of it ............ (I'd sure use them , again) .

For my set up - - (69 Nova - front drum to Disc swap) :
This was my stock brake (Disc) valves = using two valves : Metering (early style - Proportioning valve, &
Distribution block ) . . (the stock - factory set-up - in 69 ) .
Then , using INLINE Tube - use only one valve (plus , being NEW & not 50 + yrs old ) .
you get the idea . . . pictures are good =

# 1. - - stock - 69 , set up .


# 2. - - (this is showing = the Wrong M/C lines) ......... but , the same Combo valve .


# 3. = . . . I did have some 'spare brake line fittings' - I found JUST WHAT I needed too make my
brake lines fit the new (Combo) valve . I already knew about the "WeatherHead adaptor fitting" , for the rear
brake line position.
So , take your new valve to the 'auto parts store' (write down - or draw out ) , what you need & where
(position) , it fits .
= = look / ask them for their brake FITTINGS section .
Just find what extra (BRAKE LINE) fittings you may need. This made things alot easier .
.......... make sense .......... the Weatherhead (rear brake adaptor) fitting = # 7908 .

# 4 = Here's what I used . I 'bought that (Black) "Brake Light Tool" . . . but you don't need that tool' .
Simple - use Your TEST LIGHT - - (you may need a "jumper wire" = with 'alligator clips' ) . Too reach the + .
post clamp . Hook - up your Test light on the 'positive post' - (plus , side on u'r battery = "stick the point -
in the + batt clamp" . Then , "clip the other alligator clip - on the 'brake light switch' (on the combo valve) =
bingo .
I had my wife - pump up my brakes & HOLD them .
If the test light came - on .......... I knew the Combo valve HAD Tripped . = KISS .

You can Remove - that brake light switch - with out hurting anything - take a small screwdriver , and move
the brake light switch . . back too center . Then return too the brake bleeding .

note - you will need too "bench bleed u'r M/C 1st" - those small brake bleeding kits (with the plastic fittings
& small hose = works very good (at the auto parts store) .

I also find - - - too make brake bleeding easy - - - have some 'small' rubber hose (I use some clear hose -
so, I can see the brake fluid , going through ) - - - hook onto u'r bleeder screw - - - (open u'r bleeder screw) ,
and let the brake fluid gravity feed .......... into a small clear bottle . - - one wheel at a time .
Do this too each wheel ............ KEEPING your M/C = full of fluid .
Then , start the (real) brake bleeding .

You know all of this ............ Have Fun .............. we've been there - - .

jim

GM Proportioning Valve Front Disc Rear Drum – Inline Tube

I bought the ' Proportioning Valve KIT ' - - came with the mounting bracket & S/S brake lines : from
the combo valve too the M/C .

 

[74buick]

yes - you need too replace that unit (in u'r picture) ; as Adam says - - that IS NOT a :

Proportioning Valve !

It's called a "distribution block" - - which was added when GM started using the 'Dual M/C's ' to split
the front brakes from the rear brakes .............. and , have two seperate brake syetems (for safety) .
That's where that (distribution) block comes into play . (early years ,you didn't have 'That Valve' , using a
single style M / C ) .

I also bought the = more modern "Combination Valve" , from " INLINE TUBE " = with the M/C SS short
(pre-bent) lines .
info : Inline Tube - the 'Combo Valves' = are all the same (for different brands) mostly .
........... just the (pre-bent) lines are the difference . They sent me the wrong type lines
(different bends) ......... a simple phone call ........
and they took care of it ............ (I'd sure use them , again) .

For my set up - - (69 Nova - front drum to Disc swap) :
This was my stock brake (Disc) valves = using two valves : Metering (early style - Proportioning valve, &
Distribution block ) . . (the stock - factory set-up - in 69 ) .
Then , using INLINE Tube - use only one valve (plus , being NEW & not 50 + yrs old ) .
you get the idea . . . pictures are good =

# 1. - - stock - 69 , set up .


# 2. - - (this is showing = the Wrong M/C lines) ......... but , the same Combo valve .


# 3. = . . . I did have some 'spare brake line fittings' - I found JUST WHAT I needed too make my
brake lines fit the new (Combo) valve . I already knew about the "WeatherHead adaptor fitting" , for the rear
brake line position.
So , take your new valve to the 'auto parts store' (write down - or draw out ) , what you need & where
(position) , it fits .
= = look / ask them for their brake FITTINGS section .
Just find what extra (BRAKE LINE) fittings you may need. This made things alot easier .
.......... make sense .......... the Weatherhead (rear brake adaptor) fitting = # 7908 .

# 4 = Here's what I used . I 'bought that (Black) "Brake Light Tool" . . . but you don't need that tool' .
Simple - use Your TEST LIGHT - - (you may need a "jumper wire" = with 'alligator clips' ) . Too reach the + .
post clamp . Hook - up your Test light on the 'positive post' - (plus , side on u'r battery = "stick the point -
in the + batt clamp" . Then , "clip the other alligator clip - on the 'brake light switch' (on the combo valve) =
bingo .
I had my wife - pump up my brakes & HOLD them .
If the test light came - on .......... I knew the Combo valve HAD Tripped . = KISS .

You can Remove - that brake light switch - with out hurting anything - take a small screwdriver , and move
the brake light switch . . back too center . Then return too the brake bleeding .

note - you will need too "bench bleed u'r M/C 1st" - those small brake bleeding kits (with the plastic fittings
& small hose = works very good (at the auto parts store) .

I also find - - - too make brake bleeding easy - - - have some 'small' rubber hose (I use some clear hose -
so, I can see the brake fluid , going through ) - - - hook onto u'r bleeder screw - - - (open u'r bleeder screw) ,
and let the brake fluid gravity feed .......... into a small clear bottle . - - one wheel at a time .
Do this too each wheel ............ KEEPING your M/C = full of fluid .
Then , start the (real) brake bleeding .

You know all of this ............ Have Fun .............. we've been there - - .

jim

GM Proportioning Valve Front Disc Rear Drum – Inline Tube

I bought the ' Proportioning Valve KIT ' - - came with the mounting bracket & S/S brake lines : from
the combo valve too the M/C .

BIG thank!! this is very informational and honestly, I am doing this on my own, by me self with no knowledge other than what I can get here and internet. now, I do have a clear understanding and idea about this subject. Thank you very much, I do appreciate your guy's time to reply. Thanks!!!

 

[Twinshadows]

74buick ............. you're very welcome ............... then , alot of guys have some trouble doing their brake
bleeding . We're here too help .............................. hey ................ if I can do that , anyone can .

And , you can certainly buy the "Brake light Center tool" ............... your call . (I was not trying too talk u
out of buying that) . .

Now ; I also had too modify one of my front brake lines ....... (my lines = one side was correct - and one
side had the wrong size fitting) . So , I used my right front brake line - - into the correct fitting & correct hole,
in my new brake valve .
Because ........... it was much easier too remove my 'left front brake line ... too cut & remove that fitting' ...
(because the L/F brake line IS shorter , easier) . Yes = I have a brake line - "double flare" - tool .

If you Do Buy a 'new brake valve' ............. you need too also buy a new "brake Combination Valve Mounting
Bracket" ; for mounting to / beside your M/C .

Like this Bracket :

1. - -
1971-81 GM F-Body 1971-74 X-Body Proportioning Valve Mounting Bracket – Inline Tube

2. - - This is just a PICTURE , of how the BRACKET mounts : .......... click on the picture - for better look.
1971-79 GM F-Body Power Disc Brake Upper Kit Valve In Factory Location – Inline Tube

With this bracket - - - it makes 'bending & hooking up the rear brake line much easier' .

just , some info . .

note : if you do use a 'small clear hose' for "gravity feed u'r brakes / into a clear jar" .................
You can also place that jar (on the floor) . . . inside a pan / or / container , in case the jar gets full & spills
over .............. catches the mess . . .

Then , unless you = KNOW that you have New brake lines (meaning very clean lines) .......... do NOT
try too 're-use' that (excess / extra) brake fluid .............. It's Not worth IT . (once used from the can ------------------------------- it's "dirty fluid" .

REMEMBER = too keep checking u'r M/C ......... keep it full / topped off .

and , it's much easier too have your car : up on jack stands , even with the tires removed ; too get too
those rear brake 'Bleeder Screws' .................... but , that's also your call = whatever works for you .

I hope I've helped ( as th' " Flyer " , would say ) .

jim

 

[Twinshadows]

I also found a good picture - - - of my "Combination Brake Valve" (from INLINE TUBE) ..........
mounted under my M/C .

By using this 'mounting Bracket' .......... it was Close .......... for bending my
Rear Brake line - (metal brake line)
.................. it did work = just close .

again , pictures are Good . . . . . . 🍺 .

1. - - Here you can also see - - why I bought those "pre-bent M/C lines" . (very short lines) .
........... you can also see = why I used that W H # 7908 ......... rear adaptor fitting .

Everything works great ...........

jim

ps ..... 74buick ..... Would you have any type of "Digital camara" (the type that
uses the "smart cards" . That's what I take my pictures with ............ just use
that smart card for all of u'r car pictures (you will always have all you pictures saved) .

(forever) ........................................... ( Never have that ' Photobucket crap , again ) .