Proportioning valve....

[jchristians]

Doing the front disc conversion. stock rear drums. I am needing a proportioning valve for the rear drums... any recommendations? differences in valves?? thanks!

[datzenmike]

Early cars and trucks just used different size wheel cylinders to set the bias front to back. Not sure if the 521 had one. Either way it would be set for drum on the front and not adjustable. I did some crazy lifting and 4 piston calipers on my 620 and the weight would shift forward causing rear lock up even on moderate stops. The cure was to install a Wilwood adjustible proportioning valve in line with the back brake line. I mounted it under the hood near the master. To set, I panic braked on clean dry pavement and looked at th marks. I adjusted the bias until the rears locked at the same time as the fronts.

 

The adjustible proportioning valve is illegal for the street but not using it was worse for me. They were about $50. A friend who races has his mounted by the hand brake to adjust the car as the gas tank gets lighter diring a race. Do not do this for a street vehicle or you will be constantly adjusting and it's best to set it right and learn to drive safely with that.

 

 

[DanielC]

No proportioning valve in a stock 521. You could get 3/4 or 13/16 rear wheel cylinders.

[oldskoolvws]

I plan on running a variation of this http://m.summitracing.com/parts/SUM-G3910

 

It is made by one company, but distributed to everyone and their uncle plus theirs moms under different manufacturer's names, kind of like Moose Racing for the motocross world.

 

The nice thing about these is that you can use your factory firewall brake switch and it will install relatively easy at said location. A few extra brake lines and your good to go.

 

Cheapest I found was like $60 bucks, but don't have the link handy, I'm on my iPod.

[jchristians]

Yeah, I will have the 720 calipers on my front discs. A new 720 Master Cyl also. I was told I will need a proportioning valve for my rear stock drums, is this NOT correct? I am planning to do as DatzenMike did, "The cure was to install a Wilwood adjustible proportioning valve in line with the back brake line". Wow, these are illegal for the street? hmmm, whats me supposed to do?

[oldskoolvws]

Yeah, I will have the 720 calipers on my front discs. A new 720 Master Cyl also. I was told I will need a proportioning valve for my rear stock drums, is this NOT correct? I am planning to do as DatzenMike did, "The cure was to install a Wilwood adjustible proportioning valve in line with the back brake line". Wow, these are illegal for the street? hmmm, whats me supposed to do?

 

 

Basically, to add the unit I linked to or any other unit, you need to add one brake line from the MC to the PV. There will be two lines in and and three lines out. Two for the front and one for the rear. I plan to remove the factory "T" and just replace it with this style unit. it maintains a factorish style/placement with minimal reconfiguration. You will need a proportioning valve in order for the system to work right with the conversion. The hydraulic friction is different for both systems and requires different pressures to operate.

 

Here's the link to the manual for the style below: http://static.summit...s/sum-g3910.pdf (about $70 black, $100 polished)

 

 

Here's a Wilwood one ($57 Amazon):

 

Both of these have the brake light switch which makes it easy. You can use the ones without but need to add a switch to your pedal, I believe Mike Klotz did this to his.

[wayno]

Yeah, I will have the 720 calipers on my front discs. A new 720 Master Cyl also. I was told I will need a proportioning valve for my rear stock drums, is this NOT correct? I am planning to do as DatzenMike did, "The cure was to install a Wilwood adjustible proportioning valve in line with the back brake line". Wow, these are illegal for the street? hmmm, whats me supposed to do?

 

There are two lines of thinking here, the proportioning valve that would be illegal for the street is a active real time one that you can change while you are driving down the road, the street legal type would need to be adjusted till it was right by stopping the vehicle and adjusting, then driving again and hitting the brakes till you get the results you want/need, then it would be left there forever.

[datzenmike]

They are made for racing/off road and probably have never been through the expensive and time consuming qualification for certification for street use. This is part of the braking system and not to be taken lightly. You don't want every idiot out there making brake components and selling them for your car. So the package says "not for street use".

[oldskoolvws]

They are made for racing/off road and probably have never been through the expensive and time consuming qualification for certification for street use. This is part of the braking system and not to be taken lightly. You don't want every idiot out there making brake components and selling them for your car. So the package says "not for street use".

 

You are very much accurate in your statement regarding braking and street use. If you don't know what you are doing, stay away. There are other alternatives.

 

The Ford Silhouette actually had a factory adjustable valve. The older watercoolded VW line had some trick valves as well (non-adjustable). They were ball bearing based. On most trucks, up until the 2000's, LSPV, line sensing proportioning valve was the standard. It sensed the weight in the rear and adjusted the proportioning accordingly.

 

I used to work for Toyota Manufacturing and specifically the LSPV and braking testing.

[haubstr]

Basically, to add the unit I linked to or any other unit, you need to add one brake line from the MC to the PV. There will be two lines in and and three lines out. Two for the front and one for the rear. I plan to remove the factory "T" and just replace it with this style unit. it maintains a factorish style/placement with minimal reconfiguration. You will need a proportioning valve in order for the system to work right with the conversion. The hydraulic friction is different for both systems and requires different pressures to operate.

 

Here's the link to the manual for the style below: http://static.summit...s/sum-g3910.pdf (about $70 black, $100 polished)

 

 

Here's a Wilwood one ($57 Amazon):

 

Both of these have the brake light switch which makes it easy. You can use the ones without but need to add a switch to your pedal, I believe Mike Klotz did this to his.

 

The second one (Wilwood) is the one I'm using on my 521 with 4 wheel disk brakes... Got it all plumbed, just haven't got it on the road yet... (need exhaust system installed)

[ggzilla]

Datsun 610 & B210 came with proportioning valve, nissan called it the NP Valve. My 1200 Pickup with has some sort of load-sensing valve mounted under the bed and the rear brake line goes through it.

 

Volvos also came with adjustable proportioning valve instead of a fixed one like the Datsuns used.

[oldskoolvws]

Datsun 610 & B210 came with proportioning valve, nissan called it the NP Valve. My 1200 Pickup with has some sort of load-sensing valve mounted under the bed and the rear brake line goes through it.

 

Volvos also came with adjustable proportioning valve instead of a fixed one like the Datsuns used.

[merlin]

Methinks there is a proportioning valve on early 80s caddys that can be used. Came up on the patrol list.

[yellowdatsun]

I bought the one from Speedway, and installed it in my old 521. Worked fine, and is relatively cheap.

 

http://www.speedwaymotors.com/Speedway-Proportioning-Valves,23498.html

[gorillabear]

FWIW I just finished doing the front disc swap and I haven't had any issues with lockup in the rear. Maybe I haven't stomped on it hard enough yet but so far so good.