For those looking to upgrade their proportioning valve in order to get more breaking effect from the rear brakes I have found a cheap solution as discovered by Jerry Meyer but he did not have a spring part number. I ordered a stronger spring from Grainger Hardware that is quite a bit stronger than the stock spring. The part number is 1NCR5 and has 30.82 lbs/inch rate. It was a direct swap out in my 1989 GTA. I noticed that they have an even stronger spring which I did not try and the part number is 1NCF2 with a 37 lb/inch rate. One thing to be careful of is with the stronger spring it will take some doing to screw the spring cap back on the proportioning valve so be very careful not to cross thread it.

I took the car out for a test drive and every thing seems fine as I did not want the rears locking up before the fronts did. I hit the brakes pretty hard and I could tell a difference with the rear brakes now taking more of a role in the stopping process. By the way the price is around $5 for a package of five as that is the only way you can buy them at Grainger. I know this spring will work on the 1989 and up cars but I am not sure how far back you can go with it.

For those of you in Southern California that want someone to do this for you Dyno Don has the springs, so you can contact him.

 

This is the exact info I have been looking for! Thanks a bunch. I will try out both springs and post my results

 

A nice rainy day like today is a good day to try it out.

 

definitely gonna check this out too. if the only major difference is the spring between the different prop valves, this'll make a lot disc rear swaps cheaper and safer (like mine!)

 

I'll be swapping the spring I bought off of Don this weekend. I almost feel like heading to Grainger and getting a a couple of springs that are slightly higher in rating and just trying them out. I WILL be posting results, though.

 

Just for reference the story behind this. JerryWho on this board had the rear of his 90-92 Camaro on jack stands checking something out with the car in gear and the motor running. He applied the brakes but the rear wheels kept on turning. Jerry's thought was WTF. So he started investigating what the problem was and discovered the proportioning valve was the culprit. Being Jerry he made up a pressure gage that could be attached to the rear brake lines so he could watch the pressure.

In the meantime he made up an adjustable proportioning valve that he could increase the spring pressure and in turn increase the brake line pressure to the rear brakes. Jerry did not remember the part number for the spring he had bought at a local hardware store but after some research I found some likely candidates at Grainger and have listed them.

The springs are 1.5" long, with an outside diameter of .480" and a coil thickness of I believe .061" or maybe .063". They fit like a glove on my valve. Just remember to be very careful screwing on the spring retainer cap so as to not cross thread it. The added spring pressure makes it harder to do.

The bottom line is with the stock spring the rear brakes are a bit player in stopping the car.

 

Thanks for the heads up. I am planning on testing the rears on jacks before I installed the spring then afterwards, too.

 

I have been reading about swapping out the springs, it sounds too good to be true.
I put a 98 camaro with rear disks in my 88 camaro would this work for this application.
I never have done a spring swap, which end of the valve does the spring go in front or back.

Thanks Ken

 

The front controls the rear brakes.

 

How involved is this swap? Can it be done in the car or does the valve have to come out?

Will

 

I did it. I bought the spring from Don a while back. It increased the pressure a good amount. IT WORKS! The swap can be done in under 5 minutes with the valve still on the car. Be careful threading the bolt back in. You will need to bleed the rears afterwords.

 

Nice, I will have to try this!

 

How much did you end up paying for it shipped to you?

 

Something I wish I'd known before I blew 120 bucks on a new GM prop valve.

 

Does anyone have a way of measuring the spring rate of the factory 1LE spring? That would be great information to have.

 

That's a good point. Hard to say how much stronger the new spring is without a baseline.

 

I did but don't quite remember. Maybe 15#. Anyways the spring upgrade has turned out very well for me now after months of testing. No adverse effects but an increase in braking.

For those in SoCal DynoDon may have a couple left. You can always buy them through Grainger. The part numbers are listed.

 

You would think the spring rate could be measured the same way a valve spring is provided the equipment has enough scale to go as low as 15lbs/x and still be accurate.
I may try the same spring as used by 89GTA before I swap out with the new prop valve I bought. If the replacement spring works for my application (LS1 fronts and PBR rears) then I guess I'll have another spare part for the shop shelves.

Here's the spring's description copied and pasted out of the Grainger catalouge.

1NCR5
Compression Spring, Precision, 302 Stainless Steel, Finish Plain, Overall Length 1 1/2 In, Outside Dia 0.480 In, Wire Type Round, Wire Dia 0.063 In, End Type Closed and Ground, Compressed Length 0.694 In, Load 19.11 Lbs, Deflection @ Load 0.62 In, Spring Rate 30.82 Lbs/In, Meets/Exceeds ASTM A313, Package 5

 

Now that I have thought about it some more I think the stock spring was less than 15#. We used Dyno Dons spring checker to get an idea of what to look for in an after market spring for the upgrade.

 

Since brake work is next on my list of "to-do" AND since my rear brakes (disc from the factory) have never really done anything as noted on the lift like stated above, the front rotors are warpped from doing all the work and will lock the front tires if pushed very hard, making for long stopping distances. This makes me nutz as I bought a performance car with performance components (yeah right) and expected it to work as such.

So my question is this: Does this mod work in the earlier cars (1983) with the four whl db?

 

"Does this mod work in the earlier cars (1983) with the four whl db?"

I wish I could help you but I am not familiar with the proportioning valve on the earlier cars to know if the same spring would work.

 

ahh this is what i was wondering the whole thread lol.

idk why but a part of me things something was changed in the later years (or maybe its just the 1LEs) either way this is cheap enough to where i'd like to try it anyways. i have to redo my brakes soon so this would be the perfect time to do it. great info!

 

The earlier cast iron valves, whose threads are SAE and whose lines attach differently, look nothing like the later alum metric valves. Check the pics in posts #1 and #2 in the following link for a comparison.

https://www.thirdgen.org/forums/brak...rop-valve.html

JamesC

 

Going through old posts I see you were going to upgrade your brakes over the OEM package. What did you eventually come up with? I ask this so that I can compare braking systems and determine whether there's enough similarity between yours and mine to consider using the upgraded spring.
For the record I'm using LS1 fronts and OEM PBR rears with a 1LE prop valve and a J65 master cylinder.
Thanks.

 

i knew there was something!


so would there be an equivalent for us 82-84 black sheep?

 

Because of the thread difference, there's no direct replacement that I'm aware of.

JamesC

 

hmm i guess i'm back to square one, i suppose i could get one from a later year from the junkyard and do it, from rock auto for $82.xx and do it, or opt for the 1LE

 

"I see you were going to upgrade your brakes over the OEM package"

I was hoping to get more braking with less weight. That did not work out. So I just converted to Weldwood aluminum calipers up front to save some weight and high grade brake pads all around. Also the proportioning spring upgrade as posted. Car stops good enough for me.

 

I've been fighting with my rear delco moraines being unable to stop the rear wheels in drive at idle. I tried the "recall kit", re-bench bleeding the master and new pads. None of it worked. I installed this spring and re-bled the rears. After that, the rear calipers can finally stop the rear wheels.

For reference, my prop valve is from an 88 non-1le car.

Thanks for your post!

 

Where does this spring go in the prop valve?

 

Years ago I read a similar mod on here where you put a spacer either behind or in front of the spring basically accomplishing the same thing as a stiffer spring in this thread. I went ahead and made some thicker bushings/spacer than the thread I read recommended since I worked at a machine shop at the time. Added the recommended spacer from the thread I read and it improved rear braking, never tried the thicker spacers because it was a bitch to get the plug back in without cross threading it. BTW this was on my 89.

 

If you unscrew the 13/16" plug on the side of the prop valve facing the front of the car you will find the spring. In my case, the original spring is maybe .020" wider than the Grainger spring. It helps to file the inside of the very end of the top coil where the metal flattens out so that it's easier to fit the spring in the seat portion of the plug. The opposite end shouldn't need to be filed.

 

Who has extra spring i can paypal ya for. Grainger.com requires a company account to be started and all types of mess.
Anyone?

 

Ordered mines 6 bucks and some change with tax picking up at store

 

Can you use this spring on a drum brake valve for use on a drum to disc car

 

not sure..but i mean the principle is the same, if you aint getting much force out back, this spring should send more pressure, try it i think the part number is listed above from Grainger's, it should work.

 

seeign as you need a business account with grainger to buy them does anyone wanna send me just one and ill paypal you some money to cover shipping on top of like 3 bucks for one?

 

I was able to find a similar spec'ed spring at McMaster Carr also, I dont think you need a business account there.

 

hey scooter you have a part number?? thanks in advance

 

ok cool...i need sum...do u have part number?...

but im still lost where do this springs go?...

can anyone post pics of where they go?...plz and thnks...

 

i found them......

heres the part number...

9435K123

 

I have one apart on my kitchen table, I will post some pictures when I get home

 

ok thank u so much......

p.s. guys i have both stores rite down the street from me if ur having trouble ordering sum let me kno ill go get them from down the street and ship them out...

 

just ordered a pack of 5 if any one needs one pm me

 

coming your way

 

any luck with the pics?...

 

I took the pictures but I didnt get the loaded. I was going to edit them slightly, but I may just throw them up instead.

 

Mines came in yesterday, i installed it right away, it seems better, i really want to try it out on the rain to see how much pressure is going to the back brakes, dont want to flat spot my tires in the dry pavement

 

o ok ic...i just wana c were the springs go......

 

I hope this is all the explanation you need