rear brake line from MC...thin or thick line?

[monte87LS]

Im trying to find out which brake line is to the rear brakes comming from the master cylinder on my 87 MonteCarlo, is it the thinner line closer to the fire wall or the thicker line further from the fire wall, I did the Wilwood manual brake kit ,and the Wilwood residual valve is only made for the thinner line, first I was told the thicker brake line further from the firewall is for the front brakes because the front brakes do all the work so they use a thicker line, then I was just told the thicker line is for the rear, (after I already cut my brake lines and flared them for the Wilwood residual valve)...I thought I was done, am I done? or do I need to re-do them?...I would like to thank Wilwood for not posting up any neccicary info on there G-body swap kit, VERY PERFESSIONAL!!!..thanks Wilwood

 

[DailyDrifter]

I know from the prop valve its 1/4" to the rear axle, then goes to 3/16". not sure which is the right one comming from the master cylinder? If your lucky i might go to my grand mothers (thats where the cars at) to let you know.

 

[monte87LS]

thanks alot, both brake lines go to the proportion valve so I have no clue which one's which when they come back out

 

[DailyDrifter]

well you are lucky. I'm pretty sure that the small line is the one going to the front. The reason the back line is bigger is because they have to push out the wheel cylinders which involves moving more fluid. Also front brakes do more work but the rear is engaged before the front so that the front end doensnt nose dive when you hit the brakes.

 

[T- Type Tim]

The front line is for the rear

 

[1KWIKSIX]

On my vacuum master cylinder was the same as my new Wilwood master cylinder....the front line is for the front brakes and the rear brake line for the rear.
If you've installed the wilwood proportioning valve too you will need to remove the factory proportioning valve under the drivers seat which is attached to the frame. You cannot have 2 proportioning valves!

I just did the same conversion and used 3/16" brake lines from the Wilwood proportioning valve.
I got rid of both factory brake lines that were previously used.
Just grab a 3/16" brake line Tee fitting (with mounting bracket) and run a single new 3/16" brake lines to the tee for the fronts.
For the rear, run a new 3/16" brake line down to the 9/16" - 18 Dbl Flare nut on the 1/4" rear brake line. You will need a couple of brass brake adapters to get down to 3/8" - 24 Double Flare (for the 3/16" brake line) from the nut on the rear 1/4" brake line.
I can check and let you know what I used on my installation in order to keep the 1/4" rear brake line intact and reduce down to the new 3/16" brake line.

 

[T- Type Tim]

https://www.turbobuick.com/threads/brass-block-replacement.459540/

i went by the info from this thread

 

[Jerryl]

The larger line, is towards the front of the car, and goes to the rear. This is the secondary circuit.
Energuxing the rear brakes first, can make the car unstable during braking. GM had it right.

 

[1KWIKSIX]

Jerryl,
On the power master master cylinder you are correct Sir. However not the case with the Vacuum Master Cylinder which is opposite.
My wilwood MC is opposite as well.