i am going to be swapping a 4th gen rear into my 86 z28 which requires an adjustable prop valve. i am also going to plumb in a line lock on the front brakes. my question is do i still need to have the factory metering/prop valve or can i just take them out and run straight off the master cylinder?

 

the 4th gen rear doesn't require an adjustable proportioning valve. if you have the flat sided valve now you don't need to change anything. running the factory valve and an adjustable one wouldn't be the thing to do, one or the other, but you do need a porpotioning valve.

 

I do not follow....flat sided valve??

 

if i swap from the 86 drum rear to the 4th gen disk rear i dont need an adjustable prop valve? everything ive heard says i need one. what about the front brakes?

 

just get a proportioning valve for a rear disc car. then you dont have to worry about bending lines, flaring them, re flaring them when they leak. spend a little extra and get a slp line lock that comes with lines and wiring, otherwise the same will apply as the prop valve

 

the reason im asking is so i can get rid of the factory prop valve and all assiciated bent lines, then run new lines for the adjustable prop valve for the rear and the line lock up front. my intent is to make this a cleaner looking install rather than adding more lines and leaving the factory prop valve. will the line lock and adjustable prop valve distribute fluid the same as the factory valve does or is there some reason to keep the factory valve?

 

now you do realize there is a reason for the length of the tubing correct? hydralics 101 length must be the same or you will have diffrent pressure at each brake.

anyone hear of this also? i'm no expert but have asked questions in the past on older progects.

 

that is incorrect, in hydraulics, the line/hose length is NOT a factor(other than possible hose swelling) in pressure drop

with a non metered/restricted line, the pressure applied at one end will be the same at the other, as long as no air is present...why you ask? fluid does not compress!, air/gas does

 

I'll second that. the only way you lose pressure is to have something compress or expand. Thats why you need to remove all the air from your brake lines (air compresses), and also why people run braided stainless lines instead of the stock rubber ones that can expand some and cause pressure loss.

Oh and as stated before if you are going to run an adj prop valve, you don't run the stock one too.

Chris

 

Whoa...this is news to me. I'm in the middle of a 4th gen swap and all that's left is brake line work. I was going to just rip off the lines on the LS1 rear and make my own to go from the calipers to meet in the middle to use the 3rd gen T connector. I also bought an adjustable prop valve from Summit (the one with one input, one output, and a ****).

Are you saying that I can remove the stock valve...run lines straight from the master cylinder to each of the front brakes, and then just put the adjustable valve in-line with the rear brakes? I guess it makes sense.. I never thought about that.


Oh, and also, as stated above is correct. Line length means nothing..

 

No, you dont run lines strait from the MC to the front calipers. The prop valve splits the pressure between the front and back brakes. It is the next thing in line from the MC, DO NOT run a line directly from the MC to the calipers

 

...

Then why did somebody say to get rid of the stock proportioning valve and replace it with an adjustable one... or is what I bought not really a proportioning valve..it just limits the pressure in a line?

 

You replace the stock one with the adjustable one. Wait, I just reread your post, one in and one out? Thats not a prop valve, it does sound like a pressure limiter. Guess I should have read more closely the first time. I don't know what you would do with what you got.

 

lots of guys run the line from the master to a line-loc, then strait to the front brakes

the rear goes from the master to a adjustable prop valve, then the the rears



our stock prop valves do not do anything to the front pressures, just the rear, since rear drum brakes need less pressure to work

but, it you do away with the stock valve, you lose the brake pressure warning switch functions

 

I'm surprised no one has mentioned this. To keep my stock prop valve I just gutted it(rear side) and ran the line to the wilwood adj prop. The front lines go from the stock prop valve to the line lock and custom braided line to each front brake. I need to bleed the system again though. Seems kind of squishy.

 

Dave Y i agree with you. that was my original thourght, so would you say i can ditch the OE prop valve and run the line lock and adjustable valve and be ok.

 

Thats what I plan on doing when I do my C4 front/4th gen rear upgrade

 

thanks for the help

 

With this setup, the brake warning switch/sensor would still operate correctly, no?

 

Yeah, I guess I left that out. That's why I did it like that so that I could keep the stock BRAKE warning light functional if I ever have any problems or if for some freak chance I let someone else drive my car (yeah right...)

 

I appologize if I am re-asking a question, but i have searched and can't find answers...I am in the middle of plumbing the brakes on my 84 Z28 for drag racing..hard lines from m/c to l/l to prop to frame mounts to stainless braided tfe w/ -3AN fittings on stock calipers. what size is the brake line and/or the fittings...i am having trouble gathering all the peices. I can build it all if need be, but what materials do i start with?

 

what size fittings on the 84 m/c. what size fittings on the 82m/c. the 82 came with drum rear and v-6, will that m/c work on the 84 z28 four wheel disc with minimal or no pressure difference...prop not a problem..aftermarket will be in order