brake help!!!

[wilsonmotors]

ok i have a 1986 k5 that i have done a one ton swap on. the problem im having is when i swaped my axles i also up graded my mc for the bigger brakes and now my factory lines for the 1/2 ton mc wont fit the 1 ton k30 mc that i up graded to. is there any way to find out a way to fix this or does anyone know the factory k5 line and nut size at the mc and the factory line and nut size for the k30 at the mc?

 

[Deuling]

If the nut sizes are different. Take the mc you wanna use to a parts store and match it up. Put the new nuts on and reflare the lines. Or just put the old one back on and not do any of it

 

[diesel4me]

You can likely buy the correct brass adapter fittings to allow the brake lines off the original master cylinder to fit the "new" one,once you determine what size threads the "new" master has VS the original lines....in some instances you have to chop the old line nuts off and put the right ones on and re-flare the tubing though....

 

[dremu]

The K30 master is likely for hydroboost, so even with the lines fitted, the pushrod from the booster won't be right. I would highly recommend getting a new master for your truck (i.e. a K5).

-- A

 

[Deuling]

The K30 master is likely for hydroboost, so even with the lines fitted, the pushrod from the booster won't be right. I would highly recommend getting a new master for your truck (i.e. a K5).

-- A

Ihad thought of that, but unsure about hydroboost setups so i keeps quiet

 

[Lifted87chevy]

I would just stay with your stock setup. I have tons and disc all around with a 1/2 ton master. No problems in over a year.

 

[xenomarine]

I would just stay with your stock setup. I have tons and disc all around with a 1/2 ton master. No problems in over a year.

Same here, the thing stops phenomenally. Much better than it did with stock axles and 31s. Just get a new stock MC and you should be ready to roll.

 

[dremu]

Ihad thought of that, but unsure about hydroboost setups so i keeps quiet

Sadly, I have first-hand experience. On the sixpack I converted to disc and dually and hydroboost all in one go, and it's a big giant cluster-fsck of unreliable failing messy nonstandard parts.

If it ain't broke, don't fix it, and even if it is broke, keep it stock as much as you can.

-- A

 

[chulisohombre]

You can find the brass fitting at the parts store. I did on a old project. My 4 wheel disks work good on my 72 s stock master. I just gutted the pressure valve to the rear brakes. Good to go now.

 

[wilsonmotors]

my truck is a 86 k5 with 6.2 and hydroboost so i ordered a new mc for a 86 k30 4x4 with a 6.2 with hydoboost i figured it would be the same lines just a bigger bore mc and would bolt right up. i just grabbed the lines and propotioning valve off of a 84 k3500 2wd dulliey with a 6.2 and im gunna try to put the new valve and lines on my truck here in a day or two and maby it will work. i just think that with the bigger brakes of the d60 and 14ff and the new 37's i need a bigger mc to stop the extra weight of the truck.

 

[Fordum]

Remember, the smaller the MC piston diameter, the more pressure you send to the wheel cylinders per pound of pressure on the pedal, but the less volume you send.

But, with hydroboost helping, pedal pressure is not that much of a factor unless you lose boost.

 

[diesel4me]

My 82 K2500 has a 6.2 and hydroboost brakes,I put a master cylinder I had off my old 77 GMC K2500 that was from a vacuum booster system with a 400 SB,and the push rod seat is the same depth as the original master cylinder was,it bolted right up fine...the one off the hydroboost was a "square" Bendix cylinder with a small rear fluid chamber and a larger front one,the Delco one off the '77 has two equal sized fluid chambers.......................................................................................................................................................................................................---I had to use adapters to put the steel lines in the proper locations,I learned quickly you cant just swap the lines around just because they happened to fit the ports though!..I had the rear wheel cylinders hooked to the front disc chamber,and all it would do was lock the rears up instantly...after putting the lines back in the proper plce,it stops fine now...unfortunately the master cylinder now weeps fluid from the rear of it,and I must refill it every few days,so it looks like I wasted my time "saving" that rebuilt one off my old '77 GMC..have to replace it anyway...

 

[375 H&H]

to put the 1-5/16", 1 ton master cyllinder into a 3/4 ton (or smaller?), you need the 1/2" to 9/16" inverted flare adaptor, Edelman 258307 and the 9/16" to 1/2" inverted flare adaptor, Edelman 258306. these are steel and available from O'Rieleys. Weatherhead part numbers 7912 and 7913 are similar, only in brass.