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“Dylan’s” 89. Back at it!

89 Jimmy 6.0/4l80e/MAGNUM 205/d60/14bolt
Overview Gallery Discussion
I can't remember if you have rear discs or what you are running. I run an '83 Chevy P30 with disc/disc and a diesel and hydroboost MC on my '83 K5. I run a disc/disc aftermarket prop valve and also a manual prop valve on my rear circuit turned almost all the way down. It has a larger bore maybe like 1.4" or something but it works great with my rear discs. I have tons of stopping power and a nice firm pedal which is what I like. Check out my K5 build to see a little more on it.
I'm also wondering about your gutted prop valve. Did you leave the shuttle in the middle or just take out everything so that both front and rear circuits are all connected together at that point?
 
chris85 said:
It’s still a bit confusing to me how moving more volume does not mean more pressure but it obviously does.
Click to expand...

Pressure is pounds per square inch as you know. You can only put so much force on the pedal with your foot, so if you concentrate that force on a smaller area, the force per square inch, or pressure, will increase. In other words, PSI = lbs/area, so if you divide by a smaller area, the pressure will go up as it is inversely proportional to area at the same force.

Say 100 lbs for easy math (this doesn't include the brake booster or the pedal ratio that both increase the force).

Area of a circle is the radius squared times pi, or r times r times pi:

For 1.5" bore = 100 lbs / (.75 x .75 x pi) = 56.59 psi

For 1" bore = 100 lbs / (.5 x .5 x pi) = 127.3 psi

But as you found out previously, too small of bore won't move enough fluid to apply all the pistons in the wheel cylinders. Braided lines can help with that because they don't stretch as much, stretching with pressure takes unnecessary volume.
 
Last edited:
Kinda why I went bigger bore to get more volume for my rear disc conversion since they take more fluid than a wheel cylinder.
 
Truckman4life said:
I can't remember if you have rear discs or what you are running. I run an '83 Chevy P30 with disc/disc and a diesel and hydroboost MC on my '83 K5. I run a disc/disc aftermarket prop valve and also a manual prop valve on my rear circuit turned almost all the way down. It has a larger bore maybe like 1.4" or something but it works great with my rear discs. I have tons of stopping power and a nice firm pedal which is what I like. Check out my K5 build to see a little more on it.
I'm also wondering about your gutted prop valve. Did you leave the shuttle in the middle or just take out everything so that both front and rear circuits are all connected together at that point?
Click to expand...

It’s a disc/disc. I just meant by “gutted” that there was no actual valves. I guess distribution block would be the proper term.


folkenheath said:
Pressure is pounds per square inch as you know. You can only put so much force on the pedal with your foot, so if you concentrate that force on a smaller area, the force per square inch, or pressure, will increase. In other words, PSI = lbs/area, so if you divide by a smaller force, the pressure will go up as it is inversely proportional to area at the same force.

Say 100 lbs for easy math (this doesn't include the brake booster or the pedal ratio that both increase the force).

Area of a circle is the radius squared times pi, or r times r times pi:

For 1.5" bore = 100 lbs / (.75 x .75 x pi) = 56.59 psi

For 1" bore = 100 lbs / (.5 x .5 x pi) = 127.3 psi

But as you found out previously, too small of bore won't move enough fluid to apply all the pistons in the wheel cylinders. Braided lines can help with that because they don't stretch as much, stretching with pressure takes unnecessary volume.
Click to expand...

That makes sense. Yeah all my soft lines are braided and then stainless hardline the rest.

If this doesn’t do the trick I might just say sh!t on it and go hydroboost. I have the Ps pump for it already.

I have just been so confused because you see so many people on here with such different results but running almost identical setups. Of course brakes are so subjective that it probably hard to find the ideal setup. I ended up asking @nvrenuf what he was running and copied his setup. Well come to find out there are more than 1 kind of MC that was ran in the 99 3500. So what’s on order now is the same basic MC with the smaller bore.
 
Good news on the trip!

Someone needs a little better muzzle control...:eek1:

75368BD0-1B7D-4B04-8131-75F0E1C30038.jpeg
 
Well, I ordered a new driver side window seal :dunno:

Its been hard getting the motivation to work on the truck when it’s 30min away. I did see that ORD is having a Black Friday sale so maybe I can splurge on some shocks!
 
Are y'all in a new house yet or are you commuting from Jackson?
 
Finally got my crap together enough to get my baby over to the new house. Of course the battery was completely drained. Not sure if the alternator is going or if the idle is set too low. I ran it for about 30 min then shut it off. Went to crank again and it was completely dead. Even after jumping it off it would only stay running for a minute and die. Got the battery home and checked the voltage, 2.3 volts :doah:. Battery is charging and we’ll give her another try later in the week.
 
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