I can try that. Sounds a whole lot easier than converting to hydroboost.
If the trusty Googles is right if I'm getting 15-18 I'm just barely skating at the edge of acceptable.
I'm just stumped. The only thing I haven't replaced are the brake lines.
CK5
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PLAN B
This build was 2 parts 1 i have a truck I made to pretty to wheel so I'm building an ugly one I can actually enjoy.
And 2. My cousin has been trying to join us for blazer bash but his truck wont be ready so we are surprising him with this one
If the trusty Googles is right if I'm getting 15-18 I'm just barely skating at the edge of acceptable.
I'm just stumped. The only thing I haven't replaced are the brake lines.
79' block 350 with a torque cam. Nothing special.
My buddy way back had a gnarly cammed big block square body. Could only get one pump out of the pedal at idle coming to a stop sign and it was all out of vacuum and the brakes on it worked fine.
My other truck has a big cammed big block and basically the same brake setup except drums in the rear and it stops amazing.
I'm just out of ideas
I'm just out of ideas
I found my old post talking about my vacuum I was seeing. I'm back to not really thinking it's vacuum. 
@ashman called me and offered a really good suggestion. I am going to see if they can test the line pressure right off the master. If it's weak there then the issue is master, or vacuum. If it's strong there, maybe I have messed up brake lines. I'm going to see if my buddy has a Vacuum Reservoir I can borrow to test with.
After that I have run out of stuff to test
After that I have run out of stuff to test
What pads are on the truck? I saw you were thinking about slotteds and some sort of performance pad, not the option I'd go with. I didn't see the pad material though. Master could be a problem, 1.125 bore might not be happy with whatever caliper choice you chose, might have to go smaller bore to build more pressure.
Hydroboost is the bees knees, especially with low idle vacuum setup. Like anything else though the system has to work together to build the pressure. Master bore, pedal moment from your foot to the actuating rod, caliper choice, booster choice. Those are your line pressure variables. Pad material is a big one. If its a fancy pad go grab some napa fleet pads or something semi-metallic and try it (make sure you try it long enough to get the pads to transfer). If you weren't getting pad transfer that'll end your day right off the bat.
Start there with pad choice. Check your lines and bleed it again. After that its pressure related. Master bore size is a tradeoff between pressure and stroke required. This is where the calipers come into play as they have their own piston bore size that needs to be taken into account for.
Hydroboost is the bees knees, especially with low idle vacuum setup. Like anything else though the system has to work together to build the pressure. Master bore, pedal moment from your foot to the actuating rod, caliper choice, booster choice. Those are your line pressure variables. Pad material is a big one. If its a fancy pad go grab some napa fleet pads or something semi-metallic and try it (make sure you try it long enough to get the pads to transfer). If you weren't getting pad transfer that'll end your day right off the bat.
Start there with pad choice. Check your lines and bleed it again. After that its pressure related. Master bore size is a tradeoff between pressure and stroke required. This is where the calipers come into play as they have their own piston bore size that needs to be taken into account for.
I may have mentioned this before but I swapped back to 3/4 ton brakes on my Dana 60 on my K10 and it made a world of difference.
I used the brackets from Sky's off-road but there are a few others out there.
The Dana 60 caliper design is terrible with the metal on metal action instead of a dedicated slider mechanism.
I used the brackets from Sky's off-road but there are a few others out there.
The Dana 60 caliper design is terrible with the metal on metal action instead of a dedicated slider mechanism.
The front pads have been on the truck as long as the axle has been under it. Not sure what they are. The rears are powerstop extreme pads.
I have a 40mm bore master cylinder that's about 1.57" . I had a factory 1.125" bore master before that acted the exact same way.
I'm using factory style dana 60 front calipers and JB6 3/4 ton calipers in the rear.
I think line pressure is the issue not friction. I believe we should be closer to 1800psi vs 1k.
Its definitely a lower vacuum situation than most of the engines that came factory with that setup. Your MC bore size is huge and that's lowering the pressure but I can't say its the only cause. Is there a reason you need more fluid volume? I guess for diagnosis: is this a problem that crept up, or has it always been that way? If it wasn't like this before then you can probably disregard most of the below.
The rear calipers are fronts, and have a fairly small piston area comparatively speaking. causing total clamping force there to be lower. And are those ceramic pads on the rear?
Not that this matters much but I'm a believer in the rear setup causing noticeable driver 'feel' versus the front. Its what I've experienced all my life. Rear brake setup changed the way the car feels as a driver greatly, more-so than the bias would indicate. Maybe its just me, who knows.
There's probably not gonna be a magic bullet here, its all cumulative. Step to a reasonable size master cylinder instead of a huge one. Ditch the ceramic pads if that's what they are, put new pads on the front and take a cut on the rotors if you can, and grease and clean those slides as that should be normal maintenance on a 60 caliper. Bed em in to get the transfer (for brakes to do brake things well we want pad material on the rotor and pad, i.e. transfer).
If it was my truck and I was doing all that, hydroboost would be going on to. For a 40" tire truck, yes. Sure it doesn't sound like much over a 37 but it is and it can cover up alot of sizing error. With that said, get it right and you can lockup 42s.
Sorry my posts are probably disjointed, I've got short cycle times today on parts.
The rear calipers are fronts, and have a fairly small piston area comparatively speaking. causing total clamping force there to be lower. And are those ceramic pads on the rear?
Not that this matters much but I'm a believer in the rear setup causing noticeable driver 'feel' versus the front. Its what I've experienced all my life. Rear brake setup changed the way the car feels as a driver greatly, more-so than the bias would indicate. Maybe its just me, who knows.
There's probably not gonna be a magic bullet here, its all cumulative. Step to a reasonable size master cylinder instead of a huge one. Ditch the ceramic pads if that's what they are, put new pads on the front and take a cut on the rotors if you can, and grease and clean those slides as that should be normal maintenance on a 60 caliper. Bed em in to get the transfer (for brakes to do brake things well we want pad material on the rotor and pad, i.e. transfer).
If it was my truck and I was doing all that, hydroboost would be going on to. For a 40" tire truck, yes. Sure it doesn't sound like much over a 37 but it is and it can cover up alot of sizing error. With that said, get it right and you can lockup 42s.
Sorry my posts are probably disjointed, I've got short cycle times today on parts.
On the ls swap forums tons of guys convert to a 2001 Tahoe master. It's only a 34mm bore vs 40mm. I may give that a swing and see if it's any different.
I’m running factory booster and master cylinder for my 82, zero issues with the ls swap and a lumpy cam. 
Second the 3/4 ton calipers, D60 calipers and the mounting sucks…and they take a shat load of fluid to operate.
I did forget to mention one thing in the last post that is part of the equation. The proportioning valve. Once you get it all setup, brake bias needs to be adjusted. I bet this is another part of the equation that might be a little off too.
On the d60 calipers, while it does seem like it sucks and they do require maintenance to keep them nice and free, they actually do a damn good job. The internal sliders need that too. In a service environment they work and have worked for years.
On the d60 calipers, while it does seem like it sucks and they do require maintenance to keep them nice and free, they actually do a damn good job. The internal sliders need that too. In a service environment they work and have worked for years.
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^^^^ Agree
Smaller bore size equals a lot more pressure.
Smaller bore size equals a lot more pressure.
The 3/4 ton brake swap seemed like such a pain in the ass I never really considered it.
I may do a little research on that.
I was just doing some digging and I see that all the 80s 1 and 3/4 ton trucks have 31-34mm bore masters. I am thinking my master is way too big. I'm going to try the 34mm disk disk master for an 01 Tahoe. Way popular swap on the ls swap page
I may do a little research on that.
I was just doing some digging and I see that all the 80s 1 and 3/4 ton trucks have 31-34mm bore masters. I am thinking my master is way too big. I'm going to try the 34mm disk disk master for an 01 Tahoe. Way popular swap on the ls swap page
Definitely do that
The 3/4 ton swap is the same as changing axle shafts, you’re pulling the spindles and bolting on new caliper brackets, nicest part is not having to drive that stupid brake wedge back in to hold the caliper.
I measured my old master and it was also a 40mm just one for disk/drum. So the 40mm disk/disk made no difference or probability reduced rear pressure.
I have a 34mm master for a 01 Tahoe that we will try tomorrow. I suspect we are on to something
I have a 34mm master for a 01 Tahoe that we will try tomorrow. I suspect we are on to something
