New member, need advice - brakes

[ChromeDome Al]

Hello from your redneck brethren in Montana! I acquired a '70 K10 LWB (which was apparently dubbed Optimus by a previous owner) a few years ago when I lived in WA. It has a built 396 (w/ a wild cam), Edelbrock 750cfm, Flowmaster 40's, a 6-inch Skyjacker/Bilstein lift, 35-inch mudders, eats Priuses, and breathes fire. The body is straight, and sounds like there isn't any mud in the panels, but it wasn't blocked out when it was repainted (I'm guessing 10 - 15 years ago). The interior ain't worth a Thai hooker, but she gets down the road alright. Wait a sec...no, I take that back. She has some wicked gearing - Like 5.28's or something. I'm in 3rd before I leave the parking lot. No joke. Top speed - 45 mph, grandma style. I couldn't get a speeding ticket even if I wanted.

So, on to the main purpose of this post - my brakes. But a disclaimer first: I'm a self-taught, young, impressionable mechanic. I learned to turn a wrench on my '63 Pontiac Tempest and my '07 Subaru Outback XT (a turbo'd grocery-getter that knocks the socks off of hairy granola mommies.) Any future claims of stupidity are valid - I don't know what I'm doing. I have a basic understanding and knowledge of vehicles (because of youtube) and I have about 6 tools (which aren't actually mine). But I love to tinker, so let's get on with it.

I just dug the pickup out of storage in WA and brought it to MT on a flatbed. After getting it started, fighting the shift linkage, and re-installing the column, I figured out the truck REALLY wants to go, but it doesn't want to stop. I was sure there was condensation in the lines, so I bled the brakes. The fronts had a mega-strong stream out of the bleeder valves, while the rears had more of a dribble. I bought the pickup as it is now - disc front/drum rear. Also, the booster appears to be newer. The brakes have barely enough power to stop the truck from a rolling start. So they're engaging, but not very well.

I've ruled out all issues with hardware (such as pads, calipers, discs, shoes, drums). So...what are my options with the brakes? How can I tell that the master is good? Could it just be a proportioning valve issue? I assume there is no holes in the hard-lines because there aren't any drips, but is it possible there's not enough pressure to force some air out? Also, with a wicked lope on the cam, is it stealing too much vacuum from the booster? (Hopefully, my pictures have posted. this is my first time using a server-based photo sharing system.) Check out my pictures and see if the hardware gives you any clues, (such as, "hey, the ass-hat who put discs on that truck didn't put the right master on!" or any relevant notions.

Thanks for any and all input! Back to pretending like I'm working.

[cdowns]

r u positive that you have disc brakes in front?? if so you have wrong system as you r picture is a distribution block from a 4wheel drum system and it appears to have the wrong master cylinder too

[ChromeDome Al]

That's exactly what I suspected...I'm abso-tootly positive that I have discs up front. I had a feeling that some of the under-hood hardware wasn't updated when someone made the switch to discs, hence why I posted some pics. So basically, I have hardware that isn't capable of pushing the amount of hydraulic power needed for discs, making my pedal feel squishy? Like, REALLY squishy?

Thanks for the reply, cdowns.

[MFCopenhagen]

Subscribed - I have the same setup on my '69. The PO installed front disks, but didn't change out the master cylinder/dist block with the proper setup. I purchased a new setup through CPP, but have yet to install it. I should have time to tackle it this week.

[BOHICA-Chevy68]

Looks like a 3/4 ton setup as well. New proportioning valve and master cylinder should fix it.
Posted via Mobile Device

[ChromeDome Al]

Awesome, now we're getting somewhere. Thanks for the replies, gents.

MFcopenhagen - let me know how it goes. The CPP kit looks tasty. I wonder if my radical cam would steal too much vaccuum...

[ChromeDome Al]

MFCopenhagen, did you end up throwing on that kit? If I'm not mistaken, it's manufactured by Rez Engineering right here in my hometown - Great Falls, MT.

I bled the s*** out of my brakes for about 1.5 hours, until finally I got a massive pressure bubble pushed out. Now I'd say I have about 50% brake capacity - enough to get my skinny a** down the road. But I am still not happy with 50%, obviously. In hindsight, I should have bench bled the master, but it's all said and done now.

I decided against the whole kit - booster/prop valve/master. I think the booster is alright, assuming my wild cam isn't stealing too much vacuum. So I will start with just the prop valve (will pick it up tomorrow at Rez), test the brakes, then get the master if that doesn't work. 35" tires on 10" wide wheels is a lot of rotational inertia, so I'm contemplating re-doing the whole system...but first, the prop valve...

[jocko]

Originally Posted by BOHICA-Chevy68

Looks like a 3/4 ton setup as well. New proportioning valve and master cylinder should fix it.
Posted via Mobile Device

Just for SA, I don't believe it's a 3/4 ton setup - if it were, the front reservoir would be going to the rear of the distro block and the rear reservoir would be going to the fwd port on the distro block I believe.

[Roninwolf]

If the cam is as big as you say it is you need a vacum canister. http://www.summitracing.com/parts/mrg-3701

[ChromeDome Al]

jocko, thanks for your input.

Roninwolf, thank you as well. I've actually never even heard of a vacuum canister. Which is no surprise - I make a better cook than I do mechanic. Anyway, you've given me a great option. I now have a plan of attack - I will first change out the distro block and test it out (it needs to be changed out anyway.) If no improvement, I will install this canister. Then, if I still don't have any improvement, I can assume the master needs to be upgraded.

[MFCopenhagen]

I haven't had a chance to do the brakes yet. Been doing a lot of wiring and been very busy at work. Hopefully, I can get to it soon.

[MFCopenhagen]

I started a thread on this a few months back and completely forgot about it. The fellas here really know what they're talking about. Maybe it'll help....

http://67-72chevytrucks.com/vboard/s...d.php?t=562685

[ChromeDome Al]

There's some good information in there! Sounds like you're in the same situation as me...

I'm about 90% certain that my distribution block (which should be a prop valve) is at least one of the culprits, if not THE culprit. If not, I'm looking at the canister and master as well.

I didn't get the valve today, but instead purchased some aircraft stripper and sanding supplies so I can start this weekend on spiffing up the interior. But I plan to get the valve and throw it on sometime this week. Keep me updated on your progress and I'll do the same. Good luck!

[Murphy IRE]

I only had one problem with my brakes, they didn't work well.
I started with all the basics and when I got to the end; it was barely any better. How many inches of vacuum do you have? I had less than 13, so my booster won't get it done. I added an electric vacuum pump and a canister; a little improvement. I put a power assist system from ABS (they're in CA) to the power steering pump. The first time I hit the brakes ( I was going 5-7MPH) everything flew off the bench and I almost went through the window. It was around $750, but it is worth every penny. I can stop on any mountain road empty or fully loaded.
The thread is "WOW after everything, I finally have brakes!!!" The pics show the vacuum pump and now the new power boost!