I've been dying to drive the car, but it's been raining like hell. Bored, I went out to the garage to start the car just to smell it burn. Decided to power brake it a little just to see how much boost I could hold. I was extremely happily surprised as I've done nothing special; just a vacuum conversion from GBodyParts.
Holding 17 PSI on the foot brake
- Thread starter 87-WE2
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laws69cars
Active Member
- Joined
- Apr 8, 2011
Nice!!!!!!!
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Don't forget the big wheel cylinders and shoes from an S10
I forgot to post about them, but didn't forget to put them on the car!!
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turbocamino1
turboholic
- Joined
- Jul 7, 2007
did you see a difference from the p/master and vacuum,regarding the amount of boost it would hold powerbraking? I have the s-10 w/cyl's , long shoes and every piece of hardware from lines to proportioning valve and i still cant hold more than 5 lbs...thinking it may be more of a function of stall?
My Powermaster never worked well. The brakes were always touch with it. I replaced the accumulator ball one time, and they worked well for a couple of months, but my pedal would get firm intermittently while driving. Once the Powermaster motor began leaking (pretty badly), I sentenced it to death by removal and switched over to vacuum to save a few bucks and a lot of headache. The vacuum hold better than the PM, but it's not a fair comparison in my case because when I did the vacuum conversion, I did the S-10 cylinders and long shoes, plus one of the hard lines at the rear that was leaking.
My opinion (from all that I've read on here) is that IF the PM system is working 100%, they are more effective than vacuum. My issue was reliability; in that I didn't want to constantly be spending $200 on accumulator balls and having PM motors rebuilt. Since I've done the conversion, I haven't had to think about whether I was going to have to push harder than normal at the next stop light.
My post was just to indicate that I'm pleasantly surprised that I can hold that much boost with Vacuum brakes.
My opinion (from all that I've read on here) is that IF the PM system is working 100%, they are more effective than vacuum. My issue was reliability; in that I didn't want to constantly be spending $200 on accumulator balls and having PM motors rebuilt. Since I've done the conversion, I haven't had to think about whether I was going to have to push harder than normal at the next stop light.
My post was just to indicate that I'm pleasantly surprised that I can hold that much boost with Vacuum brakes.
Dan, that's fantastic! I'm like alot of other guys on here and can't seem to build much more than 4-5 psi before the wheels start to turn. I have upgraded the same as you with the vacuum set-up and s-10 wheel cylinders. What converter are you running? I still have the stock D5 and figured that was my problem.
Me too and I bent the plate that the backing plate bolts to also
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Stock d5.
Maybe it's the way you're building boost. What I do is go to neutral and rev the motor slightly (to say, 2500 rpm). Let off the gas, and on the way down, notice your boost gauge show a slight increase in vacuum. Step on the brake pedal then. Keep it to the floor and build boost slowly at part throttle. After seeing some of the comments from other members, maybe this is bad advice. I know it's hard on the converter, and I didn't think about the backing plates. I will reserve this for the track for sure.
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MonstrNrgy
Member
- Joined
- Aug 2, 2011
Antique plate that thing.. $60 for 5 years in TX with no inspection. That's how I have mine 
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The 3/4 " s-10 heavy duty wheel cylinders are spreading the brake pads apart, the wheel cylinders are bolted to the backing plates. I am thinking that the wheel cylinder "plunger" has a little side to side slop which results in the one brake pad maybe pushing out a little causing the deflection. That deflection put a tiny twist on the wheel cylinder and the backing plate gives. Now that I think about it , maybe the brake hardware tolerances need to be better and take up the slop as well as heavy duty backing plates. When I had the original brake hardware on and large equal length shoes I held more boost. When i switched back over to 3.42 gears I did a brake hardware change ( degrease, clean up type change) and thats when I bent the backing plate. I bet I looked at the original hardware and compared it to the local autoparts store, there might be some thickness differences. Hmmmm?
TexasT
Texas, Where are you from
- Joined
- Sep 10, 2002
Well, the axle is trying to spin, and the brakes are holding the drum on one end and the backing plate on the other. Just a case of the weakest link in the chain failing.
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