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    Results 1 to 16 of 16
    1. #1
      Join Date
      Jun 2009
      Location
      Bangor, Northern Ireland
      Posts
      43

      Help me diagnose hard brake pedal (Wilwood '69 Camaro)

      Hi guys

      My Dad's purchased a pro touring '69 Camaro around 5 years ago. The previous owner spent a fortune on the car but never drove it enough to iron out all the bugs. We've been gradually going round the car and addressing issues.

      We've just installed a small block 427 and got her running great. Now it's time to address the brake issue.

      The brakes are terrible. It's just a rock hard pedal and not much stopping going on.

      The brakes are -

      FRONT

      Wilwood - 140-7675

      https://www.wilwood.com/BrakeKits/Br...mno=140-7675-D

      REAR - 140-7149

      https://www.wilwood.com/Search/PartNoSearch?q=140-7149

      Basically standard Wilwood fare. 12.19" discs and Dynalite calipers


      12v vac pump

      https://www.summitracing.com/parts/clp-12vvcp

      7" booster

      https://www.summitracing.com/parts/sum-760121k

      SSBC master cyl 1 1/8"

      https://www.summitracing.com/parts/tsb-a0469-1

      The car also has Wilwood adjustable brake bias


      So, the car has always had a rock hard pedal from when we bought it. We only now are ready to finally sort it.

      The pedal is hard with engine off. it's as if it's all hydrolocked. we tested the booster with a vac gauge and it holds 18" of vac with the electric pump. When i pump the pedal a few times then start the car the pedal doesn't sink at all like it should. just stays where it was. If i push any harder you can see the booster and master cylinder moving at the bracket to the firewall.

      With the car running the pedal is still hard, when i turn the engine off the pedal doesn't sink at all.

      I looked at the pedal ratio and it looks ok, there's two holes in the pedal and it's on the lower hole (more leverage). I'm suer this is fine, if not it can be addressed after the hard pedal is sorted.

      I'm leaning towards a booster issue. there's no sound from the booster, no air hiss or anything ever.

      I'm at the point where i'm going to purchase a brake pressure gauge kit to test the pressure at the calipers. I'm at the point where i should take the booster off and see what i can see.

      We have good ingredients on the car. Just needs tweaking.

      Any advice appreciated.

      Bear in mind I'm in Northern Ireland so i can't just pop down the road and buy parts. I need to know exactly what i need before I order stuff from the States as that $100 part become a £150 part by the time it's got duty and freight added.

      Thanks!

      Aaron.

    2. #2
      Join Date
      Feb 2019
      Location
      Kankakee IL
      Posts
      362
      Of everything I see on your list the thing that stands out is the size of your master cylinder at 1 1/8" being larger than recommended by Wilwood.

      https://www.wilwood.com/TechTip/TechTroubleshooting
      Tracey

    3. #3
      Join Date
      Jun 2009
      Location
      Bangor, Northern Ireland
      Posts
      43
      Quote Originally Posted by Tsaints1115 View Post
      Of everything I see on your list the thing that stands out is the size of your master cylinder at 1 1/8" being larger than recommended by Wilwood.

      https://www.wilwood.com/TechTip/TechTroubleshooting
      Thanks for that, i'll check that out. The calliper size and master cylinder size I have are very similar to my '69 Vette which has standard brakes except Yellow Stuff pads and the brakes are amazing.

      I'm more concerned with the hard pedal/lack of booster scenario going on. If i can sort that out then i can check out other things.

      ie are there any other ways to check the booster? I'm happy to take it off, whatever it needs.

    4. #4
      Join Date
      Feb 2019
      Location
      Kankakee IL
      Posts
      362
      Honestly? Everything I build from here on out will be manual brakes and eliminate this booster stuff altogether.
      Tracey

    5. #5
      Join Date
      Mar 2005
      Posts
      345
      It may be that the booster is bad. But at the same time I'd say that the system is mismatched. The 7" booster is nearly worthless, the M/C bore is too large, and the pads are borderline.

      Stock calipers have a surface area of 6.78 sq/in. With an 11" booster and a 1-1/8" M/C.

      Now the front calipers have a surface area of 4.8 sq/in, with the same 1-1/8" M/C and a really small booster. The BP10 pads aren't that great either.

      Note that your '69 Vette has yellow stuff pads, about the highest coefficient of friction available for street use. And it is a factory balanced system.

      First thing I would do is to go with either an 11" single or a 9" dual diaphragm booster. Can also upgrade the pads at the same time or later. If new pads get installed be sure to bed them.

      Then see how the braking is. If not good enough may need to drop down in M/C bore size, probably to a 15/16".

      Bob.

    6. #6
      Join Date
      Jun 2009
      Location
      Bangor, Northern Ireland
      Posts
      43
      Quote Originally Posted by Tsaints1115 View Post
      Honestly? Everything I build from here on out will be manual brakes and eliminate this booster stuff altogether.
      Hi, i do like P/B, although I can see the appeal of manual brakes.

    7. #7
      Join Date
      Jun 2009
      Location
      Bangor, Northern Ireland
      Posts
      43
      Quote Originally Posted by a67 View Post
      It may be that the booster is bad. But at the same time I'd say that the system is mismatched. The 7" booster is nearly worthless, the M/C bore is too large, and the pads are borderline.

      Stock calipers have a surface area of 6.78 sq/in. With an 11" booster and a 1-1/8" M/C.

      Now the front calipers have a surface area of 4.8 sq/in, with the same 1-1/8" M/C and a really small booster. The BP10 pads aren't that great either.

      Note that your '69 Vette has yellow stuff pads, about the highest coefficient of friction available for street use. And it is a factory balanced system.

      First thing I would do is to go with either an 11" single or a 9" dual diaphragm booster. Can also upgrade the pads at the same time or later. If new pads get installed be sure to bed them.

      Then see how the braking is. If not good enough may need to drop down in M/C bore size, probably to a 15/16".

      Bob.
      Hi Bob, thanks for taking the time to reply, much appreciated.

      The car is in a storage unit. Dad and I are going to bring the car back to my place tomorrow after work. It'll be the first drive with the new 427.
      Once back home I can play around with the car. It would appear a bad booster is the culprit although i need to be sure.
      The car has a hydraulic clutch, the clutch master cylinder position being the reason for the 7" booster with vac pump.
      We might change the clutch master cylinder location so we can fit a stock size booster back on. I'd prefer the stock booster and the stock clutch linkage in an ideal world but too late to do that....we could always change the 7" booster out for a new 7" booster but were not sure it ever worked properly.

      We're thinking of changing the pads out for yellow stuff on the Camaro too.

      anyhow i'll do some investigating tomorrow night and report back.

    8. #8
      Join Date
      Jun 2009
      Location
      Bangor, Northern Ireland
      Posts
      43
      We have clutch and brake issues, they are linked due to the hydraulic clutch requiring a 7" booster. Just sorting the clutch issue first which may allow me to change booster size.

    9. #9
      Join Date
      Sep 2010
      Location
      Beach Park IL
      Posts
      2,838
      Country Flag: United States
      Use the DSE booster/master and their hydraulic clutch set up or equivalent and that should cure 90% of your issues here.

      1.125 master is too large. 7" booster is too small.

      Not all vacuum pumps are created equal either. I just replaced one that was making all of 15 inches and took foooorrrrever to to recover. Leed Brakes has a nice one that is very quiet.
      Donny

      Support your local hot rod shop!

    10. #10
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      15,971
      Country Flag: United States
      Quote Originally Posted by dontlifttoshift View Post
      Use the DSE booster/master and their hydraulic clutch set up or equivalent and that should cure 90% of your issues here.

      1.125 master is too large. 7" booster is too small.

      Not all vacuum pumps are created equal either. I just replaced one that was making all of 15 inches and took foooorrrrever to to recover. Leed Brakes has a nice one that is very quiet.
      ^This!

      Andrew
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    11. #11
      Join Date
      Jun 2009
      Location
      Bangor, Northern Ireland
      Posts
      43
      Quote Originally Posted by dontlifttoshift View Post
      Use the DSE booster/master and their hydraulic clutch set up or equivalent and that should cure 90% of your issues here.

      1.125 master is too large. 7" booster is too small.

      Not all vacuum pumps are created equal either. I just replaced one that was making all of 15 inches and took foooorrrrever to to recover. Leed Brakes has a nice one that is very quiet.
      Hi Donny, thanks for the input.

      We've decided to go back to the stock Z-bar setup now. I love my vette clutch feel and adjustability. I'm just ordering the parts from SST.
      So that means we can ditch the 7" booster and go for something larger, hopefully back to an 11" (will have a measure to see what will fit but a stock size should).

      If we find the master cylinder bore is too large I could always swap the SSBC M\C onto the vette and get a smaller bore for the Camaro.

      Im trying to find a calculator to work out M/C bore size.

      We're also changing the rear gears from 3.73 to 3.25, gears have arrived. need to send diff off for setting up.

    12. #12
      Join Date
      Sep 2010
      Location
      Beach Park IL
      Posts
      2,838
      Country Flag: United States
      Not all headers clear the Z bar, just so you are aware.
      Donny

      Support your local hot rod shop!

    13. #13
      Join Date
      Jun 2009
      Location
      Bangor, Northern Ireland
      Posts
      43
      Name:  IMG_1231.jpg
Views: 472
Size:  587.0 KB
      Quote Originally Posted by dontlifttoshift View Post
      Not all headers clear the Z bar, just so you are aware.
      Thanks for that, Dad and I thought of that last night. I checked today and all looks good, The Dart block has the hole for the pivot ball so I've ordered -

      -Yellow speedo gear
      -Manual throwout bearing TKO retainer
      -Z bar kit
      -GM clutch fork

      I'll be glad to see the back of the hydraulic clutch, a really bad solution to a non existent problem. External adjustability is crucial for me to achieve the correct biting point and enjoy throwing the car around.

      I will order a stock 11" booster in the next day or so.

      I'm in Northern Ireland so give it a week or so to get here.

      In the meantime we'll get the diff out (9" Ford) and send the gears off to be setup. Then once we've fitted the gears we'll take the car to a local sprayers workshop to get the gearbox out on his lift. (he sprayed my wife's '66 Mustang)

      At the same time we'll swap out the valve stem seals on the Vette. gluttons for punishment! Back soon.

      Not sure if i'd ever shown a pic of the cars before so here we go!

    14. #14
      Join Date
      Jun 2009
      Location
      Bangor, Northern Ireland
      Posts
      43
      Deleted message



    15. #15
      Join Date
      Jun 2009
      Location
      Bangor, Northern Ireland
      Posts
      43
      Ok so Wilwood have replied, they suggest a 1" or 1 1/8" M/C, we have 1 1/8" so we'll stick with that for the moment. They suggest a minimum of an 8" booster at 18" vacuum. We have the vacuum pump, but hopefully we can remove that.

      I've just ordered an 11" booster.

      The mechanical clutch parts have arrived, 3 days from US to Northern Ireland! Will wait for booster to turn up then arrange to borrow a friends lift to get the trans out.

    16. #16
      Join Date
      Jun 2009
      Location
      Bangor, Northern Ireland
      Posts
      43
      Right then guys.

      The good news is the change from the 7" to 11" booster has resulted in a much improved pedal feel. More vac assist is noticeable at the pedal and the brakes are much better. Pedal is way too high at the moment so the rod from the rear of the booster will need to be cut down.

      The vac pump is still connected at the moment although the plan is to run the booster from the manifold.

      So that's good.
      Hyd clutch has been replaced with the z-bar arrangement, massive improvement, so sign of slipping as before and a decent clutch pedal position.

      Replacing what sounded good with what works

      Only problem we have now is a whine from the Tremec in 4th and 5th. it's been there since we put the 427 in so it's nowt to do with the z-bar etc.

      We will get the car back in the workshop soon and get her running on stands to track down the whine.

      Local show we went to last week, finally got My Dad's, my Wife's and my car together at a show.

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