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08-21-2021 #1Registered User
- Join Date
- Jun 2009
- Location
- Bangor, Northern Ireland
- Posts
- 44
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.
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08-21-2021 #2
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/TechTroubleshootingTracey
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08-21-2021 #3Registered User
- Join Date
- Jun 2009
- Location
- Bangor, Northern Ireland
- Posts
- 44
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.
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08-21-2021 #4
Honestly? Everything I build from here on out will be manual brakes and eliminate this booster stuff altogether.
Tracey
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08-23-2021 #5Registered User
- 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.
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08-23-2021 #6Registered User
- Join Date
- Jun 2009
- Location
- Bangor, Northern Ireland
- Posts
- 44
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08-23-2021 #7Registered User
- Join Date
- Jun 2009
- Location
- Bangor, Northern Ireland
- Posts
- 44
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.
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05-17-2022 #8Registered User
- Join Date
- Jun 2009
- Location
- Bangor, Northern Ireland
- Posts
- 44
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.
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05-18-2022 #9