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Old 10-14-2024, 09:30 AM   #1
Knothead
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Soft Brake Pedal

Current project is using a 1979 K10 frame and suspension. Utilizing brake system from same, everything is new except hard lines. Drums , Rotors, proportioning valve , brake booster , Master Cylinder also were replaced. I can get a firm pedal but after cranking engine pedal fades to the floor? The brakes will hold the truck when in gear. Also will stop truck . Can’t get a good pedal with it running? Ordered another MC just to eliminate that as maybe the problem. I’m scratching my head on this one , looking for some suggestions and input. If it matters it is an 6.0 LS engine,thanks
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Old 10-14-2024, 10:30 PM   #2
cwcarpenter98
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Re: Soft Brake Pedal

Did you drill a new hole for the power brake pedal ratio?
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Christian Carpenter

1963 C10 - Frankentruck 283, Muncie 3 speed with overdrive
Overdrive wiring here
1963-ish truck bed trailer - Half-Wit

1981 C10 - Penny 305, th350 --> Soon to be 350, Saginaw 4 speed

1995 Dodge Dakota Sport

"I'll put it simple: if you're going hard enough left, you'll find yourself turning right." - Doc Hudson
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Old 10-15-2024, 03:40 PM   #3
forestb
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Re: Soft Brake Pedal

Are you getting enough vacuum? I had a lot of problems with brakes due to having too large of a cam which decreases vacuum.

Last edited by forestb; 10-15-2024 at 03:47 PM.
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Old 10-15-2024, 03:43 PM   #4
forestb
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Re: Soft Brake Pedal

Quote:
Originally Posted by cwcarpenter98 View Post
Did you drill a new hole for the power brake pedal ratio?
I thought that drilling the new hole was so that after converting to power breaks the brakes are too sensitive and by moving the hole you are making it less sensitive.
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Old 10-15-2024, 10:26 PM   #5
cwcarpenter98
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Re: Soft Brake Pedal

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Originally Posted by forestb View Post
I thought that drilling the new hole was so that after converting to power breaks the brakes are too sensitive and by moving the hole you are making it less sensitive.
Someone who has done that conversion will have to chime in on that question. I kept my truck non-power, even with the front disc swap. My initial question was partly to help the conversation begin since that's a common question anyways
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Christian Carpenter

1963 C10 - Frankentruck 283, Muncie 3 speed with overdrive
Overdrive wiring here
1963-ish truck bed trailer - Half-Wit

1981 C10 - Penny 305, th350 --> Soon to be 350, Saginaw 4 speed

1995 Dodge Dakota Sport

"I'll put it simple: if you're going hard enough left, you'll find yourself turning right." - Doc Hudson
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Old 10-15-2024, 10:32 PM   #6
AcampoDave
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Re: Soft Brake Pedal

^^^ I did that too. They work just fine unboosted. Sure, you have to push harder but no more so than the factory brakes required.
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Old 10-16-2024, 08:46 AM   #7
Knothead
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Re: Soft Brake Pedal

Thanks for the input, I’m chasing my tail on this one ! I did the math equation on pedal ratio and it came out to what it’s supposed to be for power assist brakes. I’m going to recheck it again and make sure I did it correctly
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Old 10-16-2024, 05:30 PM   #8
Knothead
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Re: Soft Brake Pedal

THANKS EVERYONE!!! Y’all steered me right to the problem . I had the ratios for the brake pedal backwards .I was thinking 6:1 for power assist and 4:1 for manual ???? Drilled a hole in the correct location and now I have a BRAKES and a firm pedal !!
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Old 10-21-2024, 02:27 PM   #9
MikeN
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Re: Soft Brake Pedal

Glad you got it fixed - drilling the lower hole is a must.
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Old 10-21-2024, 04:06 PM   #10
geezer#99
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Re: Soft Brake Pedal

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Originally Posted by MikeN View Post
Glad you got it fixed - drilling the lower hole is a must.
Not always!
If you have a bellcrank between your firewall and booster you use the existing hole.

https://www.speedwaymotors.com/Power...iABEgJdvvD_BwE
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