Brake issues on power brake update. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ricktfd · 10-31-2019, 09:36 PM

I have a 64 SWB C10 with brake issues. It has a 5 lug conversion, with disc front/ drum rear, but was non power. I recently installed a new dual booster/ master cylinder unit from CPP. I have good vacuum and the check valve is working properly. When I brake for regular stop and go traffic I have decent stopping. But at highway speeds or on hard braking, I have to stand on the pedal and hope I can get it to stop. It is as if I didn't have power brakes at all.
I am at loss on where to go now. Any ideas would be appreciated.

**slepysal** · 10-31-2019, 09:53 PM

How is your vacuum to your booster,where are you pulling your vacuum from? Is the check valve good? Did you re drill your brake pedal?

**Captainfab** · 10-31-2019, 11:36 PM

What is the diameter of the booster? And is it a dual diaphragm or single. The smaller the diameter of the booster, the less braking assist you will have. How much vacuum does your engine produce?

**The Rocknrod** · 11-01-2019, 08:05 AM

Do you know what the diameter of the brake cylinder is? Inside the master cylinder.
What size are your brake lines?

LostMy65 · 11-01-2019, 08:38 AM

Quote:

Originally Posted by ricktfd

I have a 64 SWB C10 with brake issues. It has a 5 lug conversion, with disc front/ drum rear, but was non power. I recently installed a new dual booster/ master cylinder unit from CPP. I have good vacuum and the check valve is working properly. When I brake for regular stop and go traffic I have decent stopping. But at highway speeds or on hard braking, I have to stand on the pedal and hope I can get it to stop. It is as if I didn't have power brakes at all.
I am at loss on where to go now. Any ideas would be appreciated.

Try adjusting the pedal rod under the dash, I struggled and struggled with mine until I adjusted it to engage sooner.

AcampoDave · 11-01-2019, 09:52 AM

Quote:

Originally Posted by ricktfd

But at highway speeds or on hard braking, I have to stand on the pedal and hope I can get it to stop. It is as if I didn't have power brakes at all.
.

Wait a minute, I have manual disc and I have never had to stand on the pedal and hope I can get it to stop at highway speeds or under hard braking. Is it possible that you already had some issues prior to adding the booster?

**The Rocknrod** · 11-01-2019, 10:46 AM

Also have you done the pedal ratio correct when you went to power disc?

LostMy65 · 11-01-2019, 11:16 AM

Quote:

Originally Posted by The Rocknrod

Also have you done the pedal ratio correct when you went to power disc?

I never did it on my 66. I left it in the same hole.

10-31-2019, 09:36 PM	#1
ricktfd Registered User Join Date: Sep 2013 Location: Owasso, OK Posts: 2	Brake issues on power brake update. I have a 64 SWB C10 with brake issues. It has a 5 lug conversion, with disc front/ drum rear, but was non power. I recently installed a new dual booster/ master cylinder unit from CPP. I have good vacuum and the check valve is working properly. When I brake for regular stop and go traffic I have decent stopping. But at highway speeds or on hard braking, I have to stand on the pedal and hope I can get it to stop. It is as if I didn't have power brakes at all. I am at loss on where to go now. Any ideas would be appreciated.

10-31-2019, 09:53 PM	#2
slepysal Registered User Join Date: Oct 2006 Location: San Jose NOR*CAL Posts: 3,080	Re: Brake issues on power brake update. How is your vacuum to your booster,where are you pulling your vacuum from? Is the check valve good? Did you re drill your brake pedal? __________________ 1960 Apache long bed fleet L6 250 Clifford intake 2 bbl carb. Langdon cast headers with dual exhaust and bellflower tips. T-5 5 speed, power steering and power disc brakes. "Over, Around or through it... "

10-31-2019, 11:36 PM	#3
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,252	Re: Brake issues on power brake update. What is the diameter of the booster? And is it a dual diaphragm or single. The smaller the diameter of the booster, the less braking assist you will have. How much vacuum does your engine produce? __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

11-01-2019, 08:05 AM	#4
The Rocknrod Moderator Join Date: Aug 2011 Location: China Spring, TX Posts: 7,280	Re: Brake issues on power brake update. Do you know what the diameter of the brake cylinder is? Inside the master cylinder. What size are your brake lines? __________________ Master Chief, US Navy, Retired 1964 C10 Step-side Short Bed - In Progress 2009 2500HD Duramax LTZ 1948 GMC Panel 1956 Big Window Stepside 1953 5 Window Chevy Stepside 1932 Coupe New Seat Foam for Bench Seats?

11-01-2019, 10:46 AM	#7
The Rocknrod Moderator Join Date: Aug 2011 Location: China Spring, TX Posts: 7,280	Re: Brake issues on power brake update. Also have you done the pedal ratio correct when you went to power disc? __________________ Master Chief, US Navy, Retired 1964 C10 Step-side Short Bed - In Progress 2009 2500HD Duramax LTZ 1948 GMC Panel 1956 Big Window Stepside 1953 5 Window Chevy Stepside 1932 Coupe New Seat Foam for Bench Seats?

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