Need help with my brakes - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1972 orange c10 · 03-14-2009, 11:17 PM

I hope someone here can help me figure my brakes out. My brake pedal has gotten really hard to push since i took my qjet off and put a holley 670 strret avenger. I just thought it was the booster so i replaced the booster and mc and bled the brakes and it was good for a day or so and now its hard again. I took proportioning valve off a parts truck i have and it didnt help. Could the holley be sucking more vacum than the qjet. If anybody could help me i would appreciate and by the way this is a awesome site i get on here everynight and get in trouble for being on computer too long. Thanks morgan

texanidiot25 · 03-14-2009, 11:20 PM

Sounds like there's no vacuum getting to the booster from the new carb... As I know nothing about holly's, have you tried swapping carbs, or where the booster plugs into for vacuum?

There should be no reason why a holly would affect manifold vacuum unless the booster is connected some place else.

72Much · 03-14-2009, 11:38 PM

Run the engine for a few mins and pull the hose from the booster. Should hear a burst of air when you do. This will let you know if the motor is feeding enough vacuum for your brakes.

1972 orange c10 · 03-14-2009, 11:58 PM

Thanks i will try that in the morning i have just got done doing a complete brake job on my four runner and messed with the truck. I have never had that kind of problems with brakes before. I do know the truck needs front brake hoses they are getting dry rotted but i didnt think that would have anything to do with a ahrd brake pedal. Thanks for the suggestions. Morgan

spinning wheels · 03-15-2009, 02:01 AM

Disconnect the vacuum hose to the booster. Insert a vacuum gauge into the hose, coming from the engine. You should be getting around 15 inches of vacuum.

Also check the valve that plugs into the booster. Its that small, round white plastic part, where you connect the vacuum hose to. They can go bad and not allow your motor to, in a word, suck. Its a one way valve.

Also, there is a small round rubber seal where the MC mates up to the booster. Check to see if it is there. You will need it. I was missing mine and the booster would not work. Felt like I had manual brakes and the pedal was hard as a rock.

Good luck

03-14-2009, 11:17 PM	#1
1972 orange c10 Registered User Join Date: Jun 2008 Location: cullman alabama Posts: 8	Need help with my brakes I hope someone here can help me figure my brakes out. My brake pedal has gotten really hard to push since i took my qjet off and put a holley 670 strret avenger. I just thought it was the booster so i replaced the booster and mc and bled the brakes and it was good for a day or so and now its hard again. I took proportioning valve off a parts truck i have and it didnt help. Could the holley be sucking more vacum than the qjet. If anybody could help me i would appreciate and by the way this is a awesome site i get on here everynight and get in trouble for being on computer too long. Thanks morgan __________________ 1972 c10 swb 406 buckets, tach, tilt, cruise, am-fm 1972 c10 deluxe highlander 350 tilt, tach, am-fm 1971 cheyenne 10 402, buckets, tilt, tach

03-14-2009, 11:20 PM	#2
texanidiot25 Eat My Rust Join Date: Jan 2007 Location: Cypress, Texas Posts: 3,362	Re: Need help with my brakes Sounds like there's no vacuum getting to the booster from the new carb... As I know nothing about holly's, have you tried swapping carbs, or where the booster plugs into for vacuum? There should be no reason why a holly would affect manifold vacuum unless the booster is connected some place else.

03-14-2009, 11:38 PM	#3
72Much Registered User Join Date: Nov 2006 Location: Newbern, Tn. Posts: 36	Re: Need help with my brakes Run the engine for a few mins and pull the hose from the booster. Should hear a burst of air when you do. This will let you know if the motor is feeding enough vacuum for your brakes.

03-14-2009, 11:58 PM	#4
1972 orange c10 Registered User Join Date: Jun 2008 Location: cullman alabama Posts: 8	Re: Need help with my brakes Thanks i will try that in the morning i have just got done doing a complete brake job on my four runner and messed with the truck. I have never had that kind of problems with brakes before. I do know the truck needs front brake hoses they are getting dry rotted but i didnt think that would have anything to do with a ahrd brake pedal. Thanks for the suggestions. Morgan __________________ 1972 c10 swb 406 buckets, tach, tilt, cruise, am-fm 1972 c10 deluxe highlander 350 tilt, tach, am-fm 1971 cheyenne 10 402, buckets, tilt, tach

03-15-2009, 02:01 AM	#5
spinning wheels Registered User Join Date: Sep 2001 Location: Hacienda Heights, California USA Posts: 474	Re: Need help with my brakes Disconnect the vacuum hose to the booster. Insert a vacuum gauge into the hose, coming from the engine. You should be getting around 15 inches of vacuum. Also check the valve that plugs into the booster. Its that small, round white plastic part, where you connect the vacuum hose to. They can go bad and not allow your motor to, in a word, suck. Its a one way valve. Also, there is a small round rubber seal where the MC mates up to the booster. Check to see if it is there. You will need it. I was missing mine and the booster would not work. Felt like I had manual brakes and the pedal was hard as a rock. Good luck __________________ '72 GMC custom camper 350/350 Last edited by spinning wheels; 03-15-2009 at 02:03 AM.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.