Brake Pedal Not Returning

[Rambo819]

Hi All, I have a '49 Chevy pickup with an LS1 swap. I am using a frame mounted 7" power booster and master cylinder. The vacuum for the booster is connected to the port on the on the rear of the intake manifold. The problem I am having is the brake pedal returns fine when the car is off, as soon as I start the truck and press the brake pedal it will not return all the way causing the brakes to drag. I then have to pull the pedal up with my toes. I have replaced the power booster with a new one and am having the same issue. I do have a return spring on the pedal, looking to go to a bigger one but I am thinking something else is wrong that is causing the pedal to hang. I have checked the fit between the booster push rod and master cylinder and it seems to be correct. Does the ls1 make enough manifold vacuum to operate the booster correctly?

Does any one have any ideas what might be wrong?

Thanks in advance!

-Ryan

1949 Chevy 3100
http://67-72chevytrucks.com/vboard/s...d.php?t=618598

[ls1nova71]

For starters, 7" boosters are junk, they are barely adequate in most cars that ive seen them in, mine included. The LS1 should operate a booster fine. Under floor boosters usually need a bigger spring on them. Also make sure the pedal isnt binding where it pivots, some of the better mounts will have a grease fitting on them so you can lube it. I have to grease mine on a regular basis to make the pedal return correctly, but im guessing if you can get a bigger spring on it, it will solve your problem. I actually have two return springs on mine, and the brake lights will still stick on, so thats when I know its not returning all the way.

[oldman3]

I also run a heavier spring to return the pedal, lots of under the floor units need this...Jim

[BR3W CITY]

7" boosters are designed to meet a need for fitment, but they don't have the best rep in terms of power. Unless your running a real big cam (if so, let us know), then the LS shouldn't have any problems providing enough vacuum to run a normal booster.

FWIW, I don't have a return spring at all with my hydroboost setup, nor did i with a full-manual setup.

[ls1nova71]

Originally Posted by BR3W CITY

FWIW, I don't have a return spring at all with my hydroboost setup, nor did i with a full-manual setup.

The spring is needed on under floor pedals more than swinging pedals. I ditched my 7" booster and went to hydroboost, works waaaay better, but still needs a pretty hefty return spring.

[Rambo819]

Thanks for all the responses, I'll take a trip to the hardware store to grab a stiffer spring than the one I have currently. Just figured I never had to use a return spring on a brake pedal before. I'll let you guys know if it seems to work out better or not.

Thanks,
Ryan

[BR3W CITY]

Originally Posted by Rambo819

Just figured I never had to use a return spring on a brake pedal before

Ya man, neither had I. I was kinda under the impression that the fluid pressure was supposed to do all the work, but the more I look around the web, I see various setups.

I've seen a few folks also do it to compensate for heavy/long pedals or pedal arms that caused "bouncing" in the pedal when the car hit bumps etc.

Got me thinking maybe adding a small spring might help with the feel of my pedal. Anyone have ideas on calculating (or guessing) the needed spring tension? I'm thinking maybe 8-12lbs?

[ls1nova71]

Originally Posted by BR3W CITY

Ya man, neither had I. I was kinda under the impression that the fluid pressure was supposed to do all the work,

I'm surprised your truck doesn't already have one. Maybe they started in '67, because every '67-'72 truck left the factory with one.

[BR3W CITY]

I don't remember ever seeing one when I was under there for the brake switch and such. My truck originally had manual brakes, so either they didnt' put them on 66's, they didn't put them on manual brakes, OR at some point someone took it off and I never knew the difference.