Is this normal ??
My brakes are generally quite poor until the engine has warmed up, but when in reverse the performance is noticeably poorer.

 

If you have drum brakes there is a self adjusting mechanism at the bottom of the brakes that sets the shoes at the proper "tension" against the drum when applied in reverse. If these are missing or corroded your brakes won't self adjust. They also won't self energize if the mechanism is missing.

 

They should not be noticeably worse in reverse. Drum brakes are self energizing, in that the leading shoe is pulled into the drum - the trailing shoe is not. That's why the lining on the front shoe is shorter than on the back shoe on a given wheel. The self-energizing front shoe requires less lining to achieve the same friction level as the non-self-energizing rear shoe. In reverse, the rear shoe becomes the self-energizing one, so it should grab a little more (though the smaller front shoe, which is now not self energizing, will exert a little less force). Since most people do not drive at a high rate of speed in reverse, this is usually not noticed.

You may have a problem where the shoes have worn grooves in the backing plates in their normal position, causing them to hang up slightly when braking in reverse.

I'd be more concerned about the brakes not working well until the engine is warmed up. Is this due to lack of power assist or something else? This would only make sense if you are running metallic linings. The metallic linings are designed to provide maximum braking when hot. Metallics provide noticeably poorer stopping performance when cold.

 

Have you checked your brakes lately. A number of things can effect them.

1. bad rear axle seals causing brake shoes to be soaked in 90 weight oil
over a long period of time
2. leaking brake cylinder causing brake shoes to be soaked in brake fluid
over a long period of time
3. What Olds64 said
4. Brake shoes and the end of there life span
5. Vaccum leak on the power brake booster or the hose from the carb to
the booster has a leak
6. Master cylinder going bad letting the fluid bypass the plunger seal.
Needs a rebuild kit

Process of elimination by checking all sources that could cause the problem. Good luck and let us know what you find out

 

They worked fine when i had the edelbrock carb on top so i'm assuming it's something to do with the new carb setup? it's under jetted at the moment as it came from a 350 Cutlass.

Perhaps "warmed up" was the wrong statement. In the morning when i start the car and drive, initially when the engine is cold the brakes don't work great, however this could be due to me not driving it at any great speed to begin with. When i eventually reach the high road and put my foot down, the performance seems to be OK.

 

Check for a vacuum leak on the line from the carb to the brake booster spray a little carb clearer at both connections if the engine revs up you have a vacuum leak

 

My power brake line goes straight to the Performer manifold, the same as it did on the stock one with the 2bbl set up