Just got the motor in the car and my brakes are very very weak! Pedal gets hard and the car coasts to a slow stop. Any suggestions?

 

what did you check so far.... Did you check your vacuum?

 

No i havent checked the vacuum but i had zero brake issues before the motor rebuild and cam swap.

 

Did you bleed the brakes when you put the motor back in?
(did you disconnect the lines when you pulled it out?)
Did you plug the vacuum hose back into the booster (and manifold) when you were done?

"Bigger" cams tend to provide less vacuum down low.
You can use a vacuum cannister or a small electric pump to overcome it.
(I run a cannister on mine)

You could also consider a mechanical pump, but they're rather expensive
and as far as I know, nothing exists that fits an LT1 without custom work.

 

Are you sure you don't have a leak in the vacuum line to the brake booster? And measuring the vacuum would tell you if you have too little vacuum. How large is the cam? Unless its huge, you should pull enough vacuum to keep the brake booster happy.

 

Its a cc306 cam. Everything is hooked backed up i checked it after i noticed the problem. I didnt un hook any brake lines when pulling hte motor, i took it out the top. Guess the next step is a vacuum test

 

Its also un tuned at this point. Will it pull more vacuum once its tuned?

 

The larger the cam, the more it needs a good tune to pull a decent vacuum. Have the valves been correctly adjusted?

You don't need a "vacuum test".... you need to hook up a vacuum gauge to one of the full vacuum ports on the intake manfold. Or if you have a scanner, tell us the MAP at idle, and the BAR reading, and we can tell you what the vacuum is.

If the vacuum is low enough to not provide any boost at all on the brakes, you should have a code for high MAP. Have you scanned it?

 

Yeah the valves have been adjusted correctly. I guess 2morrow will tell the tail, its going to get tuned. He says getting it running correctly will make it pull more vacuum. I just honestly didnt think it would be that bad and thought i might have been missing something

 

If you have a tuner handy, simply try upping the idle and see what happens just for kicks Those CC306s are on the larger side for stock ci motors

I agree with the above, though.

Mike

 

I lost my brakes with identical symptoms. Hard pedal, no stop. I was fortunate to have a manifold press/ vac gage. Idle @ 3"Hg/ cruz @ 13"Hg @ best. My app... 97ss 383ci D1 M6. I went to Summit and purchased a SSBC Electric Vac pump. They say you sould have a min of 16"Hg Vac @ booster. My brakes are back now. B.