I have installed a new motor in my 72 Chevelle and my brakes (front disc, rear drum) are terrible. I went the problem solving route of installing a vacuum canister to make additional vacuum available. However, this made the brakes worse. I could feel the additional pressure when applying the brake but never could push hard enough to stop. I unhooked the canister and went back to my beginning problem. At least I can get the pedal down to the floor and that stops a little better (like power brakes with the engine off). What in the world can I do to help my car stop without spending a bunch of cash on a modern 4 disc system and all of the associated goodies?

Hey,

Welcome to TC. Hint...always do a search before asking a question. There is so much info here it makes your head swim. smile.gif

Anyway, try this thread. Then do a search in Brakes and Suspension for Electric Vacuum Pump

http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=7;t=002976

Be sure to go to the link posted by Bob Tiley

Good Luck.

custom,
First off, what kind of cam, induction etc are you running with the new motor? Have you checked to make sure there are no vacuum leaks anywhere?

Did this just show up with the new motor? Or have you performed a disc swap on the A-body?

Little more info please! :D

Joe

Thanks guys for the help.

Bob, I will take your suggestion and do a little more research on the site.

Joe, braking system is new from firewall to wheels, no vacuum leaks, and yes, the problem showed up with this motor. Here are some of my engine spec: 350 bored .060, Weland single-plane manifold, Doug Hebert roller cam (Duration 280...288, Lift 571...592),SRP forged flat-top pistons (10.5:1),H-beam race rods (5.7"), aluminum roller rocker arms, forged crank, 202 heads, 750 double pump Holley carb.

Any additional ideas.

oh Joe, I forgot to answer your other question...the car has original style front discs and rear drums. All of which are new.

'72 El Camino Custom,

I checked out the link you supplied and that does not sound exactly like my problem. My canister seems to be holding vacuum. The vacuum pressure I feel under my pedal feels is like a manual air pump when you have put all the air in a tire or ball or something and it wont compress anymore. It is kind-of bouncy as you depress the pedal hard, it recoils slightly. (I hope that makes sense.) Under that pressure, the car just gently slows. It never seems to lose pressure at any speed.

When I unhook the canister, the pedal compresses too easy but seems to engage the brakes better. However, it is still not slowing the car at a safe rate.

Am I making any sense?

Sorry about calling you Bob in my earlie post!

How were the brakes before you installed the new motor? If they were good, I'd say its still a vacuum issue with the new mill. If they never were very good, then we need to look elsewhere. Have you bled the brakes 'really' good? Sometimes it takes two or three times to get all the air out. How old are your other brake parts? MC, booster, etc.

My friends call me Dave. smile.gif

Dave,

The brakes were fine prior to this process. However, that was a few years ago. My car has undergone a total rebuild from the frame up. I replaced most every single part of the braking system (booster, mc, lines, discs, etc.). After installing the motor, the brakes were poor. Thinking that the lines needed bled, I bled them numerous times over two days to no avail. So, I then went the vacuum canister route, which brought me here.

One thought (which might make me look stupid graemlins/clonk.gif )...could I have plumbed the canister up backwards? I have a Comp Cams canister with a straight brass nipple and a 90-degree plastic nipple. I ran the vacuum from the carb to the brass and then from the plastic to the booster. I will reverse the order tomorrow and see what happens.

I will keep you posted. If you have any other ideas, they will be greatly appreciated.

Thanks,
Jeromy

Manifold vacuum to check valve on canister,brass nipple to check valve on booster.

Thanks everyone. Simple solution for a simple mind. The canister works. So, we all know what will happen if you hook the canister up backwards! I am now off to do a little Sunday driving and stopping!
Jeromy

Well, after driving it a little more than in and out of the garage, I discoverd that the brakes still suck. It is better though. I am going to go the electric pump route I saw mentioned in other threads. Any additional info on that would be appreciated.
Thanks,
Jeromy