Power brake vacuum ?

[RShaips]

My brakes do not want to lock up when I slam on the pedal. They stop but it takes like 50 feet, otherwise they work great. I was told that I may not have enough vacuum to the booster or I have a bad brake booster. I have power disc brakes with a 383 Stroker. My vacuum line is hooked up to the back of the carb, I was told to hook it into the top of the manifold to get better vacuum but my Edelbrock intake does not have a spot for it. My master cylinder is new and the brakes have been bled. Any way to check the booster to see if its good or bad ? Thanks

[jhow66]

Check your vacumn at idle with a gauge--if you have a big cam may not be pulling enough vacumn to operate booster.

[RShaips]

It does not have a real big cam. Where do I check the vacuum and what should it be ? Thanks

[jhow66]

Just connect a vacumn gauge to the carb where there is vacumn at idle--stock cam -engine in good shape should pull 18-21 inches of vavumn. Even if you have only 12-18" still should be enough to operate bosster. Here is a way to check your booster-shut off engine-press down on brake petal and hold-start engine-if booster is working petal will go down slightly.

[D.PASSMORE]

Is there one of these in line. Should be attached with brake lines coming out of the master cylinder. Could be a problem or how old are your brake lines? Another, have you mixed any synthetic brake fluild with regular DOT fluid? This will coroide the system. My 2 cents...

[dwaite72lnghrn]

How fast are you going when it takes 50' to stop? You really don't want your brakes to "LOCKUP". If you are connected to the back of the carb you have full vacuum and moving it to the untake really won't change much. I would start at the basics and check all your pads and shoes. What changed on your truck? Or did it just start not working? Was the master cyclinder changed for the same problem?

[RShaips]

What changed on my truck ? Everything ! I had a 67 LB that I put on a 71 SB frame that had disc brakes and I used the power brake booster and portioning valve from a 72 4WD truck. So really nothing is the same. Some of my brake lines have been replaced but not all of them, they all will bleed just fine though. New wheel cylinders in the back and thats about it. I left the front brakes alone as they were in good shape. I will have to check the vacuum when I get a chance, the truck that I took the brake booster off had been sitting for a while although it did run and drive great, thats where I got the stroker motor. And the brakes worked great on the truck when I drove it home.

[dwaite72lnghrn]

When you bleed the brakes did you clamp the front button on the proportioning valve back during the whole bleed? this will keep your system equal.