So I just got done with my 383 swap and my power brakes seem GONE. The vaccuum lines are all fine, and the brakes work, but they are very hard. The pedal will barely move. We bled the system twice to get all the air out.

How would I know if the brake booster is out?

I am running a big cam, but it is a 383, so it should pull vaccuum. I DO NOT think that it is a problem because of not enough vaccuum because the car does not stop right even when I leave it in gear and engine break which should pull the most vaccuum.

Thanks,
Stu

 

Couldn't hurt to check the vaccuum for the heck of it. It would definitely eliminate one thing.

 

Well... I was proven wrong. It was only pulling 10-15 lbs vaccuum. So I found the problem.

Does this sound normal for a 236/242 cam with LE2 heads on a 383? I might have an intake leak. :dunno:

 

Vacuum is generally expressed in "inches of mercury" ("Hg). If you are pulling 15"Hg, your brakes should be fine. I run a 381 with 230/242 114LSA and it will pull 15"Hg at idle. 10"Hg seems a bit on the low side (depending on the LSA). Does the vacuum bounce over that range while idling?

 

its a 236/242 112 with XE lobes if it matters. I was thinking about using the air pump as a vaccuum pumo for the brakes. Would that work?

 

Yea I meant inches... sorry... ive been up all night.

 

Air pump creates + pressure. You need vacuum for a brake booster. 10 to 15 Hg's sounds like it should be enough for the brake booster though. Really not sure. Hmmm... Got class at 2. I'll ask my Chassis professor if he's there.

Might also just be that your brake booster is shot. Looks like they're $85 from Autozone, but they're special order.

 

If you put it on backwards, it should pull vacuum right? Just dont know if it can damage to booster.

 

I had an issue with my power brakes after having the car sit for a few weeks. Had something to do with the rain. After a bit of braking and stopping and going the brakes slowly came back to normal. Doesn't sound like this is your problem though, but just putting a bit of input in just in case you didnt try it

 

How long was the car out of commission? Long enough for the seals in the booster to get hard and cracked?

 

I would say 3-4 weeks?

 

try 9 months

 

Sounds like your boosters gone Just get a new one and I'm guessing ull be ok.