droptop306

I just installed a 306 supercharged motor and at same time replaced the rear to a 4 lug brake (disc) by SSBC. I have found that I am only getting 8" of vacuum and the car will not brake. Any one assist

disturbed471985

i have almost the same problem but mine is due to the radial cam not producing enough vacum.

91stang

did you upgrade your master cylinder as well?

samseed101

Just to hit on the obvious...is there a problem with the vacuum line going from the tree to your brake booster? Any chance the check valve broke or popped out of the grommet? Did the PCV pop out of the grommet? Get some carb cleaner or propale (if you're brave) and spray areas around gaskets or lines to check or vacuum leaks.

What type of supercharger did you install? If you tossed a nice KB on there, you may have a gasket issue between the KB and the lower. Do you have a bypass or blowoff installed? If so check the vacuum line leading to that.

Just a few quick ideas..

droptop306

what would the pvc have to do with it. I have a blow off and I install the vortech sq.

samseed101

It has a lot to do with it. The PCV runs off a vacuum (unless you disconnected it and found an alternative way to eliminate crankcase pressure.) It connects to your upper intake via a vacuum line. If the PCV valve with teh vacuum line pops out of the grommit in the lower intake, then it's no longer running in a closed system and it's pulling in unmetered air from the atmosphere. It creates a vacuum leak.

It's fairly common for those to pop out, especially if the grommit is old, brittle, and worn. And it can definately cause a vacuul leak. matter of fact, many people use the PCV vacuum to suck up Seafoam to get it into the engine.

samseed101

Did you eliminate the PCV system and run a breather-type setup or is it still connected? Unless it's 100% eliminated, you can end up with a vacuum leak (i.e. running a breather cap with the PCV still connected to the upper.)

droptop306

the performance shop eliminated mine because of the supercharger blowing the pcv out causing oil to blow out

samseed101

Yeah, that's common. Had to do the same with mine. I now went the valve covers and the PCV into teh atmosphere.

It sounds dumb, but check to make sure they properly plugged off the vac lines under the upper intake manifold. And don't forget about checking the brake booster line, check valve, and grommet.

8 inches is pretty low and it would take a decent leak. And It doesn't look like you swapped cams or did anything like that that may change how the engine runs. I would grab some carb cleaner and start spraying it around all teh gaskets and around all the vacuum lines iwth the car running at idle. If the spray gets near a leak and gets sucked in, you'll hear it in the engine. Same thing goes for propane.

droptop306

Yes I put a breather on the valve covers and the cam is a TFS 2000 499 lift. I dont know how he blocked off the pvc, I think that he ran a hose to the under side of the car not sure. But the car was smoking as well until he ran the tube from the pcv grommet area. Car runs awesome it seems that the brakes are the only thing suffering. I contacted SSBC and they told me that I need a electric vacuum pump and they recommend it. So I just bought that but will not be here utnil sat. Think that maybe the check valve might be bad? Also if it was would it have the boost guage reading it that low. Sorry for all the questions but after 3000. for installs and cant drive it kind of makes you mad