Best Power Booster Hookup Location

[kryptik]

Hey guys,



I have a DSE Power Booster/Master Cylinder Combo for a 1970 Camaro with Wilwood Discs on all four corners and a GMPP ZZ383 making plenty of vacuum.

This is a new installation with new lines. I have thoroughly bled the entire system, including bench bleeding the master ON THE CAR (where I did notice trapped air escape). I have even vacuum bled the rear brakes to get a trapped bubble out of that long line just in case.

When the engine is off and there is no power assist, the brakes feel great and solid. When power assist is achieved the brakes feel strange, almost mushy and as if the assist is too much, and the pedal can also be pushed to the floor. I do not know if this is an issue because I am aware that many modern OE fords behave the same way, but still stop the car very well.

The booster is currently "tee'd" off at the PCV port at the back of the carb, with one line going to the PCV and the other to the booster. I did this because I was told that tapping the line off of the rear of the intake manifold will cause cylinder 7 (or 8? dont remember which runner it was) to lean out.

I spoke to DSE and their first suggestion was to move the power booster vacuum takeoff from the PCV port to the back of the intake manifold, and that it would not be an issue. I was not aware that such a change would make a difference...

Any guidance and advice would be greatly appreciated.

Many thanks,
Matt

[NOGO]

Taking vacuum from the manifold port will not be an issue. Either way you hook it up I dont think you will notice a difference in pedal effort. If you have a firm pedal without the booster and the effort while driving feels good and the brakes perform well I dont think you have an issue. Judging the feel with the booster while stopped is not a clear indication of anything.

[staged67gspwr]

what size master you have ?

[Apogee]

In addition to master cylinder bore size, please post up what Wilwood calipers you're using front and rear. All that's necessary really are the effective caliper piston areas actually, so post that if you have it, otherwise we should be able to figure it out based on the Wilwood caliper models you specify.

Any time you can push the pedal to the floor, there's more than likely an issue, and 9 times out of 10, the issue is that there's still air in the system somewhere. If it's not air, then it's time to start checking the master cylinder and other components throughout the system. That may not be the case here, but it's usually best to play the odds first before assuming it's something more complicated and difficult to diagnose.

I've never had very good luck "bench" bleeding a master cylinder on the car, so after confirming that I had the proper size master cylinder for the calipers I was running, that's probably where I'd start. I've found the easiest way to verify that a MC has been fully bleed is to plug both outlet ports and pushing on the piston. It should hydraulically lock once the seals are past the compensator ports into the reservoirs, typically around 1/8" to 3/16" of piston travel. If it strokes any further and/or feels spongy at all, there is still air in the MC.

Tobin
KORE3