LilJayV10

iTrader: (39)

I'm posting this in the FI section because I "believe" it has to do with my issue.

I have twin turbos on my Firehawk and after a WOT blast, the brake pedal gets rock hard and it is damn near impossible to get the car slowed down.

It's got a donkey dick cam in it with 16 degrees of overlap and idles at 70kpa.

Normal driving the brakes are fine but after a WOT hit, it's sketch level red.

Would adding a vacuum canister resevroir help this or should I just get a pump for the booster and be done with it?

The factory vacuum line is going from the intake to the brake booster and with a Procharger vacuum log that supplies vacuum/boost to the BOV and fuel pressure regulator. If those are seeing boost, obviously the brake booster is too.

How does a brake booster react to seeing boost?

It's a 6speed car if that makes any difference.

I appreciate any input or advice.

Full Power

HydroBoost- NOW
I would NOT rely on Vacuum brakes in a car with manifold PRESSURE, That's like filling your fire extinguisher with Diesel

tryintogofast

iTrader: (2)

There should be a one way check valve on the vacuum line to prevent positive pressure from entering the booster. If it has one I'd verify it's functional.

GMCGreg

Even without the turbo your power assist would be marginal - 70 kpa is not much vacuum. Properly operating check valve at the booster will help , stock one should be fine. I bet if you were to wait a second or 2 after letting off the throttle the brakes work fine ? That's because of a good vacuum source on deceleration, not really a safe street set up . Hydroboost is a great option and not real expensive if you DIY it. Electric vacuum pump is another . Vacuum canister can work as long as it's on the right side of the check valve, in my experience probably not adequate

gametech

iTrader: (1)

Check valve to the booster must have blown out. However, if you want properly operating brake assist regardless of boost or big cam, search the conversions forum. Quite a bit of info about getting junkyard pull electric vehicle brake boosters to work.

LilJayV10

iTrader: (39)

I appreciate the replies. I will have to check out the DIY hydroboost and the JY electric brake booster.

The BallSS

iTrader: (9)

Not that you shouldn't investigate the hydroboost or vacuum motor options but a lot of guys including myself have run 4th gen f-body turbo cars with big cams for years with the factory booster and never had an issue.
My current car I switched over to manual brakes because I unknowingly broke a valve spring and as such my pedal got really hard from the loss of vacuum.
That setup works pretty well albeit you have to apply more force to the pedal, but I do like how it cleaned up under the hood and gave me more room for plug access.
Motion Raceworks makes an excellent bolt in kit for the conversion.
Just a thought.

rpturbo

iTrader: (47)

Yeah your check valve failed. It's putting pressure on the diaphragm inside the booster, and making them hard. You definitely should be able to run boost with vacuum brakes, but I personally choose not too. I like brakes when needed.