Old style vs new style brake boosters

[Dark Ride]

I'm starting to install my turbo kit in my 90, and it looks like it might end up a little tight near the booster. I seem to recall that the later model years got a different booster. Refresh my memory on these, what was the size difference and can they be swapped without changing the firewall plate. I already changed the plate when I swapped in the vacuum brakes.

[55trucker]

GM redesigned the booster with the 94 model year, it is an improvement on the earlier design.

 

The pedal effort was lessened, the reaction valve body was improved to do away with that hard feel of *pushing on the pedal but the master doesn't respond* sensation.

 

The later is a shorter booster but it still mounts to the plate in the same cam-lock fashion.

[Dark Ride]

I seemed to remember something like that, but couldn't remember if they could be swapped. I think I may swap to the newer booster to gain some room.

[White93z34]

I think placement of the master remained the same on the 94' boosters. But its a overall wider unit.

 

Factory vacuum brakes on a Turbo 3.1 car is a tight fit.

[Dark Ride]

Hmmm, well I have one in the Lumina that I can easily remove to compare. I'll let you know the verdict.

[Galaxie500XL]

I'm asking because I honestly don't know...wouldn't there be some serious issues with using a vacuum booster on a car with forced induction?

 

The booster operates on the concept of there being vacuum available at all times, which isn't the case in a forced induction vehicle, which I'd assume is the reason the car had the unfortunate booster it was built with.

 

Of course, I suppose you could use a vacuum pump to keep the appropriate vacuum going to the brake booster..

[Imp558]

It's under vacuum most of the time, I've supercharged 2 cars now and both of them stop fine. If a supercharged engine doesn't have any problem I'd assume a turbo car should be fine being they make their boost at a higher RPM range.

[55trucker]

  My Turbo Shadows that I used to own made use of one way check valves that were fitted into the vacuum hosing routing to protect the booster & the speed control vacuum diaphragm when the engine went into boost, the vacuum canister provided enough of a source to prevent the system from running short when on the throttle. 

After all, who has their foot on the brake when hard on the throttle on boost?

 

One would have to do the same in this arrangement as well.

[Dark Ride]

All the w-body vacuum boosters I've seen have check valves. Go look at yours, the little round piece that connects the booster itself and the vacuum hose is a check valve. If you take it off you will only be able to draw air through one side. You also install a check valve leading to the hvac controls and vacuum ball so those are never pressurized.

[Imp558]

All the w-body vacuum boosters I've seen have check valves. Go look at yours, the little round piece that connects the booster itself and the vacuum hose is a check valve. If you take it off you will only be able to draw air through one side. You also install a check valve leading to the hvac controls and vacuum ball so those are never pressurized.

oh that's right, I forgot those are one-way valves but you're right they are

[Dark Ride]

Anybody with the new booster wanna measure how far it sticks out from the firewall? I measured mine and it's roughly 7 inches.

[Imp558]

I can measure a 95 & 96 tomorrow

[Dark Ride]

That would be very much appreciated. Thanks!

[Imp558]

Stopped raining for the first time in days. A 1995 & 1996 look the same about 7" to the very face, 10" diameter.

Here's a couple pics you may be able to get reference points from.

 

 

 

[Dark Ride]

Dang. So not as much of a difference as I'd hoped. Thanks for the pictures for reference.

[Imp558]

this is going to sound a little wacky and I didn't measure it but it looks like a 2nd gen booster and master cylinder are a lot smaller. Also the ABS is separate from the master cylinder so it may be possible to use old school proportioning valves after it.

[Dark Ride]

I had thought about the separate master cylinder, but I measured the one on my 98 Gp, and they are still the same length, so there wouldn't be an advantage. I wonder if the second gen booster would fit? Supposedly, the 01+ montes have the smallest booster.

[Imp558]

I was looking at an 01 Monte, lol. I'll get a measurement on it after work. I do wonder if whatever extends to the back of the booster from the firewall could be recessed into the cabin an inch with a little fab.

[Dark Ride]

Even if you could recess it, I think it would screw up the pushrod going into the booster because it would be too long. I'm not real keen to try. I would probably fabricate a new downpipe before trying that.

[Dark Ride]

Edit: duplicate post

[Imp558]

'01 MCSS, again about 7" out but the diameter appears to be 8 1/2" - 9".

 

 

[Dark Ride]

So they are all the same in regards to how far they stick out. That doesn't bode well for me.

[Imp558]

Shorter dogbones to rock the engine forward a tad? I bet Chinese Matt could whip up a custom order for you, mine were custom.

[Dark Ride]

So the larger brake booster from a 99 Lumina was a no go. It did appear to be a little shorter, 3/4 of an inch at most but it was so much bigger around that it caused issues elsewhere. I couldn't get it to lock in but that may just have been hitting on stuff. Im going to compare it to a 2nd gen Monte and see if that is shorter.

[55trucker]

Now that is curious,

 

the 94-99 booster is a 12" dia item, it fits all 1st gen W platform vehicles of the year listed, the 88-93 (94 Lumina Z34) booster is a 9" dia. item, the 2000+ booster for the W platform with the exception of a few stamping differences is near identical to the 88-93 booster housing.

 

I was lead to believe that the later booster will fit the older cars firewall, going on what you have stated ....what has changed with respect to the firewall stamping that the larger dia booster will not mount to the earlier firewall? That booster is only 1 1/2" larger in radius.

 

What was in the way that prevented you from locking the booster into place?

 

The 92-93 booster has different reaction valve internals than the 88-91 booster that moderately improves the foot pedal pressure required for braking, the later 94+ design improves on this again and goes hand in hand with the redesigned rear calipers introduced with the 94 model and the larger rotors as of the 95 models.