Brake booster won't hold vacuum, should I rebuild/replace it?

@panterapatt posted:

Let me ask a somewhat stupid question - WHY do we even need the booster?  I know the GT40 and some other cars do not use one.  Is it because they had the dual cylinder system?

The stock master will supply 500-550 psi to the brakes. The booster adds 200 to 250psi to that depending on the vacuum available. Ideal would be 22 inches but  depending on what cam you have, you likely have much less.

15 is about the minimum the booster needs to work. Some boosters like in the Mustangs will work way down to about 12, with less assist though.

That's where the heavy effort comes from with manual brakes.

The leverage on the brake pedal is not optimum for a manual brake Pantera.

I have three boosters in my parts stash, two of them are the three bolt pattern

The four bolt pattern is approximately 86 mm x 107mm - close enough to say it is the same as on your Deauville.

I do not know the dates on any of the units

Larry

My Pantera is a three bolt mount.

Thanks Doug for the insight on the booster.  My motor pulls about 17.5 inches of vacuum.  

I should know better than to say 'all' when speaking of Panteras, since DeTomaso did use whatever parts he could get. If your steel firewall and aluminum adapter stand-off is drilled for only three bolts and not a dual 3-and-4 bolt drill pattern, then I shall accept that the Pantera did in fact come from the factory with both bolt pattern boosters. You have a '73, don't you, Forest?

I do know for a fact that there were at least two different boosters used- a slightly larger OD booster was used on Gr-3 street-racers since i installed one on a member's car in '83. It barely cleared his chrome bumper '72's latched front hood and to get that much clearance I had to make sure the assembly was pushed all the way down against the (4) mounting bolts and the latch pin was bent  a bit.