Bill,
It is truly, truly vital, that you find out where the problem is before
you start fixing things that are not broken. I think your brakes are
suffering because of poor engine performance and not the other way around.
I think you have a blown head gasket because this is a better way to describe
the loss of compression on more than one cylinder. The booster unit
usually only takes vacuum from one cylinder, the one immediately in front of the
driver, number eight, I think. If you lack compression on 4 & 6,
I think you said, then I find it hard to blame the booster. Before you go
the trouble and expense of changing the booster and all the attendant issues you
will have will bleeding the brakes, etc, etc, you need to find out what the
engines problems really are. There is an easy way to check to see if it is the booster. Remove the
air hoses that go to it and use one of the hoses to simply run back to where the
other one came from, thus simply cutting the brakes booster out of the loop. I
have removed my booster unit several times. It is quite a difficult
task. A special wrench, one of the ones with a flexible metallic
shaft, will prove to be invaluable as some of the nuts are hard to reach.
There are also two different sizes of nut. Over the years at least some
brake fluid will had found it way back there and you may find that the pins
holding the nuts are corroded to a greater or lesser extent. The manual is
extremely useful under these circumstances.
Hugh
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