:( In 1999 I picked up a 69 that had power brakes added by the previous owner. The reason I knew the brakes had been added, is the lines appear to have been changed from the original positions that attach to the proportioning valve and also the wire that attaches to the valve had been cut. Also the front calipers had been ground to fit behind a 14" Rally Wheel with a spacer. When stopping from speeds above 50 mph it seems that I almost need both feet to stop and I'm not sure that I could even lock up the wheels if needed. I have checked the booster and it seems to be functional according to the tests that were listed on MPBrakes website. I have a 75 Malibu Classic that when you touch the brakes, they will almost put you through the windshield so I know that stock systems will work. I have no idea if the master cylinder is correct on the 69 as I can find no numbers to cross reference the unit. I'm considering purchasing a new booster and cylinder was wondering about the dual diaphram boosters. Anyone offer any advice as to a solution to my problem. I really don't want to purchase new spindles, rotors and calipers

How much engine vaccum do you have?
If you have 18 inches or so the stock booster should work fine. You need a master cyl bore of 1 1/8" check for that by unbolting the master cyl and pulling it away from the booster enough to measure across the rear bore.

Make sure your calipers have the 2 15/16" bore and not the later GM "metric" calipers that are 2 1/2" bore.
David

i had somthing similar on my 68 ( but it wasnt power)

the rod under the dash going in to the master cylinder has a jam nut on it on mine the nut backed off and the rod was slowly "shortening up"

check that for adjustment though

I'm not exactly sure how many inches of vacuum I have. I have a roller small roller cam, nothing extreme, somewhere around .452ex and .436in. How do you measure how many inches of vacuum you have?

Vacume guage.

Do you test at idle or rev and check for highest setting while engine decreases in rpm.

check at idle.

Which line do I need to check the vacuum on? Can I use the line where the vacuum advance is or do I need to use the brake line itself?

You need to use a maniflold vacuam source.Your vacuam advance could be on either, if you get vacuam on that port at idle, it's a good one to use. If you have an auto trans that uses a vacuam line, that line would be ok for sure.

What are some of the possible ways to increase engine vacuum without having to buy an electric unit to assist with the brakes?

Increasing your idle speed will improve idle vacuum; if that doesn't do it, add a vacuum reserve tank ahead of the booster before you take the jump to a vacuum pump. graemlins/thumbsup.gif

If vaccum is OK, then try some high quality brake pads, yours might be cheap ones.