7" Power Brake Booster

I switched from 9" Single Diaphragm to a 7" Dual Diaphragm to gain more valve cover to booster clearance. 9" only had 1/4 inch at the most. The 9" I had was a repo '67 Vette style Booster & Master Cylinder unit that worked well.

Switching has a few problems that I uncovered the main being that 7" or 8" either single or dual diaphragm DO NOT have pressed/riveted bracket. I searched for quite a while and finally found a source for 63-67 Corvette booster brackets. Once I had the brackets, booster and master cylinder it appeared that it was just a simple bolt on just like the 9". Not quite. The additional length of the booster (3.5" vs. 5.5") caused the MC to touch the hood. I suppose you could go with a 7" or 8" single diaphragm but they only provide 950 psi with a 1" bore MC. The '67 style 9" single has 1100 psi. The 7" & 8" dual both provide 1200 psi. Seeing how I already had a chrome 7" dual it was time for a bracket/MC angle adjustment  J

What I did was put a 5/8 inch spacers behind the bracket at the top which pushed the front of the MC done far enough for adequate hood clearance. I used 1/2" thick wall black pipe for the spacers. One other problem I had was getting the correct length on the pedal rod. If I had known up front I would have ordered a pedal rod extension but I went to my local Autozone and got shock stud extenders. The difference in the two the best I can tell is the pedal extenders have many more threads. So I had to used a 3/8-24 die to add threads to the shock extender. Now I had plenty of adjustment.

After job was complete including bleeding brakes I now have LOTS of clearance and would be no problem install extra tall valve covers even with spacers

I found the brackets (Part #6466-7) at Pirate Jacks www.piratejack.net they also have Boosters/MC/extenders/etc. but you can also find everything except the brackets many places on the net.

Hope this will give you ideas and possible help.

Click on images for larger view

Original 9" Single Diaphragm
63-67 Brake Booster Brackets
New Threads 3/8-24
Original vs. Added threads
Treaded & Shortened
Bench Bleed
Lots of clearance