well my brake booster is definitely bad since the master cyclinder leaked into it for 10 years (before i owned it). So i was looking for prices on replacement units and i ran into a problem. autozone, napa, rockauto, oreillys all list a 7" and a 8.5" unit for the '73. I looked in my msa catalog and they listed a different unit for every couple of years and the VB catalog had 70-78 all lumped together. (rockauto has 8.5 and 10 listed for 77)So i am a little confused on what unit i need. i am now sitting here at work far away from my vb, msa, and service manual and no one on the forum seems to have discussed booster sizes before. i found a brief post on someone saying they had to mount it upside or something. anyways, if someone could confirm the size of the '73 brake booster i would greatly appreciate it.

my 1973 FSM shows no indication of booster size, but the diagram looks like all the usual 70-72 Z boosters (sorry that's not much help...) Just checked the Haynes and Chilton manuals and they don't make a reference to it...

I just looked at Ed's gallery, knowing he just finished a 1973--you may want to PM him to find out more....

Not quite enough for 2 cents,

Steve

I just measured my booster on my '73 at 8 1/2 '' form the out side edge of the flange . Hope this helps . Now , this Z is an automatic. The space between two master cylinders may not allow this size so do measure first . Gary

There was a noticiable difference between the boosters of my 72 and 73 the 73 being larger. I never measured them, sorry.

I just ordered the one listed in VB. It looked to be the same size as mine, and it's been working fine.

i didnt see anything in the haynes manual or service manual that explicitly said the actual size. I cannot figure out what the two different sizes were for. I guess I will try the 8.5” and see what happens, but that wont be until after new years.

Ack! Is it possible that the automatic cars used a bigger booster? Do I need to add a smaller booster to the list of parts I need for my upcoming 4 speed swap?

Ack! Is it possible that the automatic cars used a bigger booster? Do I need to add a smaller booster to the list of parts I need for my upcoming 4 speed swap?

The early 240Z boosters had a smaller bolt pattern

than the later ones. The small one is the booster

from a 71. They say that you can re-drill the holes

but the booster bolts in to and secures the basket

that holds the pedals. The large one is a 280 booster

Dave...

OK, so it looks like I should be OK with the early small booster that is now on the car, even when I add the clutch hydraulics. Thanks, Dave!

I just measured my booster on my '73 at 8 1/2 '' form the out side edge of the flange . Hope this helps . Now , this Z is an automatic. The space between two master cylinders may not allow this size so do measure first . Gary

My '73 is a standard transmission, built 1/73, and I believe the booster is the same size Gary is talking about -- see my photo. Outside diameter is about 8.5". The "unit number," in case not legible at this res., is 223-0 and then 1100 is stamped after that. Let me know if you need me to measure anything else or if you need a higher-res photo -- I think your life will be easier if you get the same size that came on the car.

Steve.

awesome, that is exactly what i wanted to know. thanks

I pulled a booster from a 260Z and it looks like the one SteveInOakland pictured. It is bigger in diameter but the bolts did not match my 5/70 Z. If someone wants it for the shipping cost let me know.