Power brake booster

[swedefish]

Hi guys
Have a question.
How do I measure the size of a brake booster? When it says 8” is it the diameter or?
Many thanks in advance
Swedefish

 

[SGBARRACUDA]

Yes that is the diameter of the boosters.

 

[Mtrhead]

The outer O.D. of vacuum reservoir ..seems they went to 10" after 1972

 

[swedefish]

Thanks guys
Looks like the booster in my -67 Barracuda is 7”.

 

[scatpackbee]

 

[BillGrissom]

Early A-body boosters used dual diaphragms to work with a small 7" diaphragm. They changed to ~10" single diaphragms in the 1970's. Clearing the valve cover in a V-8 is the main concern. If a slant-six, a 10" booster "should work" even in an early-A (1963-66 w/ narrower engine bay). I used a 1990's Intrepid booster on 1974 Dart standoff brackets in my 1965 Dart and just barely clear the aftermarket aluminum valve cover of my 273 engine. Indeed, I have to unbolt the booster to remove that valve cover. Best deal today is a new booster w/ brackets for ~$175 on ebay, using a GM booster and adapter. Haven't read that it doesn't clear an early V-8 valve cover.

 

[WV64Signet]

Early A-body boosters used dual diaphragms to work with a small 7" diaphragm. They changed to ~10" single diaphragms in the 1970's. Clearing the valve cover in a V-8 is the main concern. If a slant-six, a 10" booster "should work" even in an early-A (1963-66 w/ narrower engine bay). I used a 1990's Intrepid booster on 1974 Dart standoff brackets in my 1965 Dart and just barely clear the aftermarket aluminum valve cover of my 273 engine. Indeed, I have to unbolt the booster to remove that valve cover. Best deal today is a new booster w/ brackets for ~$175 on ebay, using a GM booster and adapter. Haven't read that it doesn't clear an early V-8 valve cover.

Also need to be aware of any more recent ignition items on the firewall and clearance of the bulkhead connector when/if you change the mounting bracket

 

[scatpackbee]

Early A-body boosters used dual diaphragms to work with a small 7" diaphragm. They changed to ~10" single diaphragms in the 1970's. Clearing the valve cover in a V-8 is the main concern. If a slant-six, a 10" booster "should work" even in an early-A (1963-66 w/ narrower engine bay). I used a 1990's Intrepid booster on 1974 Dart standoff brackets in my 1965 Dart and just barely clear the aftermarket aluminum valve cover of my 273 engine. Indeed, I have to unbolt the booster to remove that valve cover. Best deal today is a new booster w/ brackets for ~$175 on ebay, using a GM booster and adapter. Haven't read that it doesn't clear an early V-8 valve cover.

Early A body boosters were dual diaphragm and 6 1/4” diameter, then they upped the diaphragm to 7” in later years.

Quick way to identify the 6 1/4” from the 7” is the 7” booster has 2 dimples on each side at the master cylinder mount location. The 6 1/4 booster does not have the dimples.