Smaller Brake Booster for Big Block??
Thread Starter
Pro
Joined: Oct 2000
Posts: 558
Likes: 22
From: Vancouver, B.C., Canada
Smaller Brake Booster for Big Block??
Wondering if there is any option for a smaller diameter brake booster to replace large stock one on a big block car. Did a search but came up dry. I'm well aware of Hyrdoboost but I don't want to go that route. The brakes work fine as they are. I'm just wanting more room to run my choice of taller valve covers. Any good reasonably priced ideas??
Burning Brakes
Joined: Dec 2008
Posts: 971
Likes: 45
From: Middlesex NJ
Let me first start by saying my body is still off the car but I am converting to power brakes and a big block with tall valve covers. I am not finished with the booster install but I don't think I have missed anything yet. So treat this as information only at this point.
I have consulted with several forum members as to their success using a 7" dual diaphragm booster. My engine vacuum is just under 16" at idle so the 7" booster will cause me to have a slightly heavier pedal than a 9" but I haven't driven the car in so long that power brakes will simply be an improvement anyway.
I have removed all of my information below as to the power brake conversion and am just including the 7" booster stuff that I have found so far.
I think I got my booster from jegs or summit.
Installing a 7” brake booster
The TuffStuff 7" booster and master cylinder combo is about 2" shorter overall and 2” narrower in diameter making it more compact on the firewall and by the engine. (You may need to update your master cylinder lines due to the shorter overall length.)
Tuff Stuff Performance 2122NA
Tuff stuff 2071 master cylinder
Master Cylinder Bore Size1.125 (1 1/8) Corvette style with 9/16 in. and 1/2 in. fitting on driver side.
Booster Diameter (in)7.000. ( 2222na )
• The 7" booster rod is 1/2" shorter from the base of the booster that mounts to the firewall to the tip of the threads on the push rod. This requires the clevis to be longer or some type of threaded rod to be made up. I chose a longer clevis (see below, more info on the clevis at the bottom of this doc.) as the 1/2" is just not that easy to make up when it comes to threaded rods.
7" booster
9" Factory booster
Clevis comparison. I bought a new clevis from Mcmaster carr its forged and makes up the 1/2 I lost on the threaded rod.
Factory clevis
D = 2" from center of the 3/8" pin to the bottom of the threaded end. Threads are part of the flat stamping material.
A = It uses a 3/8" pin
B = The opening between the pin holes is 7/16"s.
It is 1" wide from the side
Threaded female shank of 3/8 x 24
The McMasterCarr clevis
D = 2 1/2" Threads extend out from the clevis body on a 7/8" shank. This gives you 1/2" of additional overall length in threads. (Its forged steel not cast.)
A = 3/8" pin
B = 7/16"
It is 11/16" wide at the side (allows it to articulate on the pedal better).
Threaded female shank of 3/8 x 24
www.mcmastercarr.com
6071K14
In stock for $7.26
Rod End Type Clevis Rod Ends
Clevis Rod End Type Forged Clevis Rod Ends
Shank Type Female Shank
Shank Thread Type Right Hand Thread
Clevis Material Steel
Finish Plain
Shank Thread Size 3/8"-24
Inside Diameter (A) 3/8"
Clevis (B) 7/16"
Clevis (C) 7/8"
Clevis (D) 2-1/2"
Clevis (E) 7/8"
Clevis (F) 1-5/8"
Specifications Met Society of Automotive Engineers (SAE)
I have consulted with several forum members as to their success using a 7" dual diaphragm booster. My engine vacuum is just under 16" at idle so the 7" booster will cause me to have a slightly heavier pedal than a 9" but I haven't driven the car in so long that power brakes will simply be an improvement anyway.
I have removed all of my information below as to the power brake conversion and am just including the 7" booster stuff that I have found so far.
I think I got my booster from jegs or summit.
Installing a 7” brake booster
The TuffStuff 7" booster and master cylinder combo is about 2" shorter overall and 2” narrower in diameter making it more compact on the firewall and by the engine. (You may need to update your master cylinder lines due to the shorter overall length.)
Tuff Stuff Performance 2122NA
Tuff stuff 2071 master cylinder
Master Cylinder Bore Size1.125 (1 1/8) Corvette style with 9/16 in. and 1/2 in. fitting on driver side.
Booster Diameter (in)7.000. ( 2222na )
• The 7" booster rod is 1/2" shorter from the base of the booster that mounts to the firewall to the tip of the threads on the push rod. This requires the clevis to be longer or some type of threaded rod to be made up. I chose a longer clevis (see below, more info on the clevis at the bottom of this doc.) as the 1/2" is just not that easy to make up when it comes to threaded rods.
7" booster
9" Factory booster
Clevis comparison. I bought a new clevis from Mcmaster carr its forged and makes up the 1/2 I lost on the threaded rod.
Factory clevis
D = 2" from center of the 3/8" pin to the bottom of the threaded end. Threads are part of the flat stamping material.
A = It uses a 3/8" pin
B = The opening between the pin holes is 7/16"s.
It is 1" wide from the side
Threaded female shank of 3/8 x 24
The McMasterCarr clevis
D = 2 1/2" Threads extend out from the clevis body on a 7/8" shank. This gives you 1/2" of additional overall length in threads. (Its forged steel not cast.)
A = 3/8" pin
B = 7/16"
It is 11/16" wide at the side (allows it to articulate on the pedal better).
Threaded female shank of 3/8 x 24
www.mcmastercarr.com
6071K14
In stock for $7.26
Rod End Type Clevis Rod Ends
Clevis Rod End Type Forged Clevis Rod Ends
Shank Type Female Shank
Shank Thread Type Right Hand Thread
Clevis Material Steel
Finish Plain
Shank Thread Size 3/8"-24
Inside Diameter (A) 3/8"
Clevis (B) 7/16"
Clevis (C) 7/8"
Clevis (D) 2-1/2"
Clevis (E) 7/8"
Clevis (F) 1-5/8"
Specifications Met Society of Automotive Engineers (SAE)
Last edited by mysixtynine; Feb 7, 2012 at 09:35 AM. Reason: had to add the new clevis info
Intermediate
Joined: Nov 2011
Posts: 30
Likes: 1
From: warrenton va
I put a 9" booster on my 75 w/ 468 big block that has the tall valve covers.I have about 1/4" clearance on the valve cover. The motor does sit lower in the car to make everything fit.I had to add a vac pump due to the cam but the car brakes well. Hope this helps
Burning Brakes
Joined: Jan 2006
Posts: 1,088
Likes: 181
From: NC
2022 C2 of the Year Finalist - Modified
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Let me first start by saying my body is still off the car but I am converting to power brakes and a big block with tall valve covers. I am not finished with the booster install but I don't think I have missed anything yet. So treat this as information only at this point.
I have consulted with several forum members as to their success using a 7" dual diaphragm booster. My engine vacuum is just under 16" at idle so the 7" booster will cause me to have a slightly heavier pedal than a 9" but I haven't driven the car in so long that power brakes will simply be an improvement anyway.
I have removed all of my information below as to the power brake conversion and am just including the 7" booster stuff that I have found so far.
I think I got my booster from jegs or summit.
Installing a 7” brake booster
The TuffStuff 7" booster and master cylinder combo is about 2" shorter overall and 2” narrower in diameter making it more compact on the firewall and by the engine. (You may need to update your master cylinder lines due to the shorter overall length.)
Tuff Stuff Performance 2122NA
Tuff stuff 2071 master cylinder
Master Cylinder Bore Size1.125 (1 1/8) Corvette style with 9/16 in. and 1/2 in. fitting on driver side.
Booster Diameter (in)7.000. ( 2222na )
• The 7" booster rod is 1/2" shorter from the base of the booster that mounts to the firewall to the tip of the threads on the push rod. This requires the clevis to be longer or some type of threaded rod to be made up. I chose a longer clevis (see below, more info on the clevis at the bottom of this doc.) as the 1/2" is just not that easy to make up when it comes to threaded rods.
7" booster
9" Factory booster
Clevis comparison. I bought a new clevis from Mcmaster carr its forged and makes up the 1/2 I lost on the threaded rod.
Factory clevis
D = 2" from center of the 3/8" pin to the bottom of the threaded end. Threads are part of the flat stamping material.
A = It uses a 3/8" pin
B = The opening between the pin holes is 7/16"s.
It is 1" wide from the side
Threaded female shank of 3/8 x 24
The McMasterCarr clevis
D = 2 1/2" Threads extend out from the clevis body on a 7/8" shank. This gives you 1/2" of additional overall length in threads. (Its forged steel not cast.)
A = 3/8" pin
B = 7/16"
It is 11/16" wide at the side (allows it to articulate on the pedal better).
Threaded female shank of 3/8 x 24
www.mcmastercarr.com
6071K14
In stock for $7.26
Rod End Type Clevis Rod Ends
Clevis Rod End Type Forged Clevis Rod Ends
Shank Type Female Shank
Shank Thread Type Right Hand Thread
Clevis Material Steel
Finish Plain
Shank Thread Size 3/8"-24
Inside Diameter (A) 3/8"
Clevis (B) 7/16"
Clevis (C) 7/8"
Clevis (D) 2-1/2"
Clevis (E) 7/8"
Clevis (F) 1-5/8"
Specifications Met Society of Automotive Engineers (SAE)
I have consulted with several forum members as to their success using a 7" dual diaphragm booster. My engine vacuum is just under 16" at idle so the 7" booster will cause me to have a slightly heavier pedal than a 9" but I haven't driven the car in so long that power brakes will simply be an improvement anyway.
I have removed all of my information below as to the power brake conversion and am just including the 7" booster stuff that I have found so far.
I think I got my booster from jegs or summit.
Installing a 7” brake booster
The TuffStuff 7" booster and master cylinder combo is about 2" shorter overall and 2” narrower in diameter making it more compact on the firewall and by the engine. (You may need to update your master cylinder lines due to the shorter overall length.)
Tuff Stuff Performance 2122NA
Tuff stuff 2071 master cylinder
Master Cylinder Bore Size1.125 (1 1/8) Corvette style with 9/16 in. and 1/2 in. fitting on driver side.
Booster Diameter (in)7.000. ( 2222na )
• The 7" booster rod is 1/2" shorter from the base of the booster that mounts to the firewall to the tip of the threads on the push rod. This requires the clevis to be longer or some type of threaded rod to be made up. I chose a longer clevis (see below, more info on the clevis at the bottom of this doc.) as the 1/2" is just not that easy to make up when it comes to threaded rods.
7" booster
9" Factory booster
Clevis comparison. I bought a new clevis from Mcmaster carr its forged and makes up the 1/2 I lost on the threaded rod.
Factory clevis
D = 2" from center of the 3/8" pin to the bottom of the threaded end. Threads are part of the flat stamping material.
A = It uses a 3/8" pin
B = The opening between the pin holes is 7/16"s.
It is 1" wide from the side
Threaded female shank of 3/8 x 24
The McMasterCarr clevis
D = 2 1/2" Threads extend out from the clevis body on a 7/8" shank. This gives you 1/2" of additional overall length in threads. (Its forged steel not cast.)
A = 3/8" pin
B = 7/16"
It is 11/16" wide at the side (allows it to articulate on the pedal better).
Threaded female shank of 3/8 x 24
www.mcmastercarr.com
6071K14
In stock for $7.26
Rod End Type Clevis Rod Ends
Clevis Rod End Type Forged Clevis Rod Ends
Shank Type Female Shank
Shank Thread Type Right Hand Thread
Clevis Material Steel
Finish Plain
Shank Thread Size 3/8"-24
Inside Diameter (A) 3/8"
Clevis (B) 7/16"
Clevis (C) 7/8"
Clevis (D) 2-1/2"
Clevis (E) 7/8"
Clevis (F) 1-5/8"
Specifications Met Society of Automotive Engineers (SAE)
Much appreciated.
