Brake Booster Vac Line
Thread Starter
Instructor
Joined: Mar 2019
Posts: 119
Likes: 3
Brake Booster Vac Line
Replaced carb with Edelbrock AVS2. The rear vac port for brake booster is smaller thread than stock metal tube fitting. Can I just put brass fitting with barb and use hose to repalce metal tube. It changes to rubber hose anyway just before the round black cylinder (filter?) then to booster. Hope this makes sense - Thx
Race Director
Joined: Nov 2006
Posts: 13,258
Likes: 7,848
From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
Bottom line, yes, you can.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Find out what diameter and thread pitch is needed for a brass fitting, then take that info to your local NAPA. I have found them there and sometimes EBay.
It needs to have the barbs on the hose end of the fitting.
Make sure that the rubber hose going to the booster is "thick-wall" and not avg rubber thickness.
That line will go to a filter and a check valve that keeps vacuum in the booster in the event the engine stalls at speed.
That line should also be solo / dedicated. Nothing tapped into it.
It needs to have the barbs on the hose end of the fitting.
Make sure that the rubber hose going to the booster is "thick-wall" and not avg rubber thickness.
That line will go to a filter and a check valve that keeps vacuum in the booster in the event the engine stalls at speed.
That line should also be solo / dedicated. Nothing tapped into it.
Pro
Joined: Nov 2019
Posts: 648
Likes: 353
From: Portland, Oregon
The round black cylinder is a carbon canister. Fuel vapors were found to be deteriorating the power brake booster diaphragm. The canister was added to condense the vapors into liquid which then drains back into the carb. It looks out of place sticking up in the engine compartment, but needs to be kept upright for the fuel to drain out of the bottom under gravity.
Charlie
Charlie
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,140
Likes: 4,248
From: US-PNW
I'd keep the GM hard tube that connects to the carb and only look to adapt its threads down to the carb threads. You really don't want any sort of bend restriction in a full rubber line to limit vacuum pull on the booster. (If GM had thought rubber all the way was a good engineering shortcut, they'd certainly have taken it.)
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
I'd keep the GM hard tube that connects to the carb and only look to adapt its threads down to the carb threads. You really don't want any sort of bend restriction in a full rubber line to limit vacuum pull on the booster. (If GM had thought rubber all the way was a good engineering shortcut, they'd certainly have taken it.)
All rubber to the headlights and all rubber to the over-ride switch under the dash, and all rubber to the vapor canister and all rubber from carb to dizzy, etc, etc, etc.
Thread Starter
Instructor
Joined: Mar 2019
Posts: 119
Likes: 3
Rochester to Edelbrock Brake Booster Vac Port
For what it's worth - Going with 1/4" brass to barb and heavy wall rubber hose to filter. . Tried to retain metal tubing from brake booster to new Edelbrock carb but could not find adapter from Edelbrock 1/4" to original Rochwester flared 3/8' tubing connector. NAPA, Winners Circle and Edelbrock all thought rubber hose and direct brass fitting is most common way to resolve this issue.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,140
Likes: 4,248
From: US-PNW
No. I mean all rubber for the power brake booster. GM, for the most part, designed that as a single isolated line on Corvettes and used a steel tube for the bend. I don't know the vacuum demands of the brakes, but it must be different enough, again for the most part, to enjoy it's own large diameter line. I think your observation about the rest of the vacuum system may bear this point out very well. The only other metal section in the entire system that I can think of is a small diameter line that runs along the various curves of the firewall below the windshield wiper motor. If GM had thought rubber all the way was a good engineering shortcut, they'd certainly have taken it.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
I have run the thick wall vacuum hose from either the carb or an Intake port, to booster for decades without issue. The trick is to use the thick wall like GM original did.
It can't kink by bending. However, few automotive stores have that in stock
It can't kink by bending. However, few automotive stores have that in stock
Race Director
Joined: Nov 2006
Posts: 13,258
Likes: 7,848
From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
The older cars never had the metal tube. Or the charcoal filter. Just a heavy rubber line. And it always worked fine. I currently run a section of AN hose. Made for fuel injection fuel delivery. Approx 3/8 inside diameter. Very heavy and stiff and looks good.
brakes work fine.
brakes work fine.