brake vacuum source
Thread Starter
Racer
Joined: Apr 2007
Posts: 492
Likes: 3
From: Temecula CA
brake vacuum source
I am putting a holley spreadbore replacement on my Vette. Can I use a vacuum port that is on the manifold, or do I have to use the source on the back of the baseplate of the carb? The new carb has a block-off screw in the port at the rear, and I have heard it is difficult to remove. Thanks!
Temvette72
Temvette72
Burning Brakes
Joined: Oct 2001
Posts: 911
Likes: 5
From: TN
spreadbore installation
I installed the spreadbore 6210 double pumpers on my 68 and 70 way back in 1974 and still in use on the 68. No power brakes on the 68, but the 70's source of vacuum for the power brakes was not changed, continued with the source from the fitting in the intake behind the Holley.
Use full time vacuum port for your vacuum advance, leave the ported vacuum source capped and not used.
Use full time vacuum port for your vacuum advance, leave the ported vacuum source capped and not used.
Melting Slicks
Joined: Mar 2006
Posts: 3,456
Likes: 102
From: Piedmont Va
St. Jude Donor '11-'12-'13,'19-'20
I just installed a Holley 4175 spreadbore Q Jet replacement. The vac port for the booster is in the base plate with 1/4" pipe thread. I found a hose nipple adapter for 3/8" hose at advance auto parts that solved the issue with a [piece of 3/8" fuel line. I also used 3/8" steel fuel line for part of the length. The block off port should not be difficult to remove if the carb is off the car. If the carb is installed, take it off to swap the plug out for a hose adapter.
Check out this photo and see if it looks the same as yours.
Check out this photo and see if it looks the same as yours.
Thread Starter
Racer
Joined: Apr 2007
Posts: 492
Likes: 3
From: Temecula CA
Thanks for the replies. My intake has a vacuum outlet on the back (between the carb and the distributor). It has three ports, one which is unused and capped. I just plumbed the brake booster vacuum right to the unused port, and it works fine.
temvette72
temvette72
