Vacuum plumbing suggestions
Thread Starter
Racer
Joined: Jan 2014
Posts: 334
Likes: 6
Vacuum plumbing suggestions
So I am getting to know my 75 I just bought. It is a 4-speed manual with a "built/bored-over 350 with a new cam.". Once started and warmed up it actually runs pretty good some punch from midrange on. (screech tires off 1st, chirps 2nd and 3rd)
Specifics: Holley Street Avenger 670 cf carb (vacuum secondaries) and Torker 2 manifold (wouldn't have been my first choice but like I said they work ok), long tube headers, dual exhaust. Manifold vacuum steady at 9 inches. Cam (meaning the idle) lopes, no vac leak found.
My issue: the brake booster and pcv are both teed together off the large brake booster port. (I never liked this arrangement, I know it has been discussed many times before.) The large pcv port off the front of the carb is connected to the headlights. I tried connecting the headlights to the small port on the front but this is not enough to work the headlights.
Any ideas on how to get a bigger port for the headlights?
The Torker 2 has a plug but the only 90 degree fittings I have been able to find that don't reduce size are for boats, anybody ever used one of these? I just want the brake booster connected to an independent vacuum source. Thanks.
Specifics: Holley Street Avenger 670 cf carb (vacuum secondaries) and Torker 2 manifold (wouldn't have been my first choice but like I said they work ok), long tube headers, dual exhaust. Manifold vacuum steady at 9 inches. Cam (meaning the idle) lopes, no vac leak found.
My issue: the brake booster and pcv are both teed together off the large brake booster port. (I never liked this arrangement, I know it has been discussed many times before.) The large pcv port off the front of the carb is connected to the headlights. I tried connecting the headlights to the small port on the front but this is not enough to work the headlights.
Any ideas on how to get a bigger port for the headlights?
The Torker 2 has a plug but the only 90 degree fittings I have been able to find that don't reduce size are for boats, anybody ever used one of these? I just want the brake booster connected to an independent vacuum source. Thanks.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The PCV system is an "input" of fuel/oil vapors to the carb base so it can be injested by the regular fuel charge. So, that PCV line should NOT be connected with any other vacuum system need. Otherwise, the incoming vapors can get sucked into the other system and do damage. If you only have two ports, hook the power brakes and the headlights together. They both just need a vacuum source. At the worst, your headlights might 'shuck and jive' a bit when they open/close IF you are braking at the same time (unlikely). Otherwise, you will not notice any difference.
P.S. It would be best to retain the vacuum reservoir tank in that system, along with the headlights and brakes.
P.S. It would be best to retain the vacuum reservoir tank in that system, along with the headlights and brakes.
Last edited by 7T1vette; Jan 7, 2014 at 12:20 PM.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Agree that the PCV needs to go into the carb connection.
If you want to use a factory-style T-adapter, Paragon and others still sell them.
https://www.paragoncorvette.com/sear...vacuum+fitting
If you want to use a factory-style T-adapter, Paragon and others still sell them.
https://www.paragoncorvette.com/sear...vacuum+fitting
Advanced
Joined: Nov 2011
Posts: 95
Likes: 6
From: Indiana
Had same problem recently and found a low profile 90 deg fitting from Jeg's or Summitt for manifold vacuum then used 1/4" spacer on carb to clear float bowl-connected carb vacuum to headlight/brake booster and manifold to PVC. Air cleaner just wasn't pulling enough vacuum to operate PVC. As stated you don't want to contaminate booster
Thread Starter
Racer
Joined: Jan 2014
Posts: 334
Likes: 6
I totally agree, I want the booster free of the pcv. I will try teeing the headlights into the booster and use the second large carb port for the pcv. If that doesn't work I will look for that 90 degree fitting for the fitting off the intake manifold. Thanks again.
Thread Starter
Racer
Joined: Jan 2014
Posts: 334
Likes: 6
7T1vette, thanks. I teed the headlights vacuum circuit into the brake booster so I could free up the other large vacuum port for the PCV. My headlights still work and I feel safer having the PCV plumbed solely to its own port.
