Ok guys I've read a ton on here looking for answers to all my questions about PCV valves, breathers, vacuum advance, etc. I found lots of great info and answers to most of my questions (Thank you all) but still have one about vacuum. I have a '69 327 with three Rochester 2g's on a new Edlebrock intake which does not have any provions for manifold vacuum. I have an inline PCV coming from the back of the center carb going to the p***enger side valve cover and a vented cap on the oil fill tube--PCV, check. I know where to run the distributor vacuum to on the center carb-- vac advance, done. Now, I believe I need vacuum for the TH350 as well as my brake booster so here is my remaining question; Where can I get vacuum for them?? Can I remove the plug in the rear of the base of the rear carb and get vacuum for the trans and booster there? If not, where? I'm not sure because I havnt seen this brought up before and I dont remember ever seeing it done like this. I've read where guys have gotten vacuum for both the PCV and the booster from the back of the center carb, and I understand how the end carbs just work as "dumpers" in a tri-power setup, I just dont know if that matters. My head tells me the vacuum is still there at the base of the end carbs if the plug is removed- but is that right? Thanks for your help... Jay
Jay - don't know which Rochesters you are using. When you do modifications, you become the engineer. Having said that, take a look at the way GM hooked up various vacuum connections: Front carb (Pontiac) 1/8 inch pipe tap on rear center of throttle body. Center carb (all) 1/8 inch pipe tap rear center of throttle body. Center carb (some) threaded hole or pipe lower p***enger side front of bowl Rear carb (Oldsmobile) 1/4 inch pipe tap on rear center of throttle body. Other - hollow carburetor stud (generally on p***enger side rear of center carb) Since you are using a non-GM manifold, and unknown carbs, I have no idea what of the above will work for you; but ALWAYS a good idea to at least look at how the factory engineers accomplished something. Jon.
As long as the vacuum source is below the throttle plates of the carb, you can use the carb base. So the carb base, a hollow carb stud that enters the intake runners, a hole drilled and tapped into the intake runner.
Pull the plug on the base of rear rochester and fitting appropriate to your needs, Brakes and whatever else needs full vac***, I built a ABS vac*** can hidden behind headlights for all the accessories ***ist. Best luck on it Sent from my SM-G900T3 using The H.A.M.B. mobile app
Offey has provision for vac already tapped. Have a look online at where they tap and do the same. Run a tee from there for your 2 requirements.
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