I'm needing some help on hooking up the vacuum lines on my 327 SBC. My setup is a vintage tri-power edelbrock intake and Rochester carbs (2g) I think they are called. there is a big vacuum port on the rear of the engine under the distributor, another big vacuum line coming off the bottom plate of the center carb, a small line on top of the bottom plate of the center carb angled down into the intake, and extra vacuum lines on the outside carb. Here's what I've got to hook up to vacuum: brake booster 350 turbo trans PCV valve distributor advance I'm guessing the 2 outside carbs only pull vacuum when the throttle bodies open up so these are not used? Any help is appreciated.
Manifold vacuum to the booster and trans, usually off the biggest one to the back. There were fittings with the big and small hose ports on them, that would clean it up a bit. Your carb locations sound like manifold vacuum vs ported (ported goes up with RPM). If your distributor curve is for load compensation (vacuum retards the timing) then it's usually at the base of a carb for quick response to throttle movement. Hope that helps. The tubes that are the same on all 3 may be for setting with a vacuum gauge, perhaps not really applied if the ends are closed for driving, open as "dumps". Any pictures?
The original outside carbs did not have any vacuum ports, they were used only at full throttle. If you have original center carbs on the outside you can plug any vacuum ports as they are not needed. You can tell the difference between the two by the baseplates, factory outside carbs have no idle adjustment screws Sent from my SM-G900V using The H.A.M.B. mobile app
When you say "big port under the distributer" I'm thinking the crankcase vent. The early to late 60's SBC's had a road draft tube or PCV connected to a vent at the rear of the engine next to the distributer. Any vacuum ports would be in the intake runners between the carb(s) and cylinder head or the carb base. I used a 90* elbow with a male pipe thread fitted into the intake runner. One side a plumbed to the booster the other side I drilled for a small piece of brass tube which I soldered in to create a fitting with two different size hoses attached. This would work for your booster and trans. PVC to the fitting on the center carb.
I have 'stock' chevy tripower like yours. I pull vacuum for the 350 trans from the bottom of the center carb, it is real tight between carbs. And I pull dist. vacuum from the port on the center carb body. The 350 will be coming out for a four speed, then the port will be plugged Its at home and I can take pic and post tomorrow if needed
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