Here’s a handy list of the sizes for the vacuum lines on a stock Buick V6 turbo engine:
Cruise Control Servo:
Large port 9/32″
Small port 7/32″
Vacuum ball 7/32″
Washer Reservoir 8/32″
Washer Nozzles 7/32″
Charcoal Canister:
To Tank 10/32″
Solenoid 8/32″
EGR to Solenoid 5/32″
Vacuum to EGR Solenoid/Check Valve for HVAC/Cruise 9/32″
Brake Booster 3/8″ (9-9.5mm)
AFR 6.5/32″
Vacuum Block:
3 ports 8/32″
1 port 6/32″
1 port 12/32″
PCV 12/32″
Wastegate Y-hose 8/32″
Total Lengths For Car:
4mm (5/32″) = 122″
6mm (15/64″) = 147″
8mm (5/16″) = 46.5″
The general consensus as to sizes, is close enough is good enough.
Some aftermarket kits (for engine dress up) are offered in a variety of colors (red, blue, etc.), and sometimes come in metric sizes (as opposed to SAE). The metric sizes don’t always correspond to the factory sizes, that’s why “close enough is good enough.”
I’ve seen some Turbo Regals where #4 braided line was used off of the vacuum block, and ran to ALL of the different connections (except for vacuum brakes if the car was converted to that). For the most part, vacuum is vacuum, although that source may respond slightly differently than originally if it has a different size hose connected to it.
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