Silly Vacuum Question

[Kevin Shelly]

Sorry for this simple question but does it matter where you connect the vacuum advance vacuum hose to the 348 engine? I see some vacuum advances are connected to the carburetor fitting on the side of the carb and some are connected to a port on the intake manifold. Is one better than the other or is the level of vacuum the same at both points? Thanks

 

[1964SuperStocker]

Sorry for this simple question but does it matter where you connect the vacuum advance vacuum hose to the 348 engine? I see some vacuum advances are connected to the carburetor fitting on the side of the carb and some are connected to a port on the intake manifold. Is one better than the other or is the level of vacuum the same at both points? Thanks

Do a youtube search on where you should hook it up your line. That way you get a visual of what you should do because reading about it is fine but seeing it done is better.

 

[blkblk63ss]

Is your motor and distributor stock or mofifyed? If stock just do as factory. If not you have to tailor it which works best for the engine.

 

[Kevin Shelly]

Thank you for the replies. I'll check out YouTube and see what I can find. To answer your question Don, the motor is rebuilt with 10.5:1 pistons and a slightly more aggressive cam than stock. The points were removed and an electronic module was installed in the distributor. It has the stock intake and 4GC carburetor.

 

[Don Jacks]

Kevin,Most Chevrolet engines like manifold vacuum better.If you have a vacuum gauge check the fitting at the side of the carb for vacuum at idle.If there's none then it's considered ported.On your engine I would start off with manifold vacuum and see how it likes it.

 

[Kevin Shelly]

Thank you Don. I'll check it later tonight. Currently the vacuum advance is connected to the port on the manifold. The port on the carburetor is connected to the vacuum module on the transmission. It seems to run OK but when looking through the shop and assembly manuals, it shows the advance connected to the port on the carb. Just was curious if there was a difference. Thanks again to all that took the time to reply.

 

[Don Jacks]

If that vac.fitting is hooked to the vac.modulator for the transmission,it must be direct vacuum.You'd be having shifting issues otherwise.That trans.must be direct vacuum,period.

 

[Kevin Shelly]

Understood. That makes sense now. Thank you Don.

 

[Jim Sullivan]

Some engines used a vacuum tee for both the distributor advance and the modulator being run off of the same vacuum source. As long as it is manifold vacuum, you can use either the manifold fitting or the carburetor fitting.