Awesome-X

I was told they're good to have for daily driving but I don't understand why. I have someone willing to sell me one for my 305 for $25 and Im wondering what the pros of having one are.

the zander

Increased fuel economy, the vacuum diaphragm advances timing at part throttle cruise facilitating more complete, efficient, combustion. I think every daily-driver should have one. Keep in mind they are only applicable to non-cc cars, computer controlled cars have the same function programmed into the ECU.

-Z

Awesome-X

Oh, well the dizzy I have on it works just fine but its been converted to carb so would it still work like it should?

the zander

If i understand correctly, you converted your fuel-injected (TPI or TBI) 305 to Carb? The distributor that originally came with the motor is therefore a computer-controlled HEI unit. Unless you retained the stock ECU alongside the Carb your distributor will most likely not function correctly. CC-Distributors dont have a mechanical advance system so as your RPM increase your timing will stay at the base value (bad).

-Z

Awesome-X

Yeah, thats what I thought...so I need to go pick up this vacuum advance one then...thank you for explaining it to me.

crytical point

Yea you do need it for more performance and I had to do it to my old camaro but I just pulled one out for the junkyard from a old truck and it worked fine.

Awesome-X

Cool, I think I'll go grab one I found on craigslist thats been recently rebuilt for $25. Hate to make the hour drive but its cheap and has vacuum advance. Stupid question I'm sure but what vacuum line should I hook it up to?

crytical point

should have one on the carb if not about any manifold vacume will work as long as it doesn't have high demand stuff on it.

the zander

actually, for it to function properly the distributor needs to be connected to a ported vacuum source. a ported vacuum source will show no vacuum at idle and full manifold vacuum from part throttle - WOT. If you connect the distributor directly to manifold vac your base timing will appear way higher than normal.

-Z