Vacuum Advance

[rokemester]

After seeing a few other 66 engine pics in different forums I see that the distributors are fitted with a diaphragm (vaccum advance) that plugs into the carb. My distributor has no diaphragm and the inlet tube on the carb is intentionally plugged with a small hose with a screw. Is this standard operationg procedure for problematic vaccum advance?

[rokemester]

Mechanical advance vs. vacuum advance? Is that the difference?

[jmartini]

Yes, that is the difference. I had a mechanical advance on my car to start with and found it hesitated quite a bit, but once I put on a vaccum advance that went away. I'm sure there are plenty of folks out there with mechanical advance with no problems at all.

[Blue Baron]

The mechanical advance distributor is the universal replacement for the stock vacuum advance unit. It has its pros and cons. The best dizzy for your engine is the one it was fitted with originally, but the stock '66 distributors are becoming scarce, and finding new parts such as caps and rotors is becoming tricky.

[rokemester]

The Bosch model number is 0231 178 009 on my 66 1300 motor. When the distributor is installed with the engine at TDC the rotor is able to rotate without turning the motor. Is this right? Shouldn't there be a positive engagement between the distributor and the engine. The rotor seems to be floating, almost like the distributor isn't quite long enough. When I turn the generator the rotor doesn't follow along exactly. This can't be right!

[Blue Baron]

You're not knocking it home all the way. Put pressure on the rotor while turning it until the shaft finds the slot.

[rokemester]

This reply is long overdue! For the past 5 years at least I have been running a 009 mechanical advance distributor and stock 30 PICT carb. Up until a month ago my car was running well until it wasn’t. I eventually replaced the 009 with the stock distributor mentioned earlier in this thread. I static timed at 0 degrees, TDC. I just want to mention how much better the Bug is running with the vacuum advance. It starts easier and most definitely easier to get underway from first year. All shifts seem smoother along with decent acceleration. I recently heard a tech from JBugs mention how the mechanical advance distributor was used by VW for industrial motor applications. Vacuum advance distributors were designed for better car drivability. This is why I went back to the SVA distributor and I’m glad I did. Maybe others have had a similar experience.

[jmartini]

Thanks for the follow up!