Vacuum advance questions

[majicwrench]

I would NOT replace the spring...the spring is there, and is as strong as it is, for a reason....and is likely NOT supposed to move with only small amounts of vacuum. You do not want that VA adding timing unless there is a lot of vacuum present. The material you make the diaphram out of is not going to make a huge diff as long as it holds vacuum.
I may have some of the original dist specs if that help...
Keith

[backyardbill]

Yes, the original vacuum advance factory specs would be a BIG help. It sure would be nice to have a graphic plot of the advance characteristics with variables: RPM; port vacuum; throttle position, vehicle speed, gear, and load. Yeah, I know, good luck with that.

I might be able to get a friend (Carl, are you listening?) to let me measure his 1980 Fiat Spider vacuum under running conditions. Basically I want to know how much advanced is introduced upon take off, and the corresponding vacuum at that point. Then use a vacuum pump and see how much the VA moves and at what vacuum.

My resoning for lightning up on the spring pressure is to compensate for the flex being introduced by the neopreme material. The original diaphram material (what was left of it) looked "shaped". Now it is flat. Sure, the spring pushes on the rod to return the dizzy plate back to zero advance. I have several springs on hand so I might try one anyway.

[vandor]

The problem with the vacuum advance units is they are expensive and from what I have understood, fail quickly.
I hope this helps not only me, but anyone who has a Fiat electronic unit. Thanks!

Clark,

FYI, we have vacuum advances for $49.90. The last one I had lasted 6 years, not bad for a rubber part that is
constantly cooked by the exhaust manifold.

[backyardbill]

know this is a little late for the response but ...

I ended up throwing the home made vacuum advance repair away, and bought an aftermarket one a while ago, but never installed it. I think I got it from Csaba.

So what is the procedure for installing it? If I install it right out of the box, it will put a load on the ball socket and I will have to push against the internal spring to insert and tighten the fasteners. Is this right?

Or should I screw the white plastic piece in until it line up with the ball socket first?

Thanks in “advance” for the advice.

[backyardbill]

Never mind all. I screwed the vacuum advance module rod (white plastic ball connector) until to matched up with the ball connector (when the ball is fully retarded position). This allowed just slight spring pressure against the ball when fasteners were tightened. Started motor, let it idle, no advance. Revved motor up a little, it advanced. Timing light shows this advance on the crank pulley. I will drive it like that for a next few weeks to test it out.