Replacing the vacuum advance unit on an '81

[Luddite]

Hi all. Upon inspecting the Marelli distributor, I noticed that the centrifugal advance springs are extremely flabby, and the vacuum advance unit doesnt move at all. (Even trying to move it with a screwdriver budges it less than 1mm). It seems that replacing the springs is a simple enough task, but I see no way to replace the vacuum unit without removing the whole distributor. Am I right about this? Can anyone fill me in on the pitfalls of removing the unit? Is there a better procedure?

Thanks for any assistance.

[So Cal Mark]

gotta remove the dist. Consider getting a new gasket and o-ring for reinstallation

[Mathew26]

It does make things easier to remove the distributor, but you don't technically have to remove it to remover your vacuum advance. No real pitfalls just a small irritation that doesn't take too long to remedy.

[Luddite]

Thanks . I'm trying to find TDC, and noticed two odd things. First, the three prong timing indicator is completely obscured by the belt - all you can really see is the hole in the bracket, the center of which appears to line up roughly with TDC. Is this normal? Second, I checked the existing timing with a light running at smooth idle (about 1k RPM), and the mark on the crankshaft pulley shows up well below the three prong marking bracket. Am I running with way too much advance at idle? Is it possible some PO put the pulley on incorrectly and messed up the mark? As I say, the Idle seemed smooth to my ears...

[rlux4]

The hole in the bracket does line up nicely with TDC. Remember though, you'll use 10° BTDC as a benchmark for timing.
Ron

[courtenay]

I believe the pulley is keyed, so it would be tough to put it on wrong.

[spider2081]

I just replaced my Vacuum advance on an 81 Spider 2000. I cant imagine getting the three screws holding it to the distributor out with the distributor on the car. also putting the new nylon cup onto the ball in the distributor was very hard with the distributor out on a bench.
I found my timing had been set well advanced of the 10 degree mark also. I even rechecked TDC by pullint the spark plug to be sure the TDC mark was correct and it was.

Also I checked the vacuum in the line to the advance and it was zero. Carbon had clogged the hole in the throttle body. I guess that is why the leaking advance chamber didn't have as much effect on the engine as it might have.

[So Cal Mark]

once the advance unit quits working, some owners advance the initial timing to 15 to try and compensate. A better solution is to modify the mechanical advance

[Cozi]

I've replaced mine at least four times. It's position directly above the header goes a long way towards cooking the diaphragm.

[So Cal Mark]

just one of several reasons our new trigger unit mounts on the block instead of the cam

[robmorais]

A few questions:
1. Is the VAM really necessay? I plugged my hose and could not feel any driving difference.

2. Since they break so easily are there any other companies that make a similar module that could be used or modified to fit.

3. What parts on the VAM fail and could we get IAP or another supplier to get something made that would not fail?

Rob
MoraisR@usa.net

[rlux4]

Because they go bad so quickly (my last one only lasted about four months) I plugged the vacuum line to it and have been running for a couple of years without it. I have good acceleration, cruising, and MPG.
Neither I nor anyone else who's driven my car notices any lack of performance.
Ron