No vacuum advance on my dist, trying to set the timing Options

[terrymason]

I'm trying to time my 1.8 with carbs, and am having a rough time. I'm not sure if I am suppose to have a vacuum advance or not on my dist. Anyone know if the dist on my car is stock, or if it's an "upgrade". If it's an upgrade, is it any good?

I ordered a new condenser for it, and the one I ordered didn't seem to be right (original had a separate bracket that held the plug in - replacement had the bracket attached to the condenser). I believe that I had to mount the condenser upside down for it to fit properly (as it was originally). If the condenser was mounted in what seemed to be the proper position, the dist would not fit back into the engine properly.

(IMG:http://img106.imageshack.us/img106/5383/picture2007012as1.th.jpg)

[Kargeek]

Terry,

You have two basic types of engine timing advance- static and dynamic. Let's say your number one cylinder piston is set at top dead center on the compression cycle- the piston is at the top and both intake and exhaust valves are closed. If your ignition timing was to fire the spark plug you would have 0- spark timing.

If let's say, the spark plug was to fire 5 degrees of engine crankshaft rotation before top dead center, you have 5 degrees of advanced timing.

If you had your distributor timing set to fire 5 degrees- after top dead center- your timing is retarded 5 degrees. Engines like to operate with spark timing advanced...

Engine distributors have a mechanical advance system that is operated by a set of centrifugal weights- as engine and distributor RPM's increase, these weights move the distributor's contact points and "advance" the engine timing. Different distributor designs and their centrifugal weights have an "advance curve"- a rate of advance and total amount of advance depending on the engine RPM's.

Now, with vacuum advance- this is a vacuum diaphragm linked to a shaft connected to the distributor contact points mounting plate. A vacuum line connected from the engine manifold or carburetor provides the necessary vacuum signal so under part engine load and idle, high vacuum "advances" engine timing.

So, static, dynamic and vacuum advance engine timing is to provide a variable amount of ignition spark timing to suit various load and speed conditions of your engine.

So, what I'm helping you to do is to get to a starting point- timing your engine at a high RPM will max out your distributor's mechanical advance and leave you at idle with around 5 degrees of static advance.

Here's an article from air cooled net- some good basic reading on distributors:

Air Cooled Net

I am sure their are other engine experts here are can shed some additional light on this subject.

And remember, do not mess with your carburetors until you have your engine timing correct.

Good luck!

DH