weber: vacuum advance info

[Petros]

You need a timing light to do it accurately. you slacken the 12mm bolt at the base of the distributor, and with the engine idling, the timing light pointing at the front pulley, you watch how it changes as you rotate the distributor. lIne up the pulley mark with the "+10" mark on the front cover. this should be done with the vacuum lines disconnected off the dist and capped, remember to reinstall when done.

You can also set the timing "by ear" and trial and error. Advance the spark timing with the engine running slightly (the engine speed will increase), and than with the engine warm go for a test drive. Accelerate at full throttle, preferably up-hill. Listen for ping, or a crackling noise coming from the inner engine, if none detected advance the timing a bit more. Once you find the point where you get the ping, back it off just enough so you do not hear it. That will be where you get the best fuel economy and power. Too much ping will cause damage to the head gasket over long term. but if it is too far retarded you will burn your exhaust valves, and get poor economy.

[dlb]

no worries man--first off, you'll need a timing gun. disconnect the vacuum advance and plug the port it was connected to. next, there are four wires that go to your spark plugs. at the other end they are attached to your distributor (often called a dizzy). at the bottom of the dizzy is a 12mm bolt. loosen it off just enough that you can turn the dizzy. now, with the car warm and idling at about 800 rpm (or whatever you have your idle set to) hook up the timing gun: red clip to the positive battery terminal, black clip to the negative battery terminal, and the clamp on the spark plug wire that is closest to the front of the car (this is the #1 cylinder). you should get a flashing light coming from the gun now. point it down between the radiator and the front of the engine and you will see a big wheel spinning really fast. there is a mark on that wheel on the edge closest to the engine, and just above that mark you should see a few raised numbers--5, 10, 15, and 20. if your car is stock, the mark on the wheel should usually appear right around the 5. now, turn the dizzy very slightly and you will see the mark move to the left or right. figure out which way it's going in response to which way you turn the dizzy, and get that mark to around the 10. now put down the gun and tighten up that 12 mm bolt just enough to keep the dizzy locked in place but DON'T OVERTIGHTEN it. re-check the timing to make sure it didn't slip while tightening the bolt, hook up your vacuum advance again, and you're done.

edit: i guess petros and i wrote simultaneously! he's just a faster at typing.

[ebayollis]

is it the red hose, the gray hose, or the green hose form the vacuum diagram under "color-coded federal vacuum diagram" post that I hook up to the gas filter on the manifold?

[dlb]

can't find the post with the diagram you're referring to. post the link and i'll take a look. or, if you have a timing gun, just hook up each port on the vacuum canister one at a time and see which one makes the timing jump up to between 15* and 20*. just make sure you plug all the unused ports when you do it.

[ebayollis]

here is the pic

[dlb]

the green hose coming from the middle port on the vac. can is the one you should hook up to the gas filter. according to the diagram, it should already be set up that way.

[deejay1272]

the green hose coming from the middle port on the vac. can is the one you should hook up to the gas filter. according to the diagram, it should already be set up that way.

After spending much of the last two nights fiddling with the distributor and vacuum advance canister and I can say that the vacuum port on the very bottom of it is the port that advances the timing. This is the one that Petros mentioned earlier. If you have the stock carb, then the vacuum diagram above should be followed closely as David mentions. However, if you are running the Weber 32/36, then you will need to connect the port on the bottom of the dist vacuum advance canister to one of the ports on the gas filter. Doing this will drive ignition timing based on manifold pressure.

[dlb]

deejay, does your vac. can have 2 or 3 ports? there are 2 versions of the vac. can out there. mine only has two and i use the bottom port as well but wasn't sure which of the ports the 3-port version used. it will be good to have a definitive guide here, and very easy for everyone if both styles of vac. can use the bottom port for vac. advance.

[deejay1272]

Here is a photo of a new vac advance (looks the same as what I have on my car). The port that advances vacuum is the one with the straight port (on the end). Hopefully this will help clear things up a bit.



If you have less than three vac ports on your vac advance, then you probably have it structured for Federal emissions rather than CA emissions.

[dlb]

bottom ports for all! huzzah!

[ebayollis]

how did you guys get to the advance? did you take off your dizzy cap? also does it automatically advance the timing or is that something i have to do manually?

[dlb]

the vacuum canister is the thing pictured above and it is located on the bottom of the dizzy. you don't need to remove anything to access it. once you have the bottom port on it hooked up to the gas filter and the other ports plugged, it advances the timing during certain driving conditions.

this is not the same thing as advancing your base timing from 5* to 10* BTDC, if that's what you're asking. the directions on how to do that are posted just above. petros and i both wrote posts on it.

[ebayollis]

The egr has a vacuum line that mounts to it. Is this vac line the one that I run to the gas filter or is the one that hooks to the gas filter already hooked to the gas filter. And I just need to block off the egr one or does it go some where else?

[dlb]

line from the lowest port on the vac. advance goes to the gas filter, egr and all other emissions stuff gets disconnected and blocked off. except for the PCV stuff on top of the valve cover, don't block that or you could be in big trouble.

if you're still unsure, check out the weber thread on the main page for this site. there's tons of useful info there as well as photos of other board members' setups. read what they did and compare their photos with your own setup.

[deejay1272]

@ebayollis

Please refer to the Weber install writeup that I posted a few weeks ago for some additional information (https://tercel4wd.com/forums/viewtopic.php?f=7&t=6009). I've been updating this post as I learn more about the Weber install. It should be mostly complete (except for some forthcoming detail about the proper vacuum advance setup that I'm still figuring out).