timing and idle setup

[gws34]

So I am trying to get my bronco ready for emission inspection in AZ. I hve not had this on the road in years and part of it was I had to replace most of the emissions stuff the PO ripped off and got rid of.

So i have replced plugs, wires, oil change, all of those things now trying to set up idle and timing.

So do I set idle to 650 with the vacuum advance attached or with it disconnected and plugged?

I thought you set idle when it is disconnected and set the advance to 8deg btdc. then when I hook up the vacuum advance it jumps up to 820 rpms, that seems to high.

what should the rpm's be with Vacuum advance disconnected? What should the advance be when the vacuum advance is connected.

Also i read somewhere that taking the advance down to 6 or 4 is better for emissions testing? is this true?

Thanks
Glen

 

[jckkys]

The settings required to pass emissions are totally different then the settings that work for every day. I always speed the curb idle to 1500 RPM and lean the mixture till the engine is shaking. Then I retarded the timing to about 6 degrees. That usually gets me through the test. Then I go home and set things to run well. The sleazy shops set up near the emissions test station do things like pulling vacuum hoses creating leaks until the engine barely runs and the CO and hydro carbon levels pass. Then they tell you to come back after the test so they can get the engine running correctly again. It's all a sham.
The best settings for your engine are just that, meaning there are no universal settings that are best for a particular engine in a particular environment.
If your vacuum advance speeds up the engine, it's likely it was attached to the wrong nipple. The ported vacuum doesn't affect the advance when the engine is at idle.

 

[gws34]

Yes I was hooked up to the wrong vacuum from the Carb. Now I have it hooked up to the nipple on the passenger side, I still get some vacuum but now I get a horrible vacuum sucking sound from the top of the carb near the barrels. IT is still enough vacuum that it drops the idle down to stall out when i disconnect the vacuum from the advance and plug it.

Yes I understand that ideal driving and passing emissions are 2 different set ups, but since I have replaced and fixed things trying to get it running and to also dial it down to pass emissions.

Hopefully I can get this solved soon and get this on the road.

Thanks

 

[jckkys]

It sounds like you have a tach but no vacuum gauge. I'd like to know how much your getting at the ported vacuum nipple at idle. First get the engine to idle with no vacuum advance. Then worry about setting the advances.

 

[gws34]

I will have to check tomorrow what the vacuum is at the ported nipple. I do not have a tach, I do have a vacuum gauge. I am getting rpm with my timing light.

I do know I am getting vacuum to the dizzy, but I am going to check all the lines. I will put the gauge on all of the nipples from the carb to check them out.

Prrt of my issue, I think, is I am trying to replicate to emissions vacuum connections. Part of the system does hook to the full manifold pressure so I will try to track down what is supposed to have vacuum and what should not.

How do I get the Carb to not have vacuum if I check all of the ports and they do have vacuum.

According to the emissions drawings I have it hooked to the port on the front, by one of the screws to set valves. Other keep saying I have to connect to the port on the passenger side. Just trying to get this thing on the road and wish the PO did not rip all of this off.

Thanks again for everyones help. someday i may actually figure this out.

 

[DirtDonk]

Not sure about your neck of the woods, but around here there is only one "best" ignition timing setting. And that's what Ford recommended originally. So if that happened to be 6° BTDC, then that's what the smog techs are looking for. No more, no less.
Maybe they have more leeway where you are, but when in doubt, factory settings are always going to be your safe bet.

Usually the original connections for vacuum advance in the later seventies, if it was connected to full manifold vacuum then, it was controlled by at least one, but often more than one temperature controlled valve before it got to the distributor. My later pickup goes through two of them before it gets to the vacuum advance fitting on the distributor.
If you're directly connected to the distributor from the carburetor though, as said you would normally want the ported vacuum.

When you connected it to full vacuum and the idle speed went up, that's normal because more advanced ignition timing usually does raise the rpm. You're supposed to go back to the carb adjustments then and turn the idle back down to where you want it.
In the case of the ported vacuum fitting having a vacuum signal, that means that the carburetor idle speed screw (or solenoid) is holding the throttle plates open too far. Usually adjusting them to be more closed fixes this, but lowers your idle. So you have to find out why your idle is so low that you have to turn up the throttle to the point it exposes the transfer port between the vacuum fitting and the venturi.

It's never the same 100% of the time, especially the first time you deal with it on a particular vehicle. Once you get everything dialed in though, future tune-ups are usually a breeze.

Good luck with the test!

Paul

 

[gws34]

Thank you Paul.

Yes after going over it and looking at many sources, i did have it in the right port to start with. Yes it does go through 2 to 3 ported vacuum switches. I will now continue to check if there are other problems. I had it at full temperature idling and it still jumps up a few hundred rpms, it seems to me that is a lot. When the engine is set to 600 rpms and I disconnect the vacuum advance (and plug the line) the engine stalls out because the rpms are too low. I will continue to play with it.

I will start another thread about the emissions questions I have that i have not found answers for here in the other posts instead of it getting lost in this string.

 

[DirtDonk]

Then either one, or more of the PVS' are bad, or the routing/connections of the tubing is incorrect. Under normal conditions you don't see vacuum at the advance through that system at idle.
I would just do what was suggested for now at least then, and connect the vacuum advance directly to ported vacuum on the carburetor. That gets you running with a stable idle and no worry about changes to the speed you set, from getting full vacuum to the diaphragm at idle.

There is no way to stop your idle speed from changing as the timing advances and retards. With more advance it's going to go up, and with more retard it's going to go down. I'm sure it's frustrating when you set it and then it changes.
And I'm not really sure (maybe I've forgotten) how you are supposed to set an idle speed, then connect full vacuum to the advance mechanism. The only way I see to set the idle speed is to set it with the vacuum advance connected.
Setting the initial timing is done with the hose disconnected, but then you have to hold the idle at the intended speed either by hand, or by setting it falsely high, then going back to low after the timing is set so that it will run normally with it connected.

All very strange, and someone else will have to figure it out and tell us what's going on. But most of us run ported vacuum (without all the smog setups and extra tubing) for just this stability reason.

Paul

 

[jckkys]

It seems absurd to think what some bureaucrat thinks has anything to do with the best timing curve. Most think the best timing would produce the most torque, HP, and MPGs. It's the absurd emissions regs you're talking about. That's the reason these trucks had anti dieseling solenoids, EGR, Thermactor, timing retard on the advance diaphragm, cats, and other gizmos that made engines run like crap. It's the last place to look for good advice. Those guys made gas can makers produce products that are guaranteed to spill gas just fueling a lawnmower. Detonation is the limiting factor in ignition timing, not an abusive, obtrusive, parasitic, incompetent bureaucrat. Detonation occurs at different advance degrees depending on octane, compression, ambient temperature, engine temperature, A/F mixture, humidity, and altitude. My 351 usually likes 20 degrees initial and 40 degrees total advance. I arrived at that by trial and error. By doing it this way I get noticeably improved performance. Different engines in different environments need different ignition timing.

 

[1970 Palmer]

It seems absurd to think what some bureaucrat thinks has anything to do with the best timing curve. Most think the best timing would produce the most torque, HP, and MPGs. It's the absurd emissions regs you're talking about. That's the reason these trucks had anti dieseling solenoids, EGR, Thermactor, timing retard on the advance diaphragm, cats, and other gizmos that made engines run like crap. It's the last place to look for good advice. Those guys made gas can makers produce products that are guaranteed to spill gas just fueling a lawnmower. Detonation is the limiting factor in ignition timing, not an abusive, obtrusive, parasitic, incompetent bureaucrat. Detonation occurs at different advance degrees depending on octane, compression, ambient temperature, engine temperature, A/F mixture, humidity, and altitude. My 351 usually likes 20 degrees initial and 40 degrees total advance. I arrived at that by trial and error. By doing it this way I get noticeably improved performance. Different engines in different environments need different ignition timing.

X2, exactly.

I bet you can run more timing at higher Tucson (the 20 degree initial number), than in lower Phoenix. at 1200 feet. Drive your Bronco up to Flagstaff and you need to bump in even more timing for the mile high elevation. This is all in the same state, with the same emission regulations. I have lived in Arizona and California and never saw them check for initial timing during a emission test during my last 50 years of paying for State DMV emission testing. They sniff it at idle and at highway RPM (maybe 2000-2500?). You pass or you fail.

State emission testing is just another State Tax. They do it in dense population areas where they can rack in the most money.

 

[DirtDonk]

Around here they tested timing on every one, every time I was either having one tested, or watched someone else's being tested.
If you were not at the factory setting you failed. If the guy was nice (most of them were) they tweaked the timing quickly for you. If not, then you had to come back after re-setting it yourself.

Paul

 

[1970 Palmer]

I think the nice guys at the independent test stations.......retarded, or advanced the initial timing to get it to read within "the allowed" Co2 parameters for the test. I don't think they cared what the factory used as a initial timing specification.

Every clean running and properly tuned car with a slipped harmonic balancer would fail their emission test if they used the timing marker as a requirement to pass.