I was playing around with the timing on the 400 today. I had the timing light on it with the vacuum advance still hooked up. What I did was advance the ignition until the motor would break up when I revved and held it @2000. If it ran smooth, I advanced it a little more. When I reached the point that it was breaking up, I backed it off just until it was smooth again. I'm not sure how far advanced it is as it's well off the timing tab now. I would guess 16 degrees (no vacuum advance) or possibly more, but the car does seem to run ok that way. I didn't get a chance to test run it out on the road yet. I'll get that done very soon I hope. I now has @20 inches of vacuum at @ 900 rpm idle. What I was trying ot do was to eliminate the bog when I floor it right off idle. It did help when I was working on it in the garage, but again I didn't road test it yet. The throttle responce seemed to be much better this way. The carb still needs to be rebuild though, but that's another project. I did try to start it a few times with it warm to see if it would affect the start up and it started up fine this way. Am I going in the right direction with this? Is this going to be too far advanced for the timing? I don't know how it will start when it's cold, I didn't try it yet after it cooled off. But again, that will depend on if the choke is going to work or not( another project ). I'm just looking for some help on this. Thanks, Dan :3gears:
You probably have too much timing, but the best way to know is to do some WOT runs and see if it pings. I have no idea how you would set timing in a driveway, unless you are only trying to match factory specs. Honestly, I would start with about 10 degrees initial (depending on your mech advance), and work up from there if possible. You might even have to retard from 10 degrees down to 8 or 6, who knows. -Bob Cunningham
I'd say the ignition is retarded if you set the timing with the vacuum advance connected. Depending on the vacuum can you probably have 8-16 degrees at idle. That part doesn't hurt, but what does hurt is as soon as you stick your foot in it, vac advance drops out and you're retarded the 8-16 degrees you had. At least until the centrifugal advance comes in and adds to the timing advance figure as the rpm's build. If your engine is close to stock, disconnect the vacuum advance at the distributor end - plug it, golf tees work great - and set the timing at 8 degrees BTDC. Re-connect the vacuum advance and you'll see additional advance at idle as well as the idle speed will speed up. There's other things you can do with a timing light and I suggest you get one. If a timing light is not available you can set the 8 degrees initial with a test light or volt/ohmmeter. More on that if you wish. A lot of guys set timing with a vacuum gauge and it does work for some of them, but most times they have too much advance dialed in. The bog you're experiencing could be a carburetor problem. What kind of carb are you running?
Dan, This has been covered before. I can't imagine why anyone would guess at what their timing is, when it is so easy to know. This is very simple. First disconnect your vacuum advance and plug it. When your foot is on the floor, vacuum will be close to 0, and vacuum advance will not figure into your total advance. Looking at the motor from the front, measure EXACTLY 1 3/4" clockwise, from your balancer mark, and make another mark with white paint. This equates to 30* of timing. Now, with the vacuum advance disconnected, rev the motor, and watch your new mark. It will move upwards towards the timing tab. At some RPM, the new mark will move no further. This is the point, where all of your mechanical advance is in. It should all be in at 2500 RPM or less. If you still have stock springs in the distributor, all your advance will not be in until 4600 RPM. You don't want to freewheel the motor up that high. Put lighter springs into the distributor. The Crane adjustable vacuum advance kit comes with 3 sets of springs that are ideal. If you have the kit, use the 2 silver springs. Once you have the right springs, rev the motor, with the distributor loose enough to turn, until all the advance is in. Then turn the distributor until your new mark lines up with the timing tab. If you want 32* total, line the new mark up with the 2 on the tab, 34* total, with the 4 on the tab etc. Most Buicks run best with total timing between 30-34* I would start with 32. Once you have done this, see where your initial timing ends up. 10-16* is nice, and allows easy starting. Initial is not nearly as important as your total advance. Once you have that set up, reconnect your vacuum advance, and check for part throttle ping. You will probably have to limit the vacuum degrees in the cannister. It's easy to do. First set your total.
I'm running the stock Quadrajet carb. I do have a timing light, and used it while I was setting the timing. I was doing it this way just to see how far advanced I could get it before I had a negative effect with the motor. The 16 degrees I have is with the vacuum advanced hooked up, but I get no vacuum to the advance at idle. The vacuum line is coming off the bottom of the carb. Checking the timing with the light at idle, it was @14-16 degrees. If i revved it up it was probably @25-30 degrees. The car seems to run ok like this, but I have not road tested it yet. Looks like it won't be today either as it's raining here. Hopefully I'll get to test it out tomorrow. Obviously if it doesn't run well, I'll adjust it then. I was just wondering if it will hurt the motor to run it that much advanced. Dan :3gears:
Set the timing without the vacuum advance hooked up. Even if you don't get any vacuum advance at idle, you wwill as you open the throttle. It needs to be disconnected. The vacuum advance will be 0 when you floor the gas anyway. If you run it at full throttle, and it is too far advanced, you can hurt something, or blow a head gasket. That's why I'm saying, why run blind when you can know for sure.
Ok, I marked the balancer on the timing mark and 1 3/4" clockwise from the mark. I warmed up the engine to 160 or a little higher before I started making any adjustments. I checked the idle speed, it does run @100 rpms more than it should. Hopefully I can address that when I rebuild the carb. I unhooked the vacuum advance and plugged it. I set the initial timing to 14 degrees. Then I revved it until the advance stopped moving and adjusted it so the second mark hit 0 on the timing tab. Then I hooked up the vacuum advance and checked it. The second mark (30 degree mark) would go up to @10 degrees on the timing tab. Would that be 40 degrees total advance at that point? That sounds like an awfull lot of advance. I don't have an adjustable vacuum advance yet, I ordered 1 today. The motor runs ok there, but again no road test today( still raining here ). But no pinging at part throttle. It does pickup way better when you hit the gas though, no popping back through the carb. Am I at least going in the right direction with this? I know I will have to wait until the new parts to show up before I can do much more. I also ordered a conversion for electronic ignition, to replace the points. I got the Crane XR-I that will install in the stock distributor for the stock look. That 1 also has the rev limiter. Thanks, Dan :3gears:
Dan, If you hooked up the vacuum advance, and reved the motor, 40* or higher is normal. When the motor is under heavy load, or at wide open throttle, the vacuum advance will drop out, and you will have 30*. Did you have lighter springs in the distributor? If you have stock springs, you might not have reached the point when all the advance was in. In that case you will have more than 30* Remember the stock springs don't allow all the advance in till very high RPM. It's not good to rev a motor that high in neutral. If you have your doubts, wait for the Crane adjustable vacuum advance kit. What I like to do is use the lightest springs (2 yellow), just for setting my total. With the 2 yellow springs installed, all you need to do is increase the RPM's to about 1600-1800, and all the timing is in. Once I set the total, I switch to the 2 silver. (advance in at 2200-2300)
I'm not sure what springs are in it. As far as I know, they are stock springs. But they may have been changed before I got the car. I'll wait until the new unit arrives to make more adjustments to be safe. Thanks Larry. Dan :3gears:
