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| Timing situation new to me https://www.slantsix.org/forum/viewtopic.php?t=43529 |
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| Author: | krytellan [ Fri Feb 04, 2011 7:10 pm ] |
| Post subject: | Timing situation new to me |
So, I know most of you tear down and build engines in your sleep. I have done some engine work in my time, and this situation seems new and unusual to me. So, in my '80 1bbl /6, the timing specs say 12 degrees BTDC. Fair enough. In my experience, when you advance timing, there is a relatively small window in which, when adjusted, your idle will steadily increase before the dropoff begins. I am less sensitive to the nuance of retarding timing as my impression has always been that advancing increases efficiency. At any rate, you increase the timing and you can get a small gain. So, there I was after the carb install doing everything tight. Had the Tach, timing light, carb idle screws... all good. I decided to simply advance my timing 2 degrees to 10 BTDC. I was out today and had a pretty bad sputter from a slow accel, and it slowly leaked over to the idle. Brought the car home, retarded the timing back to 12 and noticed a large idle increase in that 2 degrees. I retarded it more and noticed a still further idle increase and the motor smoothed out a bit. I ended up at 16 degrees BTDC before I noticed any decrease in gains. This is a winded post, but my question is can something be amiss with my timing? Is the 12 degree setting really that close to the performance drop off? Does the fact that I can retard it that much with gain mean that something is off or is my experience in these matters just misleading my interpretations? |
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| Author: | LUCKY13 [ Sat Feb 05, 2011 1:28 am ] |
| Post subject: | |
Did you have the vaccume hose disconnected? There iare some odd possiblities to it acting this way. The first thing that comes to mind is the balancer outer ring may have slipped. Your reading 12 or 16 or whatever but the timing mark is not where it is suppose to be ( slipped on the balancer) , so instead of it truely being (lets say 16) it may really be 24 ( or something even way off). If I understood what you where saying it is when you are backing ( retarding) the timing is when the engine is picking up, or smoothing out. With the balancer slipped it could act that way because you might truelly be muich higher on timing than you think ( past the point of roughness). It also sounds like you had it, but then something changed. This worries me because the balancer could have slipped, but the timing should not have changed when doing so ( except what it reads with a light, not what it really is). So either the Dizzy was to loose and moved on you, or maybe even the worst, timing chain jumped one tooth on you. YOu might even want to check the plastic gear on the end of the Dizzy, it may be getting warn enough that it jumped a tooth. Most of the time when this happens it just strips and quits, but its possible for it to just jump one tooth also. I would start out by bring number one piston up ( with the plug out, and turn the engine by hand). Use a straw, or something stiff enough to stick down in the cylinder so you can test when you have the piston at TDC. When you find TDC check the timing mark and see if its inline like it should be. If not either the balancer ring slipped, or the timng chain jumped. There is also the chance of something going wrong with the engine, and it really needs the retarded timing to smooth out now. Like valve lash ajustment, or even a valve starting to burn. A vacume gauge can give a quick check for this, but sometimes it want really pick it up unless its pretty bad. ( look for sharp spikes in the vacume at idle). The slightes bit of a valve to tight the idle will go rough and retarding the timing will help smooth it out. Maybe you ajusted the valve but didnt run it and get it hot until now so it showed up after driving. A vacume leak even could act like this. Or the carb being to lean. Everything has to be just right to get the advanced timing to work OK. And even then as you know it has its limits. Either something changed, which changed its limits. Or something on th ebad side happened like the timing chain jumping, or a valve leaking ( even if its from a to tight a rocker ajustment). Just look over everything close and see what you find. Heck even adding fuel and getting a batch that wasnt as good as you tuned on could act this way. Or a spark plug that was on the edge of fouling, worked good at the time but then it started missing. Retarding th etiming took some load off it and helped it smoooth out. Most of the time its the little things that will get you. Jess |
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| Author: | Charrlie_S [ Sat Feb 05, 2011 4:54 am ] |
| Post subject: | |
Maybe I am reading the original post wrong, but> going from 10 degrees to 12 degrees is advancing the timing, not retarding. And 16 degrees is more advanced then 12 degrees. |
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| Author: | Aggressive Ted [ Sat Feb 05, 2011 10:44 am ] |
| Post subject: | |
Good question, was your vacuum line to advance pulled off and plugged so there were no vacuum leaks? You can't set timing if you don't do this step. :shrug: Let us know. FYI, My 74 Dart loves running a 16 degrees initial but you need to turn the idle down. Mine works fine up to 20 degrees and I hit the end of the stop. |
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| Author: | krytellan [ Sat Feb 05, 2011 5:10 pm ] |
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I am, in fact, guilty of not removing and plugging the vacuum line from the dizzy. Lesson learned and I'll check it out when this LATEST dumping of snow resolves. Winter really gets in the way of car work. Damn that mother nature... |
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| Author: | BUCKET 636 [ Mon Feb 07, 2011 11:19 am ] |
| Post subject: | |
Quote: Good question, was your vacuum line to advance pulled off and plugged so there were no vacuum leaks? You can't set timing if you don't do this step.
So do you take it off at the carby end and plug it or at the dizzy end ? If at the carby end do you then have to plug the carby port ? |
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| Author: | Reed [ Mon Feb 07, 2011 12:24 pm ] |
| Post subject: | |
You remove the hose from the distributor and plug it at the distributor. Leave the hose hooked up to the carburetor. |
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| Author: | Aggressive Ted [ Mon Feb 07, 2011 5:56 pm ] |
| Post subject: | |
When you unplug the house off the distributor it is easy to plug the end of the rubber line with a pencil. That way your carb stays consistent. You don't want to introduce a vacuum leak making it run rough or speed up.... |
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