This is my happy face after getting the little DeSoto running properly in the Model A (picture 2 )! I'd bought a rebuild kit for the carb thinking that the accelerator pump wasn't working right in the original 2 bbl carb, and had time yesterday to get after it. Before I pulled carb, I pulled the air cleaner off and cracked the throttle, gas squirted in both throats, so I held back and gave it some thought. Someone had suggested that the cause of it stumbling off idle might be the advance in the ignition, so before I tore into the carb, I checked that. I don't have a timing light here, so I loosened up the distributor hold down and gave it a little, then quite a bit more advance. The idle speed went up, the engine smoothed out, and I gave each idle jet a quarter turn. It still didn't kick back against the starter when warmed up, so I bumped it ahead until it did and back it off until it didn't. Taking it for a little test and tune around the neighborhood, it now runs markedly better, throttle response is much quicker and best of all, no stumble. I think I hadn't snugged the hold down clamp enough and it'd moved after 3 seasons of use. I'll just keep the carb kit until I really need to do that, but for now it's a real treat again to drive.
Kudos for tuning timing by ear. Never was a racer but always have been happy to set the timing by what works right. Yes I do have a timing light and know how to.
Been timing motors by ear for a very long time, even when I had a top notch Sun tune up station to use. The timing marks and the spec sheets are the starting point.
I haven't used a timing light in years as tuning by ear works just fine. A vacuum gauge helps but isn't necessary. I can pull a distributor, drop another one in and dial in the initial timing close enough to start and take it from there. Good job, love the engine and nice ride!
When you use a light on older engines you need to make sure the mark has not changed. Many times I've checked the time by ear and found total timing around 50 degrees or more.
It's always nice to have a car running at top condition, and timing/spark are one of those that can be marginal enough. but not optimum. Especially as they deteriorate over time and you don't notice the degradation all at once.
Yep. The poor running happened gradually, culminating last summer when the distributor cap got wet and the contacts corroded. It ran terrible, I replaced the cap and wires, which made it at least fire on all 8 cylinders, so comparatively, it ran good. Once we got down here, the stumble got progressively worse and tried to compensate by richening the choke. That lead to more problems, but I stepped back from it, and with some help from here, looked at it with a fresh perspective. All better now.
Remember also that changing the dwell only will affect ignition timing. As points wear in the gap decreases and results in retarded (delayed) spark timing. That's why setting the timing should be done after changing and adjusting the dwell and points gap. Oddly enough, changing just the timing only has no effect on the dwell or points gap.
I remember my dad went thru this ritual when tuning up a car. Get a glass of water and sit it on the core support and start adjusting the timing, by ear, rhen turn to adjusting carb by watching the ripples of water in the glass until he got the ripples the smoothest, then go back to timing, then back to carb and water ripples. Don't know how close he got but they always idled smooth and at a very low rpm. They were smooth enough and rpm low enough that you put it in drive and it'd just about die, then he'd adjust the idle up just enough to smooth idle in drive. I guess we've become dependent on tools and trinkets that the old timers either couldn't afford or have access too so they figured out how to do it the hard way..... ....
That's essentially the same process you'd use to adjust timing and idle mixture, but using a vacuum gauge instead of a glass of water. The main difference is that if you can't get a smooth, steady idle, the glass of water doesn't help you diagnose what your problem may be. A vacuum gauge can.
These engines have such mild cams that at idle it's silent and as smooth as silk. I can see that working. Even with straight pipes this is a very quiet running engine, unless it's at WOT.
Learned this way back. Single point ignition, one degree of dwell change equals one degree of ignition timing. Dist is at half speed of crank (360 to 720), so you would think 1 = 2, but there is half a degree change on opening, half on closing, so it equals 1 to 1.
Doesn't apply in this case then. But for someone running with points it might still be helpful to keep in mind when your timing seems to retard a bit after you put on enough miles after your last tune-up. I also remembered that there is a case where a change in timing can affect dwell. It can occur when the vacuum advance is in operation. If the breaker plate pivots around the centerline of the distributor shaft it won't be an issue. But if the plate pivot is offset from the centerline (common on most stock distributors) then the plate's movement will also change the dwell. It's not to any great degree but is visible on a distributor machine and dwell meter. Something to remember if your running full manifold vacuum to the vacuum advance.
My wife followed me home from Venice today, and said the car was smoking black smoke at whenever I accelerated from a light. I couldn't see it of course, so I dialed the choke settings WAY back. It seems to be running a bit better since, and I can't SEE any black smoke, so we will see. Still starts easily warm or cold, and no stumbling, so I think I'm headed in the right direction. She also said the brake lights worked only about 75% of the time, so I fixed that too. There wasn't enough free travel in the pedal, and the mechanical switch was adjusted too tight, so that when I simply slowed, no brake lights. They came on with a firmer stop, so I gave the pedal a little more free travel and backed the switch off so it closes as soon as the pedal is moved. In the congested traffic and brain dead, inattentive drivers here in Sarasota, having brake lights that work intermittently is not good.
The Jalopy Journal
