Hot Rods DeSoto Hemi Now running GREAT!

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.

 

That's why I always set timing with a vacuum gauge...lets the engine tell you what it wants.

 

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!

 

90% of carburetor problems are electrical

 

Ain't that the truth.

 

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.

 

No points. Pertronix.

 

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.

 

It's always nice when it is something simple!

 

Running great and looking really great!!

 

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.

 

Update: After a week of running great, it started the same flat spot off idle when moving, stumbling, popping and generally running poorly. To compensate until I could rebuild the carb I bumped the choke adjustment back until it was about 1/3 closed which helped, but obviously made it run way rich. I had gotten a carb rebuild kit that, after it seemed to be cured by advancing the timing alone I hadn't used, so I pulled the original carb and went through it. The carb to intake gasket was VERY brittle, had a visible break in it, and all the other gaskets in the carb were brittle as well. I bought a can of carb cleaner, took it all apart, replaced the needle and seat, all the gaskets and put it back together. I think it must've had an internal vacuum leak in addition to the base gasket, because it runs good now. No black smoke, choke open, nice crisp throttle response and it's not embarrassing to cruise around in.

 

Maybe it's that warm, moist Florida air its breathing.

 

It's spring here, nice and warm, so that must be it! It wasn't used to good weather.

 

The never ending story continues: The car ran fine for a couple days after rebuilding the carb, then again started running awful again. Figuring the carb again was the culprit, I ordered an Autolite 2 bbl (a knockoff but I figured I'd take flyer on one as it was inexpensive) and an adaptor from Hot Heads to bolt it up. The carb came today but still don't have the adaptor, so to entertain myself on a sunny spring day, I decided I'd install the choke cable I'd bought a while ago and get rid of the automatic choke, since one of the problems I found was it doesn't work properly.
Did that, jumped in and took it around the block, sans air cleaner. Ran absolutely perfectly. Came home, popped the air cleaner back on, around the block again and it ran as poorly as it did before, smoking, popping and stumbling.
Finally, a light bulb came on. I stopped in a parking lot and popped air cleaner back off. Ran like raped ape again. No black smoke, no stumble, no popping, just great.
So, by process of elimination, after all this eff-ing around, it's the stupid air cleaner.
Now, do I just leave well enough alone, keep the new carb and adaptor (when it finally shows up) on the shelf for posterity and focus on getting a better air cleaner for it? It's an old Stelling and Helling top on (part of) the original oil bath base that clamps on the carb throat, with a small paper filter under the chrome lid, or swap cars and put a proper air cleaner on it? I'm gonna just run it around town for a bit without one, just to ensure that it KEEPS running right...

 

All I run on my roadster is three bug screens to keep the big chunks out. No other filters. If I circle tracked it would be a good idea but this is the PNW, it rains every few minutes so we have some clean air up here.

 

Can we see the inside of the air cleaner?
What's causing the lack of air flow through the air cleaner?

 

That's kinda my thought too. We don't have dust and dirt roads, although it's pollen season, and it gets actually driven so seldom it may not be worth worrying about.

 

A couple years back I ran those short velocity stacks from OTB Gear on the 97s. I ran a bug screen in the carb and another one on the velocity stack. The car ran for crap! I removed the top screens and it was fine. It is more to do with air disruption (possibly) than air restriction. You would think with the blower that the screens would not make that sort of negative effect. You would be wrong. I'm not saying it couldn't be tuned to play nice with twin screens or filters, all I am getting at is that it didn't work the way it is set up.

Pollen may make your headlights itchy and the engine may sneeze now and again but I doubt it will scar the cylinder walls.

 

So, no photos of bottom and inside of air cleaner? We might all learn something.

 

No, but I did put the base and the top cover on without the old element. It runs like a watch. So the element is definitely the culprit here. Sometimes the obvious answer is overlooked until new more money than needed is spent.