VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 Missing or bucking

Hey Guys,

So this last weekend I took the 34 to the Northwest meet and won Best of Show. I also drove the car on the tours for the first time....should have over 100 miles on it now. I notice that when I was driving at a slow steady speed like 25 or 30 I would have a miss or bucking. I'm trying to figure out where to start looking for the problem. I was thinking maybe plugs being to cold as if I rev'ed it up it would clear for a little bit. Like it was loading up or something. Or plug wires could be the problem.

Also noticed some times when I start the car it is not hitting on all 6 right away. Maybe I should look at the wires thinking about it.

It runs really nice under load and has great power....and run smooth at like 40 or 45.

Any thoughts?

Thanks,
Bruce

Bruce
While I am not conversant with the early (pre 60) but the symptoms you describe are like carb adjusted on the rich side especially in the mid throttle position. Check that the main jet is correct actual size, I have seen brass jets eroded oversize by fuel or if there is a metering needle the jet or needle could be worn in at a particular setting.
Tony

Missing or bucking can be caused by either a lean mixture or a very rich mixture. If lean pulling out choke will will eleminate the problem. Then look for an intake leak or a vacuum leak at some location.If too rich could be float setting, metering rod adjustment or some other carb. malfunction.
If an igition miss I would remove and inspect the spark plugs. If one loks as if it is burning different from the others the plug, plug wire or valves on that cylinder could be at fault.
If it is caused my an over rich mixture I would suggest changing the oil as it could be contaminated with gas.

Thanks Guys....gives me some area to start looking. I think I'll look at the plugs and wires first and go from there. I know I'm getting really good gas milage with the car. Also I did try pulling the choke when I was driving with no change. So that means its not too lean then.

Bruce

Congratulations on winning best of show Bruce, your car sure deserves it!

Plug wire problems will usually give you problems when you hit steep hills...A tell-tale sign...No difference with the choke pulled out...? That is running lean...Check plugs for color and vacuum leaks...How's your timing...?

Hey Guys!

Thanks for the complement Dale! Your car is really nice also. When are you going to come up this way and stop by?

So late this afternoon I finely got to work on the 34. Pulled the wires and the plugs out. Checking to see what they looked like....they are really nice and clean. Maybe a little carbon on the edges but think that would be OK. I did happen to check the gap with Ray's advice. Turns out they were set to .023 and not the .032 as the book calls for. I'm going to start with .035 and see what happens from there. I'll test drive the car in morning as I have a date.

Talk with you guys tomorrow.

PS....Kevin, I tried pulling the choke and no difference. Timing I think is right on the ball, but will check tomorrow morning before I start the car.

Thanks for the help.

The wider the spark plug gap, the hotter the plug will run...Not yo worry about, though...As far as the "ball" timing goes, I would still try advancing the timing a bit to see if it run any better...I, myself don't use the "ball"...I advance well past it...The motor runs hotter but better...and smoother...

Hey Guys! Just got back from road testing the car after opening up the plug gaps. WOW! What a difference in the car...it start really good, it started good before, but better. Runs nice and smooth at 25 to 35 like it should. Also notice that when I get above 40 I don't feel like I'm pushing to go faster....it now feels like it wants to go faster. It feel like the car I remember 20 years ago before we took it apart. Thanks for the help....I'm going for a ride!

Hi Bruce
I'm not sure when I'm going to make the drive up in your direction but it is on the list to do soon

One more thing to think about as far as your car goes. I'm not sure how much gas you put in the tank when you went to Flint, I know you haven't run it that much until lately. It could be that you have some gas that's starting to spoil, if that's the case take some out and put in some fresh gas. Here in California if the gas sets in a tank for a little over a year (kept cool) if will start to go bad. I think your gas may be a little better where you are as far as lifetime.

Just a thought, one more reason to exercise that beautiful car a little more!

Hey Dale....I know what you mean....the needle and seat have stuck closed twice now. And I've run most of the gas out of it since Flint.....Didn't really have much in it then. I did put a full tank in when I was up at the NW Meet and used most of that....so time for a new tank soon.

Can't tell you how much I like driving the 34!

Bruce,

I don't know much about why your car is running like a thrashing machine.

Assuming the Best of Show trophy was given with the understanding that the car ran as good as it looked, maybe you should mail the trophy back. I'm just kidding you. Congratulations on the win.

Besides, show cars shouldn't have to run at all. Just look great. That's all. That's why they make trailers.

I assume you'll not participate on any more tours until you get it fixed. We can't hold up traffic none. People got places to go. You're probably be a=holding up traffic. You know.

I hope you get the problem straightened out soon. Let us know what the cullpret was.

Best,
Charlie

Hmmm...I wouldn't think widening the gap would make such a differance...But, whatever works...! Glad to hear it was that simple a fix...!

Hey Kevin, It is simple when you think about it. On the 29 to 32 engines we open the gap up from 0.024 to 0.040 and advance the timing to 18 degrees. The reason is because it takes longer for the plugs to jump the gap.

In my case I was 0.009 closer then I should be and it took less of a charge for the plugs to fire. So I was in a way retarding the engine kind of. So the missing I was feeling was from the plugs firing just before the piston was ready to go down. At idle you can't feel it....but at slow speeds you can.

At least that is how I’m looking at it.

Bruce,
That is the correct way to look at it. Also once the spark jumps the gap it can ignite a leaner mixture. With the spark plug in a pocket the mixture at the plug is likely to be a bit leaner. By '34 the head design changed to allow more complete and effective combustion. Still the hotter spark has an advantage.

Thanks Chip!