low speed miss

[lytzge2011]

I have my timing set at 2^ past TDC. When the engine idles i think the only cylinder firing all the time is no 6 which shows no carbon. I timed the engine on no 6. I pulled the new plugs out and they have carbon on them. when starting out the engine coughs and spurts. When I reach a higher rpm the engine smooths out. the conclusion I drew from that is that the timing needs to advance. I do not believe that is what is wrong. Any ideas before I tear into the distributor and carb.

[gmharris]

When this happens to my trucks, it is usually a sign of too rich a fuel mixture caused by a leaking needle valve or float set too high.

As you increase engine speed, more air enters the engine and leans out the mixture allowing the engine to run better.

Have you noticed that you need to hold full open throttle to get the engine to start after it is warm? Does the engine idle well? Or, does this condition only occur when you accelerate?

[Gordon Maney]

I have my timing set at 2^ past TDC. When the engine idles i think the only cylinder firing all the time is no 6 which shows no carbon. I timed the engine on no 6. I pulled the new plugs out and they have carbon on them. when starting out the engine coughs and spurts. When I reach a higher rpm the engine smooths out. the conclusion I drew from that is that the timing needs to advance. I do not believe that is what is wrong. Any ideas before I tear into the distributor and carb.

Why are you setting initial timing after TDC?

[lytzge2011]

low speed miss

I am settin it 2^ after tdc

[gmharris]

Why are you setting initial timing after TDC?

The Chrysler manual for the B-1 series trucks shows the timing for the Power Wagon to be 2 degrees ATDC.

These are the only engines I know that are timed ATDC. Is this a mistake in the manual? Or, is there some reason for the late timing?

[Gordon Maney]

The Chrysler manual for the B-1 series trucks shows the timing for the Power Wagon to be 2 degrees ATDC.

These are the only engine I know that are timed ATDC. Is this a mistake in the manual? Or, is there some reason for the late timing?

I don't doubt you. I have the manual here somewhere and I have two 1948 B1's. It's been a long time since I timed one of them.

My reaction is what it must have been then. I can see not having much initial advance. I can't see having an initial retard. You want maximum combustion chamber pressure to be reached after top dead center. The crankshaft turns a finite amount during the burn time; that is typically about .003 seconds. Not much, but some. The faster the engine is turning, the farther it turns in that time.

Setting initial timing at TDC would assure you reached maximum pressure after TDC. If it is too far advanced, it will reach maximum pressure before TDC [BTDC] and cause the engine to kick back.

I could maybe see me setting on at TDC, but I am not sure I would set one after. I would be interested to see the advance curve on the centrifugal advance. I don't see it as likely, but I suppose it could come in too soon and get too far advanced, too soon. I wish I had my old Sun scope and a running flathead sitting here right now to see.

[Doc Dave]

Charles Talbert, who is pretty knowledgeable on these engines, said that the published info of 2 degrees ATC is a mistake, it should be 2 degrees before TC, if I remember the thread correctly.
One should be able to find it with a search.

[Clint Dixon]

Charles Talbert, who is pretty knowledgeable on these engines, said that the published info of 2 degrees ATC is a mistake, it should be 2 degrees before TC, if I remember the thread correctly.
One should be able to find it with a search.

If the 2 degrees after top dead center was a mistake, then that mistake was repeated over and over. I have seen it published as such in several different Dodge manuals, service bulletins, and Carter CARbureTER sheets.

For 32 years now, I have run my 230 engines with timing set right at top dead center. I have not found any gasoline over that period of time that has contained the low octane levels that were used in the late 1940's and, with the higher octane levels we have now, I have experienced no detonation as a result of advancing the 2 degrees back to top dead center. I have thought about experimenting by advancing the timing further to a couple of degrees before top dead center, but the trucks run very good right where I have had it set, why mess with it? As such, I can confidently purchase the lowest cost fuel I can find without worry about what level of octane it contains or whether it will be causing detonation in combination with too much advance.

[Gordon Maney]

I would think they could stand some initial advance. My father would road time engines. That was entirely seat of the pants. Give it a little turn, test drive it, see if it knocks when pulling slow in a higher gear. Adjust as needed. Crude? Yes. Lots of people did it.

It would be an interesting experiment to road time an engine and then put a light on it.

Objectively, a safe addition of some advance would net power and mileage.

In this moment we just don't know what would be safe.

[gmharris]

I checked the timing on my '54 FFPW today with a timing light. It was set at 2 degrees ATDC.

I then advanced the timing and it seemed much happier at TDC. Then, using a vacuum gauge, I advanced the timing to achieve maximum vacuum. The timing was then at 6 degrees BTDC. I took the truck out for a ride. It seemed to run well and I didn't hear any pinging. I will probably set the timing back closer to TDC to be safe.

I'm not sure why the book would say to set the timing at 2 degrees ATDC. I've not heard of any other engines that have timing set ATDC.

Maybe, it has something to do with the advance curve of the distributor. Or, maybe like on old Harley's with variable timing, it's to assist with starting. Or, perhaps it has to do with better cooling when the truck was used as a stationary power plant. Or, maybe, it was because of the low octane rating of the fuel back in the day.

Heck, I guess I have no idea why the timing would be set after top dead center.