Model B timing

[Kurt in NJ]

In a 1933 tune up book I found this model B timing setting paragraph, interesting that there are 2 settings depending on the gasoline being used.

Timing: Standard setting 15° (standard gasolines) or 23- (Ethyl gasolines) before top dead center. To set timing, first center spark control arm by loosening adjustment screw and moving arm so that center line on control arm scale is directly under center of adjustment screw, tighten screw. Then take out timing pin screwed in front face of timing gear case (over camshaft gear), reverse pin in hole. With No. I piston on compression stroke turn engine over slowly and press on pin until pin engages hole in front face of camshaft gear (this hole is 9½ degrees on the camshaft corresponding to 19 degrees on the crankshaft before the top dead center position). Loosen lock screw in center of breaker cam, carefully locate cam so that contacts are beginning to open, tighten locking screw.
Then loosen adjust-
ment screw on spark control arm, move arm 4 degrees to right (15 degree setting for cars using standard gasoline) or 4 degrees to left (23 degree setting for cars using Ethyl gasoline), tighten adjustment screw. Remove timing pin and replace in running position before attempting to operate car.

[rotorwrench]

Early gasoline was basically naptha so it's volatility was just above kerosene. Adding in the TEL gave it additional volatility but it still was no where near the fuel available after WWII and in the early 50s. The B-model distributor was a lot different than what the model A came with. Leaded gasoline was a new concept when it started to be affordable to folks.

[alexiskai]

This lines up well with Nu-Rex's research showing that an A engine in good condition, at normal ambient temperatures, will start just fine at up to 25° initial timing. That's with modern gas, which would have been very high octane by '33 standards.

A B engine set to 23° initial would have topped out at 37-38° total timing at around 2600 rpm.

[ursus]

Originally Posted by Kurt in NJ

In a 1933 tune up book I found this model B timing setting paragraph, interesting that there are 2 settings depending on the gasoline being used.

Timing: Standard setting 15° (standard gasolines) or 23- (Ethyl gasolines) before top dead center. To set timing, first center spark control arm by loosening adjustment screw and moving arm so that center line on control arm scale is directly under center of adjustment screw, tighten screw. Then take out timing pin screwed in front face of timing gear case (over camshaft gear), reverse pin in hole. With No. I piston on compression stroke turn engine over slowly and press on pin until pin engages hole in front face of camshaft gear (this hole is 9½ degrees on the camshaft corresponding to 19 degrees on the crankshaft before the top dead center position). Loosen lock screw in center of breaker cam, carefully locate cam so that contacts are beginning to open, tighten locking screw.
Then loosen adjust-
ment screw on spark control arm, move arm 4 degrees to right (15 degree setting for cars using standard gasoline) or 4 degrees to left (23 degree setting for cars using Ethyl gasoline), tighten adjustment screw. Remove timing pin and replace in running position before attempting to operate car.

Interesting info! How exactly does one measure off the "degrees" that Ford is referring to? The control arm has +/- gradations marked on the outer flange and I once read that each marked gradation was equal to 2 degrees of crankshaft rotation. What is the correct way to make such adjustments?

[Bruce of MN]

Originally Posted by alexiskai

This lines up well with Nu-Rex's research showing that an A engine in good condition, at normal ambient temperatures, will start just fine at up to 25° initial timing. .

Does initial timing mean at starting? Isn't it at 0 deg with manual spark advance?

[alexiskai]

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Originally Posted by Bruce of MN

Does initial timing mean at starting? Isn't it at 0 deg with manual spark advance?

Here's their article on it:
https://www.nurex.com/engine-kickbac...and-correction

The purpose of the experiment was to empirically determine whether the A would exhibit kickback if you started with the advance lever down too far. They determined that you could start the A with the lever down enough to give 25° advance. The electric starter motor is powerful enough to turn the crank over at that setting.

I once had someone question whether the B engine wouldn't have kicked back when starting at 19° advance, so I set my A engine to start at 19° and started it up and it worked just fine.

[Hitman]

Originally Posted by alexiskai

This lines up well with Nu-Rex's research showing that an A engine in good condition, at normal ambient temperatures, will start just fine at up to 25° initial timing. That's with modern gas, which would have been very high octane by '33 standards.

A B engine set to 23° initial would have topped out at 37-38° total timing at around 2600 rpm.

Are you referring to initial timing as BTDC or ATDC? Before or after top dead center. Your clarification is helpful as article links break over time and the info here will come up when someone searches the forum in the future.

[Bruce of MN]

I don't see an advantage to starting it so advanced, so I am going to stick to 0 deg to start and 28 deg btdc full advance for my 6:1 head.

[alexiskai]

Originally Posted by Bruce of MN

I don't see an advantage to starting it so advanced, so I am going to stick to 0 deg to start and 28 deg btdc full advance for my 6:1 head.

This thread is about timing Model B engines.

Originally Posted by Hitman

Are you referring to initial timing as BTDC or ATDC? Before or after top dead center. Your clarification is helpful as article links break over time and the info here will come up when someone searches the forum in the future.

Standard convention is to refer to BTDC degrees using positive numbers and ATDC degrees using negative numbers, so 23° is BTDC.

[alexiskai]

Originally Posted by ursus

Interesting info! How exactly does one measure off the "degrees" that Ford is referring to? The control arm has +/- gradations marked on the outer flange and I once read that each marked gradation was equal to 2 degrees of crankshaft rotation. What is the correct way to make such adjustments?

I just went and measured 3 B distributor plates, so I think I have the answer but check my math.

Radius from center of plate to indexing flange: 1.675"
2πr gives circumference, so 2*3.14*1.675 is 10.524"
1/360 of circumference is one distributor degree, so 10.524/360 is 0.029"

Distance covered by 8 notches on the flange: 0.46"
Degree width of 8 notches is 0.46/0.029 = 15.8
Rounding up to account for measuring error gives 16°

So per my measurements, each notch marks off two distributor degrees, which of course is four crankshaft degrees. So these instructions are telling the operator to shift the plate one notch to the right or left.

I wonder if the suggestion to move four degrees in each direction is due to those numbers being optimal, or more just because four degrees is one notch, so telling people to adjust it by 1.5 notches is just not practical.

[ursus]

I checked some unused NOS plates and came up with 0.48 inches spanning the 8 notches for 2.07 distributor degrees so thanks for your prompt on this method. I wonder if Ford ever published this sort of detail in any Service Bulletin.

I recall my Dad's 1929 Chev had a centrifugal distributor and that CM must have dealt with the limited advance range of the device with a pull-out knob on the dash that retarded the spark for starting the engine upon which the driver had to push in the knob to advance the timing for running.

[Hitman]

Originally Posted by alexiskai

This thread is about timing Model B engines.



Standard convention is to refer to BTDC degrees using positive numbers and ATDC degrees using negative numbers, so 23° is BTDC.

I’m aware of standard convention. Most people don’t but what are you meaning when you mention initial timing?

Usually things are referred to as a setting with total advance. Total advance is the end goal as determined by the total advance of the distributor. I set the distributor based on the total advance of the distributor, and its curve. Nothing more.

[alexiskai]

Originally Posted by ursus

I checked some unused NOS plates and came up with 0.48 inches spanning the 8 notches for 2.07 distributor degrees so thanks for your prompt on this method. I wonder if Ford ever published this sort of detail in any Service Bulletin.

If they published it somewhere it likely would have been in the Model B owner's manual. Anybody got one?

[Bob C]

Originally Posted by alexiskai

If they published it somewhere it likely would have been in the Model B owner's manual. Anybody got one?

March, April, May 1933 Service Bulletin states Model B
advance or retard 10 degrees of the crankshaft, each
graduation represents 4 degrees.

[alexiskai]

Originally Posted by Bob C

March, April, May 1933 Service Bulletin states Model B
advance or retard 10 degrees of the crankshaft, each
graduation represents 4 degrees.

Thanks Bob. I did dig up an owners manual and it didn't say.