Advance curve for rookies

BILL WILLIAMSON

BILL WILLIAMSON

Well-known member
Feedback, please!
I feel that many don't comprehend exactly why a gradual timing advance curve is needed. I'm not referring to the initial T.D.C. setting. I'm not too sophisticated or scientific, but I think I can explain it in a hokey- pokey manner that a layman can grasp so he can know how to work his advance properly to make the car do what it was designed to do efficiently. Some think you just set it, and forget it, WRONG!
DOES ANYONE THINK THIS WOULD BE A GOOD IDEA? Bill W.
 
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Well, I too would like to hear your theory because I kinda had the opinion that most Model-A engines wouldn't really see a benefit from it, --even with 5.5 or 5.9 compression ratio heads simply because of the slow RPMs, the combustion chamber design, and the octane rating of most fuels we purchase.

Do most Model-A drivers know exactly what their ignition timing (advance BTDC) is when they set the spark lever at any given position on the quadrant? If not, maybe that is your point. If so, how would/should they find out?

If they by chance they did know what each notch represents regarding the timing, how do they know at what RPM the engine is turning at that given moment to know exactly which notch they are supposed to have that lever positioned at for that optimal timing??

Do you feel that atmospheric pressure (altitude, weather, etc.) will affect your suggested optimal timing curve???

Do you feel there will be a difference between optimal timng settings between your reader's engine based on what type of carburetor used, and its GAV setting????

How much more engine efficiency (-percentage rate or Hp increase) do you feel we will gain throughout the entire acceleration curve by simply following your recommendations?????


Thanks in advance for your willingness to explore this and sharing your findings here with us!

.
 
I'd like for the Fordbarners to hear it from the both of you, Bill and Brent. The more ways and different depths in which it’s presented the more likelihood of someone else being enlightened or confirmed in their ideas and knowledge. Sorry Bill, didn't mean to highjack the thread but..... Bill were you planning on using some sort of analogy to help? Brent were you planning on covering the basic volumetric efficiency of the L head design? I'm sure that factors in.
Thanks guys
 
There is no definite perfect mechanical advance curve. A curve like that may be derived for an engine under full load (manifold vac = 0) on a dyno, but in real life engines are driven mostly at partial throttle with quickly varying manifold vacuum. Later in engine development the vacuum advance/retard was added to modify the set mechanical curve. Going uphill at 2000 rpm demands much less advance than going downhill at the same speed.

I would be very interested in a proposed explanation that will easily teach A drivers to think like a throttle regulated vacuum retard on top of a set mechanical advance rate or curve.:eek: Of course, that amount of constant fiddlin' with the lever will leave the quadrant worn smooth as a baby's bottom in a single driving season.
 
ctlikon0712 said:
I'd like for the Fordbarners to hear it from the both of you, Bill and Brent. The more ways and different depths in which it’s presented the more likelihood of someone else being enlightened or confirmed in their ideas and knowledge. Sorry Bill, didn't mean to highjack the thread but..... Bill were you planning on using some sort of analogy to help? Brent were you planning on covering the basic volumetric efficiency of the L head design? I'm sure that factors in.
Thanks guys
Click to expand...

Craig, I truly had/have no plans to say anything regarding this topic, and I am really only interested in hearing what he is proposing. Again, before he offered this I was of a differing opinion much akin to Mike's.

BTW, I like Mike's analogy in his last sentence above! ;)
 
What "curve" are you talking about? Are you describing an imaginary graph of spark advance verses engine rpm? In other words, slowly advancing the spark lever as the rpm's rise? Or slowly advancing the spark as the mph climb?

If so, I don't do either one, so I'm probably doing it wrong.

Here's what I do (please correct, if wrong):
1. Start the engine at full retard
2. Move spark advance to 1/3 of the quadrant to start out
3. Move spark advance to 1/2 of the quadrant after hitting 3rd gear
4. Adjust the spark advance (up or down) by listening to the motor work
 
I use a simple method, I read the owners man,---then adopted the mostly lazy method
starting--full retard

after started--1/3-1/2

driving---full advance

stopped at light---full advance (so what if it runs a little rough)---unless for some reason i want the car to sound "smooth" for the car next to me at the stop

parade-walking speed---usually almost full retard---use 0-1/2 advance to fine tune speed of car

If I hear pinging I will retard spark, but it has only happened 1 time and that was with fuel that was old and contaminated with diesel(free fuel)

It works for me, I get good fuel mileage (20s)and havn't been able to break good babbitt--even though I have tried, I drive at the speed of traffic usually--unless it is over 65

I adjust the GAV more than the spark, my plugs run a very light tan--closer to white, 40 mph is about 1/3-1/2 turn, 55+ 3/4 turn
 
All of this is pivotal on the engine condition and the components in and on the engine.
You need to define the base line engine.....
 
I titled it all wrong, gettin' too complicated already. Title should have been: "FOR ROOKIES: WHY IS ADVANCE NEEDED, AND WHY YOU NEED MORE AS SPEED INCREASES."
A rookie might say, "I can't understand WHY I would want my plugs to fire WAY BEFORE the piston reaches the top at crusin' speed, makes no damn sense to me???" Bill W.
 
BILL WILLIAMSON said:
I titled it all wrong, gettin' too complicated already. Title should have been: "FOR ROOKIES: WHY IS ADVANCE NEEDED, AND WHY YOU NEED MORE AS SPEED INCREASES."
A rookie might say, "I can't understand WHY I would want my plugs to fire WAY BEFORE the piston reaches the top at crusin' speed, makes no damn sense to me???" Bill W.
Click to expand...


Oh, ...OK.
 
Its 1928. I walk in to a Ford dealership and buy a new 28 roadster. The salesman instructs me on the basic workings of the A. Starting, Stopping, Shifting, Gas Tank, Checking the oil, Tire pressure, and the Throttle and Spark Advance levers, and i am on my way. As i drive away i start playing with the spark lever and Wow, it smoothed out at 35 mph. Within 2 days of driving and playing with spark lever from all the way retard to full advance, i think i figured out what works best for me and my motor at various speeds. And Ol Henry didn't have a computer. Amazing. Life was so easy back then.
 
If I make a fool of myself, so be it!:p At idle, spark lever up, (TDC) plug fires, flame travel time before the Big Bang allows the piston to travel slightly past TDC to get the most efficient downward "push" from the explosion.:eek:
Chief explained it like this: At TDC, put a pile of black powder on the piston, run a little trail over to the spark plug. The plug is your "match" to light it. During the time it takes the fire to reach the "pile," the piston has moved to it's best position. If you increase engine speed to 1,000 RPM, the burn time is still the same, so the piston would have traveled too far past TDC for maximum boost from the big BANG! So's you gotta' light the "trail" sooner, like maybe 5 or 6 degrees BTDC so's you out-fox the piston and the big "BANG" happens barely past TDC, like it's s'posed to do! Whew! Bill W.
 
I hope that someone with a higher compression head does not read this thread and then run their spark lever at full advance at 55 to 60 on an uphill grade! Forty degrees advance with a Higher compression head will damage the engine.

I don't know about anyone else but if I drove at 55-60 up an uphill grade with my B engine and "The head with the large B" (only 5.2 to 1) with the spark at full advance, I would destroy the bearings. It knocks and pings under this much advance.

If your engine has a head with 6.0 or 7.0 or higher it is even more important to retard the spark.


At least that is the way it has worked for the 49 years since I got the 5.2 head.

Rich Fallucca AER states that 28 degrees is the max advance recommended with his rebuilt insert engines. This is what I have found with my engine also.


Quote
"5. Maximum timing advance is 28º This is the point of no return and will promote longer bearing life."
Unquote

http://antiqueenginerebuilding.com/INSTRUCTIONS.html

Just trying to prevent a someone from frying their engine.
 
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Hmmmm.... I guess this is why they make "automatic spark advance" systems for us mechanically challenged A-Model owner/drivers.:eek::rolleyes:
Interesting thread.............;)

Bob-A:D
 
Bob-A said:
Hmmmm.... I guess this is why they make "automatic spark advance" systems for us mechanically challenged A-Model owner/drivers.:eek::rolleyes:
Interesting thread.............;)

Bob-A:D
Click to expand...

If a person installs an automatic advance system designed for a stock compression head (4.2 to 1) ( 0-40 degrees advance) it is very likely that damage will occur if they also have a higher compression head installed.

The advance mechanism must be modified to limit the max advance to about 28 degrees OR to a point below where spark knock occurs for that specific engine, carb setup, engine load and etc.

Use of a vacumn advance to reduce the spark advance under load will prevent damage. But the whole system (Vac and mech advance must be designed for the specific engine and the conditions it is operated under.

Engines are more likely to knock at lower altitudes as an example.
 
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Benson said:
If a person installs an automatic advance system designed for a stock compression head (4.2 to 1) ( 0-40 degrees advance) it is very likely that damage will occur if they also have a higher compression head installed.

The advance mechanism must be modified to limit the max advance to about 28 degrees OR to a point below where spark knock occurs for that specific engine, carb setup, engine load and etc.
Click to expand...

Actually I ran the NU REX Automatic Advance system with no problem what so ever and a high compression head from snyders. The car ran good, no knock, started perfect and never had any problems at all with it.
:D
 
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