Advance curve for rookies

msmaron said:
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.
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msmaron said:
:D
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My point exactly ... It says on their website that Nu Rex limits advance to 30 degrees. :D

There are original versions and possibly some that have been modified in the long distant past that may not be limited to 28-30 degrees.

Maybe I should have said that it is a good idea to check the operation and advance curve of any system that you plan to use.

If someone assumes that all of them are made the same way they may be surprised to find the bearings all beaten out! :D

Quote:
In its original design, the Model “A” Ford did not feature a mechanism for automatic spark ignition timing (advance and retard). The driver manually controlled timing from the steering column (similar to that of the Model “T”). For optimum fuel burn energy, spark timing should be advanced between 10 to 12 degrees per thousand engine RPM. For the 2800 RPM “A” engine, this should be 28 to 33 degrees. This NU-REX mechanical advance system has been designed to provide 30 degrees of range and is designed for use on all Model “A” and “B” engines. The external appearance remains unchanged. Its simple installation requires absolutely no modifications to the distributor, engine, or timing procedures. The kit consists of three pieces: • centrifugal advance mechanism • replacement shaft to couple it to the unmodified distributor • replacement spring to hold the oil gear shaft in place. "Unskilled" Model "A" drivers can now enjoy optimum performance at all speeds.

Unquote

The "unskilled" statement is from the Nu Rex website.
 
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For most laymen, as engine speed increases, it seems counter productive to fire a plug gradually more & more BTDC. I was just trying to explain WHY that MUST happen as to many, it seems so mysterious. I'm through! Bill W.
 
Topic is good for me.
Yes I understand what is going on and maybe how to use it.
But I wonder if I have sufficient advance in the first instance.
The static timing setup works out well.
But the running on the road shows no real difference in moving the advance until the half way point.
So am I running a bit retarded initially (no wise cracks yet, please).

Roly
 
To Benson and others, I am confused, worried, and I welcome your advice.

I have a Model A which is new to me and the history of the car and previous work done is unavailable.

Because I have measured compression on all 4 cylinders to range from 70-72 psi, I assume my engine has some kind of high compression head.

Is this correct?

I was taught to use the spark advance as follows:

-full retard upon start-up (lever pushed all the way up), then immediatly after the engine has started, advance by pulling lever down to about 3/4 down and leave it there for most riding conditions, but fully advance (lever fully down) when cruising on the highway.

Is this improper operation which is damaging my engine?

Benson indicated that this type of operation with full advance (40 degrees) not good for a high compression engine.

I have never exceeded 45-50 mph, although my accelerator pedal (and engine) has lots more room to go if I wanted to go faster. Because I do not really know the condition of the engine (including the babbits), I am afraid to wind-up the engine rpms higher than what's needed for beyond 45-50 mph.

My car seems to have great suspension, steering, brakes (completely rebuilt by myself), and brand new balanced wheels and radial tires (from Coker) but again, I do not want to beat on the engine and therefore I keep it under 45-50mph. Is this a good idea?

I really need to understand how to best use my spark advance lever to preserve my engine.

Your recommendations on how to operate the spark advance are welcomed.

Thank you.
 
Pat Martone said:
To Benson and others, I am confused, worried, and I welcome your advice.


I really need to understand how to best use my spark advance lever to preserve my engine.

Your recommendations on how to operate the spark advance are welcomed.

Thank you.
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Sometimes we get way off on this stuff and create issues for the readers. This whole thread has been a great example!!

To Pat et/al:

I realize this is gonna be tough advice for all of us 'manfolks' but one of the best pieces of advice you will receive out of this entire thread is to buy a Model A Instruction Book (Owners Manual) ....and then read the silly thing from cover to cover!!

I know this is a tough thing to do (because I fit that category too!) but every situation that could possibly arise for a newbie or veteran alike is well addressed & defined in that booklet. It speaks of how to drive with the spark lever in all conditions, and gives advice on how to drive one properly, and how to maintain your car even including the proper setting of the ignition timing. IMHO, every Model-A owner really needs to take the time to read, -and understand that entire booklet FIRST.
 
Thought the attached advance curves showing the Nu-Rex mechanical advance curve along with a B distributor advance curve might be of interest with the current topic. Please note that the values shown are referenced to the distributor RPM. Crankshaft values would be twice those shown. The data was taken on a Sun Distributor Machine and represents the results of a single Nu-Rex device and a single B distributor. With one sample of each I can't say that the results are typical for all units.
 

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I'm not going to disagree or agree either way because it would only be disagreed with by somebody here. I will just say thank goodness that I learned how to set the timing and proper use of the spark over fifty years ago. What I learned years ago must not be TOO far off because I have never beat the babbitt out of an engine with original from the factory babbit, whether I was running higher compression up to 6 to 1 or 4.22 to 1 . Explainations such as static timing,initial timing, opposit the number one contact,and rotating the dist. cam until the points just begin to open only add so much confusion that most end up with the timing SO FAR retarded that it will barely run, if run at all. Such problems as bad dist. shafts, worn bushings, bad dist. cams, excessive backlash, proper advance and retard movement of the upper plate are all important and need to be addressed but don't actually address the actual setting of the timing. Too much info is an overload and confuses the issue of actually setting the timing, so that the engine will crank and run. Worn or improper manufactured parts will effect the timing, thats just common sense. All model A's don't have worn or improper parts and a newbee just needs to know how to actually set the timing mechanically!!!!!!!!! Just one other thing while i'm at it. The owners manual is very good to have and read. The owners manual was writen when the model A was produced. Octane of the fuel was very low when the model A was made and required much more use of the spark, as in retard to prevent timing knock. Higher octane fuel doesn't need as much retard. The owners manual mentions sand beds and other conditions that require slow driving and conditions that would otherwise lug the engine and cause timing knock and require retarding the spark. We now have higher octane fuel and better roads. Some in an attempt to save their engine will go so far to the extreme with the spark that they will be running retarded to the point of overheating. I just feel that extreme either way is just as bad for the engine. It is easier for me to teach a twelve year old how to use the spark and set the timing than a person that already thinks that they know what they are doing but just can't get it to run.
 
I always get confused. Is the spark advance on the left or right of the steering wheel? The engine speeds up if I pull either one of them. The right one makes it run a lot faster.

Just kidding
 
It is interesting that the 4.6 :1 compression Model-B engine came with a centrifugal advance distributor and an initial timing point of 19 degrees BTC. The maximum advance on the distributor was 13 degrees, for a total advance of 32 degrees. Ford obviously felt this was prudent even with the improvements in average fuel octane ratings since the introduction of the Model A 5 years earlier. Or, maybe that was best achievable advance on a centrifugal system, and with 19 degrees the maximum initial advance possible without kickback ( the B did come with a handcrank!)
 
Bill Williamson

I appreciate what you are doing and presenting. I did not understand the neighborhood hoodlums and their talk about advance timing etc. until I was out of high school. They always set the timing about ten degrees more than the shop manual recommend because of the elevation.
 
I do own and have read the Owner's Manual, but it does not explain how to alter use of the spark control lever when using a high compression head.

That's what worried me when I read from Benson's previous inputs that it is bad for an engine with a high compression head to use full advance under conditions that would normally be OK for a standard compression head.

I have not yet experienced or "heard" engine knocking while driving up a slight incline at 45-50 mph with the spark lever pulled down to full advance. Perhaps I do not know what to listen or "feel" for, but I certainly don't want to be using the wrong spark advance setting.

Therefore, am I correct in assuming that with a high compression head, to play it safe, I should never use full advance?

Thanks.
 
Pat, one way to possibly get away from the "knock" is to use a higher octane fuel. You then can probably use the full advance, without fear of knock with even a 6:1 head.
 
Pat: Are there any markings on your head. What makes you think it is hi-comp?? I believe your comp readings just indicate you have good, equal compression in all cylinders. Is the engine rebuilt??
Paul in CT
 
Unfortunately, I have no information on the car I have, which came indirectly from a deceased person's estate.
The car appears to have been a full cosmetic/mechanical restoration, including the engine, from about 15-20 years ago.
Since it is a heavier, Slant Window Fordor (compared to a roadster or coupe), and it seems to have lots of power, I am guessing that it has a high compression head. A friend drove it for me and thought it had a high compression head too, but we have no data or markings on the head to confirm this.
Maybe I have not experienced knocking because today's fuels are better and the engine is in good condition, with 70-72 psi in each cylinder?
I have not tried super-unleaded fuel yet, because it seems to run nicely on regular unleaded. Is there a real benefit to running a Model A on super-unleaded fuel?
 
I, personally, wouldn't waste my money. Even the ethanol based fuel today is better than what they had back then. That's what the spark lever is for. JMO
Paul in CT
 
No benefit to super-unleaded, ...and most of the time the higher octane will actually create a marginally less horsepower reading over an 87 grade.

While I realize your perceived fear with the possibility of having a high compression head, IMO it is only after you have CRs greater than 7-7½ to 1 before you start seeing detrimental effects. Again, set your initial timing according to the Instruction Manual, and then drive according to the printed instructions, and as long as you have a decent quality of fuel in the tank, you will not see any issues created by detonation. If you are totally nervous about it still, then remove the head and verify the combustion chamber size.
 
I agree that the super unleaded gas is of no benefit . I found out in the ninties that my model A's run a lot better on the 87 octane. I believe that the higher octane in the case of the super unleaded is because alcohol is added. The Leaded premium (ethyl as some use to call it) was better for controling timing knocks. My model A's ran much better and faster with red ethyl. Anybody remember Gulf no-nox?? When it was available, ethyl gas was all that I ever bought, even for the lawn mower. Still the 87 octane unleaded is far better than the gas that was available for most of model A production. The 5.2 police head was not available until 31 when tetraethyl lead was added to the fuel.

I keep the momentum built up for the hills because you will get timing knock when the engine is lugged , even more with higher compression heads. Aproaching hills at low speed is asking for trouble. You have to realize that the model A is way under powered and drive it as such by being aware that momentum is important to avoid lugging and damageing the bearings. I feel that cruiseing speeds of 50 mph is far less harmful than aproaching hills at speeds of 35-40 mph and lugging the engine. You have to slow way down to be able to down shift and having to down shift to second and low on the steep hills sort of takes the fun out of driving.

I have read that Ford recommended that the salesmen show the potential buyer that the model A would reach speeds of 65 mph. Though the model A if properly tuned will attain speeds greater than 65 mph, I have never read where Ford suggested that you could drive the model A at 60 or 65 MPH all day long. I know that higher gear ratio will allow for higher cruising speed but only if you've got the horses to kick it. Even so with a higher gear ratio you will lose low and mid range power and that is very important to me. I may ease my souped up engines up to 70-75 Mph but only briefly.
 
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