|
Sponsored Links (Register now to hide all advertisements) |
|
|
Thread Tools | Display Modes |
12-18-2021, 11:51 PM | #1 |
Senior Member
Join Date: Nov 2018
Location: Farmington MI
Posts: 284
|
Measuring spark timing
Reading the current thread on point setting and spark advance, Raised a question... how to measure the actual advance on the car with engine running, like using a timing light as would be done on a modern car. This would require a degree wheel on the crankshaft, or at least marking the crank pulley rim in degrees.
Is the starting point at Zero advance when following the normal point setting instructions (using the cam gear pin) ? And what is the design full advance at leaver full down and the distributor plate arm full stop in the distributor "window" ? And finally, with a stock motor and modern fuel how much advance is optimal for high speed (50 MPH) driving. Thanks Joe B |
12-19-2021, 06:10 AM | #2 |
Senior Member
Join Date: May 2010
Location: VA
Posts: 1,410
|
Re: Measuring spark timing
|
Sponsored Links (Register now to hide all advertisements) |
|
12-19-2021, 07:52 AM | #3 |
Senior Member
Join Date: May 2010
Location: South East NJ
Posts: 3,398
|
Re: Measuring spark timing
How to make the simple too complex..
Follow directions found here: https://www.vintagefordforum.net/for...ing-lights-101 As for timing advance for conditions, well that requires a bit of education. Probably one of the most distructive things you can do is run the car with too much advance for conditions. You have to find the best point of advance based on the sound of the engine. |
12-19-2021, 08:09 AM | #4 |
Senior Member
Join Date: Jan 2012
Location: Western North Carolina
Posts: 3,899
|
Re: Measuring spark timing
You can buy a degree wheel and a indicator such as the one Bruce showed from Brattons. But the timing should be changed depending on conditions. It is not a set and forget.
A modern car has a computer to do the thinking for you. But in a Model A the thinking is up to you. The spark lever is there for you to adjust the timing depending on whether you are lugging the engine or cruising down a level highway at half throttle. In general the timing should be set at the knee, where advancing one notch will not change the engine but retarding one notch will. I usually try to be one notch on the retard side of the knee because I am trying to be kind to my engine, but retarding too much will burn your exhaust valves and cause other problems. I have a high performance engine but if you have a stock engine you can run right at the knee. After driving the car for a while you will get a feeling for where the ignition lever should be set for different conditions and it will become second nature.
__________________
A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
12-19-2021, 08:18 AM | #5 |
Senior Member
Join Date: May 2010
Location: Largo Florida
Posts: 7,225
|
Re: Measuring spark timing
First, full advance is supposed to be 40*. Personally I think thats too much.
Full retard should 0*/TDC or thereabouts. Normal driving should be fine with lever at 8:30/9:00 assuming the lever moves from 10:00 to 8:00. Just drive down a nice level road at 40-45mph and play with the lever. You'll find the sweet spot. Each car is different. If you want to use a timing light with piece of timing tape, thats fine. I've not found the need. Last edited by Patrick L.; 12-19-2021 at 01:37 PM. |
12-19-2021, 09:12 AM | #6 |
Senior Member
Join Date: Apr 2015
Location: Saint Cloud Mn
Posts: 745
|
Re: Measuring spark timing
Sponsored Links (Register now to hide all advertisements)
|
12-19-2021, 09:20 AM | #7 |
Senior Member
Join Date: Mar 2017
Location: Connecticut Shoreline
Posts: 1,821
|
Re: Measuring spark timing
|
12-19-2021, 11:30 AM | #8 | |
Senior Member
Join Date: Apr 2013
Posts: 293
|
Re: Measuring spark timing
Quote:
|
|
12-19-2021, 12:42 PM | #9 |
Senior Member
Join Date: May 2010
Location: Santa Rosa, CA
Posts: 1,278
|
Re: Measuring spark timing
I use the timing strip and set initial timing at 5* ATDC and use that for starting a idle for warm up. It is also useful a bit of extra engine braking going down hills. I run a Snyders 6-1 head and set the timing lever at about 9 oclock which I have set at 25* BTDC. (I have turned the steering column cover a bit so the lever will not pass 25* so I can just put it "all" the way down and forget about it.,With the timing light this comes out to about 23* BTDC and runs fine. Timing should be a less advanced for an HC head to avoid detonation. Under 25*BTDC seems common a popular with guys using HC heads.
|
12-19-2021, 01:10 PM | #10 |
Senior Member
Join Date: Jan 2012
Location: Western North Carolina
Posts: 3,899
|
Re: Measuring spark timing
Goodcar, Here is the scoop on timing and heads. The burning rate is determined by how tight the air and gasoline is packed together and how much turbulence there is. The combustion chamber design (squish area) and the engine speed determines how much turbulence there is and the compression ratio determines how packed together everything is. So a higher compression head with a good squish area will need much less advance. Also, as the engine speed increases the burning rate increases so that the needed ignition advance remains fairly constant (within limits) with increasing rpm.
There is another factor and that is the distance the flame front has to travel. So a small combustion chamber will need less advance. Or two spark plugs placed on opposite sides of the combustion chamber will require less advance. Old T head engines where the intake and exhaust valves were placed on opposite sides of the cylinder required two spark plugs because the combustion chamber was so large.
__________________
A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. Last edited by nkaminar; 12-19-2021 at 08:05 PM. Reason: fix typos |
12-19-2021, 01:38 PM | #11 | |
Senior Member
Join Date: Nov 2018
Location: Farmington MI
Posts: 284
|
Re: Measuring spark timing
Quote:
Full advance (lever full down) is supposed to be 40*/BTDC Got it ! Thanks Joe B |
|
12-19-2021, 01:45 PM | #12 |
Senior Member
Join Date: Jun 2010
Location: 34.22 N 118.36 W
Posts: 1,054
|
Re: Measuring spark timing
FWIW, I recently took the manual advance dist out of my coupe and put in a later model Mallory cent advance.
I set it up with 20° crank advance at 2000 rpm on external machine. It works pretty good, I set initial at 2-3° and that was too much, backed it down to about 0°. This motor has Lion I head and a touring cam among some other tricks. John
__________________
As Carroll Smith wrote; All Failures are Human in Origin. |
12-20-2021, 11:43 AM | #13 | |
Senior Member
Join Date: Apr 2013
Posts: 293
|
Re: Measuring spark timing
Quote:
|
|
12-20-2021, 05:49 PM | #14 |
Senior Member
Join Date: May 2010
Location: VA
Posts: 1,410
|
Re: Measuring spark timing
This forum has a lot of good info on timing, including this thread: https://www.fordbarn.com/forum/showt...on+head+timing
|
12-20-2021, 06:35 PM | #15 |
Senior Member
Join Date: Aug 2014
Location: Rhinebeck, NY
Posts: 761
|
Re: Measuring spark timing
I have a Snyder's HC head and am using the Nu-Rex auto spark advance. Couldn't be happier. John
|
12-21-2021, 08:14 AM | #16 |
Senior Member
Join Date: Aug 2011
Location: Eagle Bend, MN
Posts: 2,025
|
Re: Measuring spark timing
Listen to your engine. Advance the timing just until it starts to ping, then back up a click.
__________________
"There are some that can destroy an anvil with a teaspoon and shouldn't be allowed to touch anything resembling a tool." |
12-21-2021, 09:54 AM | #17 |
Senior Member
Join Date: Apr 2015
Location: Saint Cloud Mn
Posts: 745
|
Re: Measuring spark timing
Eagle yes it is so easy. Just listen to your engine and get a feel for how it’s running. No given spec will work. Each engine will have it’s sweet spot.
|
|
|
Sponsored Links (Register now to hide all advertisements) |
|