Timing; why is being 'dead nuts' so important?

[Jason in TX]

Timing with the pin is absolutely fine with a stock Model A.

Updating to timing light and absolute precision (in my opinion) are only more necessary when you start modifying the engine with higher compression, cam, carburetors, etc

 

[Marco Tahtaras]

Timing with the pin is absolutely fine with a stock Model A.

Updating to timing light and absolute precision (in my opinion) are only more necessary when you start modifying the engine with higher compression, cam, carburetors, etc

If you are using a stock type distributor there is NO gain from a timing light unless you have problems using the timing pin method. You should have no trouble getting within 1 degree. If you change to electronic ignition a timing light becomes much more useful. If you are using a centrifugal advance distributor, a timing light (along with a test tach) will allow you to test your advance curve. However with these four bangers you will find that your optimal timing will be found by feel/performance characteristics. The higher the compression, the more obvious any change will be. Checking it with a timing light afterward and recording the results will make life easier in the future.

 

[Richard/Ca]

If it ain't broke, fix it til it is! Been there done that a few times.

 

[GMCPASO]

Using a timing light, check the firing point of #1 and then #4 and see if you see any difference. I have found 3-4 degrees difference between them. This would seem to indicate that the cams are not precision ground or there are very worn distributor bushings. Is there a good cam that is precision ground, like originals that measured .025, .025, .025, and .025 as reported in another thread? That would be good, as long all for are the (same) ,within .0001 and at exactly 90 degrees wouldn't it.

Until then, I am going to split the difference between #1 and #4. Seems to be smoother. If we have HC heads, mine is a 6.0 to 1 with .080 larger piston, increases to about 6.3 to 1. Indications from others are we want to limit advance to 25-28 degrees. If set on only #1, then my #4 would be at 28 to 31 degrees advanced. #4 would run even hotter in the rear position as reports indicate.

Well, I did it and the smoothness of the idling engine is noticeable. When cylinders fire at different times other than 180 degrees from each other causes noticeable at the exhaust and uneven vibration in the engine. This cam had a 4 degree difference between 1 firing and 4 firing. I split the timing so 4 fired 2 degrees early and 1 fired 2 degrees late. A precision cam would even smoother, like the originals.

OK, I got a pair of Bill Spite distributor cams and installed one and WOW, #1 and #4 are within 1 degrees of each other with timing light on crank pulley markings and very stable. The engine idle is very smooth now and was able to make idle mixture adjustments to the engine will idle very smooth at ~200 rpm. I set 0 at 2 degrees after TDC at full up on spark advance lever, which allowed for easy crank starting if it becomes necessary and it is easy. Great Distributor cams. Specialty Motor Cams

Make any sense? So where is the better/precision B distributor cam made? If necessary.
It did make a difference and is very smooth running, easy to tune carburetor, a balanced Sears Marvel Scribner carb.

Off on a long trip the next couple of weeks and see what happens.

 

[40 Deluxe]

News Flash: Timing in a running Model A is set by the spark lever on the steering column, NOT by futzing with the distributor! Using the timing pin and loosening the cam, etc. only sets initial, or base, timing, which is important to avoid kickback, especially when hand cranking. Barry in St. Paul is 100% right on with his comments about the folly of trying to "set the distributor cam just right".
You, the driver, set the timing whenever you move the spark lever. Your engine never runs with the timing where it was when you went to all the trouble of "getting it accurate"! It changed the moment you pulled the spark lever down. Hopefully, you are resetting the timing frequently, as needed. Pulling a hill, you move the lever up a little. Cruising on a level road at 50 MPH? Pull the lever down a little more. Idling? Lever goes up. And so on.

 

[kenparker]

I agree with George Miller on this one. Close enuff or It 'ill do is fine if you are out in the boonies and need to get the car going again. But when in your garage and setting timing you should do the very best you are capable of with the tools you have. If that means setting with the timing pin then checking with a timing light in order to get it purrfek -then do it. ...and as George says set purrfek and it will run better.

 

[updraught]

So it doesn't break your arm.

 

[mike657894]

I would guess having your timing right on or very close to will allow you to crank start. I dont know though as my crank nut is rounded too much to use.

 

[Dick Steinkamp]

How much should the point plate rotate at full advance (spark lever fully down?) I have a modified linkage so I'm not sure if it's moving as much as it should.

Point plate should rotate 20 degrees which corresponds to 40 degrees of advance due to the 2:1 ratio between crankshaft and distributor rotation.

The cut out in the distributor cap body is going to limit the plate travel to 20 degrees. Just make sure when you move the advance lever on the top of the column full travel up and down that the arm coming off the distributor plate that attaches to the actuating rod is just touching the edge of cut out in both directions. If not, loosen the column jacket and upper support and rotate it until it does.

 

[Smooth_One]

I have had my car for two years now and have always set and checked the timing by the book and it has always been fine! I did make myself my own timing light that consists of a 6 V bulb with two wires and an alligator clip on each end. Works perfectly every time.

 

[H. L. Chauvin]

"Timing" and "dead nxxs" ........ topic on a Model A Forum?

Lots of helpful Model A responses; but at first sight, might sound to some seniors on here, like maybe seeking advice from a Marriage Consular/Therapist.

 

[40 Deluxe]

I agree with George Miller on this one. Close enuff or It 'ill do is fine if you are out in the boonies and need to get the car going again. But when in your garage and setting timing you should do the very best you are capable of with the tools you have. If that means setting with the timing pin then checking with a timing light in order to get it purrfek -then do it. ...and as George says set purrfek and it will run better.

Ken Parker, What happens to that "purrfek" setting when you start the engine and move the spark lever down?

 

[Mike V. Florida]

Glad to see these old threads are being read!

 

[RonC]

OK, at the risk of sounding really ignorant, I'll ask this anyway; why is it so important that the timing be so absolutely perfect on a Model-A? I understand the importance OF the timing, but with a Model-A, you are constantly adjusting the spark lever anyway, and I seldom run it fully advanced even at road speeds.... So, seems the key aspect would be that the spark is retarded-enough when starting, so as not to damage the engine with a backfire...?? So I wonder, how does setting the distributor cam (ie: timing) "just right" affect engine power or anything else, since you can move the spark lever to compensate to where-ever that sweet-spot is for your engine?
It's one thing to be really anal about something like bearing-shims and such, where "they are where they are, and will stay that way!". But I don't quite get the ongoing debate about a few degrees this way or that for the distributor cam. What am I missing? Is it the "full-retard" position that is very critical, for starting? (and if so, if my engine pops off with just a turn or two of the engine, does that confirm 'good timing'?)
Just curious. Easy enough to do again and again and get "just right", but I've often wondered while I'm doing it, what difference it really makes, within reason.
thanks![/QUOTEcam greeting affects that timing window ]

Because the engine is designed to run at different rpms and variable timings. Your limited to the lever adjustment while driving. If you set your intial timing to far retarded you won't get the full spark advance capability which could mean lose of potential power. This also goes for setting the initial timing to far advanced. A very small rotation of the distributor cam greatly affects timing

 

[Mike V. Florida]

OK, at the risk of sounding really ignorant, I'll ask this anyway; why is it so important that the timing be so absolutely perfect on a Model-A? I understand the importance OF the timing, but with a Model-A, you are constantly adjusting the spark lever anyway, and I seldom run it fully advanced even at road speeds.... So, seems the key aspect would be that the spark is retarded-enough when starting, so as not to damage the engine with a backfire...?? So I wonder, how does setting the distributor cam (ie: timing) "just right" affect engine power or anything else, since you can move the spark lever to compensate to where-ever that sweet-spot is for your engine?
It's one thing to be really anal about something like bearing-shims and such, where "they are where they are, and will stay that way!". But I don't quite get the ongoing debate about a few degrees this way or that for the distributor cam. What am I missing? Is it the "full-retard" position that is very critical, for starting? (and if so, if my engine pops off with just a turn or two of the engine, does that confirm 'good timing'?)
Just curious. Easy enough to do again and again and get "just right", but I've often wondered while I'm doing it, what difference it really makes, within reason.
thanks![/QUOTEcam greeting affects that timing window ]

Because the engine is designed to run at different rpms and variable timings. Your limited to the lever adjustment while driving. If you set your intial timing to far retarded you won't get the full spark advance capability which could mean lose of potential power. This also goes for setting the initial timing to far advanced. A very small rotation of the distributor cam greatly affects timing

I don't think Barry will see your response. He stopped posting in 2011.