Timing Problem
 

I could not get my '28 Speedster to run real well. Plugs were really fouled and black sooty, so cleaned them and tried adjusting the Weber carb without any results. Checked the distributor for good spark. Timing is the last thing I usually check as it should not change if one has not changed the rotor. I decided to check the timing anyway. I noticed that the rotor was just past the contact inside the distributor body. I have not taken the timing cover off, but suspect that the timing gear may have shifted (rotated) on the hub. I kind of doubt that it was installed one tooth off as I've driven it quite a bit without this problem. So, I did two things. I removed the air cleaner and I modified an old after market distributor body by cutting a new locator notch to rotate the distributor body to line up with the rotor. Bingo, runs great, but still worried about the timing gear, so will probably pull the cover to have look. The only adjustment I see on that Weber is for the idle and maybe the air cleaner was causing it to run too rich. Any ideas?? Thanks

Re: Timing Problem
 

I don't see any point in removing the timing cover if it runs good now. Must have been something else.

John

Re: Timing Problem
 

It is possible for the screw that holds the ignition cam down to not have it locked down well. So then the cam moves and your timing is wrong.

If the cam won't tighten up, the screw may be bottoming in the distributor shaft before the cam is locked in tight. If so, add a small washer under the screw head and retighten.

:cool:

Re: Timing Problem
 

If the camshaft timing gear has slipped on the the hub, the valve timing would also be off late timing or early timing. I would adjust the distributor timing and keep an eye on things, maybe have a spare camshaft timing gear on hand.

Re: Timing Problem
 

I'd like to mention that changing the rotor has absolutely no effect on the timing! The rotor is "keyed" to the points cam lobe (it can only go on one way). "Timing" is the term used to describe the exact moment the spark occurs. That exact moment is when the points just start to open. In turn, the moment of points opening is determined by point gap and the position of the points cam in relation to the position of the piston in the cylinder (it can be at TDC or either before or after TDC). Ideally, initial timing should be at TDC or 1 or 2 degrees after TDC. Once the engine starts, timing of course changes (advances) as you pull the timing lever down.

Trying to set the initial timing by rotor position is like building kitchen cabinets with a chain saw-you won't get accurate results!

Re: Timing Problem
 

Almost correct, on a Model A you can move the cam that the rotor mounts on. There is a screw under the rotor you can loosen to move rotor position.

Re: Timing Problem
 

True, but I still like using the rotor to confirm it points correctly to cylinder 1 when using the timing pin for TDC cylinder one. If something is wrong there, no need to continue to timing at the distributor cam/points. Rarely is there is an issue with TDC, I just prefer to double check.

Re: Timing Problem
 

But moving the rotor has no effect on timing. When you loosen the screw and move the cam you are changing the timing of the points opening. It is when the points open that the spark occurs, not where the rotor is positioned.

Re: Timing Problem
 

If the rotor tip doesn't point correctly the engine won't run . Where the rotor tip points is where the spark goes . The opening of the points controls when the spark happens . The points can be adjusted so that they will be just ready to open . Factory specs for points gap is eighteen to twenty two thousands . Less gap within specs retards timing , more gap advances timing . I adjust mine so that the trailing edge of the rotor tip points at the number one pin contact in the distributor cap body with no clockwise backlash . Counter clockwise backlash has no effect on timing . I then adjust the points gap within specs so that the points are just ready to open .

Re: Timing Problem
 

It is called timing pin, so it is part of the timing but is the mechanical timing of the valves /pistons to the rotor cylinder 1 TDC. Additionally the spark is then referenced to the rotor at cylinder 1 TDC via the distributor cam/points. Timing is actually 2 things.

Re: Timing Problem
 

Thanks guys for all the responses. You helped me realize where the problem was and how to fix it. The issue was that when timed properly the distributor rotor was rotated past the #1 plug contact inside the distributor body. So, I was getting a random miss on plug firing because the gap was too much. I finally realized that the problem was with the points. The contact on the points was worn .016" less that a new set. Apparently it had been filed a few times. This was enough to cause the cam rotor to rotate more and thus the distributor rotor contact was rotated past the distributor body contact. A new set of points fixed the problem, but I put a new rotor on too as that contact had been filed a few times too. The first picture shows the problem and the second picture is with a new set of points and new rotor installed. She runs really sweet now. Thanks for you help. Your participation makes Fordbarn really great!!

Re: Timing Problem
 

Well, obviously if you set the points cam so the rotor tip points to number 2, 3, or 4 terminals in the cap, the engine won't run, so we set the cam so the rotor tip is pointing at #1 terminal. But that is not what determines the timing. Timing is determined by the opening of the points. The rotor just delivers the spark, it does not time it.

Re: Timing Problem
 

Almost correct. Moving the cam to just contact the point arm sets the ignition timing. The rotor setting in its notch is just going along for the ride.

So initially pointing that notch/rotor to the #1 distributor housing contact/pin helps one determine when they are close to finding the cam gear dimple.

Re: Timing Problem
 

Here is a picture of where eh rotor should be with the timing pin in the timing gear dimple.

Re: Timing Problem
 

Actually , where the rotor tip points DOES control the timing . You can set the points anywhere you want but if the rotor tip doesn't point at the number one contact pin in the distributor cap body It simply won't run . The spark will occur but if the spark isn't sent to the correct place , it might pop or backfire but it sure as hell won't run . Ignition timing is all about where the spark is sent and when !!!!!!!

Re: Timing Problem
 

Quote: "Ignition timing is all about where the spark is sent and when!!" True. But remember, where the spark is sent is done by the rotor, but WHEN the spark is formed is controlled by the points, and when the points open is controlled by the lobes on the points cam. The rotor is indexed to the lobes by the notch in the cam. So as PatrickL stated earlier, "the rotor is just going along for the ride."
Since you cannot change the relationship between rotor position and #1 cam lobe, and since it is lobe position that determines when the points open and spark occurs, it logically follows that the moment of point opening is the determining factor for ignition timing, not rotor position.

Re: Timing Problem
 

One can set the cam lobe on any of the 4 cam lobes to just contact the the point rubbing block. Turn on the key, open the point arm and bingo, there will/should be a spark.

But, a big but, there is very little chance the timing will be correct. Close to zero chance.

Now if the timing pin finds the cam gear dimple and then a cam lobe is set to contact the point block there will be a spark when the points are opened. But the chance of the timing being correct is only 25%.

The notch in the points cam has to be oriented toward the #1 cylinder contact in the housing/ cap/ right front fender [ as in the pictures]. So when that cam is set to just contact the point block while the notch is pointed to cylinder #1 contact will the timing be correct.[ if all shaft backlash is removed]

This really is a simple procedure.

Re: Timing Problem
 

True, but then one has to wonder why there is so much discussion about it.

Re: Timing Problem
 

Because the picture shown in #11 is close but not quite correct.

Re: Timing Problem
 

[QUOTE=katy;1907473]True, but then one has to wonder why there is so much discussion about it.[/QUOTE






I agree. But it keeps things lively around here. :D