| Rotor Position Posted by Sonnie on December 13, 2002 at 04:32:45: In Reply to: Re: Static timing help posted by PeterW on December 11, 2002 at 22:43:15: Hi Nick and PeterW, Since the topic is here, I would like to ask some more question about rotor position. Logically, I think rotor position is not important, as long as we could get the proper ignition sequence and timing. So if by mistake I incorrectly insert the distributor shaft, but I am able to sequence the ignition and timing, all would be alright. Is this right or wrong? And for some additional info on setting up timing, I paste some info that I get somewhere in the web. ---start of quote--- Static, Stroboscopic, and By Ear There are many ways to set your ignition timing. One is not any better than the other, although sometimes the knowlege of several methods can really help you out. First, a bit of theory. Ignition timing is important because it is the spark from the spark plugs that causes the fuel to combust, giving force to the piston, which in turn gives revolution to the crankshaft, which through a series of gears makes you move down the road. If that spark occurs at the wrong time, you loose power. Usually the spark should occur a bit prior to the piston being at the top of it's stroke. Like a hunter leading a duck, you want the maximum explosive force occurs as the piston reaches it's pinacle. To achieve this, the actual ignition of the mixture must occur a bit before that point. If it occurs to early, the exploding fuel tries to push down a piston that is on it's way up. If it occurs to late, the exposive force is lost on a piston already on it's way down. Symptoms of timing being way off usually manifest as backfires through the carburetor or exhaust. The other factor that comes into play is fuel quality. Higher octane fuel is less combustible at a given pressure. This allows timing to be set farther in advance, giving good power at high RPM's. This is drag racing stuff. Octane of 85-90 is fine for the 2.25 engine, anything more is a waste of money. Higher octane fuel does NOT burn cleaner. In fact the lowest octane that you can run is fine for your engine, but it will be more prone to preignition. Preignition occurs when the fuel/air mixture in the cylinder ignites prior to the spark plug firing. This can be caused by sharp edges in the combustion chamber, carbon build up, low octane gasoline, or other factors. It manifests as a rattling noise when the engine is under load, often called pinging. Preignition is bad. It wears an engine out quickly, can damage piston heads, rings, valves, etc... The Rover 2.25 engine is very forgiving, it will run on some pretty trashy fuel, but you do have to have the timing in the ballpark somewhere. Before setting the ignition timing, it is imperative that the condition of the points and the point gap be checked and reset, if required. The 2.25 engine requires a point gap of .016", but realize that a wider gap will give a hotter spark at the expense of point life. An insufficient gap will give a weak spark resulting in poor running. Adjusting the point gap is really an indirect way of setting what is known as the dwell angle. Dwell is the angular period of rotation of the distributor cam during which the points remain closed. Setting the point gap with the aid of an inexpensive dwell meter is much more accurate than setting with a feeler gauge. I, however, use a feeler gauge to set the points. I guess I'm just a low tech kind of guy. Do not neglect the point gap. It is one of the most important settings on a Rover, having serious effects on performance and fuel economy. Over time the rubbing block on the points wears down, lessening the point gap, and stealing performance. For information on how to bulletproof your points, click here. If you are interested in just forgetting about points, and installing electronic ignition, click here. Now, On to Timing..... There are two ways to adjust the timing with the Lucas 24D distributor. You can loosen the clamp holding the distributor, and turn it, or there is a knurled nut that allows you to make some adjustment. Rotate in the direction of the "A" to advance, towards the "R" to retard. This adjustment screw is intended to compensate for varying fuel quality on a Rover, and track conditions for the sportscars that use the same distributor. Count the "clicks" on your adjuster nut between divisions, and divide by four for the number of clicks per degree (generally about ten per degree, but check your individual distributor). Multiply this by the number of degrees advance you require, and set accordingly. I only use the knurled screw if I begin to sputter on the road and I think the timing or fuel is involved. Even then, I set it by "ear" Because of this, I set the knurled screw to the mid point of it's range and then time the engine. Static Timing If you have had your distributor out, knowlege of static timing is essential. This simply means that the timing is set with the engine not running. If you are reinstalling the distributor, insure the firing order is correct. You may rotate the wires about the cap as long as you do not change the order. The static timing procedure is not difficult. The only equipment required is a 12-volt test light or a voltmeter. If a commercial test light is not available, a substitute may be easily made by soldering two wires to a 12-volt light bulb; one wire to the side of the base, and the other to the bottom contact. For convenience, alligator clips may be installed on the other ends of the wires. To static time your engine using a test light: 1) As accurately as possible, locate the piston of the "timing cylinder" (cylinder #1 on the 2.25 Rover engine) at top dead center, on the compression stroke. This is achieved by noting the position of the ignition rotor when the piston is at top dead center. If the rotor points to the contact on the distributor cap which leads to the spark plug of the #1 cylinder, the piston is on the compression stroke. If the rotor points away from that contact, the piston is on the exhaust stroke, and the crankshaft must be rotated one full turn to bring the piston to top dead center on the compression stoke. Check that the timing marks line up correctly. 2) If your vacuum advance unit has an adjuster, you may either proceed with the instructions in this paragraph, or skip it and go to paragraph 3, continuing from there. If your pulley or indicator is marked with degree settings, turn the crankshaft until the single mark and the appropriate degree mark line up. It is essential that a reliable workshop manual be consulted for this specification. The piston of your "timing cylinder" is now in the correct firing position, and the distributor must now be adjusted to it's firing position. 3) Loosen the distributor clamp to the point where the distributor may be rotated freely. Set the knurled adjuster screw to mid-scale. 4) Connect one wire of the test light to the low tension contact on the distributor, and the other wire to a good ground. (The low tension contact is where the thin wire from one side of the ignition coil connects to the distributor. In my picture I am hooked up to the end of the same circuit, with the cap off, because of the way I wire my points. It is not necessary to remove the distributor cap if you still have the low tension connection on the side of the distributor.) Do not disconnect the coil from this circuit. A test light with alligator clips at each end will be easier to use than the test light I have pictured. 5) With the ignition on (but the engine not running), rotate the distributor body slowly in the opposite direction of the rotor's rotation until the test light lights up, indicating that the points have just opened. Do this a few times until you have accurately determined the exact point at which this happens, and re-tighten the distributor clamp bolt. 6) For distributors with adjusters on the vacuum advance unit, only if paragraph #2 was skipped: With the piston of the #1 cylinder at top dead center (see 1.), the adjuster on the vacuum advance unit may be used to "dial in" the correct static advance setting. One division of the scale is equal to four degrees. Count the "clicks" on your adjuster nut between divisions, and divide by four for the number of clicks per degree (generally about ten per degree, but check your individual distributor). Multiply this by the number of degrees advance you require, and set accordingly. Refer to a reliable workshop manual for this setting. Be sure to turn the adjusting wheel in the direction of the "A" to advance, in the direction of the arrowed "R" to retard. 7) Disconnect the test light and start the engine. If it does not start, make sure that you remembered to replace the rotor after adjusting the points. Don't feel foolish if you find it on top of your battery or radiator cowl - there probably isn't a single auto mechanic dead or alive who hasn't had this happen. Static Timing Using a Voltometer Rotate the engine until No. 1 piston is just before TDC on the compression stroke. At this point, the rotor arm should be pointing to the distributor cap segment connected to No. 1 spark plug. The contact breaker points should be just at the point of opening in the direction of rotation. This can be verified by connecting a voltmeter between the distributor Low Tension terminal and a good earth. At the precise moment the contacts open, the voltmeter will register battery voltage. Should the ignition timing be incorrect, centralize the micrometer adjuster (if fitted), slacken the distributor clamp bolt and position the distributor to the point of contacts about to open and re- tighten clamp bolt. It must be remembered an incorrect contact gap can affect ignition timing. The contacts must be set and maintained at 0.35-0.40 mm (.014"-.016"). Stroboscopic Timing Stroboscopic timing, in theory, gives a more accurate result. I suppose on engines that have a lot of pistons moving at high RPM's this may be true. I have not seen enough additional improvement on a 2.25 Rover engine to justify the price of a stroboscopic timing light. I have also found that setting the 2.25 to specs can rob it of it's performance potential. Some folks, however, like the high tech gadgets and have a problem grasping static timing, let alone timing by ear. So here is the basics of using that light. Connect the strobe High Tension pick-up onto the No.1 plug lead and disconnect the distributor vacuum pipe. The strobes with the inductive pickup are vastly superior here. Connect the battery leads to the battery. Make sure all the leads are out of the way of the fan. The strobe light can also be used to check that the centrifugal and vacuum advance mechanisms are operating, as well as the vacuum advance. I have not found stroboscopic timing to be very efficient on Rover engines with the timing marks on the flywheel. Timing by Ear I often advise fellows to time by ear. I believe this method is superior for the Rover 2.25 for several reasons. With the timing marks on the flywheel they are simply difficult to get at. The Rover engine does low RPM work with low gears and is a bit of a tractor. It is not a high performance engine. It really benefits from timing by ear. To set the timing by ear, you must accept the premise that advanced timing is preferable, as long as the engine does not experience preignition. I have found this to be the case with the 2.25. If you set the timing advanced of the factory specs, you will often experience improved performance. You must also have a good feel for what you normally ask your engine to do. Realize that driving up a grade in high gear, hard acceleration, or when pulling a load up that same grade is the time that the engine will most likely suffer from preignition. Remember to set your points first, then find that hill, and accelerate up it in high gear, (or, this being the venerable 2.25, at least try!). If your engine pings, you should retard your timing. If your engine does not ping, advance your timing and try again. Rotation clockwise advances the timing, counter clockwise retards it. Continue to advance your timing and test drive under preignition prone conditions until your engine starts to ping. Once this occurs, retard the timing a bit until the pinging goes away. That is your engine's sweet spot. Timing advanced into the range of good performance without the risk of pinging. From here on out, you will most likely be able to use that knurled screw to it's best effect, adjustments for fuel quality. Realize that if you set your timing by ear and then hook up your boat trailer, you may have to reset. Use the knurled screw for that as well. If you experience pinging down the road, retard the timing a bit with the knurled screw, and figure out why later. How effective is setting the timing by ear? Well, Model T's had a cable that allowed the driver to advance or retard timing while driving down the road. Many race car mechanics to this day set timing by ear. They will confirm with a strobe, and take notes of the settings for later reference, but the actual setting is obtained by ear and the driver's seat of the pants impression. This moves timing out of the realm of science and onto the plateau of art.
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