How To Clean Points On Distributor
"It's not a heap, dad. It'southward a classic." That's harder to justify when your classic muscle machine won't start. Nothing like a loftier-pinch V8 combined with a battery that hasn't seen a charge for a month and a half to make for slow cranking. Add in the indifferent, depression-energy spark and incorrect ignition timing acquired by worn-out points, and you've got an engine that won't burn--oh, and wet spark plugs too.
Modern engines use estimator-controlled manufacturing plant-preset cocky-adjusting ignition systems that never change their timing, have no moving parts and never demand maintenance. Yay! A generation ago, every teenager, every mechanic and a lot of vehicle owners understood the theory and practice of changing points and setting the timing. Withal, there are notwithstanding plenty of older vehicles, outdoor power equipment, boats and tractors that demand periodic aligning or replacement.
The distributor on these older vehicles performs two related tasks. The starting time uses a elementary on/off switch, the ignition points, to provide properly timed pulses of 12-volt electricity to the ignition coil. In the coil, essentially a transformer, information technology'southward stepped up to 10,000 to 20,000 volts. Then, the high-voltage electricity from the scroll returns to the distributor, where the rotor inside parcels information technology out to the correct spark plug to ignite the fuel/air mix.
At that place's a lobed cam on the distributor shaft that pushes on a pocket-size rubbing block on the movable side of the points. As the cam and distributor rotate, the points open and close constantly. As they close, current from the ignition switch flows through the contacts into the coil'south primary windings and and so off to ground. This current generates a magnetic field in the scroll's atomic number 26 cadre. When the points open a few degrees of crankshaft rotation later, the electric current is interrupted, causing the magnetic field to collapse. This induces electrical current into the secondary windings of the gyre, where the current is raised to twenty,000 volts or more than. The high voltage now travels over to the distributor, where the rotor metes the high-voltage pulses out to the correct spark plug.
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All that electric current flowing across the points doesn't similar to finish all of a sudden, and tin can initiate a small arc, which somewhen erodes the tungsten contacts. The condenser cushions that arc, making point life much longer. But not infinitely long. Equally the contacts and the plastic rubbing block, which contacts the bespeak cam, vesture, the ignition points' clearance and timing constantly change. Later on thousands of miles, the timing has shifted enough to affect performance, and the ritual of changing the points and setting the timing becomes necessary. How often? Some vehicles need to have the timing adjusted every bit ofttimes equally every 10,000 miles to maintain top performance. Loftier-revving engines will need premium points with a high-pressure jump to keep the points from billowy at increased revs. Some points assemblies include the condenser, notwithstanding for others, it'south a separate part. Condensers are inexpensive enough that it makes no sense not to supersede them with every set of points. They should concluding equally long every bit a set of points, xx,000 miles at least.
Kettering Ignition: Charles F. "Dominate" Kettering was one of the founders of Delco, and the inventor of the battery-bespeak-fashion ignition organization, first used by Cadillac in 1910. Wear, inaccuracy and loftier maintenance have forced motorcar manufacturers to abandon this system, replacing it with computers and individual ignition coils for every cylinder--and no points to vesture out.
On Signal
The function of the ignition system is to fire the spark plugs at the correct time, just before the piston hits top dead center (TDC) on the compression stroke, to ignite the fuel/air mixture, thence producing high pressure in the cylinder to force the piston down and, after, the wheels to move the machine forward. The spark plug normally fires anywhere from x to 45 degrees before the piston reaches TDC, to allow the fuel/air mixture's flame front to traverse the combustion bedroom. It takes a few milliseconds for the force per unit area in the cylinder to build, and waiting until TDC would make the pressure peak too belatedly in the piston'due south down stroke to be about efficient. Nether some engine-operating weather condition, the advance might suit the ignition timing to as much equally 45 degrees before TDC. Signs of incorrect ignition timing include hard starting, spark knock, poor ability, overheating and decreased fuel economy.
This Chevy V8 uses an old-schoolhouse Kettering-style ignition distributor. To set the timing afterward replacing the points and condenser, you'll need, no surprise, an old-fashioned stroboscopic timing low-cal.
Avant-garde Timing
At that place are two master types of advance mechanism built into the distributor. The first is the centrifugal advance. A pair of bob-weights spin atop the benefactor shaft, restrained by small springs. Every bit the engine speeds upward, centrifugal force pulls the weights outward, which in turn makes the top of the split distributor shaft advance. Missing springs or a gummed-upward linkage tin can give also much advance besides soon, or none at all.
Similarly, a vacuum advance uses a safety diaphragm to advance or retard the timing. Vacuum from the carburetor pulls on i side of the diaphragm, pulling the points around the distributor and making the plugs burn down earlier. A leaky vacuum line, a disintegrating safety diaphragm or a gummy breaker plate can brand the advance mechanism averse.
Inoperative advance mechanisms can deliver likewise much or likewise niggling ignition advance. Too much advance can brand the engine ping. Too picayune causes power loss and overheating.
Installing the new points and condenser is simple, and usually requires no more than than a screwdriver. The proportion of time the distributor's cam keeps the points closed and open is referred to every bit dwell angle. Adjust the dwell angle initially by using a feeler gauge. Nearly V8 American iron should be adjusted to 0.018 to 0.020 inches, while four-cylinder engines, similar early on VWs, start around 0.014 inches. Shut is expert enough, because the simply really accurate manner to set dwell is with a--await for it--dwell meter. The dwell angle should exist 30 to 35 degrees for V8s and 44 to 50 degrees for iv-cylinder engines. Check the shop transmission for your car. Attach the dwell meter to the coil'south low-voltage leads and spin the engine with the starter motor to check and trim the dwell. Some cars accept a small window in the distributor to let you set dwell with the auto running, a real timesaver because you don't take to creepo the engine with the starter, adjust the points and check the dwell again.
Setting Dwell: Changing the clearance in the points affects the proportion of time the points are closed ("dwell") and the charging of the whorl. A dwell meter is needed to properly adapt the dwell angle, which is done with the engine spinning on the starter motor or, on some engines, actually idling.
Cleanup in Bay 4
Before you lot button up the distributor, make clean the point contacts of whatsoever oil left behind by your feeler gauges. Contamination will carbonize and become a resistance where there should be only metal-to-metallic contact. I ordinarily just use the corner of a business card to scrub whatever contagion off. Add a dab of point-cam lube to the rubbing block.
Adjusting dwell also changes the base ignition timing, and then whenever the dwell is adjusted or the points replaced, the timing will need to be adjusted. Some engines call for vacuum lines to exist pinched off or disconnected, so you'll need to find the correct timing procedure for your engine in the shop manual. I'll wait ...
Got the timing specs? Find the timing marks on the harmonic balancer or on the flywheel. Use some contrasting paint or a felt pen to brighten the timing marker. Hook the timing light to the No. i plug wire. Start the engine, and polish the timing light at the timing marks. Mind the whirling fan and the belts, reminds my onetime-timer mechanic pal Lefty. The strobing light will "finish" the spinning pulley when the No. i plug fires. Loosen the clamp holding the distributor downward and slightly rotate the body of the distributor to line up the timing marks. Revving the engine slightly should make the mechanical advance actuate--you'll encounter the timing marks accelerate and retreat as the engine surges. Tighten the distributor clench, reconnect any vacuum lines and drive.
Source: https://www.popularmechanics.com/cars/how-to/a6382/4338376/
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