While many car restoration hobbyists and backyard mechanics have been tuning their cars for decades, very few actually do so in the correct manner. If you are determined to do your own car tune ups you will know now the correct way to start and finish.
Before you start getting all crazy and start replacing and adjusting things for you tune up take a look at your cooling system and see if it is operating as it should be. Check to see if it is running at the proper operating temperature. Check for leaks and if the condition of the water hose connections to the plate under the carburetor to make sure they are actually connected and operating. Also check your battery make sure it is fully charged and look at your generator or alternator to make sure that it is functioning as it should. Take a look at your fuel system and make sure your filter is clean. Make sure that the pump is at the correct pressure. Check for your choke, accelerator, and transmission shift down linkages and make sure that they are running smoothly. Next take a look at the wiring what is the condition as far as whether there are any breaks in the insulation and if the connectors are rusty or loose. If everything seems to be in good condition you can now start with your tune up.
First things first, getting the ignition settings correct. You will need to start with a fresh set of points, condenser and plugs. Your plug wires may or may not need to be replaced which really depends on the mileage of your car. You should be replacing carbon core wires after about 15,000 miles on the older cars and with solid core wires should have their rubber end caps replaced as they deteriorate this will keep the wires from arching over to your engine block.
Now crank the engine to Top Dead Center as it is marked on your balancer or your pulley. Now open the distributor cap and check to see if the rotor is pointing at the number one cylinder if it isn’t marked just follow the plug wire to the distributor. If it is 180 degrees away from that position simply crank the engine one revolution back to the Top Dead Center. Next mark a line on the side of the distributor housing and you can continue it onto the engine block. This helps if you need to do a bit of realignment.
You are probably asking yourself why you are doing this well simply put you doing is to prevent misplacement of plug wires later and to make the process as smooth as possible in the removal and or replacement of the distributor if that needs to be done. Your engine is now ready to be set to operate in the proper firing order.
The next step is to pull out the old points, the condenser and rotor and then look for smooth movement of the vacuum advance plate. You can check this by sucking on the vacuum hose. Now loosen the distributor’s hold down screw enough to allow movement and rotate the distributor until the wiper arm on the points is at the very top of one of the shaft’s actuating cam lobes. You then will tighten the hold down screw and adjust the points for the proper mechanical gap in accordance to your engine manual. Now you will use your feeler gauge properly and use caution and take your time because you are mechanically setting the proper dwell angle after this you install the rotor and cap.
Next thing to take care of is to gap the new plugs and install them making sure you do not over tighten the threads into the block. Place your plug wires onto them while making note of the firing order. Make sure the wires are seated into the distributor cap and coil.
Now it’s time to get out the dwell meter and connect it. The red lead will go to the point’s side of the coil or negative terminal and the black clamps onto some grounding point of the engine. Start up your engine and measure the dwell angle. If it is not in the middle of the allowed range stop your engine and move the point gap closer to raise the dwell or if needed farther apart to lower it. Just keep on doing this until the dwell is correct and the angle has been set by properly adjusting the ignition point gap. Individual point sets can vary in their mechanical and electrical characteristics so the only way to properly set up your ignition points is with a dwell meter.
Next you will need to get out the timing light which is the most overused engine maintenance tool. If you are now scratching your head and wondering why it is overused it is because the engine’s internal components only wear a tiny amount over time which basically means timing chains or the gears do not get loose between your tune ups. The main reason your engine’s timing changes is due to the fact the dwell angle is changing as the wiper on the points wear down.
The next step is to set the timing by connecting the light either inductive or directly and then mark the correct timing position on the crank pulley or the damper. Follow the engine manual which will make it an easy to read mark with something like white out or chalk. Then you will need to disconnect the vacuum line from the distributor and just stick a pencil or a nail in it to prevent vacuum leak. Now you can start the engine and get this running to about 500 to 600 rpm’s to prevent any action from the centrifugal advance mechanism well if there IS one that is. Now slowly rotate the distributor until the timing mark lines up with its pointer and then tighten the hold down on the distributor. If your engine won’t run slowly enough, back off the accelerator linkage at the carburetor. If your engine runs too slow increase the speed of the idle and then check your timing again and you can then put the light away.
Now it’s that long awaited time that you can adjust your carburetor. You will first want to adjust the idle mixture screw or two if you have a four barrel carburetor. With your engine at the correct operating temperature , which by the way is very important so just wait until it does get warmed up, you can then adjust one screw slowly clockwise until the engine starts to stumble or run roughly, then back it up just about one turn. Next adjust the other screw the same way until your engine is running smoothly.
Nest step is to set the engine idle speed and do it according to the manual or in your own personal preference. Ideally a faster idle speed of about 800 to 900 is good but you can have this how you want it. Now readjust the idle mixture screws if you are finding that the engine is running slightly rough.
It’s time to take your car for a spin around the block and no not just because you want to show off the fact you just tuned up your car but because you need to pay attention to any rough running or any hesitation or misfiring. If you find that it is still running roughly try to loosen up a plug wire or it could be something very obvious like a faulty carburetor system or simply a lack of compression. Once you have everything running smoothly, NOW you can go take that car of yours for a spin around the block knowing that you now have the knowledge to correctly tune up your car!
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