(Continued from Part 1. This concludes the article.)
Replacing your PCV valve is straightforward. It is located on the valve cover. It’s about ¾ of an inch in diameter. With a hose coming off and going to the carburetor. Lift it out of the valve cover, disconnect the hose and install a new one.
Changing an air filter is simple. Remove the screw from the center of the air cleaner canister, remove the lid and replace the filter.
Fuel filter replacement. Note that gasoline will leak out during this procedure. If the filter is in the gas line with a clamp on either side. Remove the clamps, twist the filter, and remove the filter. Taking note of any marked fuel flow direction arrow, replace the filter and reinstall the clamps. On most Chevrolets, the gas filter is located on the carburetor. Follow the fuel line to the carburetor. Place a rag under the housing where the fuel line enters. Place a backup wrench on the filter housing and remove the gas line from the housing. Now remove the filter housing There will be a gasket, filter and a spring. Replace the filter with a new one, check the gasket and replace it if necessary. Installation is in reverse order.
Adjusting Dwell and Timing
Now you are ready to start the engine and adjust the dwell and timing. For my engine, the dwell angle is 30 degrees. Hook up your dwell meter and timing light. Most dwell meters will also read RPMs. Start the engine. If you have a Chevy and you are setting the dwell you can open the hatch on the side of the distributor cap, place the correct size Allen wrench through the cap onto the point adjustment screw. With the engine running adjust the dwell by turning the screw until the dwell meter reads the correct setting for your engine. If you have another manufacturer’s engine you will need to adjust the point gap with the distributor cap removed. Replace the distributor cap. Start the engine and check the dwell. As stated above you will need to repeat as necessary until your dwell angle is correct.
Next is the timing. Get the timing setting from your manual. In my example the timing is 10 degrees Before Top Dead Center (BTDC). Highlight the TDC mark on your harmonic balancer which is attached to the crank shaft. Clean off the teeth marks on the small timing tab that comes off the timing chain cover so you can read the numbers. Hook up your timing gun leads to the positive and negative lead on your battery and the inductive lead to your number 1 cylinder spark plug wire. Slightly loosen the distributor hold-down bolt so you can rotate the distributor. Leave some tension on the distributor so it doesn’t move too freely. Remove the vacuum hose from the distributor and plug the hose. Start the engine. Point the timing gun at the timing marks and rotate the distributor to change the timing. Once you get to the desired mark lock down the distributor so it can no longer rotate. Check the timing again to ensure it didn’t change. Reconnect the vacuum hose to the distributor.
Adjusting the Carb
The last thing is to adjust the carburetor. Set the RPMs for the setting in your manual. This applies to an automatic choke. There are two idle settings. One for when the engine is cold a fast idle (on the choke) and the other for when it’s warmed up (off the choke). I’m going to select 1100 RPMs for when the engine is cold (on the choke) and 750 RPM when the engine is warmed (off the choke). This adjustment typically doesn’t change when doing a tune up. If adjustment is needed start the engine cold and adjust the choke idle screw for the correct setting my case 1100 RPMs. When the engine warms up, usually about 1 to 2 minutes, rev up the engine a few times and let it idle. It should no longer be on the choke. Adjust the idle screw for the correct setting in my case it’s 750 RPMs. Each engine is different so you may need to change it slightly to have a smooth idle. Your manual will describe how to set the choke and idle.
The next setting is the air-fuel mixture. That’s right the old carburetors had air-fuel mixture or idle mixture screws. Oh, how the greenies hate this one. You can do this by installing a vacuum gauge and adjusting the air-fuel mixture, so you have the highest vacuum while idling. This will make sure you are not running too rich (too much gas versus air) If you want to do it that way look it up on YouTube or your manual. For this article, I prefer to do it the old-fashioned way:
Make sure the engine is warmed up. Keep the air cleaner on if possible. There are two screws. If starting from scratch turn both screws in, clockwise until they are bottomed out. Back off each screw 1 and ½ turns counterclockwise. Start the engine. Turn one screw in until the engine starts to die. Then turn it out until the engine runs smooth. Then back it out another ¼ turn. Do the same amount of turns on the other side. They both need to be set the same. If you’re not starting from scratch just start by turning one screw in till the engine starts to die and backing it out till it runs smooth. Then back it out another ¼ turn. Then set the other screw the same. You may have to take the vehicle for a ride and readjust slightly to get it just right. This adjustment may not be needed if your engine is running good after replacing the cap, rotor, plugs, and wires. The tune-up is complete.
The No-Cost Tune-Up
When I was younger and didn’t have a lot of money, I used to do a no-cost tune-up. Here’s how:
Remove the spark plugs one at a time. Run a piece of emery cloth between the center electrode and the side electrode. Clean with some cleaner and a wire brush. Gap the spark plugs with a feeler gauge and reinstall. Make sure not to over-tighten them. Install the spark plug wires and make sure you have a good connection.
Remove the air filter. Shake out any dirt. Blow it out with an air compressor if possible. Clean it by wiping it down with a rag. Reinstall it.
Remove the PCV valve. Free up the PVC valve with a little cleaner. You should be able to shake it and hear the valve moving inside. When it moves freely reinstall it.
Remove the distributor cap and rotor. Ensure no spark plug wires are removed from the distributor cap. Look inside the distributor cap. You will see little metal contacts. One for each cylinder. Scrape off any carbon or corrosion build up on the contacts. Wipe out the inside of the distributor cap.
There is only one metal tab on the rotor. Scrape off any carbon or corrosion build up and lightly sand the contact with fine emery cloth.
Lightly sand down the contacts on the points with fine emery cloth, Check the gap. Reinstall the distributor cap and rotor.
Set the timing and dwell. Adjust the carburetor and choke as described above.
Here are a few things you can look for to check the health of your engine.
Engine cylinder compression check. Check the compression on each cylinder. Your engine needs to be warmed up before this test. You will need a compression tester. The screw-in type is the best. About $32 at Harbor Freight. All the spark plugs will need to be removed to perform this test. Mark each spark plug wire at the spark plug. Remove each spark plug wire from its spark plug. Remove each spark plug from the engine. Keep track of where each spark plug came from. Disable the ignition system. Usually done by removing the low-tension wires from the coil or remove the large coil wire from the center of the distributor cap. Thread the tester into one cylinder. Turn the engine over until the tester stops increasing in pressure, usually 5 or 6 revolutions of the engine. Your manual will have a compression specification range. Usually between 120 and 160 psi. Write down the value for that cylinder. Continue with all the other cylinders. The pressures should be in spec, and within 10% of each other. If they are, then the test is satisfactory. If the pressures are not in spec it is most likely a piston ring is bad or a valve not closing all the way, usually due to carbon buildup. If one cylinder is lower than the rest remove the tester, squirt a little motor oil in the cylinder and reinstall the tester. Try the test again. If the pressure gets better, it’s a piston ring. If the pressure is still low, it’s probably a valve or valve seat problem. Most likely requiring a valve job.
How to confirm the firing order of your engine:
If there is any question as to whether the firing order is not correct or if you removed a spark plug wire and think it may have been put back in the wrong location, then you will need to verify the cylinder firing order. The firing order is often stamped on the block and sometimes you can find it labeled underside of the hood. For our example, it’s 1,8,4,3,6,5,7,2. That’s the firing order for a Chevrolet 350 CID. The firing order will also be in the manual for your vehicle.
The first step is to locate the number 1 cylinder. For our example, it is the first cylinder on the driver’s side of the car. It is stamped on the block over the cylinder. Driver’s side is 1,3,5,7 and the passenger’s side is 2,4,6,8. Next, we need to find (TDC) top dead center for cylinder number 1. Disconnect the coil wire from the center of the distributor cap. This will prevent the engine from starting. Remove the spark plug for the number 1 cylinder. Have someone turn the engine over using a socket on the crankshaft. Turn it clockwise while holding your finger over the hole the plug was in. When you feel all the air rush out of the cylinder, have your partner turn the crankshaft slowly until the zero-degree timing mark on the balancer aligns with the zero on the timing pointer. That’s top dead center on cylinder number 1. Now you will need to remove the distributor cap and see which post on the distributor cap that the rotor is pointing to. That is where the spark plug wire for cylinder number 1 needs to be located. Follow around the distributor cap clockwise. The next post on the distributor cap will be for cylinder number 8. Continue around the cap using the firing order (1,8,4,3,6,5,7,2) and install a spark plug wire to each post and route it to the corresponding cylinder.
How to check if the timing chain needs replacement:
Remove the negative cable from the battery. Remove the distributor cap. Be careful not to disconnect any wires from the top of the distributor cap. You will need to be able to see the rotor turn. Place the appropriate size wrench or socket and wrench on the crankshaft bolt. Turn the shaft in one direction either clockwise or counterclockwise until the rotor underneath the distributor cap starts to move. Now go in the other direction and notice how much you turn the crankshaft before the rotor starts to move. It should move with very little play in the timing chain. If there is a lot of slack to take up before the rotor moves, you will need to replace the timing chain.
If the engine is not running on all cylinders:
Checking to see which cylinder is not getting a spark by removing the spark plug and installing it back in the spark plug wire. Make sure the spark plug side electrode is touching metal (grounding it to the engine) Have someone turn over the engine a see if there is a spark at the electrode. This is best done in a low light area. Also keep your hands clear or you will get quite a shock. If there is no obvious blue spark jumping from the center electrode to the side electrode than that cylinder will not fire. This could mean a bad spark plug or wire. Or it could be a crack in the distributor cap or rotor. If the engine runs it shouldn’t be a problem with the distributor or the coil. A tune up should resolve this problem.
A simple spark plug wire check:
At night, start your engine. Open the hood. For safety, keep your hands out of the engine compartment with the engine running. Look around the engine along where the spark plug wires are running to see if there are any sparks emanating from the wires. If you see any sparks coming from any of the wires, then they need replacement.
Here are some other recommendations:
- Change the engine oil regularly.
- Replace the rear differential fluid.
- Replace the transmission fluid.
- If it’s a four-wheel drive replace the front differential fluid and the transfer caser fluid.
- Check the belts and hoses replace if needed. Keep spares on hand.
- Get a spare starter.
- Get a spare alternator.
- Get a spare water pump.
- Get and always carry a spare fuel filter.
- Check all the front-end components and grease as necessary.
- Check the brakes. Have spare pads and shoes on hand.
- Check the u-joints for play and grease them. Get spares.
- Stock up on all the fluids and filters.
- I like to have two sets of rims for my vehicles. One set with winter tires mounted on them and one set with summer tires mounted on them.
- Have a full-size spare tire. Check it regularly.
I hope this helps get you started. God bless and be safe out there.