how to time a 73 pontiac 350?

Answer 1

Remove the #1 spark plug on the drivers side in the front of motor. With the distributor cap off bump the starter to determine which way the rotor turns. Clean the timing marks and indicator on the harmonic balancer and timing chain cover. Make a mark at 8 degrees BTC (before top dead center) or which ever the tag on the vehicle says to time it on. It will be from 5-10 degrees BTC. Make another mark on the balancer that is 0 degrees or (Top Dead Center) TDC. While someone else bumps the starter over, cover the #1 plug hole with your thumb until it blows your finger off. At this point you want to turn off the ignition switch and turn the engine (by hand) in whichever direction it takes to bring it to TDC or 0 degrees. On the top of the intake you will find the firing order. Make a note of this order, and check later on. Your distributor should be pointing at or just before the number one plug wire on the cap. This should be with the rotor pointing towards the front of the engine. If it is out of place you need to remove the distributor, turn it to where its hitting the notch that is before the #1 on the cap. Remember it wil go down more when it goes into the oil pump. You can use a long screwdriver to turn the oil pump to where the distributor goes all the way down. With it all the way down, you should be able to turn the distributor and make the rotor point some on both sides of the #1 on the cap. If It does not do this, then you need to move to another slot until it will sweep both before and after the #1 on the cap. This will align your vacuum chamber to where it doesn't hit something when you are done. Turn the distributor till it is just a few degrees before the #1 on the cap, and the distributor is down all the way in the oil pump. Put the hold down on, and tighten the bolt to where you can turn the distributor but with a little effort to do so. Don't forget to put the gasket under the distributor or it will leak oil. Now check the firing order in the direction the rotor turns. Starting in the front of the engine toward the headlights on the drivers side, the #1 will be the first one. The second one on that same side will be #3, and #5 and #7. From front to back on the other side of the engine it will be #2, and #4, and #6, and #8. After you have checked the firing order, you are now ready to start the engine. Have something like a wet blanket or towel handy in case you are out a notch and it backfires through the carburetor, as this can make a fire. If it doesn't start right away, you are in the wrong notch, and will have to remove the distributor and start over. Remove the #1 plug, get it on the compression stroke, see if the rotor is point at or just before the #1 plug wire on the cap. If you have it there then you are in the correct notch. It is easy to get off one notch and this can be a pain to get right, but you should be able to fire the engine without grinding on it. I should start right up, and run pretty good. Now use a timing light when you get the engine warmed up to operating temperature and the idle speed at about 750-800 RPM. Plug the vacuum hose that goes to the distributor, and adjust the timing to spec's, or about 8-10 degrees BTC.
Glad I could help. Good Luck!!!

Answer 2

First of all you will need a timing light. Then find the timing marker (A little piece of metal shaped like an arrowhead pointing at the harmonic balancer at the front of the motor.) and hook the timing light up to the battery, and the correct spark plug wire for your motor. (most times it is the #1 plug.)

Loosen the distributer cap hold down nut and get ready to turn it left or right in small increments. Shine the light on the timing marker (the little arrowhead) and look for the lines to show up on the balancer.

The lines are degrees of BTDC and ATDC. (Before Top Dead Center and After Top Dead Center.) If you know the # of degrees you need just turn the distributer cap until that line on the balancer shows up with the arrow.

Don't go nuts turning the distributer cap! If you go to far BTDC you can get detonation. On an engine of that age I would tend to stay closer to BTDC unless it has been rebuilt. Playing with the timing is a cheap way to get power, but tends to be hard on the motor.

Answer 3

Also:

The engine sould be warm and idling.
Vacuum line to Dist. Vacuum advance should be disconected and plugged.