Replacing distributor in 1998 chevy k2500?

Do a compression test.
Verify plug wires proper distributor cap to cylinder.
Check timing, physically set cylinder 1 TDC compression, then check rotor position relative to cap 1 position.
Check vacuum.

With the engine at #1 TDC your rotor bug should be pointing at your #1 plug wire.

firing order on chevy v8 is 1-8-4-3-6-5-7-2 number one cyl is ft left of engine left side being 1-3-5-7 from ft to rear 2-4-6-8 right side ft to rear

You need to pull the distributor back out, put motor to TDC
now you say its always a tooth off...the timing chain may be alittle worn..so when you are trying to put the distribor back in ...put a socket or something... to move the crankshaft.....move it back and forth untill the distributor falls in....AT the number one plug on cap....
Hope this helps you out ??

the best way to do it is to remove no 1 spark plug and get the eng on tdc of the compression stroke and one of the marks will line up.hope this helps.good luck.

The ignition timing is not adjusted with a timing light or with the engine running, and to set the ignition timing follow these procedures.

There is a mark or notch on the distributor housing that the rotor should be pointing to when the engine is on TDC. (Top Dead Center) This "Static" timing is all that matters and the computer will be able to control the timing as long as the ignition rotor is in that position when the engine is at TDC.

1. Place the engine at top dead center.

2. Look under the distributor cap and find where the number one terminal runs under the distributor cap, and where that position on the distributor cap corresponds with the distributor housing, and it should match up to a mark or a notch on the distributor housing (usually has a #6 for 6 cylinder engines or a #8 for 8 cylinder engines) indicating the number one TDC alignment position.

3. With the engine on top dead center the ignition rotor should be pointing to the number one TDC alignment mark or notch that is on the distributor housing, if it is not then loosen up the distributor and turn the distributor until the ignition rotor is pointing to and aligned with the TDC alignment mark or notch on the distributor housing and then tighten down the distributor, the engine should now be "Static" timed. (The more precise that you are aligning the TDC alignment mark with the ignition rotor the better the engine will run, and it will be less likely that there will be a camshaft to crankshaft correlation problem)

If the distributor can not be turned enough to align the ignition rotor with the number one TDC alignment mark on the distributor housing, or the distributor does not set properly and will not allow the installation of the spark plug wires then the distributor is not installed correctly and is most likely a tooth off and it will need to be re-installed correctly. (The distributor should set like it is shown in the firing order diagram when it is properly installed)

Here is a firing order diagram to also help assist you.

tdc is usually set at 8 degrees BTDC for an automatic and 4 BTDC for a manual transmission. This may help. Does the engine run rough at start up being set at 0TDC?

on a chevy carb engine you only need to run a switched 12 volt to the distributor.

Is the vacuum hose removed from the dist when the timing is being checked?
Are you connected to the first plug wire (closest to the rad) on the drivers side?
If this is being done.....remove the cap and rotor and check the springs on the mechanical advance,the advance should be tight to the shaft and springs tight.
I would set the base timing on this set up .....at idle speed...... at between 5 and 10 before TDC.

Remember......timing marks on modified engines are not always accurate. Parts from this year and that year put together.

you need tdc compression stroke when you turn the motor and it puffs when 1# is up thats the one you need. then put #1 on the cap where its pointing. but you will hear and feel the comp stroke tdc