The timing depends on model and year. Try 8 degrees BTDC. It should run fine at that setting.
Top Dead Center
with no.1 cylinder at top dead center, line up the mark on the cam gear with the mark on the crank,and install the timing chain.
That would be the biggest and widest mark. Are the first mark on it when turning it clockwise to the pointer.
On a 1996 Chevy Astro Van, the timing mark on the crankshaft pulley that indicates top dead center (TDC) is typically aligned with a mark on the timing cover. The mark on the pulley is usually at 0 degrees, which corresponds to TDC for cylinder number one. To ensure accuracy, it's advisable to verify this with the vehicle's service manual or specifications, as markings can vary or may be difficult to see.
It is look like ruler with 0, 10, 20 number XXXXXXXXXXXXXXXXXXXXXXXXXXXXX The timing scale will have an "A" at the top and a "B" on the bottom. In the center is a "0". The "A" is for after top dead center. The "B" is for before top dead center. Each mark on the scale is 2 degrees. Timing is always set on before top dead center.
When timing the timing belt you use the mark for top dead center on the crank. To do that you will have to do a few different steps.
One is advance mark, one is retard mark, one is dead on mark.
4 degrees btc-before top dead center with the vacuum spark line disconnected.the timing mark location is on the harmonic balancer. this is for a 327 engine
what do you mean by change there is only one position for the timing mark and that t.d.c. top dead center
TDC, top dead center is when the number 1 piston is at the top of the cylinder. 8 degrees before TDC is where you set the distributor so that is when the spark plug fires. You use a timing light to set the distributor. There is a timing mark on the crankshaft pulley and a series of marks on the timing chain cover that will show where 8 degrees before is at. The timing mark on the pulley is a small notch in the edge of the pulley closest to the timing cover.
The cam gear is on top/ and the crank gear is on top. Both at 12:00.
The timing mark on a 3400 Chevy Venture engine is typically located on the harmonic balancer and aligns with a pointer on the engine block. For proper timing, you need to set the mark to the specified degree before or after top dead center (TDC), depending on the engine's requirements. Refer to the vehicle’s service manual for the exact timing specifications and procedures. Always ensure the engine is at the correct operating temperature when making adjustments.