I have a 1969 GTO with the YS 400 engine I set the timing at TDC now I can't get the car to stop backfiring.

Answer 1

that's because the timing should be set BTDC not at it. First make sure your Dwell is set right--or set your points with a feeler gauge. then make sure your idle speed is correct (see if your spec if an automatic--and if it should be set in gear). Remove the vacuum advance. then set your timing to somewhere between 8 and 10 degrees before top dead center. this depends on how stock and what kind of fuel your using. The Ram Air 400 in my 1968 Firebird uses 120 -132 octane and is anything but stock and sets at 18-20 degrees before top dead center.

Answer 2

With the vacuum advance hose unplugged from the vac. advance on the dist. and the motor idling, set the timing to around 8 degrees before top dead center. Then check the performance. All motors can go with more advance as long as you don't start getting pinging or backfiring. If you go too far, you will have to retard it a little. It will all depend on your particular gas quality being used and the elevation you are running in as to how much you can advance the timing. Also make sure the mechanical and vacuum advances are working properly as these can cause you grief as well as power. Good luck.

Answer 3

Are you sure you have the spark plug wires in the correct order? Some of the older models are set a bit off TDC. Did you check the line up dots on the timing gear before installing the timing chain?

Answer 4

it needs to be before top dead center. i am not sure of the setting but i would try 7 degrees before top dead center, then adjust as needed. you can call autozone and they can give you the timing setting.