Just did 2 to 4 bbl swap car starts wont stay running please help
This is a dumb question but how will i know the mechancal advance is all the way in? Still new to this stuf tryin to learn all i can
No such thing as dumb questions LOL,
basically Ignition timing consists of 3 parts within the distributor that have to work together to make the engine run properly throughout the rpm range, and during different driving conditions. I'll try to keep it simple ha ha.
There are 3 parts to the distributor timing; initial timing, mechanical timing and the vacuum advance canister timing.
First initial timing:
this is the timing of the distributor at idle (around 750rpm). It can be changed by loosening the distributor lockdown nut and moving it clock-wise or counter clock-wise to either retard the timing or advance it.
Mechanical timing:
there are small weights in the distributor that as the engine RPM increases get pushed out (called centrifugal force) and due to these moving weights extra ignition timing gets added to the initial timing. (this is engineered this way since the engine needs different timing settings at different rpms)
Vacuum advance timing:
this is the vacuum canister that is attached to the distributor and has a rubber hose that is plugged into a ported manifold port on the carb (the port above the carb throttle blades). This adds additional timing to the initial and the mechanical timing to help out with better fuel burn during certain engine operations like highway cruising or diving up a steep hill when the engine is under load.
When you are setting your timing you want to make sure your vacuum advance canister is disconnected and the port is plugged off (so that you get a proper reading while setting your initial and mechanical)
Every engine is different and since we all use different than stock parts (cam, headers, aluminum heads etc.) it is impossible to give the exact timing numbers that your car would need but as a good starting point it is pretty safe to have:
10 degrees initial timing (at idle) and a total (initial+mechanical) of 34 degrees.
At what point all your mechanical advance (the weights in the distributor) comes in depends on what they call the
advance curve. The mechanical weights have springs attached to them and at what rpm the weights reach their max travel depends on the strength of these springs.
To check at what RPM you have all your mechanical advance in; you'll have to have either a dial-back timing light or a degreed dampener. A tach would also really help.
Bring the rpms up and check at what point the timing mark on the dampener stops moving, that is the rpm when the weights in the distributor have reached their maximum travel (make sure the vacuum advance is disconnected). Now you can set your timing at that rpm to 34 degrees, If you bring the engine back to idle (750 rpm) it will probably show around 10 degrees of initial timing (no mechanical advance since the engine rpm is too low)
Sorry for the long post guys, I probably should have just sent you a PM.
