Thread: hard start timing issues

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ok guys i have a 427 lower compression engine, when i setthe timing where it runs well it drags the starter and wont start back it off where it starts it doesnt run worth a flip. It has a mini starter with no shimming issues and new msd street fire distributor wth adjustable vac advance. i have the advance adjust as far as advanced as possible with direct vaccum so when it starts it pulls alot of advance the distributor has the factory set heavy springs. i have the distributor set at number one with the piston set at 4 deg like all the service manuals say set the base timing around 18 like the manuals say it starts with ease but runs horrible set it up further around 22 25 runs great but drags bad and kicks back. am i missing something? thanx in advance.

FIrst, fire up the engine and bring it to full operating temperature, remove the vacuum line to the distributor and plug it. Advance the initial or idle timing 2* and shut it off, let it sit for 1-3 minutes and allow the engine temp to spike. Now try to start the engine...is it trying to pull the starter down? (Like a dead Battery) On the other hand, is it kicking backwards and blowing air up through the carb? If not repeat the procedure adding 2* at a time until these conditions appear, now back it down 2* and you have determined the total initial timing the engine combination can handle. This is where we want your initial timing to be set.

The second timing event is what we refer to as “Mechanical Advance”.
This part of the advance curve is controlled by Engine RPM only and has nothing to do with load on the engine or cylinder pressure, it’s simply RPM activated through the weights and their retention springs. Sometimes this is referred to as “Centrifugal Advance”. When we add the static or initial timing to the amount of Mechanical timing we get what we refer to as Total Timing. So if we set the initial at 10* and allow the weights to pull in another 25* of timing we would have a total of 35* of timing at the RPM where the weight travel is maximized or they hit what we refer to as the Advance Limiters.

The third and final timing event and probably the most misunderstood is the “Vacuum Timing”. Vacuum timing has nothing to do with total under load timing or performance tuning. Vacuum timing is controlled by “Manifold Vacuum”, as soon as you accelerate the vacuum in the manifold drops and the Vacuum Timing is released and the timing events are then controlled by the Mechanical and Initial timing settings. So to achieve this, the vacuum unit is connected to a “MANIFOLD or CONSTANT” vacuum port and can be set to add anywhere from 5 to 20* more timing in the motor when high vacuum readings or low load conditions are present.

So now to calculate the total timing at idle or low load we add together the static or initial, the Vacuum timing and whatever mechanical timing we have based on RPM. Going back to the previous example you would add the 10* initial setting and say 15* of Vacuum timing for a total of 25* at idle or low load, low RPM cruise. Because the vacuum timing is progressive to and directly related to manifold vacuum as the manifold vacuum increases (Light Load) or decreases (As you accelerate) the timing in the motor changes accordingly to keep the efficiency at optimum. The mechanical timing will come and go as engine RPM increases or decreases.
Hope this helps.

so if im reading this correctly the vaccum advance is basically for idle and the mechanical is for higher rpm advance?

It works from Idle up to WOT. It is variable. Doesn't effect start up unless it is stuck.

i didnt think an engine especially with a big cam had much vaccum at wot?

thanx guys think ive got this part figured out