I have a 383 stroker motor with a set of vortec heads, 480 lunati cam, flat-top kb pistons, and a 750 holley. At first i had bad spark knock but fixed that with thick copper head gaskets to drop the compression. I am having trouble getting the engine to run smooth and I don't know where to set the timing for one i just turned it by ear till it quit jamming the starter. Does anyone have any advise that may help me.  

I'm running a 383 in a Malibu Wagon. Set the timing initially at idle or about idle to around 16 degrees. then adjust the carb to bring the idle down. Recheck the timing again then reset it again to 16 then readjust the timing again. I found the more timing you nput in it the more you have to idle the engine up. my car likes 16*. I idle at about 750 to 800 in gear  and neutral. My cam is a little bigger. 519/525 lift. You may have been getting the knock from too much timing and too low octaine fuel. also what do you consider smooth idle. a 480 cam will give the motor a little lope.    

Lots of reasons why an engine doesn't run smooth, one is too much advance, which can also cause the detonation problem you described. Advance breaks into several principle areas each needs to be addressed and finally integrated into a running package.

I'll start at total advance and back thru the elements that need to work together. There is some point of total advance where the engine will develop it's best power. This is variable with combustion chamber shape, sparkplug location, ratio of fuel in the fuel air mixture, altitude/air pressure/humidity/temperature, exhaust efficiency including any pressure wave generated by the headers, gear ratio both through the transmission and overall ratio, and vehicle weight. All these elements and some I probably didn't mention have an effect upon advance bot in total amount, rate at which it's put in or taken out, and the ratio of the base (initial) setting to the amount that is built up by the counter weights/vacuum/ or computer program. The end result most likely will be that the ignition advance will not and cannot be that which develops the ideal maximum power setting. Too much causes detonation and power surging.

Backing away from the concept of total advance, which will usually be in the upper 30 degree range to maybe the lower 40s mostly in by 3000 RPM, is the division of total into a proportion of some amount of base or initial setting to how much and how fast the remaining advance is put in by the fly weights or computer program. Here total is a limited amount, your first problem is to determine which the engine within the constraints of its installation wants between X degrees of base and X degrees of adjustable. If you start with a total setting of 36 degrees and the distributor/computer is designed to have a 10 degree initial setting, then there will be 26 more degrees of advance that comes in by what ever automatic comtrol function being used. If, for example the engine pulls weakly on the bottom end, it could be decided to add to the inital advance. Lets say the decision is to bring the inital base setting to 16 degrees, this means that the variable advance needs to be reduced by 6 degrees to a maximum of 20 degrees. If this adjustment in the variable advance is not done the total advance would become 42 degrees which will push the combustion chambers into detonation and will also cause spark surge that results in an unstable running of the engine. The variable advance would also need to be adjusted to accommodate a change in the base/initial setting that reduced the advance by 6 degrees. In this example if inital/base was reduced to 4 degrees, the 6 degree reduction would have to be added into the variable timing to back to the defined optimum spark lead of 36 degrees. Otherwise the total timing would fall to 30 degrees which would reduce total available power and may result in overheating the exhaust system if not the engine because there would be insufficient time in the combustion chamber for the burn to complete, so the reation finishes in the exhaust system, which is OK if this were a jet.

There are 3 different types of advance mechanisms out there, mecahanical, vacuum, and computer. The most common on older cars and favored by hot rodders is the older method of controlling variable advance with a mechanical flyweight system that may also include a vacuum system. Electrionic controlled engines, usually with fuel injection, have the advance mapped into the computer chip that controls the engine. In the latter case the distributor is usually set at 0 degrees and the computer controls the base and advance timing setting by reading a program the deduces the proper advance from sensors that feed it information on air temperature and density and engine loading (most similar to vacuum advance), and engine RPM, road speed and transmission gear selection (most similar to mechanical advance), as well a sensing detonation and making running changes to accommodate its elimination. The computer system is extremely effective and has become pretty much standard in NASCAR and the various internation formula type race engines as it does a much better job at matching the engine's changing requirements to the best advance rate for the situation. Mechanical, which we are most familiar with and seemingly partial toward, simply moves a distributor "cam" (whether that "cam" opens points or magnetically/optically effects a Hall Sensor, magnet, or light/laser sensor) by using spinning flyweights against spring force. By changing the flyweight mass, spring strength, and including a positive stop mechanism, the rate and maximum amount of advance is controlled. This type advance only is sensitive to engine RPM it doesn't understand the concept of engine loading. For example, if the engine turns 3000 rpm it gets maximum advance whether that 3000 RPM is done in your garage, out of gear and standing still, or if your going up a mountain in 2nd gear at full throttle, towing a 4000 pound trailer. Vacuum advance is used to control advance in proportion to engine load. But its really a crippled system as there are many situations it cannot respond to so its minimum purpose is to provide additional advance when the engine is under light load. The low real compression pressures of a throttled engine cause the mixture to burn slowly while manifold vacuum is high. This reduces power and causes you to compensate with more throttle which in turn uses more fuel than the conditions really warrant. By increasing low speed, mostly closed throttle which creates a high vacuum, timing a substantial improvement in burn rate and quality is achived. This develops more power on less fuel thus increasing efficiency. When properly installed the vacuum advance receives its signal from a timed port in the carburator's throat close to, but slightly above, the throttle's closed position. When exposed to high vacuum by slight throttle opening, the system applies advance. As the throttle is increasingly opened manifold vacuum is reduced and the vacuum advance is likewise reduced. The theory here is that RPMs thus mechanical advance are increasing with the throttle opening which reduces manifold vacuum and thus the amount of vacuum advance. The basic defficiency of this system can be seen when going up that mountain grade with a load in 2nd gear. It's possible to get into a situation where there is insufficent RPMs to maximize mechanical advance and too much throttle opening to get vacuum advance; power falls off and you start searching for a lower gear to get the revs and the advance rate up to where the engine is making power again. So you can see that the mechanical/vacuum system under many operating conditions is a very gross approximation of what's needed. Modern computerized system are much better at keep the advance amount optimized for operating conditions, which is a major reason why these engines get such good power and mileage compared to their older versions.

I haven't even got to the carb and it's potential contributions to your problems. But that's got to wait for a later time.

Oh one last thing, vacuum and mechanical advance should not be additive to each other. One should work for low speed high vacuum situations the other for high speed low vacuum situations. But as we've seen there are cross over areas where these systems can be fooled.

Bogie 

Thanks for the advise and schooling. I am running a Vacuum advance HEI. At the time being i am idling about 950 in park and 550 in gear i have no vacuum leaks so the problem has to be in the timing/carb setup please help as you have time.