Just wondering if some one has information, or preferrebly a schematic of the timing curve for a stock HEI, Hei distributor is out of a 1978, it is installed in a 1966 Chevelle 396SS.
Any help would be much appreciated.

 

The HEI came with numerous timing curves and configurations...

What are you trying to get at....

What all do you have in the 66 396? gears, tranny type, (if auto, stall speed), tire size, compression, cam specs, intake, carberation, what do you use the car for, (racer, daily driver etc..)



G

 

The '78 is a computer ( although crude ) controlled distributor. All distributors have four things to look at. The rate of advance ( spring pressure ),amount of mechanical advance ( distance the slots below the weights move ), the vacuum advance amount ( distance the vacuum lever moves ) and the vacuum pressure amount ( amount of vacuum needed to move to full vacuum ). All of these things are important to distributor advance and all are engine design related. You need to test the engine vacuum to determine how much pressure You have to work with for the vacuum advance. If it's a performance engine with a pretty big rear gear, You need to advance quickly and this is controlled by the springs. The mechanical and vacuum amountl is what Your distributor has for total advance. The vacuum works at low RPM and retards the distributor for idling and low RPM application. It goes away as RPM's go up and vacuum goes away. At this point You have only mechanical advance to work with. This is why You time Your Engine with the Vacuum advance disconnected. The combined Mechanical and Initial ( where You set Your timing with a timing light ) is Your total timing. A professional who has a Sun Distributer machine can properly recurve Your distributor for Your application. If You cannot find anyone in Your area, call Tommy Kendrick at (210) 337-0838. He's the best I've ever found at doing this. You can ship Your distributor to him or or just have Him build one from His stock.