Ignition Timing

[molyorange 77]

This might need to go to the engine forum, I bought a performance distributor from Davis Unified Ignitions and I'm a little confused on what to set the timing at. Here is the engine specs chevy 388 6" rods flat top pistons comp cams XE294 grind, It reads 175 cranking compression on all 8. They are telling me to set initial timing at 10-12 degrees and the dist has 22 degrees built in and the vacuum can add as much as 15 degrees for a total of up to 49 degrees. This sounds like alot does anyone agree. Let me know what you guys think or If any of you have a similiar engine what do you run. When I ordered the distributor I gave them all of the engine specs to build it for this application.

[molyorange 77]

Wrong forum, I guess.

[68Formula]

Vacuum only comes into affect when you have light loads not WOT, so 49° is fine. It should be adjustable by inserting an allen wrench into the can (at least most aftermarket are). This way if you have part throttle pinging you can dial it back. Between 50 and 56° at cruise is possible.

Mechnical-wise if you start with 12 degrees and have 22 degrees centrifugal then the total of 34° is safe in most cases. Also depends on what rpm it reaches max. Usually you want it all in between 2500 and 3000rpm.

The main factors which will determine maximum timing are cylinderhead design, bore, compression ratio, gasoline octane, air/fuel ratio, engine heat, and boost when applicable. How fast it should ramp in is dependent on those factors plus camshaft specifications.

You need to have a little more patience. Next time give it at least 24 hours. Some of these child forums just don't get the traffic as much as others do. Putting it in the wrong one would not be acceptable either. If it's a real emergency, then post it in that section.