I recently rebuilt my engine, 396 (+.030) using comp's EX268 which I like at this point. I am still running the stock 396/325 distributer which will be upgraded later. I am confused about the best timing for this engine/cam combination. I would like to know what the best inital and total timing has been for anyone using this cam. Thx.

The original specs are going to call for something like 6* or 8* BTDC, but your gonna find that the engine is going to like 12*-16* BTDC initial, depending on the quality of the fuel available. This is about the time of year that stations start changing their blend (winter oxygenated fuel sucks).

Total timing is likely to be best in the 36*-38* BTDC. The more agressive your driving habits, the earlier you'll want it all in. If you tend to do alot of "load" driving, don't rush it so much (especially with sh!tty gas) 2500rpm is a good place to start.

When it comes to timing some of the specs are much more critical than others.

For example total timing of 36* or so all in around 3000 RPM without vacuum advance is critical. Now some may argue with 1-2* more or less timing and some may argue that a different RPM is better, and in certain circumstances they may be right. But these specs will get you pretty close in most circumstances and are not dramatically affected by cams and such (they are more a matter of combustion chamber and valve design).

Next most critical is cruise timing. This is with some or all mechanical advance plus full vacuum advance. The number to shoot for is 50-52* here. If you have full mechanical advance at cruise, this means you need no more than 16* from the vacuum advance (8* distributor).

Below these two things get much more variable and also much more subjective.

In general your initial timing, again without vacuum advance, will be set by where you put your total timing. Whatever amount of mechanical advance you have, subtract that from your total and there is your initial. Thus initial is whatever it happens to be. UNLESS you modify the mechanical advance to increase/decrease the total advance movement.

In many cases a motor will want more advance at idle than the initial setting. Here you have to look at vacuum at idle and vacuum configuration of the vacuum advance can. You want the vacuum can to provide full advance at 1-2" less than vacuum at idle. Then if you connect it up to manifold vacuum, rather than ported, you will get full vacuum advance added to the initial at idle.

This can make a very big difference in idle quality especially with bigger cams.

Joe,you need to run approx 16-18 deg btd intial timing with that comp 268 cam.

As mentioned above you may need to have your dist recurved to limit the mech to approx 18-20 deg for a total of 36-38 deg btdc not inc vac advcance.

Listen for detonation during this dialing in process back of he intial timing a deg or 2 to stop it if you hear it.

Scott