302 timing

[moar_carbz]

Originally Posted by 1795

Gary is right in that Webers require different timing than a 4 barrel carb. They like a lot of advance and they like it early. I would pay attention to what he asks and says, I have followed his posts and the advice is typically good.

I would say that Webers don't "require" different timing than other carbs, but rather that other carbs can't handle the timing that Webers work well with.

What I mean is this. With typical setups of 4-barrel carb and manifold, it's not unusual (we might even say quite common) to have different cylinders getting different amounts of air and different mixtures. Some cylinders could be running rich, (11:1 AFR) and some could be running lean (17:1 AFR) at the same time, but even a modern sensor in the exhaust is only going to read the combined result of all this and give you whatever number in the middle it figures it's seeing. This also results in emissions that really are dirtier than necessary. Because of this mixture disparity, too much timing is going to cause detonation problems really easily, so you can't throw too much timing at it. With your typical Weber setup, you can more reliably get every cylinder to have the same airflow and same mixture under any and all conditions. It's a more ideal situation that the engine is seeing and it will respond well with a lot more timing thrown at it. If you want to, once the carb jetting is pretty close, you could go to a dyno shop and tweak and tune everything, including seeing just how much timing the engine is willing to take.

To the OP: a lot of people do well with 34 to as much as 36 degrees of timing all-in. But as stated elsewhere in this thread, once your timing is at a safe ballpark setting, let's chase down your mixture situation. Buckle up.