Vacuum Advance and why to use it on the street

[PxTx]

It can be tough to tell when an engine is pinging. It isn't always audible. Pinging on throttle can be bad enough to be heard but not always. I'm sure many know this, but I figured it is worth mentioning. My point is that you can have a car that is beleive to be in a good state of tune, but pining is occuting. Just because it is being driven and seems to have good power does not mean there is not room for improvment.

I didn't want it to be overlooked that pinging can also occur off throttle when the VA is too much. That is why it is best to limit the VA to 10 degrees on cars with a "Hot" camshaft. I'll qualify a "Hot" camshaft as being over220 degrees @ 0.050. These will like more initial advance and less mecahnical for a total of 32-36 degrees. Running the stock L78 VA with todays fuel can cause pinging off throttle and may not be audible.

Just to clarify Keith, these adjustable VA canisters you are refering to do not adjust the # of degrees, correct?

I would say the majority of the cars we discuss here are best served with a VA with no more than 10 degrees of advance when run on todays fuel. We can discuss the rest of the tune, but that is a key component for optimizing these cars for street duty with as little performance sacrifice as possible.