n00b question from a 57 year old

New to working on cars, other than changing plugs, oil, brake pads, etc.

What is re-curving the distributor? And why/how do you do it?

Thanks.

 

Well...you know how the distributor shaft is straight? You wanna put a curve on that thing to make it look cooler under the hood at car shows.

just kidding...
Recurving a distributor means changing the springs and weights inside the distributor. Typically, it’s done so that changes in ignition timing happen at a desired RPM, i.e., an advance in timing to take advantage of the “sweet spot” an engine has at a given RPM. Essentially, by changing the weights and springs to a more responsive setup, a change in timing can be brought into play when the engine is more able to take advantage of it.

of course, there are PhD level engine guys on this board, and my explanation may be childish in comparison. I’ll defer out of my immense respect for them.

 

Check out Larry's explanations in his "Power Timing" thread. It's a sticky in the Buick FAQ section.

Or click here......https://www.v8buick.com/index.php?threads/power-timing-your-buick-v8.63475/

 

Here is a rough graph to show you the idea. We start out with the initial timing setting and then inside the distributor is a set of weights and springs that allow the timing to advance as the RPM changes. The distributor has a designated amount of timing that it can add on top of the initial timing setting. The weights and springs allow the timing to gradually increase as the RPM raises. Changing to different weights and springs can change how quick the timing is added. Bushings can be added to the distributor to limit the amount of timing that is added.

The quicker the timing can be added the better the throttle response and fuel mileage, up to a point where the spark coming in too early and causes damage to the engine through detonation. So we normally experiment and get the timing coming in quicker than stock while ensuring there is no detonation by checking the spark plugs for signs of detonation or using a knock sensor. If we are happy with the timing curve however it is detonating at the top of the RPM range then we will either lower the initial timing or preferably adding bushings to limit the timing.

 

what happens to me on aggressive advance curve on pump gas is trying to balance the curve for no detonation. you can't always hear the detonation but the car will go slower.