Hot rodding the HEI distributor
(Add text) |
m |
||
| Line 182: | Line 182: | ||
*'''Total timing''' is the initial timing plus the mechanical timing. | *'''Total timing''' is the initial timing plus the mechanical timing. | ||
*The '''vacuum advance'''- while important- is usually considered separately from total advance in most discussions on setting up a performance timing curve. In other words, you might hear "the engine runs best with 38 degrees total advance". That's '''initial''' plus '''mechanical''' advance; the amount of vacuum advance isn't added to that figure. | *The '''vacuum advance'''- while important- is usually considered separately from total advance in most discussions on setting up a performance timing curve. In other words, you might hear "the engine runs best with 38 degrees total advance". That's '''initial''' plus '''mechanical''' advance; the amount of vacuum advance isn't added to that figure. | ||
| + | |||
| + | ==Disclaimer== | ||
| + | Because this article came from several authors, the statement of having about 50 degrees combined advance (initial, mechanical, and vacuum) at cruise rpm can be a bit misleading. That's the max some tuners would ever want to see, and some recommend using less- somewhere around 46 degrees combined advance would be perfectly acceptable in many cases. | ||
| + | |||
| + | The same holds true for the exact amount of initial and mechanical timing. It is all but impossible to give ''exact'' numbers because of the variations in engine builds and conditions in which these engines run. | ||
| + | |||
| + | But any way you slice it, it's still trial and retrial to get the curve dialed in. No matter what we do (short of digital control), the timing curve is always somewhat of a compromise, being as how all engines and vehicles (and all the other considerations) are different from case to case. So don't be surprised or alarmed if you end up with a curve that is different from what is presented in this article. | ||
==Tuning the advance curve for performance== | ==Tuning the advance curve for performance== | ||
| Line 277: | Line 284: | ||
So say the mechanical advance at 2000 rpm is 12 degrees. The max mechanical at 3000 rpm is 18 degrees. The "missing" 6 degrees can come from the vacuum advance. One thing to watch out for by using more vacuum advance is the engine can 'surge' at elevated advance settings and also there's the chance it will have a transient ping when hitting the throttle quickly when the vacuum advance is all in. That said, being as how we're only talking about 6 to maybe 8 degrees added vacuum advance, there's a good chance there will be no problems at all from using more vacuum advance. | So say the mechanical advance at 2000 rpm is 12 degrees. The max mechanical at 3000 rpm is 18 degrees. The "missing" 6 degrees can come from the vacuum advance. One thing to watch out for by using more vacuum advance is the engine can 'surge' at elevated advance settings and also there's the chance it will have a transient ping when hitting the throttle quickly when the vacuum advance is all in. That said, being as how we're only talking about 6 to maybe 8 degrees added vacuum advance, there's a good chance there will be no problems at all from using more vacuum advance. | ||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
==Example of a "typical" performance ignition advance curve== | ==Example of a "typical" performance ignition advance curve== | ||
Your Privacy Choices