total timing is set at what rpm

StrokerScamp said
LOL. You're preachin to the CHOIR and don't even know it. Let me break it down for you. "I" don't worry about initial timing. It's irrelevent. All you need is enough for the engine to run so you can set the rest. I remove the vacuum hose from the can and run an extension to a vacuum gauge taped to the windshield. I note my vacuum reading in high gear at 2000 RPM while just cruising. It is at this point that the timing should be all in.....at least for "me". Then, I go back to the driveway, disconnect the hose and reconnect to the vacuum can and take a timing reading at whatever reading I got on the vacuum gauge. It will of course be at a higher rpm, since we are now static in the driveway and not under load. This is why you don't use a tach to set timing. I let the mechanical advance in the distributor alone. I simply limit the vacuum can to whatever I want the total timing to be at at whatever given vacuum reading I got on the test drive. This is actually the most accurate way. While it's true you can play around with the mechanical advance some, I have found through the years, very little performance advantage in doing so on a street car. Of course, if using only a mechanical advance distributor, you must address adjustment, since that is your only means of advance. I have only on one or two occasions in better than thirty years found it necessary to adjust mechanical advance in a distributor using a vacuum can. I've read all the books. I've spent time at the tracks. I've set it to the inth degree as described above, but this method has worked best for me. It will on any street car, too. It's a good shortcut that will get you so close if not right on top of the technical guy's timing, it ain't funny.

Your post is confusing and could tend to mislead folks trying to set up a distributor on a significantly modified engine.

The mechanical advance is rpm dependent and vacuum advance is load dependent. Together they do a pretty good job of providing the timing the engine needs over it's operating range. For full out performance the mechanical advance is the only thing that matters because in these situations the throttle is open and there is little or no manifold vacuum and the vacuum advance does not work.

If your engine is close to stock the way the distributor is set up from the factory is close and what you describe is OK. But if significant modifications have been made then you need to take structured approach to dialing it in; initial, mechanical, rate and vacuum will all need to be addressed. The process I described in my post will minimize the interaction between these and minimize the back and forth fiddling.

To say initial timing is irrelevant is simply wrong. If you don't care about a stinky rich idle that you can't adjust out, or having to set the idle in park of your auto car at ~1200 rpm to keep it idling in drive at 700, or you don't care about sluggish response off idle then by all means ignore initial timing. Of course if your engine is basically stock setting the initial to the factory number or reving the engine until the mechanical stops and set the total timing you are close. But if you have made significant changes to the engine especially in cam duration/overlap then it just won't run as well as it can if you don't.

If you have significantly changed the initial timing then you need to address the total mechanical timing or in most cases you will have more timing than the engine needs to make max power and can also create detonation problems. Also, if you have replaced your old school heads with modern heads with efficient chamber designs you will need to address total mechanical since in these heads typically require less than the old school heads.

The rate at which the timing comes in is a place where the factory made significant compromises to address the bad driving habits of the people that purchased these cars. They gave up performance to protect the engine from detonation folks using the wrong fuel or lugging the engine or general poor care. Speeding up the rate with lighter springs even on a stock engine will give you noticeable improvements in the performance.

After all these items have been addresses you can adjust the vacuum advance.