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Wed Jun 11, 2014 4:46 pm

Why do we set all in timing at or by 3000 RPM when the original distributors on factory engines had as much as 34 degrees capable. What happens after 3000 rpm at say 30 degrees btdc. That might be the safe setting but I occasionally go over that. On MSD distributors the silver spacer I would think is best choice and set it at 30* btdc at 3000 rpm. That would give you another 4 degrees to use above 3000 rpm. Why do we want the timing to stop changing at 3000rpm ?

Wed Jun 11, 2014 8:35 pm

With most distributors with mechanical advance timing is set after full mechanical advance is at full advance - and full advance is set by the distributor's weights and springs. And full advance may or may not be all in at 3000 rpms. Some mechanical distributors are at full advance at as little as 1800 rpms - most are at full advance by 3000. Timing at full advance is the preferred method with SVDA distributors too. Simply remove the vacuum from the dist and rev until the timing marks stop advancing - set timing at 28-32 lock down the dist - connect the vacuum hose and you're done.

With a vacuum only dist it needs to be set according to the year/model at idle with a timing light - or with a static light by rolling the motor past the timing mark while observing the test light - ignition on of course.

Wed Jun 11, 2014 10:20 pm

The very simplified answer is that spark timing needs to be advanced as the revs climb to compensate for mixture burn time. However, as revs climb and load increases, conditions in the combustion chamber change and for many reasons, in most engines, there is no need to advance timing any more past ~3000 RPM. These are general terms but apply to a surprising amount of different engines under different conditions.
Hope this helps.

Thu Jun 12, 2014 4:01 am

So with the factory distributor having something like 34* advance which brought it another 4 or so degrees into rpm above 3000 the best thing to do is keep a eye on temps and air fuel mixtures. Thanks for the inputs. I want to try the silver bushing in MSD distributor but will have to keep close eye on it

Fri Jun 13, 2014 5:22 am

Actually many OEM distributirs had over 40º total advance. But that's including both mechanical and vacuum advance. You lose vacuum advance at full load, and full load timing is the most important for both performance and engine life. So you disconnect the vacuum advance before adjusting. Vacuum advance helps increase fuel mileage.

Fri Jun 13, 2014 11:36 am

Thanks for the info. Am I risking by using MSD distributor ? Besides the normal flack....

Fri Jun 13, 2014 5:50 pm

MSD distributors are 'ok'. Personally I'd never buy one but if I had one I'd probably use it. I like the stock SVDA style myself. I use one thats been altered on my 2110 with excellent results.

Sat Jun 14, 2014 7:30 am

diferent combos&tunes,driving style,load,location,fuel,exhaust,induction,etc require different curves. for me I like a smooth curve that is all in by 2033~2246 rpm with a base idle timing of 14~16. total of 28~32 for acvw with a turbulant chamber.