Timing points ignition

[400brian]

Has anyone ever put a timing light on a points ignition engine? How much do you allow for the mechanical advance?
I can't find any reference to this in the book. The 72 340 is timed at 23 thou BTDC, and at 2000 rpm I'm seeing around twice that. I'm having problems feeling good with results I'm seeing with the flashlight tester.
As the engine dies, the timing drops down around the 23 thou, which sounds good, but its not running all that impressively.

[HoosierDeereMan]

Brian,

I have no idea what total advanced timing would be.

I know this is a points engine but on the cdi engines they tell you to run the engine at 4,000 RPM and check the timing with a light. By doing that it eliminates any timing changes by the governor weights at the slower RPM. Would the same not apply to the points engine??????? Also do you know where #2 is firing? How close is it firing in relation to #1 cylinder? I've never been able to get them to fire dead on at .023" but usually within .005" of each other. Dinosaur Dan had a in depth conversation with us in the UP on trying to tune a engine while running higher oil ratios for engine break in period. It was over my head but I caught bits and pieces. It really effects the octane rating by oil fouling the combustion charge. Whichin turn effects how crisp or responsive a engine runs.

How does it feel to have gas running all over freash paint and see black goo running from fresh painted exhaust joints? Remind me why we all do this again

Good Luck and keep us posted.

Troy

[JDT]

Am I incorrect in thinking that the mechanical advance mechanism is only there to aid in starting the engine?

With a recoil starter you are not able to spin the engine as fast as it would turn at idle therefore the mechanical advance is there to make it pop easier.

Once over 3000 RPM the advance does nothing.

Have I been wrong all these years?

[400brian]

I think you are correct to a point. My recollection is that as the engine would spin down, you'd hear an audible click, and then it would die. I've always assumed that was the advance snapping shut.
But; when you static time the engine with a light to a certain distance BTDC, that is with the advance closed. Once running, the advance would be in play. Wouldn't you need to know how much the advance was adding to the total to check the timing with a timing gun? The CDI engines have no mechanical advance, so timing with a gun is straight forward. On a points ignition car, you'd time it with the idle low enough that the mechanical advance would not yet be opened, and you would disable the vacuum advance while doing it.

On my X8, the test light would dim very dramatically when the points open, pretty much a no-brainer. On the 72 400, I'm just not getting anything as clear cut at all. The light flickers, dims momentarily, and you can't always get it to do it in the same place. Nothing at all like the X8.