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sundown
07-18-2014, 02:30 PM
I want to check the ignition timing this weekend I have an older craftsmen timing light and rpm/dwell meter I have removed and blocked off all of the emissions stuff the distributor is capped also. I read somewhere in the forum you now need an advance timing light does that mean the one I have is nogood

TR3driver
07-18-2014, 04:44 PM
Not really necessary. The pointer on the engine should be marked with the "static" timing point (10 BTDC in 73), which is where you want to set the initial (idle) timing if the retard is disconnected or non-functional.

If the pointer is missing, you can add the marks to the dampener yourself. If you suspect that the dampener might have slipped (they do sometimes when they get old), then you should probably start by verifying TDC with a piston stop and work from there anyway.

PS, Or no doubt Ken will be along soon to explain how to set timing with a vacuum gauge :)

Geo Hahn
07-18-2014, 05:11 PM
Without an advance feature on your timing light you can still set the timing for speeds beyond idle. On one of my engines this is how I routinely set it -- start with the diameter of the pulley, use your 8th grade math to work out how many inches (or mm if you like) of the circumference equals the timing your distributor should have when it is all in (high RPM. no more advance possible). Make a little white paint mark on the pulley at that spot and that becomes your timing mark for the max advance.

The nice thing about this method (on the engine I use it on) is that vacuum advance, vacuum retard, and all other bits and bobs can remain connected as you're only interested in the final number. Of course, you still have to find out what ideal total advance should be on your engine.

As noted, a piston stop can be useful if there is any doubt that your timing mark/pulley is not right. A simple one can be made from an old spark plug and a long bolt:

https://i1214.photobucket.com/albums/cc499/Ahwahnee18/TR4/PistonStop.jpg

poolboy
07-18-2014, 06:59 PM
Yes, Randall knew I couldn't resist chiming in on this.
I do think comparing the engine performance using both a timing light and a Vacuum Gauge could be interesting.
https://i233.photobucket.com/albums/ee300/poolboy_album/TR6banjo.jpg (https://s233.photobucket.com/user/poolboy_album/media/TR6banjo.jpg.html)
A 73 should have a banjo fitting like the fitting in the middle. The big nipple is for the brake servo Vacuum and the nipple pointing to the right is for the Anti Run-on Valve. That's the one to connect the Vacuum Gauge to.
You'd like to see manifold Vacuum around 17 to 18 in-Hg at idle speed of 850-900 rpms....if you have a stock cam and if you are at sea level.
Once you get that combination, you are getting close to if not dead on your engine's ignition timing sweet spot...
PLUS..the reaction of the Vacuum Gauge needle will indicate certain abnormalities in the condition of your engine
LINKS:
https://www.centuryperformance.com/forum/showthread.php/42-Engine-Tuning-Using-a-Vacuum-Gauge
https://www.secondchancegarage.com/public/186.cfm
AND a VIDEO:
https://www.youtube.com/watch?v=utUSI-JYhVU