Dial back timing light - how do I use it. [Archive] - Chevelle Tech

: Dial back timing light - how do I use it.


66velle
Feb 9th, 02, 1:38 PM
I have everything hooked up and ready for use. How do you use the timing light dial back feature? How do I get total timing with a a stock 350ci 250 hp with a 4 barrel carb, HEI distr, with an auto tranny? What would be good for what I have? What do I add to get total timing and how do I achieve in getting it? I have my initial set at 8 degrees. I do have weights and springs if needed.
Thanks,
Stan

70L34
Feb 9th, 02, 2:21 PM
A dial back light delays the strobe light in the amount of the # of degrees on the dial. With a conventional light, in order to check total timing, you'd disconnect the vacuum advance, rev the motor to 3000rpm (that's usually fast enough to ensure the distributor timing is maxed out), and you'd pull the trigger to check timing. Chances are your timing mark is way beyond the 12 degrees or so of your timing "tab" (the degree marker mounted to the front cover). Now, with a dial-back light, and the engine at 3000rpm, turn the dial clockwise and you'll see the timing mark on the balancer "retard" and move closer and closer to the 0-degree mark on the timing tab. Keep turning the dial until the timing mark lines up with the 0-degree mark, check to see how many degrees you've dialed in on the light, and that's your total timing. Easy!

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Tony Nausieda
1970 SS 396-4??hp
1977 Caprice, no dingle balls or hydraulics
1966 Buick GS 4-sp vert
1965 Le Mans EFI'd 468, 4-sp
1639 total cubic inches :)

Barista
Feb 9th, 02, 2:41 PM
I've been told that the dail back lights are not accurate with HEI ignitions. According to Ignitionman they will usually be off by 4 or 5 degrees at 36 degrees advance. The only way to be certain you've got it right is by putting a degree tape on the balancer and using the light "straight up".

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Bob Von Kaenel
70 SS 402ci TH400

DjD
Feb 9th, 02, 3:27 PM
Bob - I may have mis-understood but I thought it was just MSD boxes that dial back lights didn't get along with. Most HEI's should read fine. On the MSD site they speak of the problem with their ignitions systems...

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...Dennis
The '69 (http://chevelles.com/showroom/fine69_03.jpg) & the '96 (http://chevelles.com/showroom/fine69_02.jpg)
Team Camaro (http://www.camaros.net)
Camaros Limited (http://www.camaroslimited.com)

66velle
Feb 10th, 02, 11:15 AM
Thanks to Tony and everyone. Went to the Pro Bowl yesterday and will do my testing today.
Stan

66velle
Feb 10th, 02, 8:14 PM
When I dialed it back I got 40 degrees total at 3000 rpm. When I changed to a a lighter spring the initial timing just up from 8 to 16 degrees. What's up?
Thanks

sschevyfan
Feb 10th, 02, 9:12 PM
If your saying the initial timing jumped up from idle then you either have to much idle speed or really light springs!How high is the idle?Is it over 1000 rpm?

DjD
Feb 10th, 02, 9:44 PM
<BLOCKQUOTE>quote:</font><HR>Originally posted by 66velle:
When I dialed it back I got 40 degrees total at 3000 rpm. When I changed to a a lighter spring the initial timing just up from 8 to 16 degrees. What's up?
Thanks<HR></BLOCKQUOTE>

If you had plotted out the curve (say every hundred rpm) before changing to the lighter springs you might have found that the heavier springs really didn't allow the weights to move much until you got the rpms up a bit. The total is still fixed with the lighter springs but less rpm's is needed to start pulling them apart. You should also be seeing the total reached sooner than it was with the heaver springs.

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...Dennis
The '69 (http://chevelles.com/showroom/fine69_03.jpg) & the '96 (http://chevelles.com/showroom/fine69_02.jpg)
Team Camaro (http://www.camaros.net)
Camaros Limited (http://www.camaroslimited.com)

66velle
Feb 10th, 02, 11:48 PM
Idle was at about 700 rpm. I guess this spring is too light. I try to plot the rpm in relation to the degrees and see what happens.