Timing mark?


Jul 26, 2022
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Bedford County, Virginia
I want to dial in my timing... 400ci 2 barrel. I don't quite understand the timing mark / indicator. The line on the pulley is clearly visible each revolution but it's the indication on the block that I don't quite understand. There's a plate and it has a hole in it (see picture). Is that hole the zero degree mark? I have a light with an advance knob, so normally I'd set it to the desired btdc and adjust dist till i have zero indicated.
The hole is TDC. On either side of the hole, there should be index lines with stamped degrees. If you clean things up, you should be able to see the index lines. Factory timing should be 5 degrees before TDC.

Use a small wire brush to clean the quadrant plate and use whiteout in the line on the dampener and at 5º BTDC, makes using a timing light a breeze.

By getting a good read on the timing tab, you can guess what your total advance is at a couple thousand RPM - it's usually past the plate's edge - unless you have a deluxe timing light with an "advance knob" like my old Snap On, you can read total timing on the light, which brings the light back to the zero point showing corresponding number on the knob.

I stopped using a timing light to time engines years ago, would use a vacuum gauge instead.

Sometimes, reverting back to factory timing is far from an improvement, so know where you are to start with so you can go back.
Ditto on the vacuum guage and timing light with advance feature.
With today's corn fed gas pumps, factory timing specs can be tossed out the window.
Once you clean the timing marks on the tab, set at 10 degrees BTDC.
Any mopar engine will start and run at 10.
Using vacuum guage, goal is 17 to 20 inches of vacuum.
Increase/ decrease timing as needed. Road test check for ping.
You may have to adjust the mixture scews as well.
Big blocks like lots of timing. Total advance all in with today's gas can range between 32 to 35 degrees depending on engine mileage/ wear.
Hope this helps.
The emissions label on our '72 Newport Royal 400-2bbl states " 5 degrees BTDC + or - 2.5 degees BTDC" as the hot idle base timing. Be sure to unhook the vac advance vac line, pluuging it temporarily, during your timing settings.

I know many others have had good luck with vac gauges, but that has not been my experiences, starting in the late 1960s. Never could get the gauge to read the 18" Hg at idle, for some reason, as others stated they normally got that on their engines. So, I suspected that my inexpensive vac gauge vs what they had was a possible issue. I have had better luck not worrying about the numbers and usuing it as a diagnostic tool to look for a too-rich idle mixture or a burnt valve.

Others seemed to have luck "timing by ear", but I liked the security of knowing where the initial setting was with a timing light. Just me.

Just my experiences,
Given the unknown state of most distributor internals when it comes to advance governance, I like to time an engine, any engine, with the most advance it can have before pinging, but not so far advanced as to fight itself starting, so as much advance as possible without either problem and you're there.

Requiring no light, no gauge, just brief test drives and stationary starting tests.

A good distributor wrench is your friend in some cases, keep one handy.
Ok I cleaned up the timing plate. It's at 22 degrees advance at idle. (It starts and runs fine). Possible that the damper has twisted? I reduced advance to 16, which lowered the idle. Vacuum is 18. Not sure if it should disregard the reading and just tune by ear, which is what I usually do. Is there another data point available for timing at another rpm so I can see if the curve is in the ballpark.
Is there another data point available for timing at another rpm so I can see if the curve is in the ballpark.
This is where the timing light withvthe advance feature comes in.
As you may already know, when using the light, and revving the engine, the mark dissappears.
With a buddy opening the throttle, and you with timing light, put engine at a steady rpm say 2800 give or take.
Then point the light to harmonic balancer. Adjust the advance button on the light and put the mark to zero on the balancer/ timing tab.
Then relaese throttle and read how many degrees its reading at the button. Thats your total mechanical advance. Anything over 36 degrees will ping.