The Stovebolt Forums Forums The Shop Area The Engine Shop Adjusting Dwell - '54 3100 six

I only post this question after researching here and beyond. Simply put, how do I adjust the dwell on my '54 3100 with original six. PO switched from 6 volts to 12 volts, but still running 6v coil. Also, published dwell angle is 38-45. Is anywhere in this range ok, or is there a more accurate recommendation?

Explained here: https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=686472

Getting hung up on a dwell reading is wasted effort. Set the point gap to the specification the distributor serial number calls for (not the year of the vehicle or the engine), set the spark timing, and drive on. There's no telling how often a stovebolt distributor has been changed over 70 years or so, and not all distributors have the same dwell specification.
Jerry

There’s a wrinkle I never knew about. Where would a guy find points gap by distributor serial info?

I actually did set my gap via dwell last time I did it. I thought it worked pretty slick but I may have just gotten lucky.

Thank you G&F for the link and info, that's one I didn't see in my research on this forum. And thank you HrLincoln, valuable info as always.
However, I'm still stuck with the basic question of "How do you adjust the dwell setting?" Still on that quest....

Adjusting dwell is easy enough but as HRL pointed out, it’s not necessary on these engines. Hook up your dwell meter per instructions with the instrument. Remove the distributor cap and set it off to the side. Remove the rotor. Loosen the point hold down screw slightly and have someone crank the engine while you use your screwdriver to move the point adjustment slightyone way or the other until you get the reading you desire. Tighten the points and reinstall everything. Start the engine and see how well you did. Warning, you can chase the adjustment all day if you have a worn out distributor shaft/bushing. Good luck.

I’d have to go verify, but fairly certain I set my 235 dwell at 31 degrees.

Spec is 31-35 from what I looked up. Went to the numerically low side of the range so that it’s still in spec as the rubbing block wears.

I would be more concerned with using a 6 volt coil with a 12 volt system than what the dwell is. The proper way for a 12 volt system to work is with a ballast resistor and a 12 volt coil designed for that system. You are likely not getting the correct voltage for the engine to run properly.
Fred

Thanks rfs56trk. Interesting. Had a new 12v coil installed and the new points got burned pretty bad. Assumed might be the 12v coil, so reinstalled the 6v and it started up ok.
Would be interested to know if ya'll think the coil could have burned the points up.

Putting 12 volts to a 6 volt coil is a guaranteed way to burn the points, as the coil is designed to work properly at 7.5 volts (charging system voltage with the engine running, against a fully charged 6V battery). A 12V GM coil operates properly at around 9.5-10 volts, and is designed to use a resistor to drop the charging system voltage (14.7 or so) to the lower voltage. During engine cranking on a 12V system, a bypass circuit allows the coil to run on straightr battery voltaqe. Simply swapping coils is not sufficient to make a 6V-12V conversion of the ignition system.

A dwell meter is nothing but a voltmeter with a specially calibrated meter movement. It is actually measuring an averqge of "points closed" voltage measured downstream of the coil (zero volts) and "points open" voltage which is the same as battery voltage. Changing the amount of time the points remain closed alters the apparent voltage the meter sees.

Around the time Chevy switched from a 6V to a 12V ignition system, they changed the profile of the distributor cam, and also changed the specification for the dwell setting. The point gqap also changed, from .016" to .019", which accounts for the difference in dwell. For instance, a 1954 standard transmission distributor, P/N 1112388 calls fpor 38-45 degrees of dwell. A 1955-56 distributor P/N 1112403 calls for 28-33 degrees. All of the rest of the 12V distributors call for the lower setting. The 1112403 distributor is specified for all 6 cylinder passenger cars through 1962 according to my Motr Magazine service manual. Truck distributors might have a dirfferent part number.
Jerry