Does anybody know what the dwell on a 68 ford 390 should be? I've been told to just set the points to 17 thou, but I want it in deg dwell.

Thanks.

 

26* - 31* if the memory is still working.

 

31 sounds about right to me

 

28-32. Closer to 28 is best.

Mike

 

Actually:




Curb Idle 550 Dwell 26*-29*
Cold Idle 1400 Point Gap 0.017"
Plug Gap 0.032-0.036"
Initial Timing
w/o exh. Emissions 10* BTC

 

Hmmm... I just looked this up in the '68 truck shop manual. If you have the single-diaphragm vacuum advance your point gap is .017" and the dwell is 26-31 degrees. If you have the dual-diaphragm vacuum advance the point gap is .021" and the dwell is 24-29 degrees. Says the same thing in the '68 truck service specifications booklet.

Barry

 

[updated:LAST EDITED ON 26-Apr-02 AT 10:19 AM (EST)]According to my genuine Ford Motor Company publications, all 1968 Ford truck engines, save for heavy duty models which the 390 is not classified, were equipped with exhaust emission equipment, whether it was the Imco or the Thermactor. Again, per Ford Motor Company's official publications, the dwell angle for 360's and 390's is between 24º and 29º. Hope this clears up the issue.

 

Hi Jim,

Not trying to be difficult or anything but my data is also from the genuine original ’68 Ford truck shop manual and the original ’68 Ford truck service specifications booklet, all from Ford. I was a service tech at a Lincoln-Mercury dealer in the early ‘70’s in the quick service and electrical department and went through all the dealer training on this for tune-ups, still have the training books with the slide presentations (makes for exciting slide shows at home!). They explained the differences between IMCO and Thermactor along with the single/dual vacuum advance units. It all has to with the geometry of the movable breaker plate vs. the breaker cam. The pivot point of the breaker plate is not concentric with the cam so instead of rotating around it, it really swings an arc across it. This changes the dwell angle as the breaker plate moves. It wasn’t so much a “problem” with the single advance but with the introduction of the dual advance they had to increase the point gap so that when the plate moves forward on retard the point gap doesn’t get too small. It was never really meant to go in this direction. That’s why the two different gap settings. It’s a cheesy design, that’s why I remember .017” = 26*-31* and .021” = 24*-29*. Anyway, don’t want to “dwell” on this to long, in this day and age of electronic ignition it seems “pointless”.

Barry

 

Atkman, Barry is right, this is not something we should be dwelling on. It shouldn't even be discussed, throw away those points and get a duraspark or a pertronics. Points are really nowhere.....it IS 2002. DF