Steve,



No ballast resistor on a 55 6 volt. OEM coil should work OK, as dwell will not be maximized (want to keep point gap on the high side).

6 VOLTS/POS. GRD. NW INDIANA

Daniel - Which coil and ballast resistor have you accumulated to run with this outfit? Extended dwell (from the dual points) is part of the equation - how about the in-rush amps? I realize inductance measurements would be impossible to obtain - but the sum of coil primary resistance and ballast resistance is worth knowing. A little paint could help make a "hotter" coil a little less obvious.

My '56 outfit had so much small diameter wire (and old connections) in the ignition circuit, that the voltage at the ballast resistor didn't match the battery voltage too well.

 
 Steve Metzger       Tucson, Arizona

Better have a hot, strong spark to fire lean mixtures at idle.[/quote]



Extra dwell from the dual points should help. Higher C/R & octane will add unknown factors though. Having two distributors will be an advantage, as I can set one to factory specs. and A-B compare any modifications to the other. Finally finished the mechanical advance limiter rig. It works great on the Sun machine (currently set to add max. 36 crank degrees), but unfortunately can't do a road test as car up on blocks for the winter. Will thus have plenty of time to play with the springs, and calculate new curves for larger displacement motor on the way (it occurred to me that more venturi vacuum will likely be produced at the same RPM).



P.S. Had to go through a half dozen sets of points before finding two that would adjust to proper spring tension (why I started this thread) within the allowed travel range.




6 VOLTS/POS. GRD. NW INDIANA

Lots of low rev, low/no load (idle) spark advance isn't necessarily "rough". Mine runs smooth and makes lots of vacuum - that it doesn't make if I take the extra vacuum advance away. Better have a hot, strong spark to fire lean mixtures at idle. 

 
 Steve Metzger       Tucson, Arizona

This brings up an interesting point: The engine damage likely from prolonged pinging under load (pre-ignition/detonation) is well documented. But, what about rough-running from hyper-advance at low load? Aside from disconcerting, what are the long term effects, if any?

6 VOLTS/POS. GRD. NW INDIANA

Daniel,

  50 degrees of advance at 20 inchs of manifold vacuum ( this is very low load, low throttle application, cruise condition) IS NOT EXCESSIVE. This is what is desired for HIGH MPG. AS soon as you give it throttle, the manifold vacuum drops, the timing retards, and the rpms pick up.

  I feel you are trying to fix a problem that does not exist. If your engine pings, there is a problem. If there is no pre-ignition (ping) then there is no problem. Pete

Forgot to mention: After setting up a Loadomatic last night with factory springs/advance curve, I then applied a full 20"s of Hg. (low-load cruising manifold vacuum). Assuming the spark control valve orifice actually passes full manifold vacuum to the distributor diaphragm, that would produce over 50 degrees of crank advance, even if the initial timing was set to factory spec.! No wonder there is so little latitude in boosting initial advance before experiencing low-load rough running.

6 VOLTS/POS. GRD. NW INDIANA

Thanks Paul,



I had forgotten about that article. Combined with the 55 shop manual rpm/vacuum specs., and other Y-Block performance curve data found, I should be able to come up with a solid baseline for modification.



One MIGHT infer that RPM & corresponding ''inches-of-Hg" specs would indicate a standardized teapot venturi vacuum at that engine speed? Of course, the only way to be certain about a specific carb/engine set-up would likely be to drive around with an accurate manometer spliced into the distributor line, and record the #s.

6 VOLTS/POS. GRD. NW INDIANA

Daniel: For more info that might be relevant to your question, go back to Home on this site, then to Articles. Scroll to Hot Rod (1956 mag) article. Open, & scroll down to the ignition section. The discussion there may be helpful.

Paul

Bill,



Been looking high & low unsuccessfully for that tool (SnapOn MD5). Twiddling those posts with an ordinary wrench a tricky operation while the distributor is running at 2000 rpm in the Sun machine. Would also be handy for point aligning.



P.S. Total of 4 springs to adjust in a dual-point Loadomatic.


6 VOLTS/POS. GRD. NW INDIANA