Hi all. I have been reading through the forums herein as prep for fine tuning my 1951 Plymouth Flathead 217 cu. inches. I have identified a discrepancy w my ignition based on my readings that I would like some input on. I have read that blue/white spark w a popping noise is a strong or hot spark that we should see. A yellow or reddish spark is a weak spark. I checked my spark and was surprised to see a thin yellow red spark and hardly a popping sound. The spark can be as long as 1". I have been trying to pin down the causes for such weak spark. Long story short I looked closely at the markings on my sparkplug wires and note that they are NGK resistor wire. I switched the coil lead to a solid core copper wire and checked spark noting a strong spark...blue w nice popping sound. I also checked spark this way on a few vintage hot rod coils noting same results. When I changed the coil secondary lead back to the NGK lead I got the yellow red spark on all the other coils. QUESTIONs 1. Should I always be able to get blue spark regardless of type of spark plug wires being used???? From reading through the forum it seems the answer is yes. If it should always be strong blue spark then I may need some guidance on where to look next. 2. My Autolite #86 spark plugs are gappped at .030". I just found instructions for my huge beehive coil 6 volts (mfg is Holthouse) and it indicates gap should be .020 to. 025 Max. I would think this is not the reason my spark is yellow. My spark was yellow out of the coil when I touch the secondary coil wires to ground....so its yellow long before sparkplug. I thought with a hotter ie higher coil capacity / voltage availabilty you could open the gap up a little for a hotter spark longer spark. I understand that a wider gap increases resistance and therefore increases required voltage to jump gap. So if my coil has ample available voltage and can therefore handle bigger gap I should benefit by a larger gap. Are there any errors in my thinking here. Overall just wondering when a wider or narrower gap is appropriate? Ie if my coild can handle .040" wouldnt this be a stronger longer spark for better combustion? For now I will change my gap back to the recommended .025" but I am only doing it because the instructions to my 1950s nos coil say to. I would like some input on when increasing or decreasing spark gaps is necessary and the related benefits . Background info: I ask this because I am trying to determine why my car is slightly harder to start as compared to year ago or so after warmed up. Thus i am startng my tune up procedures now. Could the condenser be wrong or not working....though its only one year old and was a nos blue streak condenser. Could this be suspect? How can I test this? Engine: 100% stock except it has dual carter b&b stock carbs on an Edmunds intake and cast iron split headers from Stovebolt Langdon. I have been checking voltages at battery coil and ignition switch and starter solenoid to help identify why my car starts a little harder than it used to....6 to 7 volts every where. Car runs and idles fine. No flatspots or high speed miss or detonation has been noted. Engine burns oil. Has 90 to 100lbs of compression among its 6 cylinders last I checked a year ago. High miles on motor. Dwell as tested on my sears penske analyzer indicates 35 degrees though the point gap was about half the stock gap suggested in car service manual. Spark plugs are sooty but I believe this is from sitting at idle and driveway running for a while. I beleieve if I went for a drive it would yield tan dry plug coloring. I am going for a drive now to confirm this as car has been sitting for a while. Posted using the Full Custom H.A.M.B. App!
That's a lot of info.... From my past I owned a Plymouth 230 flathead. It really woke up when I did Tom Langdon Mini HEI. and converted it to 12 volt. I would not use anything but copper wires on it, I would make sure the wires from the dist to coil are not brittle, and no cracks causing grounding as the pass through the dist to the coil. I would not go over ,030 on a gap. The wider gaps where for HEI application. Set it stock.... If it starts harder then it used to, check the carb, this new fuel is playing havoc with carbs.
The Jalopy Journal
