I feel compelled once again to write about our stock ignition systems and provide testimony to the quality of the stock Ford system.
We turbocharged engine folks are walking a thin line of spark, air charge temperatures, and turbo flow and boost pressure. The best possible insurance against poor drivability, blown head gaskets, and other engine damage due to detonation is a good air charge cooler, and good (higher octane) fuel.
Retarding timing by setting initial at 10 degrees will affect Exhaust Gas Temp (EGT) and consequently Air Charge Temp (ACT). It is certainly a balancing act, and each of us needs to work out the best combination for ourselves with carefull experimentation.
(Spark plug firing voltage is a function of chamber pressure, Rick's motor has WAY higher chamber pressure than street cars so his test values apply DIRECTLY to us. Ed)
On the subject of MSD. I finally use a MSD 6AL unit on the Bonneville car. I do this partially because it was part of the DFI system I converted to earlier this year, and it was best to not mess with what was previously working on another engine and car that makes as much or more power than I. I found no significant improvement in anything with the MSD, in fact when we had problems with the calibration at speeds below 3000 RPM I switched back to the production Ford coil and there was an improvement. A big improvement. I continued to use the Ford coil for the rest of the meet, including the 208+ MPH pass. My point is again that there is no advantage to using aftermarket ignition products. This is not just opinion, I have the data. Last years records of 199.036 MPH was with 100% stock distributor, coil and wires. We had ~425 HP with that pure stock configuration. Now at 650 HP I truly believe the stock system would perform. The big reason is that I (and most of us) do not buzz the engine over 7000 RPM. I shift at 7, but my 208 pass was at 6700 RPM, and that is right where the engine HP peaks..... Again, I implore you guys to think thru the purchase of aftermarket ignitions. Save your money for a really good air charge cooler.
I agree with Rick 100%. My brother has a 69 428 CJ Mustang that he drag races in stock class. I do all the electrical work on the car. Going from the stock points system to a MSD made a big difference, since the original system was less than adequate for the RPMs his motor now turns, but once he had a good ignition further improvements made little difference. We took his old 6AL and put it on his SVO and the car ran much worse than stock in the mid 3K rpm range with light throttle, flooring the car and the MSD was fine, but for everyday street driving it wasn't worth a cent over the stock ford coil.
I ran a Crane Hi-6 on my car for a year or so and the whole time chased a 2800 RPM stumble, unplugged the Crane and the stumble went away. I also have a Jacobs Omnipak (or something like that) and all I can say is that the car does sound a little different at high RPMs, but not $150 worth over stock.
I think I've wrote this to the list before but for the new guys save your money! Spend it on a used SVO or TC intercooler (~$100), a K&N cone or drop-in ($30-40), an exhaust, or even a good tune up with all Motorcraft parts including the TFI/PIP.
Big HP improvement is not in the ignition on our cars.
How to trouble shoot COIL
Bad coil is usually indicated by a high speed miss.
According to the official electrical trouble shooting guide. Test continuity first. Primary winding 0.5 Ohms (between the two terminals on top of the coil) The secondary (where the Red/Lt. Green) should be 8,000 to 11,500 Ohms and infinity from any terminal to ground. Make a spark gap by taking an old spark plug and bend the "L" electrode way out or remove it altogether. Hook the main spark line to the plug after removing the wire from the center of the dist. Lay the plug on a ground. The top of the alternator is a convenient place.
Get three alligator clip leads (Radio Shack) and a known good ignition breaker point condenser. The condensor should be 0.25 to 0.35 MFD but any standard part from an American car should be fine. Plug in the coil. Unplug the connector from the TFI on the distributor. Locate the Dark Green with Yellow Dots wire in the TFI harness. Push a simple straight pin (new shirt kind) into the connector terminal (the book actually says this) associated with the wire above. connect one end of a clip lead to the ground side of the condenser and attach the other end of the lead to a good ground. connect one end of another lead to the pig tail of the condenser and the other lead end to the shirt pin in the connector. connect one end of the third lead to the ground end of the condenser. Turn on ignition. Touch the loose end of the third wire to the pig tail then remove immediately. Never hold the wire in place for as much as one second. Every time you disconnect the touched wires, you should see a bright blue spark in the spark plug gap. No spark or yellow spark requires further circuit checking or a new coil.
Hope this helps, I just had to do it last week to diagnose a bad TFI unit.