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I am at the point now where I don't want to do anything on the car without consulting this discussion board first. I hate having to buy parts twice. Last year I purchased a Delco replacement coil for my 57. It was listed as covering 56-74. This year I purchased the correct 0.2 ohm ballast resistor. I am now aware that I should be using the '091' coil for that resistor. I am fairly sure the car will run with the generic coil, but I am not sure sure for how long or how well. Am I better off replacing the coil or should I just wait and see what happens? Thanks in advance.
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Re: 57 Ignition Coil
The replacement coil will work just fine, later if you find the 091 use it to be correct # -
Re: 57 Ignition Coil
What is your objective - minimum points deduction or just a functionally correct and reliable ignition system?
The 0.3 ohm ballast allows greater primary current, but reduces point life and creates greater coil heating. The purpose was to create greater ignition energy, but it comes at a price. Unleaded fuel and "hot" plugs (AC heat range 5 or equivalent instead of the OE heat range 4) will usually prevent plug fouling when used with a generic coil and 1.8 ohm ballast.
The "Delco Replacement coil" you bought is probably just a generic replacement coil that is available in many other "brand" boxes.
You're probably better off running a 1.8 ohm resistor with the generic replacement coil. Most coils have primary and secondary resistance that is optimized for adeqate spark energy and long coil life with 1.8 ohm ballast.
If you're looking to minimize judging points deduction just install the "correct" resistor and a "correct" coil for judging, only. A review of the judging sheets for the points loss with "incorrect" ballast and/or coil and knowing what correct parts cost allows you to compute a cost/point ratio so you can determine if it's worth the cost or whether you can get a lower cost/point ratio elsewhere on the car.
DukeComment
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Add on...
Duke's got the right answer...you trade off for hotter spark is lower point life and lower coil life as you're running more current through the primary side. I guess designers felt folks buying these cars KNEW they were getting a slice of high performance that came as a double edged sword in terms of periodic maintenance.
Note the same ignition system was used into 1963 ('091 coil and 0.3-ohm ballast combo) when a running change was made. On the low HP cars (hydraulic lifter) they changed back to a standard passenger car ignition setup ('087 coil and 1.8-ohm ballast) but kept the 'hot' ignition running on solid lifter engines.
At the time, a technical bulletin was sent out telling dealership mechanics about the change and the reason given was to address customer complaint(s) of low ignition component life. In that bulletin they advised mechanics to 'fix' existing systems where customers were complaining of short ignition component life by removing the 0.3-ohm ballast and replacing it with the standard passenger car 1.8-ohm resistor.
By 1965, ALL Corvettes would drop back to the lower current ignition setup except those using the optional transistorized ignition which had it's own unique spark current profile...
So, by seeking a correct '091 coil and 'correct' 0.3-ohm resistor for your car, you're simply drumming up judging points and doing so at the expense of tune-up maintenance! Plus, if you buy one of the 'correct/original' 0.3-ohm resistors made under GM License by Shafer (that's what all the catalog houses are selling these days), expect to take additional deductions because while this part is touted as correct and original, it lacks certain construction attributes that original ballast resistors of the period actually had. Savvy judges will spot it for what it is (an imperfect reproduction) and deduct accordingly.
The alternative is to be tempted to bid into the stratosphere on eBay for a real McCoy GM old stock 0.3-ohm resistor. In that case, about 90% of the time, you're going to get a service replacement form of the part that was built in the late 60s (or later) and that's what Shafer 'copied' to make their incorrect 'correct' reproduction....Comment
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Re: 57 Ignition Coil
Mike -
Your points will last longer with the later resistor; the reproduction Paragon sells for $20.00 (#2516) measures 1.8 to 2.2 ohms and will work fine.Comment
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