What is the correct location of the embossed "091" in the ignition coil case for the '57 vette? I heard that there is a version with the "091" close to the bottom and one in the middle of the case. Thanks.
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Re: C1: Location of Embossed "091" in Coil Case
There were a number of running changes in this part over time. For your '57 you want/need the 'early' configuration of the coil. NCRS member Kenneth Kayser wrote two articles on the running changes made to ignition coils based on GM drawings that appeared in past issues of the club's 'Corvette Restorer' magazine. Some members commented and an editor's note followed explaining that the phase-in of certain changes appeared to be quite lengthy (up to a year or more) based on original owner survey/comments. Here are the basic construction issues Ken wrote about:
(1) Early, metal case, 091 embossed 'high' on the case, +/- primary posts on platforms with two holes for the 'tang' of the locking clip (wire terminal washer) to enter to thwart rotation/twist.
(2) Jul/Aug '60: added raised bosses on the center tower (coil secondary outlet) adjacent to the +/- primary post platforms to give further assistance in preventing locking clip rotation.
(3) Apr '62: original locking clip with 'prongs' replaced with non-pronged locking clip that relied on the bosses presented by #2.
(4) Sept '66: eliminated the holes in the +/- primary post platforms that accommodated the early style pronged locking clip AND moved the emboss (091, Etc.) on the case 2.5 inches lower.
Also, some judges scrutinize the font used to emboss the metal case with the belief that original '091 coils used a smaller "1" digit that was, perhaps, 3/4th the height of adjacent digits. Can't remember if this is the 1-digit in '091', the 1-digit in '12V' or both....
Later, it's reported Delco changed service replacement parts a few more times (cost reduction?). First, they went to a metal case with the ID (091 12V) silk screened on vs embossed. Second, the original metal case was changed out for a non-metalic case.
So, a 'correct' coil for your Corvette probably has more than one consideration regarding construction/configuration if it's a matter of factory concours scoring points you're weighing. -
Re: C1: Location of Embossed "091" in Coil Case
Jack,
Thanks for the information. It sounds like for '57 the location of the "091" should be higher in the case. Also, the presence of the two holes for the "tang" and the lack of the raised bosses is a good identification of the originallity of early "091"'s.
VassComment
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Re: C1: Location of Embossed "091" in Coil Case *NM*
Bill Clupper #618Comment
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