They have different part No's. 253 is set at 6 degrees before TDC and 308 is 8 degrees before TDC.
They have different part No's. 253 is set at 6 degrees before TDC and 308 is 8 degrees before TDC.
Yeah fair call. But GMH lists different versions for automatics and manuals and those with cruise control. So stating 253 or 308 means nothing if you don't knowOriginally Posted by bobsmith380
auto, manual or cruise control models. The upshot is they all fit both engine sizes and need tuning to suit.
I had the 6 & 8 BTDC around the wrong way. To clarify HEI distributor details: 5.0 Litre V8 (Man or Auto) Part No. 92009979 - Initial Distributor Advance = 6 Degrees BTDC. Identification on White label on vacuum advance unit - None. 4.2 Litre V8 (Man or Auto) Part No. 92004474 - Initial Distributor Advance = 8 degrees BTDC. Identification on White label on vacuum advance unit - Blue Dot.
Last edited by bobsmith380; 23-04-2015 at 06:12 PM.
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