CUTLASS 1985 Cutlass 307 V8 Spark Plug Wire Factory Lengths

Here's something you don't see every day. A chart showing the factory spark plug wire lengths as sent out on the engine. I searched and searched and I could not find anything that showed me this so I made my own.

Measurements are made from outside the cap boot all the way to the spark plug boot end. Thus, the entire length which includes some rubber of the boots. The actual wire cable is slightly shorter, but these are the assembled lengths.

Keep in mind, this is for the FACTORY wires that were secured with the FACTORY looms. Custom setups will not be the same, obviously.

Cylinder # and length in Inches (nearest 1/8").

Aaaannnnnd....if you need to know how the wires are routed and how they lay out on the distributor cap, here's a couple of pics of that. Note too, that correct placement of the distributor for 307 engines place the rotor to #1 cylinder at TDC in a position of POINTING AT THE DRIVER'S SEAT. Closer to the back, and not at the front like many older V8 engines.





V6 applications




307 applications

Of course, when I said I couldn't find anything that gave me lengths, I'd find it. It's not in the Olds parts books, but apparently elsewhere in Chevrolet and Cadillac parts books. There's a chart for spark plug wires that shows part numbers for each plug wire by cylinder position, but simply gives part numbers. I did find a reference in an older Chevy parts book showing type, mm and inches of each part number spark plug wire.

Again, though, the lengths found are "nominal" lengths, and not exact, like what I measured. So will they work. Of course. They've been this way for years. There's been SLIGHT changes over the years, but all Olds V8 HEIs use the same part numbers in various locations. I've found that regardless, they didn't use anything over 40" long on the engine (#2 cyl).




Here's all the part numbers for each wire that has the "U" type, which is the straight rubber boot on the plug end. Over the years, the wires changed from retainer ready cap ends with the rubber nipple on top, and then later when they went with the smooth top that didn't require the retainer. Plus, some came black, some came gray. Again, these are nominal length numbers. I'm supposing that Delco simply added 2" to the wire for every part number change save for 1203928-931 where they bumped them 4" difference at a time.


Part number/Millimeter/Inches/Type