Plug wires

[1985gmc1500]

Hi The stock spark plug wires on my 1985 GMC Sierra 305ci are 8mm. I am running the wires via looms that bolt onto the valve covers. Since this is not the original wire routing the stock plugs you can buy will not fit correctly I am looking for red wires that I can cut to my own length and will fit on the stock distributor. I can not find these in 8mm would it be ok to use the 8.5 mm that msd sells?

[bd]

Using 8.5 mm MSD wires is fine, but first make sure the loom clamps will accept the larger diameter wire.  I also recommend MSD's terminal crimpers, or similar, to properly crimp and permanently secure the ends without damage.

[LTZ C20]

I used the 8.5mm MSD red wires you speak of. I cut and crimped every single terminal my self using terminal tool WT 105 from Matco tools. They are good quality. I even used the extra wire and made a spark plug wire test wire for problem diagnosis.

[Jim_Hensley]

the mm size really doesnt matter, it just thicker insulation, More of a marketing gimmick,