hello all.  i am working on a 1992 base vette with manual trans.  i was concerned about the size of the spark plug wires i had to purchase in a hurry from a local auto parts store.  they measure 7mm and are ac delco part # 708w, gm part # 19351556.  the wires will be replacing aftermarket 8.5 mm wires.  i believe everything else in the engine compartment is stock other than the wires.  plugs are ac delco original part # also.  i have no plans to change anything engine wise in the future.  i haven't been able to find any info on what size wire came on the 92.  the car is a weekend warrior in the summer month's of south jersey and sits more than it is used in the winter.  other than one hour, one way rides to the a.c. casino's and car gatherings in s.j., the car doesn't go far or on any long trips.  the mileage is aprox 90,000 miles.  ok i can't think of anything else that might help you help me.  thanks for any advice you can pass along, joe

7mm wires will work fine, as long as you are using the stock ignition system. Just be sure to route them properly, and keep #5 & #7 apart as far as you can.

ok.  thank you for your response and will take care with 5 and 7.  

Greetings, I have a 93'. What's the issue with the separation? 

 hello manchester.  i do thank you for responding but i'm not sure what you mean by the seperation question.  if you are referring to the #5 & #7 spark plug wires mentioned in the adam response, i have to be honest and say i do not know why the 5 & 7 wires need to be seperated as far as possible but i will follow adam's advice and look into it down the road.  sorry i couldn't give you a better response.  thanks, joe

Mark, the concept of keeping #5 & #7 plug wires separated is that those cylinders fire one right after the other, 1-8-4-3-6-5-7-2. With cylinders 5 and 7 right next to each other, and firing one after the other, spark can jump from one wire to the next creating a misfire, or even a backfire. This is one of the reasons a lot of folks use the larger diameter plug wires....they have more insulation to help prevent cross-firing. The best solution is to keep those two wires as far apart in the loom/holders as possible, putting at least one of the other two wires(#1-#3) in between to separate #5 & #7. New wires are a good start to help with eliminating cross-fires, but they are not a positive fix. I have actually seen spark jump from a plug wire to a vacuum line before....rubber has a high carbon content, and...most plug "wires" are actually made of carbon strands, so...

Anyway...it's just a good idea to keep 5 & 7 separated to prevent a possible backfire or misfire. hth 🤠

A BIG Thanks for that explanation on plug wires. I had an idea that was the reason for the separation, but wanted a conformation. Preciate it. 

   double preciate on the explanation.  thanks, joe