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Old Jun 13, 2020 | 10:42 PM
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Default Spark plug wires

Okay so my 74 crate 350 currently had 8mm spark plug wires. Unfortunately they’re slighty too big for the wire brackets I have.

does the wire size matter? could I drop down to a 7mm wires?

first corvette so. I don’t want to kill the performance of the car, but it’s also not a performance corvette. Just a weekend car I suppose?.?
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Old Jun 13, 2020 | 10:48 PM
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Originally Posted by Samuel’s 74
Okay so my 74 crate 350 currently had 8mm spark plug wires. Unfortunately they’re slighty too big for the wire brackets I have.

does the wire size matter? could I drop down to a 7mm wires?

first corvette so. I don’t want to kill the performance of the car, but it’s also not a performance corvette. Just a weekend car I suppose?.?
Does size matter? Only on breasts.
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Old Jun 13, 2020 | 10:51 PM
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Originally Posted by Big2Bird
Does size matter? Only on breasts.

well that isn’t wrong.
but could you give me any more information? I’d like to know why one size is better or why it doesn’t matter.. I don’t want to mess it up doing something to it
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Old Jun 13, 2020 | 10:55 PM
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Originally Posted by Samuel’s 74
Okay so my 74 crate 350 currently had 8mm spark plug wires. Unfortunately they’re slighty too big for the wire brackets I have.

does the wire size matter? could I drop down to a 7mm wires?

first corvette so. I don’t want to kill the performance of the car, but it’s also not a performance corvette. Just a weekend car I suppose?.?

okay so apparently size doesn’t really matter. And I’m glad I can use the 7mm.

but I’d still like to know why.. why is the bigger bot better?
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Old Jun 13, 2020 | 11:21 PM
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Unless you have a modified ignition system generating higher secondary ignition voltage there is no purpose for 8mm.
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Old Jun 14, 2020 | 12:13 AM
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For stock ignition, 7mm was standard Packard wires.
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Old Jun 14, 2020 | 05:55 AM
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Bottom line. The wire on the inside, is the same. With differences in copper or spiro core wire's of course. The difference in size is the thickness of the insulation. Thus the explanation of the the 8mm for very high output system's.
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Old Jun 14, 2020 | 08:22 AM
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Default Thank you!!

Thank you everyone!! I’ll pick up some 7mm and swap them out!

here is a pic, if you zoom in on the bottom left you can kinda see what I’m talking about.

I just painted my air filter housing and my valve covers. And they’re alittle darker in person.
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Old Jun 14, 2020 | 10:13 AM
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Originally Posted by Samuel’s 74
Thank you everyone!! I’ll pick up some 7mm and swap them out!

here is a pic, if you zoom in on the bottom left you can kinda see what I’m talking about.

I just painted my air filter housing and my valve covers. And they’re alittle darker in person.
Appears that you have an hei distributor so remember to ask for 1975 or later wires as the 74 and earlier engines had points distributors and different ignition wires.

Last edited by wilcar; Jun 14, 2020 at 10:33 AM.
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Old Jun 14, 2020 | 02:51 PM
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I recently installed a set of AC Delco Professional series wires on my 69 BB. They fit better than the set I had on there from AZ. Also got rid of a low speed miss that I had trouble tracking down. Cheap from RockAuto.
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Old Jun 14, 2020 | 02:52 PM
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Default AC Delco

Originally Posted by Sayfoo
I recently installed a set of AC Delco Professional series wires on my 69 BB. They fit better than the set I had on there from AZ. Also got rid of a low speed miss that I had trouble tracking down. Cheap from RockAuto.
I have heard that AC Delco is good so I’ll definitely get theirs.

but I don’t know what a low speed miss is?
my first corvette, and car basically so.. gotta learn as I go.
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Old Jun 14, 2020 | 08:24 PM
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Originally Posted by Samuel’s 74
I have heard that AC Delco is good so I’ll definitely get theirs.

but I don’t know what a low speed miss is?
my first corvette, and car basically so.. gotta learn as I go.
My car had a misfire at idle. I checked all the wires with a meter, and they tested fine. But, after 20+ yrs I changed them out and the car does idle better and faster, so, obviously, 1 or more was bad.
Added fyi
Current AC Delco does not mean "GM made is the USA". Lots of china stuff.

Last edited by Sayfoo; Jun 14, 2020 at 08:25 PM.
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Old Jun 16, 2020 | 05:25 PM
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Wiring inside is NOT always the same. Some wires are just that....solid wire. Most aftermarket (and replacement stock) wires are 'resistor wire'. With solid wire inside, the thickness (and composition) of the insulation is important to prevent 'cross-talk' arcing (high voltage bleed-off). For resistor wire, 7mm (good quality) insulation is just as good as 8mm.

If you have a street cruiser, you probably need resistor-type spark plug wires.

Last edited by 7T1vette; Jun 16, 2020 at 05:27 PM.
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