Joined
·
62 Posts
I have a 91 GT with a vortech 8-10psi. what is a good spark plug and do I need to run a colder plug. If so how much colder than the stock ones.
1991 Mustang GT Spark Plugs
- Status
1 - 11 of 11 Posts
Joined
·
1,396 Posts
Go with Autolite 25's (copper core). If you run 87 octane, I'd gap them at 40, if you run 91, gap them at 35.
I'd go with NGK Iridiums. They made a noticeable difference in gas economy AND power. Iridium plugs are the best, newest, and most expensive technology out right now. Autolite does make a version of the Iridium plug too. My friend bought those for his Dakota R/T and loves them.
Joined
·
31,118 Posts
I would say get 1 step colder than stock, and stay away from platinums.
Joined
·
1,396 Posts
Fox Body Mustang's run the best with basic copper core plugs. Just because an automotive product is the newest and most expensive technology, doesn't make it the best. Everything having to do with cars is application specific and it's impossible to make a product that is the BEST choice for every car. You need to remember what the technology was like in 1991 (the 5.0L in question), ultra new, super expensive spark plugs were not designed for this particular motor. Why? Because it's been proven 10 times over that Motorcraft or Autolite copper core spark plugs are the BEST selection for these motors. Comparing the spark plug operation on a Dodge Dakota really doesn't compare to the operation of a Ford Mustang, at all. The Dakota r/t is a hell of a lot newer and is controlled more by the ECU and less from analog engine components. "Newer is not always better".
Joined
·
2,802 Posts
The stock plug was Motorcraft ASF42C, which is equivalent to Autolite 25.
One heat range colder is ASF32C or (Autolite) 24.
Two heat ranges colder is ASF22C or 23.
One heat range colder is ASF32C or (Autolite) 24.
Two heat ranges colder is ASF22C or 23.
All's i'm sayin' is I put iridiums in my mustang and I have better gas mileage than ever before with nothin' else done to it. I also felt a difference when I changed from the copper core plugs. And newer is better. I think that in 20 years spark plug technology has advanced just like everything else advances with time, research and new materials. My friends R/T needs good spark to run just like every other computer controlled car and I KNOW that with all gas engines the bigger the spark the better the bang. Copper core is fine if you want fine. Iridium is best if you want the best. I'd do research before buying any part, so you know what you're getting.
Joined
·
246 Posts
Thats I argument that can go for days. I say if it works for you use it. I know I had bosch plat 2s and got Autolite 25 ran smoother. Then again I'm not super charged either.
Joined
·
1,396 Posts
Sorry dude, newer is not ALWAYS better. Also, whats this business about "the bigger the spark, the bigger the bang" regarding spark plugs? Thats just completely false. Different spark plugs don't create a bigger or smaller spark. The different spark plug materials used (platinum, copper etc.) only act as a conductor, they don't have the ability to increase or decrease the size of the spark. Plus, maybe you confused bigger spark with spark duration (gap) between the electrode and the ground. The voltage sent across the gap ISN'T determined by the spark plug, its originated at the ignition coils!!!!! Also, the size of the bang (regarding gasoline engines) does NOT convert to more power. You want the most EFFICIENT combustion possible for A SPECIFIC APPLICATION to get the best performance possible. I'm not making any of this up, I'm a mechanical engineer.
Joined
·
2,802 Posts
Platinum, Iridium, etc. are NOT pure to the core. They are just a coating over a copper core.
Joined
·
1,396 Posts
Yes that's true.
1 - 11 of 11 Posts
- Status
Join the discussion
