Category: tech faq


They seem simple on the outside; just some wires for conducting spark. Simple as running to the parts store, grabbing some performance wires and finished — beer time. While this will work just fine for many vehicles, you might want to take a second look if your application is any more complex than a 60-year-old pickup.

More than just a wire

The job of a spark plug wire is simple: conduct the amount of current necessary to bridge the spark plug gap and trigger adequate fuel burn. Maximizing fuel burn is the key to optimizing engine performance, but there’s more to it than just delivering the most charge.

A spark plug wire can have up to seven different layers, cluing you in that there’s more going on than meets the eye. The outer layer of the wire is made from silicone and available in many different colors. All too often, a wire set is bought on appearance alone, but the silicone layer is designed to protect the wire from abrasion, heat, moisture and corrosion. A layer of braided fiberglass is next, and it provides strength to the wire and helps secure plug ends, preventing them from coming off when you pull on the wire instead of the terminal. The next layer is insulation, usually a silicone type, which is another layer of heat defense and prevents the escape of any electrical charge that has leaked through. Wrapping the braided core is a suppression layer that can vary by brand. It is the primary insulator, keeping electrical current from leaving the core and protecting it from any outside charges.

Fire In The Hole B5

The problem

The original solution for conducting spark followed the same method we use to conduct most anything else, solid wire. This method was simple and provided low-resistance conducting, but caused some problems as electrical systems advanced. The current flow of each individual charge passing through the wire creates a magnetic field, which is switched on and off as each charge passes through. This results in an electromagnetic emission that can interfere with nearby electronic systems. The resulting radio frequency interference (RFI) was picked up by car antennas and heard through radios. In modern electrical systems, RFI can cause faulty sensor readings and interfere with solenoids and modules.

The OEM fix

The first solution for reducing RFI was the incorporation of a resistor on the wire end, reducing current flow and RFI. The logical next step was to turn the spark plug wire itself into a resistor by designing a completely new core.

Most OEM wires are the carbon-core type. Carbon-core wires replace the solid-wire core with a nylon or Kevlar core with embedded carbon fiber. Resistance is both the upside and downside of the carbon-core wire. It limits the current flow in the wire as a resistor, which keeps RFI down, but also limits the amount of current that reaches the spark plug. Carbon-core wires are a cost-effective solution for manufacturers, but their high resistance (over 10,000 ohms/ft. in some cases) is a limiting factor in performance applications, and carbon cores tend to be fragile and fail more often.

If you’ve upgraded your vehicle to make more power than stock, it’s recommended that you upgrade your plug wires. For a given cylinder displacement, all performance upgrades must increase cylinder pressure or rpm. With increasing cylinder pressures, you need increasing electrical current to bridge the spark plug gap and trigger complete combustion. This is the point when wire resistance is no longer your friend.

Solid core

While we’ve made solid-core wires sound like an antiquated solution, they’re still used today in many high-performance applications. The core in this type of wire is usually made from braided stainless steel or copper, which conducts current very well and has the lowest possible resistance numbers. This allows them to transfer the most electrical charge to the plug and make the most power. However, they do not suppress RFI and can’t be used with modern electronic systems. Generally, these types of wires are only used with high-performance engines using a magneto, or a points-and-condenser-type ignition.

Spiral core

The most common performance plug wire is the spiral-core type. Spiral-core wires start with a nonconductive core of nylon or Kevlar, which has an alloy wire tightly coiled around it. A coating is then applied as another layer of RFI suppression. This form has less resistance than the carbon-core wire, but produces less RFI than the solid-core wire. Spiral-core wires usually have resistance figures under 50 ohms/ft. and will help you get the most out of an upgraded engine with any sort of modern electronics.

So what should I buy?

Armed with this info and a basic knowledge of your vehicle’s electronic systems, it should be fairly easy to decide what plug wires are right for your project. The name of the game is obviously to have the least resistance possible, but the type of electronic systems in your vehicle is really the limiting factor. Good-condition OEM wires are perfectly adequate for (mostly) stock vehicles. These wires usually have around 3,000 ohms/ft. of resistance and up. As a bare minimum, you’ll want to stay above 500 ohm/ft. with a stock vehicle. If you’ve done some performance mods, it’s time to upgrade to a spiral-core wire to deal with increased cylinder pressures. Good spiral-core wires can have less than 50 ohms/ft. of resistance. A solid-core wire can measure virtually 0 ohms/ft. and is the best performer in theory, but the lack of RFI suppression limits its use to old-fashioned ignition systems.

Article Courtesy of RCN Mag


Mechanical vs Electric Fuel Pump: How to Do It Right

Want an electric fuel pump to last forever and work right? We’re going to show you how to install it and wire it up the correct way!

Ok, let’s talk about the mechanical vs electric fuel pump. There is a lot of confusion and misunderstandings about them. There is also a lot of potential danger when people don’t do it right because they don’t know the right way to plumb them in or wire them…

So, let’s break it down:

When do you need an electric fuel pump?

Is an electric fuel pump reliable?

How do you keep an electric fuel pump safe?

How should you wire an electric fuel pump?

-When do you need an electric fuel pump?

Usually, a mechanical pump is preferred over an “aftermarket” electric fuel pump. They tend to be more reliable. However, sometimes that won’t work.

In my old ’47 Chevy, the engine I had swapped in had an issue. The cross member was in the way of the mechanical fuel pump. So, I ran an electrical fuel pump and had many trouble free miles.

Sometimes, people will plumb them inline with a mechanical fuel pump to add more volume and pressure. This is more for a full on drag car though…

-Is an electric fuel pump reliable?

Yes, they are. Hey, there’s about a billion cars running around right now with them. All new cars have them.

With aftermarket mechanical vs electric fuel pump though, YOU have to install them. That’s where some problems can start.

We’re here to show you the right way to do it!

So, what do I use? For a stock or performance street car, I like these Facet/Purolator mechanical vs electric fuel pump from Napa. They are quiet and work well.

A lot of people complain about some aftermarket electric vs mechanical fuel pump being junk, but usually, there is a reason they go out. It’s often the way the person installed it. There are a few things that kill them.

-Do not run them dry.

-Always run a filter before the mechanical fuel pump.

-Keep them as close to the tank as you can. Electric fuel pump pushes fuel much better than they can pull it.

-Mount them away from heat sources such as exhaust.

-Electrical Fuel pump power to them is everything. You must have the correct wire size to it. A relay is preferred. You may be getting the proper voltage to it, but not enough amps. Remember, the longer the run the more the power will drop.

-Also, the grounding of it is critical. Many people will scrape the area where they mount it or even add a ground wire. However, they forget that they don’t have a good ground from the body to the frame or to the engine. This will kill pumps real quick.

Tip: Screw into metal to the ground, not through it. “Star” washers are your friends…

Preferably, run a ground wire to the front. Many professional auto electricians will run ground wires from a unit to a common grounding point in an older car, just like in a fiberglass car. That way, there is no question if your ground is good, and it’s just 1 extra wire…

Once, a buddy and I were going to a show in his ’26 Buick roadster. It was built much like a T-bucket and it had an electric fuel pump. It was wired incorrectly and grounded by screwing into the frame by the electric vs mechanical fuel pump. We were about 50 miles out, and the pump quit…


What happened was the older metal of the frame simply wasn’t carrying the current well enough. The mechanical fuel pump overheated and shut down.

Fortunately, he had some extra wire and we screwed one end to the ground wire at the back and ran it to the front where we attached it to the negative side of the battery.

The pump started back up after it cooled down and we were trouble-free all the way there and back. When we got home he wired it in neatly and never had a problem after that…

-How do you keep an electric fuel pump safe?

The electric fuel pump can be dangerous?

Yep, without some way to automatically shut them off, they can be VERY dangerous.

But they don’t have to be.

If something lets go in your engine bay like a fuel line, the engine will eventually quit. However, if you don’t have a way to automatically shut off your electric fuel pump you will keep spraying raw fuel all over your hot engine and wiring.

Also, in a crash, your pump can continue to run feeding a fire if you don’t have a way to stop it.

Note: Never mount an electric fuel pump in an enclosed area such as the trunk or interior space…

Ok, so how do I do it right?

The easiest way is to use an oil pressure switch. The switch will stop the pump whenever the oil pressure in the engine goes away. So, whenever the engine is off, the pump will turn off automatically.

Some switches just do that. But how do I get the pump to run when I’m trying to start the motor and the oil pressure’s not up yet?

You use a three prong switch like this Standard Ignition PS-64:

The switch will also let the pump run when you hit the starter because the engine doesn’t have oil pressure yet.

Electric Fuel Pump

One wire goes to the pump, one to the start circuit, and the other to the ignition circuit. So, when there is no oil pressure, the switch connects START to PUMP, and as soon as you start cranking it runs the pump. When the oil pressure comes up, the switch connects IGN to PUMP, for normal running. When oil pressure goes away (because you just hit that rock and tore the pan off the engine, for example) it again connects START to PUMP and disconnects IGN from PUMP, so the pump shuts off.

Don’t worry, it’s easy to wire…

-How should you wire an electric fuel pump?

Since you need the fuel pump back by the tank and at the same level as the fuel or lower, that usually means you’re going to have a long run of wire. So, you need to have really good wiring going back to it. Wiring that will carry enough current. Running the current through your ignition switch isn’t a good idea since it’s probably already overloaded, and will kill the voltage. That will kill the pump. However, it’s nice for convenience. That’s why a relay is really good to use.

It lets the ignition switch activate the pump while keeping the power from having to run through it. It will keep your pump alive and happy because it is getting full voltage. A good way is to mount a relay beside a power distribution block on the firewall (see Improved Power Circuit) and get the power from there.

Here is a diagram on how to wire and plumb your pump:



Our Picks

All four of these manifolds serve their purpose in the performance community. The GT manifold is probably best suited for road race and autocross cars looking for the power coming off the corners. If all-out high horsepower for drag racing is your thing, then stick with the Cobra Jet manifold. The BOSS 302 is a cost effective upgrade as a mid-level upgrade for the 2011-14 GTs and the GT350 respectively for the 2015+ GTs.


  • 1 hp at 6,900 rpm
  • 2 lb-ft at 5,400 rpm
  • Average Power: 373 hp, 376 lb-ft – 2,800-7,500 rpm

BOSS 302

  • 4 hp at 7,600 rpm
  • 4 lb-ft 5,400 rpm
  • Average Power: 376 hp, 361 lb-ft – 3,000-7,800 rpm
  • +/- to GT manifold:+19.3 hp, -30.8 lb-ft

Cobra Jet

  • 2 hp at 7,600 rpm
  • 6 lb-ft at 5,400 rpm
  • Average Power: 386 hp, 370 lb-ft – 3,000-7,800 rpm
  • +/- to GT manifold:+40.1 hp, -20.6 lb-ft


  • 8 hp 7,500 rpm
  • 6 hp 6,100 rpm
  • Average Power: 381 hp, 365 lb-ft – 3,000-7,800 rpm
  • +/- to GT manifold:+24.7 hp, -26.6 lb-ft

More OEM Goodness from Ford Performance

When we asked what’s in store for 2015+ 5.0 enthusiasts, Kershaw remarked, “We are really close to releasing our Power Upgrade kits for the 2015-2016 Mustang GT and Power Upgrade 3 that includes the GT350 manifold. This is the first time we’ve offered one of our manifolds with a CARB EO. You can now rev over 7,000 rpm and it picks up huge of the stock manifold, nearly 70 hp at 7,500 rpm!  However, it loses some mid-range and is pricy. The Power Upgrade 2 uses the GT350 throttle body and CAI picks up 21 hp peak, over 40 lb-ft at 1,500 rpm and will be a very reasonably priced.”