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Owners of the ’05 to mid-’08 Mustang GT are quite familiar with the dreaded spark plug issue these 4.6-liter 3-Valve V8-powered cars suffer from. If you’re not familiar with the issues yourself, allow us to introduce the problem (and the solution) thanks to the help of our friends at Brenspeed and Brisk Racing.

To keep things short and simple, the ’05 to mid-’08 Mustang GT equipped with the infamous 4.6-liter 3-Valve V8 (as well as some 5.4-liter 3-Valve V8 applications) are notorious for breaking spark plugs when removed. This happens because of a few reasons unfortunately, but the main inherit issue is that the factory spark plugs are a two-piece design.

Some have speculated that Ford used this style of spark plug in an effort to reduce cost, while others have claimed they were used to reduce installation time on the factory line. Whatever the case may be, these plugs are almost always prone to breaking during the removal process because of a number of reasons.

Our completely bone stock 2005 Ford Mustang GT only had 70,000 miles on the clock at the time of replacing the spark plugs.

Our bone stock 2005 Ford Mustang GT had 70,000 miles on the clock at the time of replacing the spark plugs.

Generating A New Spark

Our replacement spark plugs were Brisk Racing Silver spark plugs, PN 3VR14S from Brenspeed.

Our replacement spark plugs were Brisk Racing Silver spark plugs, PN 3VR14S from Brenspeed.

As we mentioned above, we turned to Brisk Racing for a set of its silver core one-piece style spark plugs for our application. At the recommendation of both Brenspeed and Brisk Racing, we chose a one-step colder style of spark plug for a few reasons.

The first reason being that our 3-Valve Mustang GT will soon be receiving some much needed forced induction, thanks to our friends from Vortech Superchargers. We’ve decided on the centrifugal route with a Paxton Novi 2200SL supercharger that we’ll be detailing in a future segment. Expecting around 450 horsepower and torque at the rear wheels after installing our Novi 2200 and applying a custom tune from Brenspeed, Brisk Racing tells us these plugs are perfect for what we’re after.

Luckily for us, our new Brisk Racing silver spark plugs are easy to gap thanks to a traditional electrode style. We gapped our plugs to .35 per Vortech and Brenspeed's recommendation for our soon-to-be supercharged 3-Valve.

Luckily for us, our new Brisk Racing silver spark plugs are easy to gap thanks to a traditional electrode style. We gapped our plugs to .35 as per Vortech and Brenspeed’s recommendation for our soon-to-be supercharged 3-Valve.

“Upgrading to a one-step colder plug [which is also a one-piece style at that] is the best move you can make on these 3-Valve Mustangs,” Martin Uhlir, Director of Operations at Brisk Racing told us. “Because these spark plugs use a silver core, as well as a traditional style of electrode [unlike the factory Motorcraft pieces], enthusiasts can expect a spark plug solution which is extremely easy to gap, as well as a more precise and consistent spark for forced induction applications.”

Martin is of course referring to the electrode style known as a ‘cut-back’. It’s the most traditional style of electrode available today, and for good reason. “One advantage of a silver core is the intensity of the spark. It is much brighter and much stronger because the silver electrode is less dense. The maximum lifespan on a silver-core plug is about 30,000 to 35,000 miles depending on the gap.

“The energy of the spark on these plugs is much, much higher,” Martin further detailed. “It’s also the best conductor of heat and electricity. Utilizing a silver-core conducts 560% more electricity and 480% more heat than platinum. It’s a huge difference in thermal conductivity. In performance applications, what limits the spark plugs is the electrode material and any deposits that may form from running a rich air-to-fuel ratio.”

Installation Tips & Tricks

We started the process by removing the factory coil plugs.

We started the process by removing the factory coil packs.

George Dockery, Installation Facility Manager for Brenspeed, was the shop manager for many years before transitioning into his role today; turning wrenches and building enthusiast’s cars everyday in the shop for nearly a decade.

George explained that there are different methods for removing the factory spark plugs. The TSB procedure can be found in the tech section on Brenspeed’s website as well [detailed below]. “You’ll want to get the engine warm [we recommend the engine being warm anytime someone is removing 3-Valve spark plugs],” George explained.

First plug down, and lady luck strikes. This plug had definitely seen better days.

“My personal favorite way is to get the engine all the way up to operating temperature [this can be achieved through a 10 to 15 minute test drive]. Then, we remove the spark plug boots. We’ll spray some PB Blaster [though you can use penetrating oil] into the spark plug well, around a quarter of an inch or so. This coats the threads of the spark plugs. To break the seal on the threads, we crack each one of the spark plugs about an eighth of a turn. We let them soak for about 30 minutes or so, then come back to them. After soaking, it’s business as usual–back them out like normal, but at a slow and steady pace.”

Fortunately for us, we were able to remove every single plug without any of them breaking, thanks to George's method. We suspect the previous owner used a high quality fuel during their ownership, as there was barely any carbon build-up on the plugs.

Fortunately for us, we were able to remove every single plug without any of them breaking, thanks to George’s method. We suspect the previous owner used a high quality fuel during their ownership, as there wasn’t a lot of carbon build-up on the plugs.

What If Things Go Wrong?

Old vs new. The difference in the two is astounding to say the least.

Old vs new. The difference in the two is astounding to say the least.

“If you’re backing the plug out, and you feel some resistance, but you can tell it doesn’t feel quite right, then the spark plug itself probably isn’t turning,” George said.

“Because the factory spark plug is a two-piece design, the second portion of the spark plug is turning [top piece], but the bottom threaded portion is not,” George continued. “It begins to separate from the bottom, and it never loosens up. The head of the spark plug where the socket locks onto will look closer, but all that happens is the thread backed out–and now you’re in a position where you have to break the spark plug off. At that point, you’ll have to use a removal tool to remove the broken plug stuck in the head.”

Many Mustang enthusiasts highly recommend the Lisel broken spark plug remover tool for this job (PN LIS65600). This tool lists on Amazon for $59 before tax and shipping.

George reminded us to apply a small portion of nickel anti-seize to the threads of the new spark plugs, as well as some dielectric grease to our coil packs. Be careful not to apply any anti-seize to the electrode of the spark plug, as this can cause several issues.

“The great thing about these 3-Valve engines is that as long as they’re well maintained, the stock bottom end assembly, timing components, cylinder heads, etc, are all pretty good,” George said. “There’s a couple of small things you have to work through every now and then–but all around, it’s a great engine.”

Brent White, owner of Brenspeed reminded us that on its website, there’s a tech section where enthusiasts can find a compiled list of the company’s own tech articles. One article in particular that will come in handy before purchasing a new set of spark plugs for your ’05-’10 3-Valve powered Mustang can be found here.

And just like that, we ended the night with some awesome new spark plugs and new outlook on our 3-Valve engine. That, and of course some well-earned beer.

And just like that, we ended the night with some awesome new spark plugs and new outlook on our 3-Valve engine. That, and of course some well-earned beers.