Muscle Mustangs & Fast Fords
Yo Ken! - Tech Q & A - August 2013
Answering Your Technical Questions
Spring It On
I’ve been reading your magazine since 2004. It’s been a great help to me over the years with my project car. Keep up the great work.
I have an ’89 coupe with an Eibach Drag Launch spring kit. I’m adding a UPR Pro Series rear suspension kit so I can tune the suspension at the track. Are the Eibach drag springs the best springs for the job now, or should I replace them for a new set with an equal spring rate? If new springs are the best way to optimize my car’s performance at the track, then which spring rate and length should I go with? The car is driven half street and half track. Any info would be much appreciated!
Edmonton, Alberta, Canada
Clay, the Eibach springs are the right choice for your car. One of the key components for your suspension upgrade in a drag racing application is the antiroll bar. UPR Pro Series kit incorporates it; combined with the other components in its kit, you have an excellent package. I used this kit on my SN-95 and was impressed by how well it worked. You will not be disappointed.
I’ve been a reader and avid Mustang owner for years. I’m on my tenth or so Stang; currently my wife and I both own one.
My question is pertaining to the bellhousing mounting differences between the 5.0L Coyote and the 3.7L in my wife’s 2012. She has a six-speed, and health issues in her wrist may necessitate an automatic. I’m looking at Performance Automatic’s 4R70W swap for Coyotes and wonder if the bellhousing mounting pattern is the same. Ford has verified the flexplates for 3.7 and 5.0 cars are the same part number, but the transmissions themselves are different part numbers. I suspect this may be due to internal gearing differences as with the V-6/V-8 T-5s in Fox-bodies and SN-95s. Any help would be much appreciated!
Port Wentworth, Georgia
The 3.7 uses the same bolt pattern as the Coyote 5.0. I think you would be better off going with the 5R55S trans from Performance Automatic (www.performanceautomatic.com). It’s the stock transmission that came in the Three-Valve GTs, and it would make the swap much easier. For overall performance, the 3.7 works the best with the five-speed auto over the four-speed auto. Check out PA for more information.
10s Only Please
About a month or two ago, I wrote you lamenting about the lack of published articles and performance parts geared specifically for the 4.6L Three-Valve (315 hp) found in the ’10 Mustang GT.
I did some Internet research and found the cheapest (non-supercharged) budget (under $1,000) performance mods are either exhaust or intake. Right now, I’m leaning towards intake—CAI, performance tune, and maybe a new throttle body. I don’t know if a new intake manifold would help. And I’m not sure if a performance exhaust would yield the same results, though both would be better.
What mods would you recommend—exhaust or intake?
North Royalton, Ohio
Ed, the intake side with a tune will give you the most bang for the buck. The exhaust will yield a small gain in performance, and is something you should consider if you continue to modify your GT. The stock exhaust is adequate for basic mods, but will need to be upgraded to get the maximum performance as you add your mods.
A friend of mine recently picked up a ’10 GT500 with only 20,000 km on it. She has immediate plans to change the suspension, rims and tires; upgrade the cooling system; and upgrade the brakes. The parts list has been assembled, and she is in the process of making the order.
Will the previously mentioned parts bolt on to my ’05 GT? I am wondering about suspension geometry and pick up points—are they identical? I assume they are since they share the same chassis, but I want to make sure before I spend money on what I see as a cost-effective alternative to the aftermarket.
Cochrane, Alberta, Canada
Clint, the GT500 is built on the same platform as the standard GT. Everything that bolts on to a GT500 will bolt on to your GT. Except for the cooling system, which does not need to be upgraded, you can ask your friend for her take-off parts. This is a great way to upgrade your GT. You will see a dramatic increase in handling and stopping power, along with an upgrade in the looks.
Bag It Up
I have an ’08 Bullitt that I use regularly for performance-driving track days. I replaced my two front seats with racing seats so that I can use a five-point harness. My factory seats had airbags; my replacements do not. Can you tell me how to safely get the correct resistance reading so that I can suppress the dash light and keep my front airbags operational? Is there a factory plug I can use on the yellow connectors?
San Antonio, Texas
Kyle, there are a few ways you can go about turning off the dash light. Not to worry though, even if your dash light is on, the front airbags will work. You can put a resistor inline from Ford (PN XF2Z14B022AA), or you can get a universal side-airbag-bypass kit. Motorsportseats.com has them in stock. Remember that the removal of an airbag system constitutes a violation of federal law.