What gear would be best for my car?
This is one of the most commonly asked questions we get. There are always concerns over gas mileage, street-ability and highway cruising. The decision between 3.55, 3.73 or 4.10 gears is usually a monumental one for people but shouldn’t be.
The best all around performance gear is the 3.73. Gas mileage isn’t really affected, in fact we’ve had customers report better gas mileage when going to this gear from a 2.73 or 3.08. The 3.73 gives an excellent increase in acceleration and top speed isn’t decreased because you are able to wind out overdrive further. With a 3.73 your rpm in 5th gear at 60 mph will only be 2005, not at all what you would call “too high”. As we said, your top speed will not decrease when putting lower (numerically higher) gears in a car with overdrive. You will simply wind out 5th gear further than you could with the higher gears (numerically lower).
The 3.55 is also a good choice for a daily driver but does not offer the acceleration potential of a 3.73. With a 3.55 your rpm in 5th gear at 60 mph should be right around 1908. To sum it up, for a 5 speed car we feel the 3.73 is the best all around performance choice but either gear will make your car feel 1000 lbs. lighter and a whole lot quicker.
Now, if your pony car has the 4 speed AOD it’s a whole different ball game. The AOD is not the most responsive transmission Ford has ever made and it needs all the help it can get. For the AOD, 3.55’s are simply not enough. 3.73’s are a good choice for automatic cars and again, they don’t hurt gas mileage very much and the car remains as street-able as it was from the factory, only it accelerates much better. 4.10’s are also a good choice for automatic cars, and we prefer them. A 4.10 may sound extremely steep, but because the AOD’s 1st gear is so high (numerically low) and 4th gear (overdrive) is steeper than the T-5 it’s a very good choice for the driver interested in making their car perform better.
As for the 4.10 in a stick car, we really don’t recommend them for stock engines, but if you’ve had other work done like an intake and heads they’re an excellent choice. At 60 mph in 5th gear 4.10’s will bring cruising rpm up to 2204. 2204 rpm still isn’t bad on the expressway but in the city you’ll be doing a lot of shifting, but if that’s not a problem, 4.10’s offer a hellatious launch and rate of acceleration.
How much horsepower will a cam change give me?
Contrary to popular belief, a bigger cam will not necessarily make more power, in fact it can sometimes cost you performance. The stock 5.0 HO cam is actually a very efficient profile and can propel a naturally aspirated Mustang into the 11’s with the right pieces.
A larger cam will generally shift the power band of an engine upwards. This is fine if your engine is set up to make higher rpm power but the stock heads and intake are done making power right around 5000 rpm, so it doesn’t do any good installing a cam that makes peak power at 4700. Often a cam change will make a car seem faster because it’s down on power in the low rpms and then suddenly at 4000 it comes to life, but when you go to the track you may find it isn’t going any faster, or maybe picked up a tenth, and there are a lot of cheaper ways to pick up a tenth.
The bottom line is that if your car has stock heads, intake or both, installing a larger cam is a waste of time and money because your car will most likely go slower. We’ve gotten cars to go low 12’s and high 11’s with the stock cam. In fact our ’88 LX ran a 10.89 with the stock cam. On the other hand, if you’ve got a good set of cylinder heads and the right intake, a cam change can be worth the effort.
I’m on a fairly tight budget, what is the best way to spend my money?
Without a question the two most effective modifications you can make are headers and the right gear. Headers and a gear will make your car a whole lot quicker than the guy in the other lane (providing they didn’t have the same idea). After headers and a gear change there are a few other cost efficient modifications that can make a big difference. A few good suggestions are under-drive pulleys, 1.72 Roller Rockers, K & N air filter and a performance tune up. All of these items are included in our Street Fighter Performance Package, a good buy for the money and an excellent way to get your car in front of your competition.
I’ve done everything you said and when I took my car to the drag strip it wouldn’t even run 13’s!
Your car could have 500 horsepower but if you can’t get it to the ground it doesn’t do any good. Perhaps the most important piece of equipment you need to make a car run good numbers is a set of slicks. Even on the street if you’re interested in leaving the line before the other guy you need traction. Peeling out may have been cool when we were teenagers, but when you’re making real power and trying to get it to the ground tire spin isn’t cool, it’s a problem.
We’ve seen completely stock Mustangs with a set of slicks pull away from mildly modified cars that are defiantly making more power. In a race, if someone puts two or three car lengths on you right out of the gate it’s always difficult to catch up. As a general rule of thumb, a good pair of slicks is worth 4 tenths, although cars making more power will benefit even more.
A few years ago when our ’88 LX was running low 11’s, we put a pair of street tires on just for fun. The tires were awfully wide, 295’s to be exact but they were still just a radial street tire. The car couldn’t even get into the 12’s! It ran a couple 13.0’s but couldn’t go any quicker. We were spinning tire almost to the 1/8 mile mark. After bolting the slicks back on the car promptly ran 11.20’s. So in our case the slicks were worth 1.8 seconds, that’s roughly 18 car lengths in a race!
So now you’re asking what kind of slicks should you buy. We’ve found Mickey Thompson, Goodyear, Hoosier and Firestone to be excellent choices, although the Mickey’s seem to offer the best traction at the strip and on the street. If you’re driving on the street and don’t want to run the risk of getting caught with non-DOT tires, M & H DOT slicks aren’t bad, but they’re not as good as a true slick. Mickey Thompson now offers their ET Street, which has D.O.T. approval and works as well as their ET Drag. If that’s still too serious for you and you’re looking for a full tread tire, Mickey Thompson Sportsman Pro’s, Hoosier Quick Times and BFG Drag Radials are the next best choice. Once you’ve got a good tire on the car, traction bars like Mega-Bites are the next logical step and work well in putting power where it should be.
How fast will my car be if I install a Vortech Supercharger?
This is a tough question to answer. There are a lot of variables which determine how fast it can run. In optimum conditions, an otherwise stock engine making 8 lbs. of boost is capable of running very low 13’s and high 12’s. Of course traction is a major concern and times like these will never be realized without slicks.
Some customers have gone much quicker than this with just a few simple bolt ons. One customer has gone 11.93 with an 8 psi Vortech, and our Street Fighter package with a 3.55 gear, and the car remains as street-able as it was when it ran 14’s. With the addition of GT-40 heads and a little more boost another customer has gone 11.40’s and the car is perfectly street-able and gets excellent gas mileage.
These results are not unusual, and it’s easy to accomplish them when you know what you’re doing. Even with a 5 psi kit a Mustang is fully capable or running mid to low 13’s. considering there is adequate traction.
If I install a Vortech Supercharger what other modifications do I need to make?
When installing a 5 psi kit on a Mustang, truck or any other vehicle no other modifications need to be made. When installing an 8 psi kit it’s a good idea to make a few other important mods. Vortech’s new HO kit comes with everything you need. A bypass kit to cure reversion, an 8 rib belt kit to minimize belt slippage and ensure full boost, an adjustable boost retard to avoid deadly detonation and the new T-Rex Fuel Pump to ensure adequate fuel delivery. All of these items can be purchased separately if you have a 5 psi kit and want to make more power.
I want to put headers on my car / truck, should I use full length or shorty headders?
With the variety of exhaust headers on the market this is always a confusing dilemma. Full length headers offer a more substantial horsepower gain than shorties. The problem with full length headers is that there are currently no emissions legal versions on the market and when installing them it is necessary to modify the exhaust system to accept them. Shorties offer a more cost efficient way of scavenging exhaust fumes and almost all are emissions certified. When installing shorties it is not necessary to alter the exhaust system in any way, they bolt right in place of your factory exhaust manifolds. In either case we have found MAC exhaust products offer extremely high quality, are an excellent fit and are 100% American made. We can also recommend local exhaust shops that can build you a custom exhaust system or connect your existing one to a pair of full length headers.
How much will traction bars help my car?
Southside, H.P. Motorsports and Lakewood traction bars all do a good job of planting the rear tires and eliminating wheel hop. If you’re not using slicks or a sticky tire, traction bars won’t do much more than eliminate wheel hop. But if you have a pair of slicks, traction bars can give you the needed traction to pull a wheelie off the starting line. Polyurethane bushings on the rear control arms are also an effective way to increase traction and handling.
I was thinking of getting a nitrous system but someone told me it would blow up my engine.
That’s completely untrue. In the sixties and late fifties when racers were first experimenting with nitrous oxide it was unpredictable at best, primarily because no one fully understood its violent nature. Today there are several companies who have engineered excellent nitrous systems that when properly installed pose no direct threat to the health of your engine. As long as the system is jetted to a power level that your engine is comfortable with you’ll have nothing but fun and brute acceleration that allows you to embarrass other cars at will. At the lower power levels, no other modifications are necessary and many manufacturers offer upgrade kits should you decide you need more power. A 100 horsepower shot of nitrous can take a 14 second car into the high 12’s with no other modifications except adequate traction.
I want to do a fairly simple bolt on that will give me a few extra tenths, what do you think about computer chips?
The EEC IV is one of the most efficient engine management computers in the industry and does an extremely good job of producing power with the factory Ford programming. One thing that a custom chip can do incredibly well, is fix drivability problems. We program custom chips to help smooth the idles of big cams and fix drivability problems with more radical combinations. But at this time we have seen no significant performance gains by reconfiguring EEC IV that can’t be found through traditional tuning. A much better choice for added speed would be 1.72 rockers, under-drive pulleys, a gear or headers. A custom chip should be a consideration once you have a larger than stock camshaft and good heads, not when the car is mostly stock.
My friend and I have identical modifications but his car always seems to beat me, why?
Driving style and shifting can make a big difference in cases like these. A Hurst shifter can really decrease the amount of time spent in between gear changes and allows more precise shifts. Power shifting can be worth up to two tenths over granny shifting if you’re willing to take the chance of missing 3rd gear and buying a new T-5. Also, try to limit tire spin as much as possible, find a happy medium between peeling out and bogging. The launch is very important and many races are decided by who leaves the hardest.
We’ve tried to assemble and answer the most commonly asked questions we’re asked. These Q & A sections are divided into different categories and are constantly being updated and added to as we find the time.
If you’re a customer of ours and don’t see the answer to your question as always please feel free to call the shop.
5.0L Mustang Tech Q&A