Strength of materials

[Para]

I am inches away from ordering a roadster kit and giving away possibly 1 year of my life

That said, I want to do this job once and not have to go back in there and replace things. Most of these components come from a 5.0L mustang or simliar
I had two 5.0L Mustangs in my youth, an 1984 with a 7.5" rear end and a 4 speed. I also had a 1992 with a 5 spd and an 8.8" rear end
The 1984 I destroyed the rear end AND the transmission at about 60,000 miles....and that was with an anemic 175 Hp carbed 302
I have to say with the 1992 I had no powertrain problems at all, but that was with 225? Hp driving it, not the 350-ish Hp I want to deliver to get an 11 sec car

1) Can a stock 8.8 handle the day in day out abuse of a 350 Hp engine and occasional burnouts?
2) Can a Ford T5 handle the same? ...Seems like the Tremec is not rated for much more either

[Jeff Kleiner]

13 years... 26K street miles...Hundreds if not thousands of autocross runs...Dozens of track days...Several drag strip excursions...350ish HP...3.55 geared 8.8...World class T5...Since day one it’s been whipped like a borrowed mule...So far so good :)

Jeff

[Para]

How 'stock' is your 8.8 ? ....any mods?
The T5 comes straight out of a Mustang? I seem to remember something about T5's with and without a neutral safety switch and how it interacts with computer (If you choose EFI)
Is 3.55 gearing good for road racing and 1/4 mile?

[mcondos]

these cars are so light, and traction is so poor, the stock parts hold up pretty well. Not sure if you'll see 11's on 350hp tho.

[Para]

When you say 'so light' that means alot of things to me. 1) so light the tires just sit there and boil ? 2) I am not so sure how much being light compensates for something that is not strong enough
A 1/4 mi calculator said at 2,145 lbs and 350 hp I should expect an 11.08 1/4 mile....with perfect hookup. With those giant tires these things just sit there and boil ?

Which gets me to my last question: If they are real light and sit there and boil, whats the practical limit to how much Hp you want to have?
Took a ride in a 650 Hp Hennessey Camaro and driving straight at 60 mph, hit the gas, rear end breaks loose.....on the hiway !!!
W/O some sort of traction control system all that Hp becomes close to useless (unless you have a death wish)
I suppose thats why alot of supercars have a 'launch control' mode

[Para]

So whats the trick to making a really quick Roadster? I don't know of anyone that makes an aftermarket traction control system you could add in.
What about the various 3 link, 4 link, etc rear ends, does one of them put the power to the ground better?
The last thing I want to do is spend all this $ and time and end up with a 12+ sec car....I can just by a camaro or mustang and get that with a fact warranty !

[Avalanche325]

A huge portion of how well parts hold up is your driving style. One guy will release the clutch quickly, the other sidesteps it and shocks the drivetrain. One guy will touch the rev limiter, the other guy will ride it like Seabiscuit.

A Tremec is considerably stronger than a T5.
T5 = 250 lb-ft.
T5 world class or Z-spec versions up tp 330 lb-ft. Depending on the exact version.
TKO = 500 or 600 lb-ft
There are several upgrades available for both.

I did wreck a synchro on my TKO-600 behind a 500hp 347 that gets street, autocross and track thrown at it. I did have the factory installed leak, which I am sure didn't help. But all it takes is a bad shift or two. I did an upgrade when I replaced that for better and safer shifting.

[Avalanche325]

So whats the trick to making a really quick Roadster? I don't know of anyone that makes an aftermarket traction control system you could add in.
What about the various 3 link, 4 link, etc rear ends, does one of them put the power to the ground better?
The last thing I want to do is spend all this $ and time and end up with a 12+ sec car....I can just by a camaro or mustang and get that with a fact warranty !

I have a friend that has Race Logic traction control and ABS in his with a supercharged Coyote Aluminator. Oh, and he wrecked it.


OK. Brass tacks time. The trick to a really fast roadster.......... is the driver.

Don't take this as me being nasty. This is my real world view. If you are a show and shine guy, it doesn't really apply. But you sound like you are looking to put your foot through the floor. We lost a guy a short while back that was all about his 700+hp. I don't think he had the car on the road for three months.

You had better know what you are doing in one of these if you are going to get aggressive. And that doesn't mean you have stomped the pedal to the floor on a couple modern electronic nannied up cars. If you sit there and spin the wheels at any HP level, you don't know how to control your car. The safest place to learn these skills is autocross in my opinion. Lower speeds, no walls, very few things to crash into. And you will never drive as hard anywhere else.

If you are looking for a drag racer. Why in the world would you be looking at a Cobra? These cars are road racers. (Yes, there were the dragon snakes. But that is a special setup) Short wheel base, traction limited and concrete walls sound like a bad combination to me.
If you want to be competitive in autocross. You wouldn't look at a Cobra. You might have more fun than anyone else though.
If you want a fast car that has some modicum of safety that you can stomp the pedal, steer, and survive. You wouldn't look at a Cobra.
Track days are where these cars really sing. But again, they are a handful.

If you want a car that is temperamental, hard to handle, nothing but compromises, loud, smelly, and is ready to kill you the second you lose respect for it........THEN and only then, do you want a Cobra.

You want to go really really fast? Buy a Nissan GTR. A Cobra is really about the vintage race car experience.

[NAZ]

The TKO-600 is rated at 600 lb ft of torque stock and Liberty Gears can make it handle 700+ and they can also fix the high speed shifting issues. The 8.8 can be made to handle lot's of torque, my Moser Engineering 88 has 35-spline axles & spool and will handle my 1,100 HP nitrous power with wrinkle wall drag slicks on a prepped drag strip with way more traction than you'll ever see on a street. If you've never walked on a drag strip starting line it's like walking on fly paper, it will literally pull your slip-on shoes off. If you chose wisely, your trans & rear end (and don't forget the driveshaft) can all be spec'd to handle any amount of power you want.

Forget the roadster if you're interested in drag racing -- it's a lot of trouble to make them compliant with NHRA rules and the car will no longer look like the original "Cobra" Shelby built. Of course if you live somewhere that has an outlaw track you might get away with running an open cockpit car with a funky single roll bar. But even then that's a risky endeavor. If you've never rolled a car before you likely just don't know enough to be scared -- I've rolled two and walked away with a much better understanding of how inadequate a roll bar is in an open cockpit.

Traction is not a problem if you stay away from the IRS and know how to design a proper four-link and have the fabrication skills to implement.

But if you want to drag race your car be advised that FFR does not build a kit car that is NHRA compliant and some are harder to make compliant than others.

[Jim1855]

Para,

The new Super 8.8 that is now standard with IRS is a lot stronger than the old T-Bird 8.8. I ran a Torsen T2, 3.27 gears and 440hp/435tq at the wheels with the T-Bird unit and have friends with a lot more power than that. Didn't break gears or axle splines although I have friends that did. Don't think you'll break the new diff, gears and axles.

The TKO-600 held up to most of the abuse that I know of. I'm not a drag racer but have a few hole shots behind me, that and 65k of banging gears. The new TKX trans is supposed to be as strong and by design shifts better.

Just build a real motor and you should be fine. 350 hp is just a start.

Jim

[Mike N]

What tires are you going to run? You are far more likely to kill the T5 running slicks than sticky street tires. I have a rebuilt T5 in mine with all stock parts but with a careful rebuild by Bob Hanlon. The 8.8 rear has Dutchman axles which I replaced when I did the 5 lug conversion but I did not upgrade to 31 spline. No other changes. On a dynojet it puts just over 420 ftlbs to the tires so way above the torque rating for the transmission. With street tires the car runs consistent mid 11's and has not broken anything yet after dozens of 1/4 mile runs and 100's of auto X runs. I don't abuse it but it does get beat on a lot. Of course your mileage may vary. I know people that have scattered some pretty heavy duty drive train parts. They do not get to drive my car ;)

[mike223]

When you say 'so light' that means alot of things to me. 1) so light the tires just sit there and boil ? 2) I am not so sure how much being light compensates for something that is not strong enough
A 1/4 mi calculator said at 2,145 lbs and 350 hp I should expect an 11.08 1/4 mile....with perfect hookup. With those giant tires these things just sit there and boil ?

Which gets me to my last question: If they are real light and sit there and boil, whats the practical limit to how much Hp you want to have?
Took a ride in a 650 Hp Hennessey Camaro and driving straight at 60 mph, hit the gas, rear end breaks loose.....on the hiway !!!
W/O some sort of traction control system all that Hp becomes close to useless (unless you have a death wish)
I suppose thats why alot of supercars have a 'launch control' mode

So many thoughts to address...

For perfect hookup you would need drag slicks / drag radials might do (and also might break things too) - 200TW tires are going to boil, and into 2nd gear - and as mentioned, you're not going to get to do it because the insurance companies are all over NHRA + IHRA tracks to ensure these specific cars meet tech - and you're not going to pass tech in anything that still resembles a roadster (for the speeds / E.T.s you ought to be capable of).

I've got 500hp/500ftlbs/T56 - with a 3.55 rear gear (TBird IRS 8.8) it lights 200TW tires in 3rd gear, easing onto half throttle @70mph - careful what you wish for, that's not as much fun as one might think (but it doesn't break parts with street tires).

I was aiming for a low 10 second ~135mph street car, and I intended to pass tech - put those thoughts out of your head - by the time you pass NHRA tech it won't be safe to drive without a helmet on - there's not enough room for all the required bars and your head too.

400/400 *appears* to be a sweet spot for these cars on street tires - 350/350 *may well* be more like it.


So it really does become a question of what tires do you want to run, and what is it that you want to do with the car?

[NAZ]

Remember that the torque rating on the trans is for 1st gear as it is the gear that multiplies the engine torque the most. Want to be easy on the trans, light throttle in 1st gear. Just for grins, multiply your peak crankshaft torque by the 1st gear ratio to see how much torque your trans has to handle. Want to see what your rear axles have to handle, multiply the 1st gear peak torque by your rear gear ratio. My Moser 88 35-spline gun drilled axles have to handle 14,757 lb ft of torque, it'd be much more but my 1st gear ratio is a tall 1.80:1.

[Para]

What is 'the new Super 8.8' ? Can I get that at a junkyard out of the proper model ford? Or, is it something F5 sells?
I have come to a similar conclusion that about 350 hp might be nice for an overall driver, wont beat a Z06, but may give it a run
Can the T5 handle 350 hp over the long haul? If its rated for 400-ish hp, that sounds marginal to me

Oh, before I forget, is there a better clutch setup for the T5? I used to waste a clutch every year or two in my mustangs. Does Anyone make a dual clutch setup with a hydraulic actuator ?
(That manual clutch in traffic was like doing 50 reps on a leg press manchine!)

[Hoooper]

What is 'the new Super 8.8' ? Can I get that at a junkyard out of the proper model ford? Or, is it something F5 sells?
I have come to a similar conclusion that about 350 hp might be nice for an overall driver, wont beat a Z06, but may give it a run
Can the T5 handle 350 hp over the long haul? If its rated for 400-ish hp, that sounds marginal to me

Oh, before I forget, is there a better clutch setup for the T5? I used to waste a clutch every year or two in my mustangs. Does Anyone make a dual clutch setup with a hydraulic actuator ?
(That manual clutch in traffic was like doing 50 reps on a leg press manchine!)

The super 8.8 is in every mustang model (except maybe gt500) since 2015. There are hundreds of them in every junkyard

[Para]

So the super 8.8 is an IRS unit, Hundreds of them in every junkyard? Have that many less than 5 yr old mustangs been wrecked so far?....
When you say T-Bird 8.8, why do you call it a T-bird 8.8? Didn't that same rear end come in explorers ad mustangs too?
I am a bit confused about the terminology you guys use

This is starting to give me a headache

[mike223]

The first IRS setup FFR sold was based on 1989-1997 TBird 8.8 IRS (cast iron) - Also found in aluminum case in a few IRS Mustang Cobras + Lincoln Mk8(?) town cars - this IRS unit is no longer sold by FFR in current production kits.

The new super 8.8 from the new Mustang IRS is the basis for the current FFR IRS kits.

Not sure what is current on the solid axle cars.


Regarding clutches - in my experience any V8 Mustang clutch will do on street tires - because you just put it in a vehicle that's 1000lbs lighter - it now burns tires, not clutches.

[CraigS]

"The last thing I want to do is spend all this $ and time and end up with a 12+ sec car....I can just by a camaro or mustang and get that with a fact warranty !"
With this thought of yours in mind I will say, as nicely as I can, meaning no offense, that maybe an FFR is not for you. Most of us build these because we have wanted a cobra for a long time and because we enjoy the building as much as the driving. Few look at it as a way to have a car at the end of X months work that is perfect in every way and that we will never have to touch again other than putting gas in the tank.

[rich grsc]

"The last thing I want to do is spend all this $ and time and end up with a 12+ sec car....I can just by a camaro or mustang and get that with a fact warranty !"
With this thought of yours in mind I will say, as nicely as I can, meaning no offense, that maybe an FFR is not for you. Most of us build these because we have wanted a cobra for a long time and because we enjoy the building as much as the driving. Few look at it as a way to have a car at the end of X months work that is perfect in every way and that we will never have to touch again other than putting gas in the tank.
I agree, maybe not the car he should get, almost sounds like a kid in the basement just day dreaming.

[Chris @ Forma]

Para,

Yes they are light. Our shop Roadster has a Gen 2 Coyote slightly detuned from the orignal 435 HP driving through a 6 speed MT-82 tranny and it will light the tires in 1-3 very easily. Our Coupe is also Gen 2 Coyote but makes a bit over 800 HP and it easily will spin the tires at 120 mph. Just remember more HP beyond what you can connect to the pavement only increases your tire budget.

[mike223]

Our Coupe is also Gen 2 Coyote but makes a bit over 800 HP and it easily will spin the tires at 120 mph. Just remember more HP beyond what you can connect to the pavement only increases your tire budget.


Assuming you survive long enough.

The list of those who got in over their heads is long + tragic.

[mcondos]

What is 'the new Super 8.8' ? Can I get that at a junkyard out of the proper model ford? Or, is it something F5 sells?
I have come to a similar conclusion that about 350 hp might be nice for an overall driver, wont beat a Z06, but may give it a run
Can the T5 handle 350 hp over the long haul? If its rated for 400-ish hp, that sounds marginal to me

Oh, before I forget, is there a better clutch setup for the T5? I used to waste a clutch every year or two in my mustangs. Does Anyone make a dual clutch setup with a hydraulic actuator ?
(That manual clutch in traffic was like doing 50 reps on a leg press manchine!)

Yikes! You may want to go with an auto, it'll be quicker for you in a drag race probably anyway.