Cobra power, how much is enough?

[john chesnut]

I think it comes down to how the car will be used. I have had some big horsepower replicas. Expensive, noisy, gas guzzling, and finicky. Fun on the track but not great if your driving on the street a lot.

My scratch built Cobra replica has C5 Corvette suspension, brakes, wheels and tires, stock 405 rated HP LS6, Tremec 6 speed, The C5 diff (converted to take a driveshaft) with 3:42 gearing. (I know, I am a black sheep for using the Vette parts). I drive it a lot. For 3/4's of the year it is my daily driver. It's a joy to drive. Plenty fast, (I won the Run and Gun road course for cars with street tires with it), as reliable as a new Vette, and averages around 30mpg. For me, balance, driving dynamics, and handling is more important than brute power. I don't drag race.

[John Owen]

My favorite engine for street driving is a 521 in Yard Dog that makes 553 hp at the wheels. Caution in first and second, then WOT in third with good tires. However, my 393 with 400 at the wheels was a relaxed but fun drive in Fire Ant, much more practical. Fire Ant now has an 1130 crank HP all natural 600 inch Boss 9 from Kaase, and it is not a pleasure to drive on the street. On the track .........

[RICK LAKE]

It's about TORQUE, this is what moves the car front stop until your HP crosses your torque band in the higher rpms. Heres a couple of questions for you to answer and think about,
Sound like you have a great car already. It has everything to protect you, launch control, ABS, traction control, reduced power if tires spins, I think you get where this is going, the most you will get for a cobra is power steering and MAYBE an ABS system if you build it yourself.
Every time I have added more power you have to learn how to drive the car all over again, rolling on and off the gas smoothly. Same for the brakes.
Alot dending on who's car you buy and what chassic configuration is under the body. some cars twist more than others. You can drive a car with 400/450 HP and Tork and have a great street car and a little fun. I started with a real numbers 452 motor with 348hp and 446ft of tork at the crank. Car will run 12's in the 1/4 mile. idle at 700 rpms smooth and little noise. The key thing for this is setup of rearend ratio and manual trans ratios in the 5 speed and then 6 spd. You don't need to turn 7,000 rpms with these motors. I have a limiters of either 6,000 rpms or 6,200 rpms MAX. I have gone to a 482 stroker with 620 ft of tork and 540 HP at the crank. It has become a hand full. Having the suspension and good tires help alot, but can still smoke 335's in the mid range of the car. Sometmes fun, sometimes not fun. With going to a driving school for a week, a good 500/500 will be a safe range. Start here, get the power bug and build bigger in a couple of years. The last question is how deep are your pockets?? This may limit your power wants and have you asked the boss???( other half) Have a good day Rick L.

[madmaxx]

It's not hp 90 percent of time it's torque. 275hp and 600 ftlb torque

[tirod]

And the conversation focuses on what's under the hood - when the record shows that the 289 won the championship.

Balance is more important than engine. If the chassis can't put 550 hp or 600 ftlbs of torque down to the pavement, you get exactly what everyone describes - tires spinning in third gear at 60mph.

That is NOT something you want to happen turning in to a tight corner in traffic on cool pavement at dusk as the dew is forming. It IS exactly why the big blocks were termed dangerous - don't forget, Shelby sold every 289 built, but it took 18 months longer to push the 427/428 off the lots. They were not considered user friendly. Bill Cosby shipped his back. Smart man.

Read very carefully, many of the 500 hp proponents aren't using this as a daily driver. But the small blocks were - and still are. They didn't abruptly break away and lose traction because of driver error.

If you need a testosterone injection on the weekend, a big block will certainly do it, if you want to use the car daily, consider carefully. Balance is much more of what cars have now, not brute levels of horsepower stuffed into a vintage chassis. What good is 550 hp if you can only use it 5% of the time? Better to size the motor for what you can do 85% of the time, and develop the chassis to use what it has.

Check the lap times of the day, the 427 was a bare few seconds ahead on tracks - it's poor handling from traction limited it's potential for what it was built to do - race on road courses. Ford just needed a counterpoint to the 427 Vette, and they got it, another overweight poor handling bull in a china shop.

[FatBoy]

Originally Posted by tirod

And the conversation focuses on what's under the hood - when the record shows that the 289 won the championship.

Balance is more important than engine. If the chassis can't put 550 hp or 600 ftlbs of torque down to the pavement, you get exactly what everyone describes - tires spinning in third gear at 60mph.

That is NOT something you want to happen turning in to a tight corner in traffic on cool pavement at dusk as the dew is forming. It IS exactly why the big blocks were termed dangerous - don't forget, Shelby sold every 289 built, but it took 18 months longer to push the 427/428 off the lots. They were not considered user friendly. Bill Cosby shipped his back. Smart man.

Read very carefully, many of the 500 hp proponents aren't using this as a daily driver. But the small blocks were - and still are. They didn't abruptly break away and lose traction because of driver error.

If you need a testosterone injection on the weekend, a big block will certainly do it, if you want to use the car daily, consider carefully. Balance is much more of what cars have now, not brute levels of horsepower stuffed into a vintage chassis. What good is 550 hp if you can only use it 5% of the time? Better to size the motor for what you can do 85% of the time, and develop the chassis to use what it has.

Check the lap times of the day, the 427 was a bare few seconds ahead on tracks - it's poor handling from traction limited it's potential for what it was built to do - race on road courses. Ford just needed a counterpoint to the 427 Vette, and they got it, another overweight poor handling bull in a china shop.

I'm sorry, but most of that is just plain rubbish. An iron block 427 has pretty much perfect balance (mine is 48/52 front/rear). The myth that big block Cobras are nose heavy is just that, a myth. The reason that Shelby didn't race the 427s was because they weren't homologated and focus moved to the GT40.
I'm pretty certain that given the same conditions, the same track and equal drivers, a 427 would comfortably beat a 289 every time.
I've driven original spec Kirkham 289 and 427 back to back and the coil sprung chassis is in a different league to the leaf sprung 289.

Lights blue touch paper and stands back.

Paul

[mdross1]

Originally Posted by FatBoy

I'm sorry, but most of that is just plain rubbish. An iron block 427 has pretty much perfect balance (mine is 48/52 front/rear). The myth that big block Cobras are nose heavy is just that, a myth. The reason that Shelby didn't race the 427s was because they weren't homologated and focus moved to the GT40.
I'm pretty certain that given the same conditions, the same track and equal drivers, a 427 would comfortably beat a 289 every time.
I've driven original spec Kirkham 289 and 427 back to back and the coil sprung chassis is in a different league to the leaf sprung 289.

Lights blue touch paper and stands back.

Paul

I agree 100% my 460 car when scaled with iron heads intake and water pump was 48/52 now all parts are aluminum.As long as you drive the car to the limits of the tires your running and the suspension is setup correctly,all cars are prey.No doubt the big blocks have the torque hit to shred the tires just have to know when it could happen and drive accordingly.Besides I need the fix when opening the hood of my car for myself and to hear the reaction it always gets from those that want to see it.

[B.M.B.C]

Im split on this, because of the reason that in the 60s they 427 was just that...... 427 ci 500/500 at the very most. Now 50 years later there are cars and owners with anything upto nearly 600ci and 700/700. And that's due to modern devolopments with big blocks. Added with chassis technogoly and alloy blocks that have nearly halved the weight of a 427 type car. Horses for courses and brings it into a whole different ball game. The 427 was always gonna be a straight line car cause it was designed and built for big tall Texans that lived on straight roads.
Let's get the big shot gambling guys back with the Kirkham and the 458 and put them round the Ring at Nuremberg . That would be a decisive result.

[lippy]

I'm questioning the same thing. I would build a small block 289 fia but I just like the look of the 427 better. One idea I have is to build an aluminum 427 with more of an oversquare geometry - built more for responsiveness and revving than for high HP. Im starting to think a big HP 427 stroker is too much.

[FatBoy]

Originally Posted by B.M.B.C

Im split on this, because of the reason that in the 60s they 427 was just that...... 427 ci 500/500 at the very most. Now 50 years later there are cars and owners with anything upto nearly 600ci and 700/700. And that's due to modern devolopments with big blocks. Added with chassis technogoly and alloy blocks that have nearly halved the weight of a 427 type car. Horses for courses and brings it into a whole different ball game. The 427 was always gonna be a straight line car cause it was designed and built for big tall Texans that lived on straight roads.
Let's get the big shot gambling guys back with the Kirkham and the 458 and put them round the Ring at Nuremberg . That would be a decisive result.

I think you mean the Nurburgring? Nuremberg was where the big post WWII trials were held.
I also dispute your suggestion that the 427 was designed for straight roads. I understand it was possibly the very first CAD designed car chassis. Some subsequent compromises had to be made due to constraints from AC Cars, but it was lights years ahead of the leaf sprung 289 chassis.
The assertions that 427 Cobras are lumbering nose heavy beasts are almost certainly made by people who have never driven one, or at least with any degree of gusto. I find mine an absolute delight to drive on a track and relish the neutral handling.
For the record, I suspect a 458 would run rings around pretty much any Cobra on a track, especially one as demanding as the 'ring, but so it should, it has the benefit of over 40 years of technology and knowledge.

Paul

[patrickt]

Originally Posted by FatBoy

I think you mean the Nurburgring? Nuremberg was where the big post WWII trials were held.

Nuremberg is exactly where these debates belong. Then, the participants should be forced to walk to Bataan.

[B.M.B.C]

Fatboy I do agree with you that's why I have a split in this topic. Sorry spell check malfunction on earlier post.

[bobcowan]

Originally Posted by PHC1

how much is enough to keep the car fun to drive and feel you have neither over-powered or under-powered the car with the choice of engine?

This question comes up a lot. I always give the same answer:

There's no such thing as too much power, only not enough control.

That sounds like a pat answer, but it's not. 650hp in a car with good tires, a good driver, and a well sorted chassis is a real joy to drive. Safe, smooth, and fun. OTOH, 350hp in a car with old hard tires and a poor suspension can be real nightmare to handle. It's a night and day difference.

Another aspect is not so much how much Hp you have, but how you get it. You can get 650hp from a turbocharged 2.2l 4cyl. But it may not be much fun to drive around town in. But that much power from a well built stroker SB is smooth and easy on pump gas.

You can use the advertised numbers to compare engines from the same builder. But looking at HP numbers doesn't really tell you a lot. To start with, most numbers are somewhat inflated to make the seller look better. Second, you're more interested in area under the curve, rather than peak HP.

As for the 289 vs. 427 debate - who cares? Not many people are going to use parts and technology from 1965 to build their performance engines. Why would you?

[rpatton3]

Yes, the Ferrari 458 driver in the $400,000 drag race is identified as "the Jew" and the Kirkham driver as "the Judge" and the obligatory bunny starter.

If the Kirkham has an aluminum FE, who knows about a hypothetical road race?
It is all driver skill.

Thanks,

Russell

[Silverback51]

Here is my car after I did the corner weighing. It's a Superformance with a 385 series (460) in it. I weigh in the 240 range and you can see that the F/R balance is 47.8 / 52.2.

Not nose heavy by any means.

[patrickt]

Originally Posted by Silverback51

I weigh in the 240 range and you can see that the F/R balance is 47.8 / 52.2.

Alright, it's yogurt for you for the rest of the summer. What was your final verdict on the corner weighting? Could you tell a difference in just normal, around town, type driving? Not autocrossing or racing, just regular stuff.

[Silverback51]

Well Patrick, our weather here in the not so great northwest has sucked big time. Cold and wet for the most part, with 3 of the first 7 days setting records for rainfall.

I put my wife on a plane this morning for Houston, so I'm hoping that tomorrow will be nice enough that I can take it out and be by myself so I can push it a little.

Forgot to mention this. I passed 200 pounds when I was 13 and have never looked back. Don't think me getting down under 200 is in my near future.

[Bruce M]

My Contemporary has a 502 BB with 505 HP on Dyno running 93 octane on Hoosier tires and Watts linkage. This combination puts the power on the ground and is more fun to drive.

[tirod]

Balance in the way I meant it isn't about weight distribution, it's about relative grip of the front and rear tires under power.

Since the rear tires also have to deal with torque, the point of the 427's poor handling was that those cars - on those tires in those days - would break loose the rear.

You all know the traction circle diagrams for road racing - a tire only has so much frictional capability, and if it's already on the edge of adhesion, suddenly adding another 200-300 foot pounds of torque means the rear loses grip and slides out.

It's not necessarily caused by jumping on the throttle - but poor linkage design that tips them open in a geometric increase can create it. Nobody talks about how to finesse the linkage to work the power output in a way that creates a linear response.

The 427's had a well deserved reputation on the track of suddenly letting go of the rear end - were all those drivers throttle dumping boobs incapable of controlling it? No. It just took a lot more driver skill than the average Joe buying into the ride.

Raise the hp levels, add some more grip, finesse the throttle and suspension for 40 years, things are going to improve, but the basic problem is still there, just at a much higher point - it's more power than the average Joe is used to.

As specifically said by many, they started out with a "small" hp motor and grew up with it, learning the car, and then moving up if and when they felt more comfortable in their ability. Maybe they didn't say it that way, but that's what is happening.

I wouldn't recommend a 550 hp car to any new driver, or one who's been in cookie cutter commuters most of their life. It's a big step up, and all too many will make a mistake that will crunch the car.

It's moving from a snail like 10 - 12 pounds per hp to 6.5 as it is, jumping into the sub 5:1 ratio is another significant step up. It's simply not allowed in most racing leagues to drop a driver into that kind of transition without a lot more under their belt, and shouldn't be recommended for a street car used on public roads.

Drive closer to the edge, it's a sharper break point.

[patrickt]

Originally Posted by tirod

I wouldn't recommend a 550 hp car to any new driver, or one who's been in cookie cutter commuters most of their life. It's a big step up, and all too many will make a mistake that will crunch the car.

There's merit to that statement. Now suppose, and I'm not saying he did, the OP worded his question like this: I don't plan on racing my Cobra, in fact I probably will never even autocross it in the high school parking lot, and I have never even been in a 500 horsepower car, and the only sub 2500 lb. car I've ever driven was a VW bug back in high school, so do you think just a 400 horsepower Cobra will be ok for me on the street?

I say a 400 horsepower Cobra would be just fine.