Small block to big block (FE)???

[Allen Mulcahy]

Changing from a 351W to a 427/496 FE. Superformce car, Tko-500 trans, 3.73 rear, FE motor 596 hp @629 ft lbs torque , iron block. Question is how much driveabliy will I lose/gain with this engine change? Not a race car, street /show cruiser. This is not a done deal yet, on the fence. Also will this trans hold up with this new motor? Helpppppp

[blykins]

Unless your cam is very wild, or you have to run race gas, I don't think you'll lose any driveability at all.

The TKO500 is rated for 500 lb-ft. I would think as long as you didn't bolt on a set of slicks, you'd be ok. You're gonna lose traction before anything breaks.

[RedBarchetta]

Let us know how it goes and document/photograph the transformation.

-Dean #747

[wtm442]

The one thing you will notice is that you will probably have a faster idle with the big block. So taking off from a stop will be somewhat different, but with a 5 speed and the 3.73 rear end, it will be just a minor difference.

Also, the steering effort at slow speeds will increase due to the increased weight.

The one place where the drive-ability will change dramatically, will be at WOT

You will be able to make the Cobra lose traction and spin out much easier with the torque monster. But go for the big block. Enjoy! You did not buy the Cobra for good gas mileage! Take the jump. If and when I blow up my 425HP small block, I will go the big block for a replacement.

I have never heard anyone on this forum say that he (or she) had too much horsepower!

[Nantucket427]

Almost five years now with a similar FE combination. First gear is useless with the big block but they put it in for you little block guys. Oh, Oh, I don't want to start that debate again but it is friday.
The first thing those guys(with SB) tell me is they are making five hundred horse with there small block so, No Worries.

[RACER X #99]

Congratulations on going back to the Big Block that Ford gave up on so many years ago. You did say that you are a cruiser/ show guy so that makes sense.
You will notice that you will get all kinds of attaboys from the cruiser crowd and some BS from those of us who don't go along with the crowd.
Congratulations "Car Guy" I know you will please everybody at the shows and cruise ins.
If it's any consolation lots of racers have FE's in their tow vehicles.
Good luck.

[xlr8or]

You are almost as predictable as Evan these days.

[Barry_R]

Originally Posted by RACER X #99

If it's any consolation lots of racers have FE's in their tow vehicles.

I have a small block in my lawn mower....

[RICK LAKE]

Allen Driveability is a large area. You will have your hands full with the gearing of 3.73. With this kind of power and a 5 spd trans, I would drop the rear to 3.20's to 3.40's. That trans is good for 500 hp and tork. You are pass the max spec on both ratings. Will the trans hold up, depends on your driving. Normal driving with street tires BFG's no problem. Go to a Kummo,or Goodyear street slick and 3,000 grand clutch drops. Say goodnight to Hollywood. You will have a race between the Speedo gauge and the fuel level gauge of who gets to 0 first. With the added weight in the front end, you may adjust the weight in the car around and have the wheel alignment rechecked. If you have P/S, I see no problem with driving. A diaper and spare underwear in the glovebox for just in case. You are going to have your hand full with another what, 100 hp? Just be careful, that's all. Rick L. Ps I am going to a 496 motor next year with a 200 hp and tork increase.

[ENTDOC]

I agree with Rick on the rear end gearing. One of ther advantages of the 5 speed is that you can raise your diff ratio and enjoy good cruising RPM's. I have a 427w Roush in my Daytona and a stroked 427so in my Kirkham and I can tell you the FE is hands down a more fun motor that will absolutly walk off and leave the Daytona. Get a reliable builder however, Craft or Guessford come to mind. chuck

[Lowell W]

Is this new motor in a car now? Can you drive it? Or, can you compare dyno graphs from both motors?

I think Racer X is getting a little "cranky" lately...sure seems to be bothering him that anyone would even consider putting a big block in a Cobra.

In a Kirkham or an ERA, the FE would be a no-brainer. In a SPF, it's a toss-up.

I like the motor I have in my car, which is somewhere in between your present motor and the one you're considering: plenty of oomph, yet with enough room to work around. I've never really wished for more horsepower and what I REALLY wouldn't want is increased gas consumption. On the other hand, if 100 miles is a long drive for you and you like the way the big block looks (and sounds-a big FE just sounds cooler than anything else) and you don't mind having a motor which may require more maintenance, hey, it's YOUR car.

I've seen and heard of more guys going from small block to big block than the other away around, if that's any help.

And yeah, the 3.73 gears are pretty much useless, even with a smaller motor. Figure in the cost of new gears and set-up for the differential on this project...also likely new half shafts if you have the Ford 8.8 and, if you're upgrading the half shafts, you might as well go to 31 splines, which would mean upgrading the differential as well. Ditto the U-joints. You DO have a good driveshaft loop (or loops) don't you? The original SPF is NOT. Your tranny may take it, may not... You'll also need new headers for the FE.

And then how will your car drive? I doubt you'll gain any "driveability". Depending on how the engines are built, the FE may not want to run as smoothly at low RPM's as the 351. It'll be hotter and noisier and may need race gas, depending on the CR.

Bottom line? If you're contemplating this change to increase driveability, I think you'll be disappointed. If the WOW factor and a HUGE horspower increase are worth what may be a major expense and possibly an increase in aggravation, well, that's something YOU'LL have to decide.

Lowell

[Barry_R]

really depends on the engine he's buying. An FE can easily be as smooth and as driveable as any small block in a comparable state of tune. A larger displacement engine can deliver the same power at a lower RPM - means a milder, more reliable package. If weight is a big issue, an aluminum FE is now readily available and renders it pretty much a toss up.

As far as breaking driveline parts - that's up to you. I can put together a motor that can break most anything...

[Allen Mulcahy]

Can change trans to a TKO-600, 5th gear .82 or .64? I know this would help in the torque. Weight.... can build aluminum block to help with front end weight, cam specs 280/286 in/ex duration .590/.590 in/ex lift at valve 106 in centerline angle 114 ex centerline angle.10.5 compression ratio,Bore 4.310 Stroke 4.250, bigger bore w/smaller stroke or smaller bore bigger stroke?? Will probably not change rear end. THANKS for response Allen

[RACER X #99]

There is a good reason that most Superformance Cobras are fitted with 351 Windsors. Former Cobra racer and full time driving school owner Bob Bondurant was quoted years ago that the 351 Windsor is the perfect combination of weight to HP and makes for a better handling Cobra. Will it WOW them at the car show? Of course not. Will it outperform the FE on the track? Most former Cobra racers seem to be of that opinion. Since most Cobra owners never hit the racetrack in their Cobras and since the majority seem to be impressed with FE's than you will probably be real happy with your new FE.

[Anthony]

Originally Posted by RACER X #99

There is a good reason that most Superformance Cobras are fitted with 351 Windsors.

Yes there is. It's because there was (is) no reliable source for FE "crate" motors, and alot the FE's that were installed were built by "wannabe" engine builders, and the engines failed after being installed in new customer cars, and as superformance was marketing there cars as "factory built new cars", I don;t think they wanted a bad rap for unreliable engines. Superformance also reccommended 460 engines as well as 351's, again mainly because of reliability, but as we all know, the 460's are even heavier than the FE's.

Originally Posted by RACER X #99

Former Cobra racer and full time driving school owner Bob Bondurant was quoted years ago that the 351 Windsor is the perfect combination of weight to HP and makes for a better handling Cobra.

He also stated that alot of "new" cobra owners were wannabe race car drivers, with no real racing experience, and have never driven a true 600 hp car before, so the 351 was a good fit for wannabe cobra racers.

Originally Posted by RACER X #99

Will it outperform the FE on the track? Most former Cobra racers seem to be of that opinion.

I would think the late Dick Smith would probably say the 427 would be the faster car. However, I don't ever remember seeing a quote from him comparing the 289 vs 427 vs 351 cobra's. I've seen some interviews from him talking about replica's, and he was always very politically savy.

Originally Posted by RACER X #99

Since most Cobra owners never hit the racetrack in their Cobras and since the majority seem to be impressed with FE's than you will probably be real happy with your new FE.

Obviously, most cobra's are really street machines, not race cars. Using your reasoning, then you should put SBF's in all ford street macines, rods. There would be really no place for flatheads, SCJ's, Boss 429's, BBF's, as all of these cars never really see the strip or track. Why even put webers on an engine, as again most people don;t race their cars.

[82ACAUTOCRAFT]

Originally Posted by Allen Mulcahy

Changing from a 351W to a 427/496 FE. Superformce car, Tko-500 trans, 3.73 rear, FE motor 596 hp @629 ft lbs torque , iron block. Question is how much driveabliy will I lose/gain with this engine change? Not a race car, street /show cruiser. This is not a done deal yet, on the fence. Also will this trans hold up with this new motor? Helpppppp

I think everybody is missing the point, what Allen is asking is how will the car handle? well! I you install an all iron engine, your car will handle like a pig compared to the small block. If you install an aluminum engine, the car should drive almost the same with much more torque of course. An iron block, aluminum heads and manifold should be fine provided you re-tune the suspensions. It all depends what type of driving you like, If you like to drive on canyon roads then the SB is the answer, if you drag race then of course a BB would more appropriate. Most cobra owners I know think the best combination for a road car is the big 4" coil spring chassis powered by a small block like the old AC 289.

[RACER X #99]

Allan,
Just like everybody here on this board I was a nubie and a first time Cobra owner. And just like most here I too just had to have a 427 SO, so that was my first engine. Like a lot of guys I grew tired of the car show scene and after my first experience at open tracking I was hooked. I put a couple of thousand miles on the track with my 427, and admittedly it was a bone stock medium rise 427. it sure was a lot of fun. Unfortunately for me the 427 did not hold up to the rigors of 7,000rpm shifts. and a rebuild was in store. My pro engine builder told me this engine is too old and to valuable to be beating up on the track and he convinced me to sell it. It now resides in a CSX street car.
After reading about Bondurants opinions on the 351 Windsor I bought a 385 HP crate engine from Ford and again started open tracking. I have to tell you and this is what you asked, the car just felt better on the track. It was in all honesty not able to accellerate as fast as the BB but it does corner better and stop better.

I have since upgraded to a Dart 408 and have yet to find a 427 that can keep up with me.(not even Dick Smith at VIR last year.)

So unlike so many others who only have experience with just Big Blocks or small blocks, I have thousands of track miles with both in the same car.

No facts here just an honest opinion.

RD