Motor question

[bruin_d]

New to the forum. I'm transferring soon from sea duty to shore duty (Navy) and am planning on building a Cobra in my free time. As all of you have done....I am bouncing around on motor selection. I've been doing quite a bit of browsing the last couple weeks and have a question that I have not been able to find the answer to. I have come across a lot of "wouldn't it be cool if...." type discussion but that's about it. I am curious if anyone out there has done a Boss 9 motor (460 with "semi-hemi" heads) in a Cobra. That top end setup that Jon Kaase sells continues to make me drool.

[Bob Cowan]

The problem is the sheer size. The Cobra isn't much bigger than a Miata. In some dimensions, the engine bay is smaller than a Miata. That engine didn't fit the '69 Mustang without re-working the shock towers and some other stuff.

[Jeff Kleiner]

I have the same thoughts as Bob, specifically regarding width.

For comparison (these dimensions are from the cylinder head edge, no headers):
302--- 24" wide
351--- 25" wide
460--- 27" wide
4.6--- 26 5/8" wide
Boss 429--- 30" wide

Jeff

[CraigS]

There is a guy on the other forum doing a Boss so search there.

[68GT500MAN]

There was a roadster at last years HB event that had a Kasse Boss 9 in the engine bay. It was a very nice build.
Doug

[Dan Babb]

Here's the thread from the other forum.

The motor looks awesome...but it's huge. Won't fit through the hood opening with the heads on...but that's probably not a big deal.
http://www.ffcars.com/forums/17-factory-five-roadsters/472674-merry-xmas-me.html

[bruin_d]

Here's the thread from the other forum.

The motor looks awesome...but it's huge. Won't fit through the hood opening with the heads on...but that's probably not a big deal.
http://www.ffcars.com/forums/17-factory-five-roadsters/472674-merry-xmas-me.html

Appreciate the link Dan. I am going to check it out. Below is my most recent build. Looking forward to joining the Cobra crowd.
40353

[Avalanche325]

"Pricing starts at $22,900 for a Dyno Tested ready to bolt in Kaase Boss Engine." Whoooooohoooo. You go baby!!!

That is an awesome engine. You might need to do a flip front to get to anything on it.

It is not exactly going to help the handling, though. That is going to have some serious weight. I hope you plan on just going in a straight line. (And good luck with that!) Let me know what brand of tires you are going to use. I want to buy some stock.

[edwardb]

I don't want to turn this into another "How much horsepower is too much" thread. But just a simple question. Have you ridden in or driven one of these? If not, you should. While that much engine and power is amazingly cool, this may not be the right platform to feature it. Just my opinion.

[bruin_d]

I don't want to turn this into another "How much horsepower is too much" thread. But just a simple question. Have you ridden in or driven one of these? If not, you should. While that much engine and power is amazingly cool, this may not be the right platform to feature it. Just my opinion.

Haven't driven in a Cobra yet but I've driven a few cars with horsepower around the 4 digit range. I know it's quite a bit of power for the length/weight and am OK with that.

[Davidbr_48]

Choice of engines is a personal choice and depends on your objectives: Are you interested in building a "period correct" replica? a track-oriented racing machine? a street legal machine just for fun? etc. My objectives were to build a modern, 21st century street version so I built my Roadster with the new Ford "Coyote" engine. It's rated at 412 horsepower, and in my humble opinion has way more than enough power. The engine is all aluminum, fuel-injected, computerized, etc - clearly a 21st century engine and not appropriate for a "period correct" build, but it was perfect for me. A new Coyote crate engine from Ford Racing is about $8K - much less than you'd pay for a high-performance pushrod engine, etc. It all depends on what you're aiming for!

Davidbr / Tucson AZ

[Avalanche325]

Haven't driven in a Cobra yet but I've driven a few cars with horsepower around the 4 digit range. I know it's quite a bit of power for the length/weight and am OK with that.

Just realize that 500HP in one of these, at 2150lbs, is equivalent to around 900HP in a modern Mustang. Add in a short wheelbase and being confident without knowing these cars will get you killed very quickly. There, I said it. My conscience is clear. You may be a combination of Mario Andretti and Don Garlets for all I know.

What are your objectives for the car? That may let you know if that engine, and the hassle of doing it, are right for you. There is one out there with a Ferrari V12, so pretty much anything can be done.

[AnthonyS]

Just realize that 500HP in one of these, at 2150lbs, is equivalent to around 900HP in a modern Mustang. Add in a short wheelbase and being confident without knowing these cars will get you killed very quickly. There, I said it. My conscience is clear. You may be a combination of Mario Andretti and Don Garlets for all I know.

What are your objectives for the car? That may let you know if that engine, and the hassle of doing it, are right for you. There is one out there with a Ferrari V12, so pretty much anything can be done.

I'd argue that having the same power to weight ratio in two different cars is not the same. The Mustang is much longer wheel base. Having recently owned a Coyote Mustang I can assure that they are very easy to drive even though they have 420hp. It's stable, controllable, hooks well, corners predictably and puts the power to the ground nice and smooth. Honestly after growing up around race cars my whole life I'm shocked at how well modern cars make power and control it at the same time. I remember the day of undriveable 400hp cars. Now you can take them to get groceries and take the kids to school. And then you take a platform like the Corvette and at speed it is even more stable and can handle even more power easily.

I haven't driven a Cobra roadster yet, but 95" of wheelbase and only 2200ish pounds doesn't provide a lot of opportunity for error since traction will always be an issue. If you go into the theory of racing and look at the "traction circle" the Cobra by design will always be closer to the edge than most any other car by design. Once you cross the edge of the traction circle you are at the mercy of luck and no longer driving.

[edwardb]

I'd argue that having the same power to weight ratio in two different cars is not the same. The Mustang is much longer wheel base. Having recently owned a Coyote Mustang I can assure that they are very easy to drive even though they have 420hp. It's stable, controllable, hooks well, corners predictably and puts the power to the ground nice and smooth. Honestly after growing up around race cars my whole life I'm shocked at how well modern cars make power and control it at the same time. I remember the day of undriveable 400hp cars. Now you can take them to get groceries and take the kids to school. And then you take a platform like the Corvette and at speed it is even more stable and can handle even more power easily.

I haven't driven a Cobra roadster yet, but 95" of wheelbase and only 2200ish pounds doesn't provide a lot of opportunity for error since traction will always be an issue. If you go into the theory of racing and look at the "traction circle" the Cobra by design will always be closer to the edge than most any other car by design. Once you cross the edge of the traction circle you are at the mercy of luck and no longer driving.

For the record, the Factory Five Roadster is only 90 inch wheelbase, not 95. That's the authentic size. There are some mfg's that have stretched it a bit, and most look like it. The coupe is closer to 95, as I understand.

[Dave Howard]

DIDO the remarks from Davidbr from Tucson.

For me, the Coyote was the way to go in my MkIV. I considered a variety of options. I looked at buying a beater FE and rebuilding it. The cost got to be too much. I looked at a variety of crate small block push rod engines. For a 350-400HP power plant I was looking at $10-12K. The Coyote with controls was about $8K. All aluminum DOHC with super strong 6 bolt crank mains. 412HP while in the crate, but with good intake and exhaust flow (Stainless Headers), and a couple hours on the Dyno for a mild tune and it's now a very reliable 480-490 HP. Modern horse power with no timing or fuel mixture issues to worry about. Bolt it in....wire it up....plumb it and turn the key. And a 2 year warrany to boot. Try to negotiate that from you local engine builder. These things are just over 29" wide and fill the engine bay. My boys just picked up a MkIV and a 33 kit and are both putting Coyotes in after enjoying their driving experience with mine.

[AnthonyS]

edwardb yes you are right about the 90" wheelbase I was thinking of the coupe which is 95". For reference the old Fox Mustang was a 102" wheelbase and the new S197 Mustang is 107.1" wheelbase. Wheelbase and track width are your friends when it comes to high speed stability. At 90" it won't take a lot of power in a Cobra for it to have a natural propensity for the rear end to want to pass the front end. I can't begin to imagine how unforgiving the factory Ford 4 link quadrabind must be in a roadster kit....

[bill32]

Do you want a really fast car that is also comfortable to drive? Or do want a beast that just spins its wheels? That is the question you need to answer. After building two FFR cobras, I am convinced that the Ford 302 crate motors are the best choice. Reason, these motors have years of real testing, are bullet proof, will spin the tires easily when YOU want to and will scare the crap out of you with their 335 HP.

[AnthonyS]

Do you want a really fast car that is also comfortable to drive? Or do want a beast that just spins its wheels? That is the question you need to answer. After building two FFR cobras, I am convinced that the Ford 302 crate motors are the best choice. Reason, these motors have years of real testing, are bullet proof, will spin the tires easily when YOU want to and will scare the crap out of you with their 335 HP.

I think in the car hobby the big block guys seem to forget that 335 real 2014 horsepower is very different from 335 1965 horsepower too. The way horsepower for automobiles was rated changed significantly in '72. Even with a small block ford the roadster has a lot of advantages in exhaust flow and lack of emissions equipment to overcome. A plain old stock 225 hp 5.0 is going to be closer to 250+ or more in a Roadster with the better exhaust system and loss of EGR, smog pump, and sometimes A/C and P/S too. It's really really easy to build a 350 hp small block for a Roadster thanks to the 5.0 aftermarket.

[Doug_Scott]

Sometimes people just want to do something because they can. Much like the people that climb Mt Everest. It is done purely for personal reasons. If you are going to use the "too much power" card, that also applies to any engine over 150hp in a street only driven car. Even that is excessive, requirements to drive the speed limits are far less than even 150hp.

Personally, if I were going for a unique power train, I would go either original BOSS302, or newest BOSS302, or the new Kasse P-38 canted valve Windsor heads, on a Ford Performance 302-347 hi-po short block to get the BOSS block and internals. Apparently a mild cam in a stock 302 with single plane intake will give 500hp, use the 427 small block, mild cam, single plane intake and get over 700hp.

[edwardb]

Sometimes people just want to do something because they can. Much like the people that climb Mt Everest. It is done purely for personal reasons. If you are going to use the "too much power" card, that also applies to any engine over 150hp in a street only driven car. Even that is excessive, requirements to drive the speed limits are far less than even 150hp.

These are, by definition, performance cars. They are a tribute to the original concept of taking a small engine out of a sports car and replacing it with an American V-8. In its original form, the AC Ace was also capable of easily meeting or exceeding speed limits. But that's not the point. There is nothing about these cars that can be argued in the same context of a daily driver/grocery getter. They are not particularly practical, certainly not economical, and of limited value on a pure transportation basis. So the "too much power" discussion is not on that end of the spectrum. It's on the other end, where driveabilty, traction, and the driving skills of (most of us anyway) amateur drivers must be taken into account.

Personally, I'm learning first hand that anything over 350-400 hp is very difficult to use without going to full-on racing tires or drag slicks now that I'm driving my new Mk4 compared to the past three seasons with the Mk3. Pretty much confirming the 400 hp "sweet spot" for power in these things. More than that fits into the "because I can" category and for the oohs and aahs when opening the hood at car shows. But that's part of the fun too for some, and people should build their dream however they want. Just don't big HP expect to have any real use in street driving without serious safety and/or speed limit issues.

[RonnieType65]

I went through the same "which engine" dilemma. I ended up on the combo in my signature solely based on lb/hp calculations. Assuming a standard 15% drivetrain loss, you can safely guesstimate that my car makes around 370 at the flywheel. Given a 2200lb weight, thats puts you at 5.9lb per hp. Here is a nice list showing whats near that number....

2014 Ford Shelby GT500 ($55,110) – 5.808
2014 Jaguar F-Type R Coupe ($99,000) – 6.615
2014 Chevy Camaro ZL1 ($55,355) – 7.103
2014 Chevrolet Corvette Stingray ($53,000) – 7.248
2014 Jaguar F-Type S ($92,000)– 7.416
2014 Chevrolet Camaro Z/28 ($72,300) **– 7.564
2014 Cadillac CTS-V Coupe ($64,900) – 7.585
2014 Cadillac CTS-V Sedan ($64,900)– 7.590
2014 Porsche 911 Carrera S ($98,900) – 7.688
2014 Mercedes-Benz E63 AMG S ($99,770)– 7.697

This is why a solid built 302 is enough, in my humble opinion.

[BEAR-AvHistory]

Car & Driver did a road test of the FFR with a mild stock Mustang Donor engine. IIRC the horsepower was in the upper mid 200's. 0-60 in 3.5 I believe. Positive about the 3 not sure of the tenths.

Went for a Coyote for ease of install & DD. Light tune for 93 octane, no addional hardware, is 446WHP. Will spin NITTO 315 555R drag radials in any gear with a clumsy throttle foot. Best is the engine only weighs 444lbs.

[Bren]

Car & Driver did a road test of the FFR with a mild stock Mustang Donor engine. IIRC the horsepower was in the upper mid 200's. 0-60 in 3.5 I believe. Positive about the 3 not sure of the tenths.

Went for a Coyote for ease of install & DD. Light tune for 93 octane, no addional hardware, is 446WHP. Will spin NITTO 315 555R drag radials in any gear with a clumsy throttle foot. Best is the engine only weighs 444lbs.

Are you talking about this: http://www.caranddriver.com/comparisons/2004-factory-five-racing-mark-ii-roadster-page-2

0-60 in 3.6 seconds and 350 hp.

Or this one: http://www.caranddriver.com/reviews/factory-five-racing-spec-racer-specialty-file-nuetral-handling-page-2

0-60 in 4.8 seconds and 225 bhp

[Al_C]

l'll add my two cents... Here is the best writeup I've seen on choosing an engine: http://www.ffcars.com/FAQ/powertrain.html

It's an analysis you'll find in the other forum off the FAQ page. I think it's good reading, and offers rational advice, but then again, who the heck is rational that's engaged in this activity? (Irrationality is half the fun...)