Best overall SBF combo for a street/strip Cobra

[eschaider]

Small bore sizes will cost you valve curtain area because of reduced valve sizes, which will cost you pumping losses that translate into torque losses. Stay in the middle of the sandbox, and you will be happy. Go to the extremes and you will not.

Compression braking in a Cobra, in anything but a straight line, is a good way to swap ends in a New York minute. Don't build or do weird $hit. You will enjoy your car more and longer, spend less money and crash it less.

[Buzz]

The video of the guy balling up his newly delivered car in the "This gives all of us a bad name" thread is a perfect example of what poorly or accidentally applied trailing throttle oversteer will do in a Cobra.

[twobjshelbys]

Two solutions. Of many. All yield different personalities and behaviour. None are better than the other, just different. Noone will change the other person's "I like this one best" opinion. It's like trying to convince me to vote for the other candidate.

[patrickt]

Remember, these are just toys, and FEs are more fun to play with than SBFs. For that matter, they're more fun to stare at, show off to othrs and more fun to mop up after. The list just goes on and on.

[twobjshelbys]

And they have the joy of petty oil leaks. Usually not enough to fix right now but enough to be annoying.

[Streetwize]

Yeah this thread wasn't intended to be a P!ss!ng contest.

The motor I outlined was what I felt would make the best "goldilocks/just right" type powerband for a Cobra...again my opinion only. I wanted to hear your opinions, never presumed that anyone would think I was trying to prove what was best.

The first few replies actually "got it" . It's more about tractability... and tractability is subjective, it depends on the car and how the driver likes to drive.

My 427 SBWF cruises at 65 mph on the highway and the tach is turning about 1800 (3.5 gears with a .68 od and a 28" tire) rpm, and the way I have the carb set up I can roll on to redline very easily without downshifting. But that's with a 500 horse 10:1 motor with modest sized ~200 cc ports and a 5500 rpm redline. I cruise around in fourth below 65 because to me it feels pretty much exactly how a Real 427 FE should feel in terms of torque. The motor has been running great since I first built it in 1996.

If I had a 289 FIA style car with less tire and super light like a FFR, Thats where I would build a big bore short stroke 363 and maybe a 7200 rpm redline, I would want less roll-on torque down low but produce the same HP up top....just spread out over a wider, more gradual powerband. More like an italian sports car type rev range. Yes you can use any bore stroke combo you want to make the power you want with the right heads and cam....I just like tailoring my motors to roll-on power and sound the way I want.

but there are clear 'seat of the pants' correlations between bore/stroke and how the power applies through the powerband for a given compression ratio and induction/head/exhaust flow, even if peak torque and hp are the same, I'm more concerned about part throttle drivability and how the motor pulls during roll-on acceleration. 85% of the time your motor is not at WOT....so part throttle transition of the carb circuits is real world. Cobras are a bit easier because they are light and typically have 3.50-3.90 ish rear gear ratios.

back in the early days of NASCAR running 358 small blocks, they ran bigger bore shorter stroke combos on the super-speedways, and smaller bore longer stroke motors on short tracks, mainly because they only had 4 speed transmissions and the cars were heavy.
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And Again 3000 or 3500 to initiate a dyno pull for a Dyno Mule or a Drag car is great, but 2500 is more realistic real world test to see how various motors pull on the street (from out of the basement) under real world conditions. If the engine doesn't run well or stabilize against the load at 2500-2800....Well That's exactly my point, On the street the engine does run and pull load under 2500rpm....a lot.

And I agree that with todays heads and cams, there are many more ways to make and apply power.

Sorry for any panty-wadding, It was never my intention.

[blykins]

We don't pull engines that far down on the dyno, whether they're street or race. Lugging an engine down low at full song is a good way to damage an engine.

It's very apparent by higher rpms if the torque curve exists down low or it doesn't. No need to pull the guts out of them to find out.

[Streetwize]

Brent I hear you

My thought was the 2500 in a Cobra is a pretty typical cruising speed in fourth, ....but I get your point that nailing the throttle in a cobra (with torque multiplication through at least the rear axle) is a lot different than a direct driven Dyno Water brake, so I understand you!

I've worked with a lot of the F.A.S.T./N.M.C.A. drag racers that are very tire limited (because they have to run OEM stock appearing 70's skinny vintage tires) many of these guys really have to come the line not much above idle and many stutter ramp the ignition to "traction control" the launches... but I know many of the High torque/Low RPM combos (like 455 buicks and 440 mopars) do get dyno tested at lower RPMs with fairly tight converters. But most of them run Vacuum secondary OEM carbs like q-jets and thermoquads....so even if you load them at WOT the back barrels aren't even opening.

Do you work with any of those guys? It's really interesting the power they get using OEM heads/Intakes and only 2.5" dual exhausts

[blykins]

I'm having trouble understanding why you came back a month and a half later just to post what you posted????

[Streetwize]

IDK...maybe I just got bored. Maybe I missed you, Brent!

No TBH maybe I just didn't like the way the tone went when the question original post had actually some traction...I really wanted to hear what other people thought was their "perfect" cobra motor.

I like Cobras, I like Engines, and I was genuinely interested hearing other points of view.

Hope that's ok with you....Sheriff?

[Streetwize]

And although it's been more than a month, it's the first "action" in the whole SBF thread since the LS Oil cooler!

Sorry to wake anyone up!!

[Ace23]

Brent specified a camshaft for my 427W back in the winter of 17 when we were freshening up the motor and upgrading the car. I’m running billet half shafts from the drive shaft shop, 3” fire fly stainless side pipes, 325/50/15 nitto drag radials, 4.30 rear gear and a T56-6 speed. The car pulls like a freight train. It’s 100% a street car…and I would 100% go larger cubes or whatever combo could get me to 750hp on pump gas with a hydraulic roller. I want the power when I feel like using it. What I hate about these cars is the hot air they are sucking under the hood, there is no cold air setup unless someone does some full blown custom solution for you. I would imagine 750 crank hp is 600whp in one of these cars. Each to their own but 7k rpm with 700hp+ /550-600tq is what I would build.

[Ace23]

Brent specified a camshaft for my Keith Craft 427W back in the winter of 17 when we were freshening up the motor and upgrading the car. If I recall Keith built the motor back in 04. We gave Brent the specs on the engine and the Brodix heads they used back then. The car idles 1000-1050k and it sounds the drum intro to Van Halen’s Hot For Teacher. I’m running billet half shafts from the drive shaft shop, 3” firefly stainless side pipes, 325/50/15 nitto drag radials, 750 QF mechanical secondaries, 4.30 rear gear and a T56-6 speed. The car pulls like a freight train. It’s 100% a street car…and I would 100% go larger cubes or whatever combo could get me to 750hp on pump gas with a hydraulic roller. I want the power when I feel like using it. What I hate about these cars is the summer time driving with the hot air they are sucking under the hood, there is no cold air setup unless someone does some full blown custom solution for you. I would imagine 750 crank hp is 600whp in one of these cars. Each to their own but 7k rpm with 700hp+ /550-600tq is what I would build. In a perfect world I would do an in-tank fuel pump and 13:1 compression running straight 110 VP on the street. I want to feel like I’m driving a sprint car when I’m in my cobra. It was 45 degrees out today and I got a blood rush to my head doing a WOT 2-3rd from 4K…it’s brutal.