The difference between a 408, 393, and 383 are negligible, assuming the same cam, heads, and compression ratio.

408 472hp@5500 498ft*lbs@4000
393 474hp@6000 486ft*lbs@4000
383 475hp@6000 476ft*lbs@4000

These are assuming pump gas 10.5:1 CR, AFR 205cc heads, headers, 750cfm carb, 228/233 duration @.05 roller cam with .647/.654 lift using 1.7 rockers, and a great dual plane intake. As you can see, it really does not make much difference. You gain torque with stroke, but actually loose a little horsepower which makes since b/c strokers produce power lower in the rpm band. The redline on these motors is going to vary depending on what you spend on parts, but in general the 383 is going to safely spin higher than the 408.

 

In addition, be realistic concerning how high you want to rev the engine. I don't think your street car would ever need to rev past 6000 rpm (especially with all that low end power from a long stroke engine).

 

I know that 7000rpm are out of my range (of do-ability and price), but isn't 6000rpm a little low for a 383? Maybe 6500rpm+ might be, but 6000 doesn't seem right. Oh, urban where did you get those hp/tq numbers? Very interesting. Looks like I'll be going with a 383 then...

 

Those numbers were quick comparisons I ran on DynoSim 5. I have found they are pretty accurate.

As for spinning...piston speed is dependent on stroke length. A stock motor should not exceed 3,500 fpm (cast crank, stock rods and cast piston). A heavy duty motor should not exceed 4,000 fpm (forged crank, peened rods w/ good bolts, forged piston). A drag racing motor should not exceed 5,000 fpm (forged crank, alum rods, lighweight pistons, etc.).

These limits DO NOT take valve float into account. You could have a great bottom end and still float a valve and kill the motor.

A 3.75 stroke (383W) will have a piston speed of 4062fpm @ 6500rpm. At 7000rpm, the piston speed will be 4375fpm.

A 4.00 stroke (408W) will have a piston speed of 4000fpm @ 6000rpm. At 7000rpms, the piston speed will be 4666fpm.

As you can see, as you go up in stroke, you need really strong parts to continue to spin the motor at the same rpms without breaking.

It is easy to hit the 7000rpm rev limit chip in my 383w in first and second gear without realizing what happened. The first time it happened, I thought the fuel pump was giving out. It spins up fast. For that reason, I put a shift light in that lights up at 6300. By the time I grab the gear, I am probably at 6500 and thus stay under the safe limit of 4000fpm piston speed for my 3.75 stroke motor.

That is why short stroke motors can produce horsepower and not torque...they simply can spin high . A well built 302 5.0 motor can spin to 8000rpm without exceeding piston speed recommendations. Stroker motors can make lowend torque but high horsepower is hard b/c they cannot spin very high. It is all about physics and material limitations.

Here is a website to calculate piston speed.
http://www.csgnetwork.com/pistonspeedcalc.html

 

Wow! That was some great information! Is there anything you don't know urban? lol

 

LOL. There is plenty I do not know, but I have come a long way through building my Mustang and Bronco and screwing things up as I go. Information is the necessity of building a performance hotrod. I have hung out with drag race guys who have been breaking stuff for decades, so they have helped in pointing me in the right direction and wading through the bs. There is a bunch of miss information out there. That is why I always want to know how someone is producing the horsepower and torque claims. Maybe they are full of bs or maybe they know something that will help me. I am not saying I do not relay miss information, but I try to read and verify everything I post.

Dynos and Dyno programs are great for cutting through the bs. Something that you thought was going to make a bunch more power, may only give you more torque where you did not want it. It is no easy task in getting a naturally aspirated motor above 550-600hp. Stroking a motor will only get you so far.

Anyone can buy and drive a hotrod. In fact, many mechanics do not have a good knowledge of physics and limitations of the internal combustion engine. Half the fun for me is doing the research and learning what works and what doesn't. Good luck and have fun learning .

 

on a sidenote. a ~400ci engine has such a brutal torque that you don't really need to have that spinning tover 5000 to have a _lot_ of fun. i think anyway

 

Great posts guys, certainly helped me make my decision!