Bleach

You can run a very strong engine with dual SU's.
No, minor mods will not do 200+hp. To get that kind of hp at the wheels you will need major mods and you'll barely make it to 200hp.

I saw a car on a dyno with tripple webbers, a cam, shaved and ported head and he only got 151hp at the wheels. Maybe he was using a 3.54 rearend though... and the carbs could probably be tuned for a bit more power.

You'll need to get a performance jetting kit for the SU's and port out that intake manifold and intake runners in the head. Get a long duration cam and tight springs. Make that engine pull hard to 7000 rpm. A low geared rearend like a 3.9 or 4.11 will help a lot too.

TheeZ

HP is tricky, an unusual measurement. I know gears add torque wich is what really counts on a per turn or take-off basis, the ability to force those tires against the ground and apply more force. Gears add leverage (torque) just like a classic lever does. Your crank torque is multiplied through your driveline to what ultimately comes out at hubs, then is lost by exerting it over the radius of your wheel/tire. HP is exactly that power. 1 hp is equal to the amount of energy taken to move a 1lb frictionless block 1ft. Sort of confusing when you are talking about a car. Hp has the equivilent metric measurement of kilowatts, ya the stuff thats in you powerlines at home. The simplest analogy i've read was this: Imagine you are workin out in the gym. The amount of weight you push is the torqe exerted. The number of times you do it or reps are equivilent to your rpms. The sum of all the power used in pushing the weight (exerting torque) x the number of times you did it (rpm) is the HP. Thats why (to a certain extent) HP increases with revs. By putting a 4.11 (which i did) or 3.90 rear end you multiply your torque exiting the trany 4.11 times or 3.90 times respectively as opposed to the 3.36 or 3.54 multiplier. But just like a lever, the more torque you multiply up comes at the cost of more revs or your top speed. I hope this helps more than confuses you...; )

Bleach

Ya, true that the rearend doesn't increase your engine's power, but I'm usually thinking of what is at the wheels.

think of it this way, at low rpm or at high rpm, what gear has the most power at takeoff? The lowest gear of course. If 1st gear at the same gear ratios as 2nd gear, you'd take off slower and have less torque and horsepower; but the engine's horsepower is unchanged.

Not only does a lower geared rearend get the rpms spun up faster, but you have more power (at the ground) at any given rpm in any gear because your final drive gear ratio is lower!

If you drive a 280ZX with a 3.9 for a long time and then get in an amost stock 280zx with a 4.11 rear and the same transmision, you'll be sold. That little bit of gear change makes a noticeable difference.

TheeZ

ya i had a 79 w/ the stock diff. pretty sure it is a 3.36, but i never bothered opening it up after i got my 4.11 in. whhooooo it was a big gear change, but i also put in a newer trany which is higher geared than the 79, but i love it. freeway drivin aint too bad 3200rpm @75mph, but do i have some pickup on the freeway with my revs up. It pulls hard in 5th even up hill on the frwy. I recomend it to any one with a n/a, maybe turbo but ive never driven one so i dont know how much it needs it. For all you people out there asking how much hp or how much of a difference an intake or exhaust will give you go out an buy a $100 4.11 diff. and be amazed. Definently near the top on my recommended power hunter to-do list. the r180 to r200 swap was kinda tricky but a very ingenius design by nissan made the swap simple once you figure out their trick. I know allllll about it for any one planning on doing it! I had fun with my car on jackstands for a week while i ran back and forth to pick n pull one an a half hours away from me trying to figure out exactly what parts i needed.

Lazerus

Gears will increase the ammount of horsepower at the wheels, since WHP is based on your cars ability to spin tires really quickly. And as for turbo cars, unless you are running an automatic then it is better to stick with numerically lower (taller) gears since they allow more time for boost to build and it keeps the turbo spooling for a greater ammount of time.

-Matt

futureZowner

Which diff. would be good for better acceleration and still allow me to drive it on the highway without problems? What all will i need to do to bolt up a different rearend on my '79 NA? I think it has the r180 with like 3.36 gears, but I would like to get a higher geared differential. Is it hard to put on a different rearend and from what cars could i get one? I hope this post makes sense, and thanks in advance for any help.
-Randy

Bleach

we're talking power at the wheels, and yes a different gear will change how the power is transfered to the wheels. Read the posts. Also, it was already stated that the gears don't effect the engine's power output. Horsepower is just torque applied over time. You will increase your horsepower and torque by changing to a different gear. Shops run the car on the dyno in 4th gear which is 1:1 ratio. if you did the dyno run in 3rd gear, your final drive ratio would be different and you would end up with higher torque in the low and midrange rpm and more horsepower at high rpm. The traveling speed however would be much less just as it would be slightly less with a lower geared rearend.

Like with your LS1, some vettes run a 3.3, 3.5, and some guys say they swap in a 3.7 rear. Even they use gears to help with 1/4 mile runs. It does change your power on the ground.