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Torque vs Horsepower

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bravo1218

Silent Prop
R. I. P.
So what am I looking for, torque or hp? I am getting ready to do some Hi Performance mods on my airboat but I am not sure what I should be more interested in. I understand that with the 2:1 belt drive I will run a max 6k rpm so I will want something that starts early. My cruise rpm is between 3000 to 3500. I am running a zz3 stock with a holley 650 double pumper, mechanical secondarys, no power valves. Stock HEI distributer with quick advance springs.
I plan on leaving the bottom end stock the changes would be to cam, intake manifold, carb, distributer.
At present I have a wide blade wood prop but that will be changed to a varable pitch composite prop. Most of my running is in water but I want to be able to run dry, including stoping and restarting dry areas. I do have polimer in the bottom.
Thanks in advance for all help and comments.
Tim
Thanks for all
 
bravo1218,

From what the guys on here have taught me...torque is the answer!

I've got 425 H.P. 454 Chevy that don't seem to pull itself out of it's owm way if ya' know what I mean!

Waterthunder builds a LS1 Chevy engine with half the weight of my big block with probably almost twice the torque.

Hope this helps.

Basketcase
 
torque gets you goin horsepower keeps you going least that is what I have been told now I may be wrong but if I am someone on here will set us straight for sure.
 
Are you looking to get out of the hole faster, top end, cruise, fuel economy, etc. ?

I like those old zz3 chevys. Seemed like they would absorb more abuse than the newer zz4, especially with temperature issues. Spent alot of time running them. But the aluminum heads on both (especially zz4s) will warp fairly easy when water temperatures get up over 220. So be careful.

You might consider looking at new iron heads with the new cam. Should be able to gain quite a bit of HP and not have to worry as much about temps. But I am not a mechanic, just passing what I have been told.

But the guy to ask for what to do with SBC for performance is waterthunder. He will see the thread and maybe give some suggestions.

That switch to a composite propeller will provide lots of choices. You can really alter your hole shot, top end, cruise/fuel economy with just changing the pitch. Might be something to think about first. A 3 blade power shift is my opinion.
 
The real bottom line is it's always about torque..Even if it's a high RPM small engine in a drag car. HP is just a calculation of TQxRPM/5250. So even in a high RPM engine you want torque...Just higher up in the range. HP is just a measurement of work done, and the "work" you need to be concerned with is at the prop (after the torque multiplier/gearbox). So if you are running that box, and your RPM is set pretty much at 6000...The two things you don't want to do is build a 9000RPM screamer, OR a 3000 RPM torque blob Caddy or Olds. You want your peak power to be around 6000, and to build a well designed combo that also will make torque below that...Bottom line....Make the power for you peak requirement, and what seperates the men from the boys, is how to make the power curve as broad as possible.

As for the ZZ motors....Aluminum heads are actually superior (especially in airboats) , but the GM castings are VERY thin and tend to have problems with warping and valveseats. The ZZ4 just makes the proplem moreso than the zz3. A good aftermarket head makes way more power, torque, and is much more reliable. But if you are basing things off the basic combo you have....Keep the water temp low, do some basic headwork, and consider a better designed cam for starters. Just my 2 cents

Felber
 
FELBER632 said:
The real bottom line is it's always about torque..Even if it's a high RPM small engine in a drag car. HP is just a calculation of TQxRPM/5250. So even in a high RPM engine you want torque...Just higher up in the range. HP is just a measurement of work done, and the "work" you need to be concerned with is at the prop (after the torque multiplier/gearbox). So if you are running that box, and your RPM is set pretty much at 6000...The two things you don't want to do is build a 9000RPM screamer, OR a 3000 RPM torque blob Caddy or Olds. You want your peak power to be around 6000, and to build a well designed combo that also will make torque below that...Bottom line....Make the power for you peak requirement, and what seperates the men from the boys, is how to make the power curve as broad as possible.

As for the ZZ motors....Aluminum heads are actually superior (especially in airboats) , but the GM castings are VERY thin and tend to have problems with warping and valveseats. The ZZ4 just makes the proplem moreso than the zz3. A good aftermarket head makes way more power, torque, and is much more reliable. But if you are basing things off the basic combo you have....Keep the water temp low, do some basic headwork, and consider a better designed cam for starters. Just my 2 cents

u might try a cam intake matched combo been told eldenbrock torker n cam for rv is a reliable cheap way to go with huge difference over stock
aircraft should be so cheap to modify
Click to expand...
 
Bravo,

Good to see you're getting some good stuff from KnowHow Guys. :)

And just for mention; When I quized a couple prop people via phone abt the diesel we wanted to use they first asked, What is the HP & at what RPM isit? Notice that they didn't mention torque just HP.

So when I would say 250hp@2300rpm where did that lead to? Some kind of a little motor that didn't need much of a prop. And then in both cases I asked if they needed to know abt the torque. First one even said no but when I offered it anyway(688lbs@1900rpm) I could tell by the reaction he thot I was surely unfit for the Airboat community :)

It is just whatever people get used to doing & sometimes causes a lapse or the like in things which may call for a little different setup.

Just 2 sense,

Gben
 
I would recommend a cam change something around a 108 or 106 centerline. I deal directly with Comp Cams and they are producing some custom airboat grinds that really work great in airboats. I would give them a call. Install a set of 1.6 ratio rockers to increase valve and intake charge velocity install a RPM airgap intake. If you want to go all the way and reap all the benefits have Felber632 work on your heads and do a 5 angle valve job, some bowl blending and chamber work. If you really want to make it a beast up grade to an aftermarket aluminum head it’s easy as falling out of a tree to get 450HP plus out of your motor with only top end mod’s. If your interested I could put a package together cheaper than you could buy that would be perfect for your boat. My horsepower to torque theory is making the motor as broad as possible with a flat torque curve and linear power. I have destroyed several boats that made 100, 200 even 300 more horsepower on the dyno but those peak numbers mean NOTHING IN AN AIRBOAT. People throw around horsepower number they don’t mean S%&# a broad motor making a 100 less peak horsepower but makes an average of 50 more HP across the board will win every time. My little pee wee 550HP LS1 will eat some 650HP 700HP boats up only because it makes power everywhere.
 
I found this quote regarding horsepower and torque.

"People buy horsepower, but they drive torque." Torque is force, and force causes acceleration. Power is marketing, and marketing causes poverty."

I got a little chuckle out of it. :lol:
 
As Felber said HP is just a calculation of TQxRPM/5250. So horse power and torque are related however most marketing sells you otherwise. It’s easy to make 800HP from a small block just turn it 9,800RPM. Most airboaters don’t realize the HP ratings for crate motors are at RPM’s they will never reach in an airboat let alone they only make that power in a very narrow RPM range. Every airboat motor I build is intended for the boats RPM range and the specific needs of the boat it's going on. That’s why I ask how heavy is your boat, what gearbox ratio do you have, what type of ridding do you do and what prop are you using. You must consider all these components in order to properly match the power plant to the customers needs. I must admit though it’s much more profitable and easier to say here is a 330HP crate motor it’s the motor you need and sell that same motor for all airboats.
 
Thunder, Since most airboats do operate from about 1500 to 4000rpm's ,why are not more blowers used on the boats. Ive always felt that a 4.3L or 383 with a small blower would be great on a ride boat . Silky smooth idle,great low end torque, and a better whine than any woman! :shock: Just wondering?
 
They problem is most blowers as in a 6-71’s and 8-71’s are roots style blowers and require up to a hundred HP to turn them also at low RPM’s they are not very beneficial almost a hindrance let alone their weight. If you run a little blower like a 4-71 you will weigh less but not make much more power under 6,000RPM’s. A well designed normally aspirated motor will smoke it. The only blower that will work in an airboat is a centrifugal because of the way they function they don’t require as much horsepower to turn however you must run fuel injection on the automotive ones. Centrifugals are also very expensive so now you have a heavy expensive blower with an expensive fuel injection system. Two things I don’t like on an airboat is weight and a fragile computer controls or electronics. 99% of the time a good old simple carbureted motor will whip a blower’s but in an airboat. I’m sure some people are going but what about a supercharged 0-540 well they run a centrifugal super charger as I mentioned and their blower was designed and intended to run under 3,000RPM nobody really makes a car motor blower for an airboat. The power a blower adds under 6,000RPM will not over come the weight and horsepower requirements it takes to run. In my opinion the best power adder for a car motor boat besides (NITROUS) would be a twin turbo utilizing two smaller turbo’s so the motor will spool up quickly. Turbos really don’t require additional horsepower to run
 
Guess I am going to confirm what many have suspected about BigDaddy for some time now - abundant dumbness.

Seems almost every month we are faced with another airboat sounds objection eruption in some community near where we all like to run.

I really, really wish the car motor folks would forget a SBC could be made to turn above 5K. The noise generated at those high rpms carry for miles no matter what muffler is attached.

Firefighter Harry T runs a SBC with an Eldebrock intake and alum heads system. His motor is "set ??" to max out at 4,800 rpm and he turns a low rpm Sirius Powershift. All this on a 14' Heartline with polymer and ss rigging. Seating is two up and three down. He pulls dry ground better than most aircraft boats and does not turn the very loud higher rpms. His boat is not a sounds monster.

I have the greatest respect for Waterthunder's and Felbur's knowledge - in fact, I watched Felbur tune the twin turbo monster at Diamondback a few weeks ago. Top of Class - both. Just PLEASE, show us all how to make car motor boats perform at bearable rpm / sounds ranges.
 
I a preacher of more gearbox as in 2.68 ratio but run ton’s of pitch with less RPM. I run all my combo’s around 5,00RPM down to 4,700RPM. My boat and several of my friends boats run this set up and are some of the quietest airboats on the water. I can’t even hear my buddies 550HP LS-1 run when he rids with my neighbors 4 banger 180 Lycoming. All you hear is a 4 banger and his wood prop. It’s that quite all you hear at cruising RPM’s with the 550HP LS-1 is the gearbox. Anyway our boats are very quite.
 
I have been following this talk about airboat noise for some time now on this sight Over the years Ive build eight different style of boats and found that the noise coming from an air boat was from the motor and prop in combination if you put an exhaust on a motor it will quiet it down but leaving your prop turning @ 3000 rpm is still deafining You have to exaust your engines and reduce your rpm on both your motor and prop .There is only one way to do that and that is to use a reduction gear .If you really want to reduce the noise in the air boat community you will have to spend some money which most of us really dont want to do because it is very expensive but it is the only way we are going to be able to quiet these big boats down. I run a 350 built 30 over aluminum heads special cam etc. but I do run exaust.I have a 2.3 to 1 belt reduction gear and a 80 inch wide blade senenich prop I have it pitched @ 2.5 so it turns a maximum 2400 rpm but when cruising we can carry on a conversation in the boat.Remember it aint what motor or prop you run its what you do with them ,when it comes to noise slow the rpm down.Just my oppinion COPPERHEAD
 
Your dead on! On most of my LS-1 combos in a 14Ft or smaller boat I recommend a 2.68 gearbox with a 78’’ Power Shift Flacon prop pitched to turn 5,800RPM so the prop is only turning 2,164 RPM. Far below even the manufactures suggested RPM however with that much pitch and the multiplied torque from the gearbox I could haul a complete 0 540 airboat around on my bow and still run dry. I have towed a airboat on the hill before to prove this point. On top of all of this your prop sound signature is quieter.
 
Big Daddy and Waterthunder,

There is a lot of info on this site about running quiet. I am pretty familiar with this forum and it is difficult to find this stuff. Rick has set aside a new area for this subject with the hope that it will be easily accessible.

Dave, it would be nice if you could find the time to do an article on your latest boat and pont out your findings on how to make them quiet. If you need help with pictures or anything else please let me know. You have postd most of the info, but it is really spread out.

Jim
 
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