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  #1 (permalink)  
Old 07-17-2009, 11:32 PM
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high hp low tq sbc

i have been trying to basically creat a motor (sbc) that is highin hp but low in tq the actual numbers im looking for are 400hp 300tq. i dont want alot of tq due to the weight and setup of my car. so i haev been reading about high rpm motors. but i have also seen motors (sbc) that make this kind of power without being a high rpm motor.

how is this done? cam specs? heads? cheapest block to do this with?

im trying to keep it low baller as possible.

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Old 07-18-2009, 03:10 AM
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A good 350 block (like the 3970010), solid cam, and a used single plane like a Victor Jr. could be start. Use ARP studs throughout.
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Old 07-18-2009, 06:14 AM
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The formula for Horsepower is; Torque X RPM / 5252 = Horsepower


You can attain your 400hp/300tq but it will come at a high RPM


400(Horsepower) X 5252 / 300(Torque) = 7002.666(RPM)



No matter what engine you use, 4 cyl, 8 cyl, normal aspirated, or turbo charged, this same formula applies. A 4 cylinder Honda struggles to make 300tq. to get 400 Horsepower, you spin the wee out of it.
A 350 Chevy will make the 300tq in stock trim. Any mods and you increase the torque. Typical 350's break the 400tq mark with ease.



Here's a link to a low torque high horse build up.

http://www.hioutput.com/tech/400hp/400hp.html
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Old 07-18-2009, 08:58 AM
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thanx a bunch. any other ideas guys?
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Old 07-18-2009, 01:45 PM
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You would have a hard time obtaining that much HP with that little torque from any carbureted small block chev. Most 400 hp configurations will have way more torque than 300. The closest thing is probably a 302. A solid cammed 283 with a good set of heads would probably be real close torque wise and not too spendy, but I think it would fall well short of 400 HP.

There are little hitches to building up some of these old SBC configurations too. For instance the 302 is legendary and it is nothing more than a 327 block with a 283 crankshaft. The caveat is piston availability. Your only options (that Ive seen) are 12:1 compression pistons (and they are spendy) or custom pistons. Not good options for a simple street build.

Ive been researching the old L-76 327, that might be a good option for you. It is basicaly a hot 327 with the old 30-30 solid cam which can be had relativly easy. In a nutshell its the 327 version of the DZ 302. It makes for a weak bottom end torque motor but screams in the upper rpm band. One source states that Gm actualy put them in a very limited number of chevelles in '64 and then put the kabosh on that combo stating that the L-76 was "too wild for a chevelle". Afterwards it was strictly a corvette engine.

They were rated @ 365 hp and 350 ft lbs @ about 3400 rpm. Most other 327's hit their peak torque way before that because of the camshaft. What car are you building?

Actualy, you could probably just stick that old 30-30 cam in any garden variety 350, give it a decen set of heads and get similar results. That old cam grind is notorious for killing bottom end torque and moving the power up high..

Last edited by 65smallblock; 07-18-2009 at 01:56 PM.
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Old 07-18-2009, 09:31 PM
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so where do i get this cam you speak of? this is awsome this is exactly what i am looking for. i am building a very low buck sbc s13 (or for those in the lesser know- a 1990 240sx coupe - non hatchback)

what heads do you recomend i go with- i can find a 327 but i dont know if i can find that cam if its a stock cam as you make it sound. at least not with the 327. is there something that crane cams or someone else that makes something like that or exactly that?

i learn knew stuff from you guys everyday - thanx a bunch!

any other input guys?
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Old 07-18-2009, 09:39 PM
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"30-30" cam is still available from Elgin Cams -- #E901. E901M includes the lifters 115 bucks from Competition Products www.competitionproducts.com
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Old 07-18-2009, 09:51 PM
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anything else i should know about this? what heads should i use etc.?
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Old 07-18-2009, 11:49 PM
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You do know that HP output is directly related to torque output right? Why would you want to spin a motor to extreme rpm to produce less torque just to hit a specific HP figure? What does the weight of the car have to do with the rpm the HP is produced?

This makes no sense at all, you should be trying to produce as much torque for the rpm limit of the engine you are building...this is a basic tenet of all hotrodding engine building. It sounds like you want an engine that can turn a bizzilion rpm just to hear the thing spin like a 4cyl and limit how much hp it makes at that rpm?

Why? I don't get it.
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Old 07-19-2009, 12:47 AM
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Quote:
Originally Posted by 4 Jaw Chuck
Why? I don't get it.
Maybe this post from one of his other threads will clear it up for you......


i have a 1990 240sx coupe with a swapped ka24de (was a sohc no dohc) now there is a kit from mckinney motorsports to swap in a sbc with a couple different trannies. after the motor swap is done without the strip it should way about 2700 pounds i can take about 500 pounds off that by various components being tossed. it has independent rear suspension (irs for short) and a r200 (non possie or vlsd). so this means it has axle shafts and a somewhat small diff.

i dont really want a large amount of tq i want hp. and to rev the piss out of it.

i have been doing alot of reading i have been told that a 302 will just by basic setup will rev higher than a 327 (or so i have read) and seeing that i dont have 20k for a orginal 302 im taking a 327 small journal and putting a 283 crank in it (therefore making a 302)

i also have been told that running longer rods is better for a motor that revs higher weather this is true or not i have been told both ways but it appears that more agree with the longer idea. yes alot of it is in the heads bla bla bla

ive built honda little ricer motors i know the best head bla bla bla.

well this is a low buck project as low as possible that is. i have not bought the motor or the tranny yet or crank for future ref. either i am trying to find my best bang for the buck to get this motor to rev.

oh my goals here are to get it to rev to roughly 8k as a red line (hopefully ...crosses fingers...) im not going to get into why i want this btw to long of an explanation.

id like about 400whp through a world class t5 5 speed that will run to the r200 nissan differential. tq perferably lower like MAYBE 320wtq -

yes one usually sees these numbers out of a import or stock nissan BUT have you guys ever priced out what it costs just to tune one of these little rice rockets? lots of mulla cash $$$ etc for example

ka24de 2.4 lt 155 hp 160 ftlbs turbo 300 manifold 900 (for a decent one) new computer that will not let it blow up oh about 1200-1500 yeah....... that does not include the tuning itself. then all the gages more - then the wide band o2 like 300 for a decent one oh and stock internals break between 250 and 350 so yeah... here comes the forged piston rod stuff 1500 for a kit. this just keeps going fellas.... so that is why i am goign sbc best bang for the buck.

also if your interest;
http://www.youtube.com/watch?v=KKCf...feature=related

http://www.silviav8forums.com/forum/

http://www.drag240sx.com/

http://www.club240.com/forums/showthread.php?t=30440

http://forums.nicoclub.com/zerothread?id=197243&page=1

if you want more pm me or email me at dupontlm@gdnmail.net

oh lastly all your guys help is awsome- so with the more info here what is your guy's ideas?
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Old 07-19-2009, 07:09 AM
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THANX MUCH! to the poster of my postage

to the asker
yeah............ so there ya go buddy- your very wrong in your statements about what i am doing- it is extrememly performance driven-

a couple of my friends whent to school for grand prix racing and i have alot of buddies around mn that are into all kinds of racing. you dont have to shift as much with rpm- less tire where (well ... sort of - kind of hard to explain this one via internets TM george bush) just lots of reasons why a high rpm v8 is the way to go.

years ago f1 found out that small displacment lots of cylidners and high rpm (some boosted some na) are the way to go... oh and very kight weight and aero of course.

to me it does not make sence to argue with one of the highest levels of racing.
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Old 07-19-2009, 09:21 AM
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I don't know what kinda of driving Blight is aiming to do but the low torque is easier to launch with. The guys in the silviav8formum say a stock LS1 with headers and an intake can break the tires loose in 4th gear if you shift hard. The torque isn't going to hurt much. Those rears are bullet proof. Mine was going 10.90's with a 406 on NOS and sticks. (all stock with 4 lug hubs.) With the 385hp 331 is could do 40mph smoking roll ons (285/50/15 street tires) There is another guy in that forum that is dropping a LS7? (new Z06 500hp) crate motor for road racing. Those seem to be torquey enough.

You can figure how much torque you need at what RPM to get hp with this formula
HP= peak TQ x RPM achieved at
5252

You are getting hasseled because reliable high RPM motors are not "low baller as possible". Most of the guys here set a goal for the most hp they can use with the fastest torque curve then build every thing else to cope. Why cost your self performance.
If you want a high hp high spinning motor go to a junk yard and buy a wreck Hayabusa. Slap a turbo on it. You can get 500hp at 12000rpm that way.
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Old 07-19-2009, 02:41 PM
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The easiest way to get that power is to get a Vortec block, install a bigger cam, and install it retarded a LOT, with the appropriate valvetrain/short block modifications you can hit 400hp easily, if you need to pull the torque down even further then retard the timing.

SBC's are getting to a point where its hard to make ONLY 400hp.

As far as high revving power being an advantage- its not, making 400hp at 5500 RPM will probably be a tick faster than making the same power at 7000 RPM, IF your gearing is set up correctly.
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Old 07-19-2009, 04:56 PM
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i have a 4.08 rear now in my r200.

i just dont want to get the tq all the way for the sane reason sam_bo3 mentioned - i dont drift- this is not going to hook with a traditional v8 setup-

as to low baller as possible- my view on it is this; why spend more money when you dont have to? i picked up my 240 very clean with 40k on it for 700 bucks. usually jsut a very clean shell goes for like 2k because all the drifters. i have money i just want to spend as little of it as possible just kidn of one of my things- there is no real budget on this project- just why spend 10k while 5k will do?

"why buy new when slightly used will do?"- i may get sued for that lol
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Old 07-19-2009, 06:30 PM
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Quote:
Originally Posted by Ohio-Dan
The formula for Horsepower is; Torque X RPM / 5252 = Horsepower



Here's a link to a low torque high horse build up.

http://www.hioutput.com/tech/400hp/400hp.html
This is the "stupid" equation". The definition of horsepower is: The measurement of an engines ability to perform outside WORK. Nowhere in that equation do you see WORK. (technical term, btw) Torque X DISTANCE = WORK.
I cringe every time I see that equation because I know the response is totally bogus.
Displacement makes torque. Torque X Distance = HP. Therefore, the more displacement + more RPM (multiplier of distance) = more HP....

Sooooo, the smaller the engine (displacement), the more RPM (distance) you need to make HP. It's a big balancing act. Make your choice and live with it or change it.
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