# 300 hp @ 4000 rpm...can it be done?

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#### TXFlyGuy

##### Well-Known Member
Here is a question for you "Hot Rodders"...can a 4.3 V6 be built to put out close to 300 hp at 4000 rpm? With the 1.71 PSRU I can't go over this limit with the 88" prop.

#### TFF

##### Well-Known Member
Probably not without turbo or supercharger. I would guess 200hp at that rpm.

#### Toobuilder

##### Well-Known Member
Log Member
I'm guessing you are looking to retain a "scale" prop?

We've discussed it before, but a big inch LS series V8 should pull 300 HP at 3000 RPM direct drive. You certainly are not going to swing an 88 inch prop at that speed, but the 184 PSI BMEP required of a 430 inch LS is in the realm of possibility. Should end up comparable in weight to the V-6/PSRU combo as well.

#### Detego

##### Well-Known Member
Here is a question for you "Hot Rodders"...can a 4.3 V6 be built to put out close to 300 hp at 4000 rpm? With the 1.71 PSRU I can't go over this limit with the 88" prop.

John Steere’s Supercharged Thunderbird

"The engine is a 90-degree, 3.8-liter V-6 from a 1990 Thunderbird Super Coupe.
It is supercharged by an Eaton blower and inter-cooled.
The compression ratio is 8.2: 1 and the fuel is supplied by six fuel injectors.
The engine is rated at 210 hp at 4000 rpm and delivers 315 lb-ft of torque at just 2600 rpm.

Among other essentials such as a Northwest Aero Products 1.7:1 ratio cog belted propeller speed reduction unit (PSRU), this automobile engine conversion includes the standard automotive sensors, multi-port fuel injection system, and computer ignition systems, less the standard emissions junk. An emissions air pump (not standard in the car) was added to serve as a vacuum source for the flight instruments."

08/08 - Hangar Talk - John Steere’s Supercharged Thunderbird Powered BD-4

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#### Lemans

##### Well-Known Member
You may expect 240hp@4000rpm for a normal aspirated 4-stroke 4.3 V6 if you if take your engine to an experienced engine engineer.
Up until now the spreadsheet has shown 'real world' figures.

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#### TXFlyGuy

##### Well-Known Member
You may expect 240hp@4000rpm for a normal aspirated 4-stroke 4.3 V6 if you if take your engine to an experienced engine engineer.
Up until now the spreadsheet has shown 'real world' figures.
Thank you! I cannot open this file...can you send it in a PDF?

#### TXFlyGuy

##### Well-Known Member
Thanks! I ran numbers from 298 hp @ 4000 rpm to 258 hp @ 4000 rpm. We may bore & stroke this engine to 287 ci. This would be 3/4's of Chevy's famous 383 engine. The 4.3 V6 is a SBC minus two cylinders.

E

#### ekimneirbo

##### Guest
Thanks! I ran numbers from 298 hp @ 4000 rpm to 258 hp @ 4000 rpm. We may bore & stroke this engine to 287 ci. This would be 3/4's of Chevy's famous 383 engine. The 4.3 V6 is a SBC minus two cylinders.
I know people get an idea and want to stick with it, but look at it this way. An LS?
V8 Chevy will weigh about the same as a cast iron 4.3 (262 cu in) V6.

You will have to stress the V6 with higher rpms while a 415 cu in LS3 would basically
loaf along and easily produce 300 hp way below 4000 rpms.

You can purchase aluminum heads for the LS dirt cheap while aluminum heads for the 4.3 will cost you more than the basic engine. Personally I plan to use some LS1
heads which should keep the air flow plenty fast (2700 rpms in my case). You can purchase 2 used LS1 heads for $100-$150 on ebay easily. This will also allow the use of the cheap and easy to find LS1 intake manifold if you inject it. I don't recommend the LS1 block because of thin cyl walls that don't allow much reboring.

You might even be able to produce the 300hp at a lower engine rpm and slow prop speed even further.
There is a shop on Ebay selling 415 stroker 8.5 to 1 compression ratio forged crank and pistons professionally machined and assembled short blocks for about $4200. Bolt the LS1 heads on with a factory GM parts intake and carburetor. Ignition system may take a little work......crank trigger maybe. The point is that you have a far more efficient engine design that is all aluminum and very strong, and it doesn't have to work hard to get the power. If you read anything about these engines you will see that power is rediculously easy to extract from them with just a few mods. Price for building and stroking an alum head V6 will be comparable and you will have a lot more harmonics to consider with the V6. Also, GM changed the firing order from the old 18436572 of the small block Chevy so that the engine produces less harmonics from the firing order. #### TXFlyGuy ##### Well-Known Member I know people get an idea and want to stick with it, but look at it this way. An LS? V8 Chevy will weigh about the same as a cast iron 4.3 (262 cu in) V6. You will have to stress the V6 with higher rpms while a 415 cu in LS3 would basically loaf along and easily produce 300 hp way below 4000 rpms. You can purchase aluminum heads for the LS dirt cheap while aluminum heads for the 4.3 will cost you more than the basic engine. Personally I plan to use some LS1 heads which should keep the air flow plenty fast (2700 rpms in my case). You can purchase 2 used LS1 heads for$100-$150 on ebay easily. This will also allow the use of the cheap and easy to find LS1 intake manifold if you inject it. I don't recommend the LS1 block because of thin cyl walls that don't allow much reboring. You might even be able to produce the 300hp at a lower engine rpm and slow prop speed even further. There is a shop on Ebay selling 415 stroker 8.5 to 1 compression ratio forged crank and pistons professionally machined and assembled short blocks for about$4200.
Bolt the LS1 heads on with a factory GM parts intake and carburetor. Ignition system may take a little work......crank trigger maybe.

The point is that you have a far more efficient engine design that is all aluminum and very strong, and it doesn't have to work hard to get the power. If you read anything about these engines you will see that power is rediculously easy to extract from them with just a few mods. Price for building and stroking an alum head V6 will be comparable and you will have a lot more harmonics to consider with the V6.

Also, GM changed the firing order from the old 18436572 of the small block Chevy so that the engine produces less harmonics from the firing order.
Yes, you are correct. But the problem is weight & overall dimensions. Our V6 is all aluminum, so it is lightweight. Plus we have a very well engineered and tested PSRU drive system that is lightweight as well. This V6 with the stroker kit will easily put out 300 hp @ 4,500 rpm. And it will loaf along at 2400 rpm cruise which is where the torque numbers are real good.

As much as I would like to drop in a GM crate 350, it just will not work without major engineering issues being solved.

E

#### ekimneirbo

##### Guest
Yes, you are correct. But the problem is weight & overall dimensions. Our V6 is all aluminum, so it is lightweight. Plus we have a very well engineered and tested PSRU drive system that is lightweight as well. This V6 with the stroker kit will easily put out 300 hp @ 4,500 rpm. And it will loaf along at 2400 rpm cruise which is where the torque numbers are real good.

If you already have an all aluminum V6 and a PSRU then I assume you are locked in to using that combination. I mean these as objective comments so please take them in that context. First, a PSRU that will survive 300 hp will probably weigh about 80+ pounds which coupled with an aluminum V6 will be comparable to an LS V8 with a direct drive bolted to it. Lengthwise the V8 should be slightly longer but it depends on the driect drive length and the PSRU length. I had a Geschwender PSRU and it was over 80 lbs without any oil or attachment bolts.
The V6 crankshaft design is not as strong as a V8 because of design compromises to make it work. Special balance shafts were incorporated to compensate for vibrations caused by the odd balance/firing order.So, resonance may be a problem.....maybe not. Since you are running a stroker, maybe your crank is designed differently from an OEM ???

I'm a little confused as to your RPM calculations.At 4500rpms/300+hp I assume your prop will be turning 2700 rpms. I don't have time to calculate tip speed cause it quitting time. If the above conclusion is correct, then at an engine speed of 2400 which is slightly morethan half of 4500 your prop would only be turning slightly more than half of 2700 rpms .....say 1500 rpms. If you mean that the prop will be turning 2400 rpms,then your engine would be at 4080 rpms. So maybe I'm misunderstanding what you meant. The upside of the PSRU is making thrust line location easier if its
a high wing application. If its a low wing, it may raise it too high. How about a little more specifics on what you are building and what you want to accomplish? It sounds like an interesting project, so I hope your ideas do work for you.

As much as I would like to drop in a GM crate 350, it just will not work without major engineering issues being solved.
xxxxxx

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#### Armilite

##### Well-Known Member
While 4000rpms is not really working any of these Small Block Engines very Hard, there is No Substitute for Cubic Inches!

262ci = 4293cc(4.3) at 4000rpms at Stock 90% = 182hp, at 95% = 192hp, at 100% = 202hp

262ci = 4293cc(4.3) at 4000rpms at Turbo 4lbs of Boost = 257hp. At 75% Rpms = 3000rpms = 193hp

262ci = 4293cc(4.3) at 4000rpms at Turbo 5lbs of Boost = 271hp. At 75% Rpms = 3000rpms = 203hp

262ci = 4293cc(4.3) at 4000rpms at Turbo 6lbs of Boost = 285hp. At 75% Rpms = 3000rpms = 214hp

262ci = 4293cc(4.3) at 4000rpms at Turbo 7lbs of Boost = 298hp. At 75% Rpms = 3000rpms = 224hp

262ci = 4293cc(4.3) at 4000rpms at Turbo 8lbs of Boost = 312hp. At 75% Rpms = 3000rpms = 234hp

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415ci(LS3) = 6801cc at 4000rpms at Stock 90% = 288hp, 95% = 304hp, 100% = 320hp (Without a Turbo).

415ci(LS3) = 6801cc at 4000rpms at Turbo 2lbs of Boost = 364hp. At 75% Rpms = 3000rpms = 273hp

415ci(LS3) = 6801cc at 4000rpms at Turbo 3lbs of Boost = 386hp. At 75% Rpms = 3000rpms = 289hp

415ci(LS3) = 6801cc at 4000rpms at Turbo 4lbs of Boost = 407hp. At 75% Rpms = 3000rpms = 306hp

415ci(LS3) = 6801cc at 4000rpms at Turbo 5lbs of Boost = 429hp. At 75% Rpms = 3000rpms = 322hp

415ci(LS3) = 6801cc at 4000rpms at Turbo 6lbs of Boost = 451hp. At 75% Rpms = 3000rpms = 338hp

415ci(LS3) = 6801cc at 4000rpms at Turbo 7lbs of Boost = 473hp. At 75% Rpms = 3000rpms = 355hp

========================================================

427ci = 6997cc at 4000rpms at Stock 90% = 297hp, 95% = 313hp, 100% = 329hp (Without a Turbo).

427ci = 6997cc at 4000rpms at Turbo 2lbs of Boost = 374hp. At 75% Rpms = 3000rpms = 281hp

427ci = 6997cc at 4000rpms at Turbo 3lbs of Boost = 397hp. At 75% Rpms = 3000rpms = 298hp

427ci = 6997cc at 4000rpms at Turbo 4lbs of Boost = 419hp. At 75% Rpms = 3000rpms = 314hp

427ci = 6997cc at 4000rpms at Turbo 5lbs of Boost = 442hp. At 75% Rpms = 3000rpms = 331hp

#### TXFlyGuy

##### Well-Known Member
As the engine of choice for the T-51D Mustang is now the LS3 6.2 V8, it will easily make 300hp at 4,000 rpm. And normally aspirated. Note that it makes 400 lbs of torque at the setting also.

Of course, this is a sea level number.

#### Winginit

##### Well-Known Member
As the engine of choice for the T-51D Mustang is now the LS3 6.2 V8, it will easily make 300hp at 4,000 rpm. And normally aspirated. Note that it makes 400 lbs of torque at the setting also.

Of course, this is a sea level number.
. Shush! Torq is a four letter word around here.:gig:

HBA Supporter
CUBIC INCHES

#### TXFlyGuy

##### Well-Known Member
For those who have followed the thread on the Hot Cam, 300hp can be made at 3500rpm, with the LS3 V8.

#### WonderousMountain

##### Well-Known Member
Okay, so uh,

You're gonna need boost. Either more revs needed (a lot) or more cubes. You can turbo though, there's no law against it.

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#### TXFlyGuy

##### Well-Known Member
Okay, so uh,

You're gonna need boost. Either more revs needed (a lot) or more cubes. You can turbo though, there's no law against it.