Which is best for boosted power potential??

[Fiftydriver]

Have a question for you that know a lot more then I do about this subject. I have been researching my engine upgrade for a while now and have decided I want to go with an LSX block. That's about all I have decided. Do not care about the extra weight, want the strongest block I can get for the money and from the sounds of it, the LSX is pretty hard to beat.

I will be running a supercharger, right now have the Maggie but that is not a requirement. Would be nice to use it on this next long block but we will see.

My question is that I hear all the time that larger displacement makes it easier to make more power. But also hear that the 454 is not a good option for a boosted application.

What would be better then, take an LSX 376 block with 4.065" bore and add a 4.000" stroke to produce basically a 416-417 ci displacement.

OR

Get an LSX 454 block with 4.185" bore and basically destroke it by using a 4.000" stroke instead of the 4.125". This would make a 440 ci motor.

Everything I have read is that the 4.000" stroke is perfectly fine for boosted application as long as the block has cylinder walls thick enough to support the stress.

It would seem to me that a destroked LSX 454 block would handle the boost fine yet still offer the advantages of the larger displacement.

Anyway, educate me. Not looking to make huge boost, 10-15 lbs max. What would make the most streetable power, LSX 4.065x4.000 or LSX 4.185x4.000, all else being equal. I know there are a lot of variations to consider but just trying to figure out which is best for streetable power in the idle to 5500 rpm range where I run most often.

Basically looking to over build this engine simply for longevity more then anything.

[Detoxx03]

376 is all that's needed. Boost will make the power for you. A centri or twins would be better forms of forced induction also especially if you wanted to move to something like a 416.

[AGP Turbo]

4.00 stroke for sure
4.06 bore is big enough and will have best head gasket sealing if you decide to up your goals later.

[Rumbumbees$ponsor]

I wanted to do same but you need ERL block with thicker liners apparently the lsx 4.185 under boost will Crack the sleves.

If you have blower that can move the air(fill cylinders) then a 4.125 bore and 4.125 stroke would work. And be bad ass!

There's seems to be a few basic rules engine builders follow.. with ls3 lsx blocks..

ls3/l99 block no bigger crank than 4.00 no bigger bore than 4.70 for boost

Lsx block no larger crank than 4.125 no larger bore than 4.125 seems to be some sealing issues and cracked sleeves going any larger.. and the stroke for street any thing larger and pistons don't have a lot skirt on them and toward the bottom of the liner aren't stable.

It all depends on goals if you go over 800 rwhp then your spending 3000 to 4k on another fuel system..

I had same idea.. here's why from what I experienced with a 376 I'd rather have a largest possible cubes that has the most power before I stuck a power adder on it. Once the motor gets hot and out side temps are blazing and your stuck in traffic you lose a lot of power to me you can't take away the cubes.. if your 417 boosted motor makes 500 hp NA then you add your power adder and squeeze out 800 hp on a glory dyno run but then your car hot, outside temps hot, humidity.. now you got 690 hp..

Now you got a 441 it make 605 hp na and on boost it makes 800 hp same thing hot out side ect.. now your 730 hp

To me you can't take away cubes there all ways there even when hot..

1 psi adds what 20 hp or with tuning

And stroking from 3.62 to 4.00 adds 25 plus and going up to 4.125 maybe 55 or 60?

When it gets hot the tune can't take that leverage away..

Until someone shows me that a 417 made more power 441 or 454 with the same power adder then I believe my thinking.. I see a lot of the motors 417 427 to me like there building assembly line not trying new stuff using parts that manufacturer have on the shelf in certain strokes or bores.

if more cubes didn't make more power we be running 3.00 inch strokes with 4.125 bores.. turning 10k rpm but then the valves train geometry won't allow that :( a whole other discussion ..

just do what everyone else does here.. 417 for 800 rwhp using a alum block or a LSX block with 4.125 427 for 1200 or so..

[Fiftydriver]

Originally Posted by H-E

Would you be happy with a reliable 800rwhp that comes on as soon as you hit your throttle?

I am at around 580 RWHP, I would be very happy with 800 reliable, streetable RWHP!!! In fact that's kind of my goal.

I know, no need for the LSX block but again, I want overkill for long life and as my ride is 100% a street ride (no 1/4 mile ever), the bit of extra weight does not bother me a bit.

If I remember correctly, you have a blown LSX454??? May be wrong but I thought I had followed some of your posts in the past. That would be sweet!!!

[Fiftydriver]

Originally Posted by Rumbumbees$ponsor

I wanted to do same but you need ERL block with thicker liners apparently the lsx 4.185 under boost will Crack the sleves.

If you have blower that can move the air(fill cylinders) then a 4.125 bore and 4.125 stroke would work. And be bad ass!

There's seems to be a few basic rules engine builders follow.. with ls3 lsx blocks..

ls3/l99 block no bigger crank than 4.00 no bigger bore than 4.70 for boost

Lsx block no larger crank than 4.125 no larger bore than 4.125 seems to be some sealing issues and cracked sleeves going any larger.. and the stroke for street any thing larger and pistons don't have a lot skirt on them and toward the bottom of the liner aren't stable.

It all depends on goals if you go over 800 rwhp then your spending 3000 to 4k on another fuel system..

I had same idea.. here's why from what I experienced with a 376 I'd rather have a largest possible cubes that has the most power before I stuck a power adder on it. Once the motor gets hot and out side temps are blazing and your stuck in traffic you lose a lot of power to me you can't take away the cubes.. if your 417 boosted motor makes 500 hp NA then you add your power adder and squeeze out 800 hp on a glory dyno run but then your car hot, outside temps hot, humidity.. now you got 690 hp..

Now you got a 441 it make 605 hp na and on boost it makes 800 hp same thing hot out side ect.. now your 730 hp

To me you can't take away cubes there all ways there even when hot..

1 psi adds what 20 hp or with tuning

And stroking from 3.62 to 4.00 adds 25 plus and going up to 4.125 maybe 55 or 60?

When it gets hot the tune can't take that leverage away..

Until someone shows me that a 417 made more power 441 or 454 with the same power adder then I believe my thinking.. I see a lot of the motors 417 427 to me like there building assembly line not trying new stuff using parts that manufacturer have on the shelf in certain strokes or bores.

if more cubes didn't make more power we be running 3.00 inch strokes with 4.125 bores.. turning 10k rpm but then the valves train geometry won't allow that :( a whole other discussion ..

just do what everyone else does here.. 417 for 800 rwhp using a alum block or a LSX block with 4.125 427 for 1200 or so..

I would agree with most of what you say, at least as far as my knowledge on the subject goes. In my opinion, I would rather have a stout 440-454 breaths really well and only needs 6-8 lbs of boost then take a 376 and have to run 20 lbs of boost to get the same power.

Again, this is not a 1/4 mile car, its a street car. I do 80% of my driving OUT of boost with my current Maggie set up which is why I would love the idea of big cubes for most of my driving and then when the boost kicks in....!!!!!

[Fiftydriver]

Originally Posted by AGP Turbo

4.00 stroke for sure
4.06 bore is big enough and will have best head gasket sealing if you decide to up your goals later.

Again, I have no plans to ever 1/4 this car so if I can get into the 800 RWHP range I would be very happy. I hear ya on the better head gasket sealing. How critical is this with a good tune, the 6 bolt head configuration and the multi layer steel gaskets we have today.

Again, looking to hit around that 800 RWHP range and no more.

[Fiftydriver]

Thanks for your time and replies guys.

[AGP Turbo]

Originally Posted by Fiftydriver

Again, I have no plans to ever 1/4 this car so if I can get into the 800 RWHP range I would be very happy. I hear ya on the better head gasket sealing. How critical is this with a good tune, the 6 bolt head configuration and the multi layer steel gaskets we have today.

Again, looking to hit around that 800 RWHP range and no more.

If that is for sure all the power you will ever want then I really question the need for the extra weight of the LSX block. But if you are doing that anyway and you live in a cold weather area, then may as well go 454. A good 454 will do 600whp n/a so adding in just 200extra with the blower is not too hard.

6 Bolt heads don't seem to help with cly-cyl sealing problems, only blowing out at the spark plug area. But none of that is going to matter down at 12psi.

Just so you know, it could be dead reliable with a nice light weight LS3 block at 416ci.

[Unreal]

I wouldn't run >4" stroke on a street boost motor on an LSX block. Liner just isn't long enough. With an ERL block or Darton block with longer liners it would work better.

Extra cubes will just eat up the power that blower can make. For a PD blower in the <3L size a 376-390ci is a good size. 416+ if you do a large centri.

This concept of a 500hp motor then add blower, or 600hp is just wrong. You don't build a 600rwhp motor. A blower motor will have a mild cam, less compression, and depend on the power adder for power. You aren't building some 600rwhp 427 then adding 200hp in boost. Hell my 1200rwhp 427 car would probably make 400-450rwhp NA if I took the blower off.

What I would do for a fun 800rwhp car? Sell maggie, intake, headers, catchcan. Pocket $5000-6000, drop $8k on AGP kit with Meth, bolt on, enjoy 800rwhp. Out of pocket in the end will be $2000-3000 compared to $8k+ more in mods.

[AGP Turbo]

I didn't even comment on the blower cause he acted like it would be upgraded when he got to that point. He's very concerned with keeping everything WELL within it's abilities to be trouble free. So that rules out a small blower that would have to be over spun all the time just to not choke off that big motor. YSi or turbos or something capable of 1000whp to keep with the moto of a nice simple 800whp.

[Unreal]

If you are keeping the Maggie, just do a nice forged ls3 setup. Drop some pistons/rods into your motor, and enjoy. That will max out the blower just fine.

[jessrayo]

Unreal kind of covered this in his post but I'm going to give you a little more detail to try to understand this. The displacement of the motor does not matter with a PD top mount supercharger. A 376 will make very close to the same power as a 454 if everything else in the motor is equal. But the 376 will have more metal in the cylinder walls so it will be a stronger block.

First off power is a direct relation between air and fuel. The amount of air in the engine is always what limits power, if we can get in more air we just put in bigger pumps and injectors. Getting more air into the engine is how you make more power.

With a naturally aspirated engine the engine draws in air directly related to the displacement of the engine. If it is a 5 liter engine it draws in 5 liters of air, if it is a 6 liter engine it draws in 6 liters of air. There are differences in friction, mass, etc but more displacement gives more power.

When you get to a PD supercharger everything changes when the bypass closes and the supercharger is providing boost. The supercharger has a fixed displacement 2.3 is most common and whatever speed that thing is turning is how much air it is going to push. Let me repeat that again, the air entering a supercharged engine will be mathematically the rotor size of the supercharger x rpm. Air is air, you mix it with fuel and it burns. It is going to push the same amount of air into a 376 as it will into a 454. It will just show more boost on the 376. If you change the cam and port the heads it will provide similar improvements in both engines. Yes more boost is equal to more heat and more heat is slightly less power. But you can add induction cooling to balance this.

With most turbos or really big centrifugal's this is not true because they are not limited by rpm like the pd blower is. They can generally push more boost than the engine can handle.

I would not bore out any LSX block for more power if you plan on running a blower. I do like the 427 when the engine is not in boost... (most of the time) but when you hit it, it is really all the same.

[Unreal]

If money was no object, but IMO spend the money that would go towards a 454 on tires, suspension, etc and have a better hooking well rounded car. Now if money isn't a concern, go for it. Just be aware that dropping an extra $5k+ on a 454 isn't going to be faster or more powerful than a 376 maggie car.