hotparts

Guys i need a new motor and think about a RHS with only 364 CI with the YSI instead of the 402 or 427.
The motor should work better with the blower and it makes much more boost.
What do you think is better, what are the differences in torque and rwhp and what is better for the circuit?

Thank you

croatbob

uhm why? im running a ysi n went with rhs 427. not expensive to upgrade blowers. it is to upgrade engines

lt1z

Why not a 388 with a big bore head? Might as well if you go RHS block

hotparts

I thougt about the reduction because of the blower.
I spinned the YSI with a 402, the 2.75 and a special balancer to the maximum impeller speed and hat around 22 PSI.
A friend told me that he was extreme faster at the 1/4 mile with the 364 instead of the 402 conversion with the same YSI.

I think we have to change the way of thinking with a blower motor.
The blower has a lot more work to fill the bigger volumen.

Is there anybody that made this experience?

Thank you

ProEFI

I see no reason to go that low buddy get your self 402 to 427.

turbotuner20v

I run a built 365ci motor and like it. Did it mostly to decrease rod angle an be more reliable at high rpm, as well as fit the blower and cam better. Powerband was great at 930whp, hoping for the same around 1100.

Pitufina

I never understand the need to go with a bigger engine when using forced induction. Shoot, those new 5.0s are running crazy numbers on the dyno and the track with a heavier and less aerodynamic vehicle on the stock unopened engines. How do the accomplish that? Pretty easy, they have nice flowing heads, compression and rpms. Also the TiCVT helps a ton too and the gearing that most GM vehicles lack. Sometimes I wish I had kept my '11 GT but had a bad experience with it and traded in.

Anyways, I just wanted to show my point. Sorry for the little hijack.

Unreal

Talk to arun. He ran a 388. More boost isn't better. It is about power not boost. 1000rwhp on 18psi or 30 psi is still 1000rwhp. I've seen my 427 ysi overlayed with a 037680rwhp and for drag they made almost the same 5500+ but below that the cubes had a big advantage.

Mustangs are fast from the solid axle and hooking. Biggest advantage is that not the motor.

slow ride

It's a lot easier to make a street friendly DOHC small 4 valve hydraulic head rev to 8000-9000 rpm than a pushrod head with hydraulic valvetrain. Most of our normal ls built heads with average stainless solid valves and good springs are finished around 7000 rpm or a little higher depending on spring pressure, cam lobe, etc. Add better parts and you might take it close to 8000 still hydraulic. Our stock intakes target peak power in the 6000-6500 rpm range so it makes fitting anything under the hood a pain and expensive while reducing power under the curve. Our rpm limitations are top end related and not shortblock so we build big engines and make our powerband start early. If one were going to max out a compressor it would be best to do so at a higher RPM so in some cases it is better to run a smaller engine with peak efficiency occurring higher in the powerband.

blackz97

Personally i think the 388 would make a more usable power band. The 4" stroke motors will make more average power every time but how much can you actually use on a street tire? I like the idea of a long hooked up pull to 7500rpm instead of just melting the tires in every gear.

Unreal

My car hooks 60 just fine on a 345/18. I bet it is even better when I put the 15s on.

Might as well put some smaller heads/intake on it so it sees 30+psi.

Ls240sx

332ci twin s256's, 31psi, 1100hp. Works for me...

I will say I did lose a noticable amount of low end going from the 6L.

blackz97

Thats impressive. What kind of tire is that 345/18? And 60 in 3rd gear im assuming. Cant imagine 2nd gear working on any car making 1000 or close to it.

The smaller heads idea is silly. Defeats the whole purpose of the large bore. I bet you were just trolling with that comment. Its not like im advocating a more restrictive setup just to see a higher boost number.

The one thing I can say is that the bigger motors are gonna have better "street manners" when putting around town. That being said if you keep the 388 closer to 10:1 and dont get ridiculous with the cam I bet it would be comparable.

DANZGLASS

I love my 325ci single turbo. Be around 1000whp on this turbo and motor. at 850whp on the stock 5.3 drove fine around town and got 23 mpg ave. like 35 on the highway. got to love it.

Unreal

345 et streets, 60mph is 2nd gear. 3rd gear would be 90-95+ from a roll.

The comment of going smaller just to see more boost is silly, just like going to smaller heads just to see more boost is silly. Do what makes power.

ajrothm

+1

And more boost can equal more head gasket problems, more potential for detonation and more potential to cause major failure..

A blower at its max is only going to support X amount of air flow. More cubes are gonna eat up that air flow, resulting in less boost/squeeze... They will make all the power the blower will support, only not being pushed as hard.. The downside is they will peak earlier and not hold on as long up top.... That is the juggle you have to make...you need to have the power max where you need it most...thus the depending usage..

On the other hand, the smaller motor is capable of the same power (whatever the blower will support) and more capable to carry that power higher up into the power band for longer... This a great for drag racing and land speed racing...Ofcourse everything else will have to be setup to get the car into the power band.. The smaller engine will be compressed much tighter, (say 30 psi boost vs 20 psi) which is hard on head gaskets, and the valve train has to be very stable up high (7k+)..

Once again, this is a tap dance.

But in reality, I don't think there is much difference from a 365" to a 402" in regards to consumption... Not as much as people think.. Now a 346 to a 402... Or 365 to a 427, that's a big jump in air demand. There will be a big difference in power under the curve but if the small engine combo is geared or stalled correctly, it won't make much difference.

Me, I'll take big cubes and a big lung any day...but you can't argue with what people are doing with 5.3's with baby cams and big turbos, they go against conventional wisdom.. They can shift at 6k, trap at 6500 and run 165 mph in the 1/4...

BOO666

Unless your in a class that limits your engine size I would keep my cubes . As long as your engine was built for boost why not change out head unit . I ran outlaw 10.5 for years . Every motor I went bigger . Look at the lynch mob at pro line . Cubes rules . You want more boost . Get a bigger blower . You just need engine management via tuning to put down the power . I ran everything from 363 to 670 ci . There is a learning curve but no comparison . Get big stuff 3 , fast , Motec ect . and multistage boost controller with a big blower and keep the cubes .

hotparts

...so the smaller motor and higher boost makes more traktion at lower rpm, makes the car more driveable there and a longer lasting power band at higher rpm but it costs power at lower rpm.
So a 427 with the YSi 8,50" crank and 2.750" pulley at the blower plus the impeller uprade, is the max that is possible without Biturbo.
Maybe a little smaller block would be better to have the bigger bore and no issues when going hard on the racetrack?

What is to get with this combo and impeller upgrade?
Is it at the end from the 1000 injectors when i use the meth only for cooling the IAT?

QKSLVRZ

This is my guiding theory, backed by a lot of software dyno runs on configurations you'd (I) never afford to build.

Bigger bores hold more valve area, and as long as you get port velocity up to the 700'-750'/s port speeds you'll be happy. Conversely longer stroke just lowers the peak tq/hp rpm (which is set by this magic 700'-750'/s port velocity).

What you have to think of is that the engine takes a gulp of air, the bigger the gulp or the faster it takes one in the more power you make. The tq peak is the rpm of best breathing, and even as it takes in less air, rpm goes up faster than the volume/cycle goes down, and you get peak hp at the rpm of most breathing.
If you run a displacement limited class, short stroke 4 valve engines, as long as you can get the port velocity, makes the most hp (think F1). A longer stroke just increase port velocity at that rpm, at 6,000 rpm with the same cam the valve is open the same amount of time whether you're trying to fill a liter cylinder, or a half liter cylinder.
On the other hand, a 4L short stroke v8 with big valves, might need to spin at 12,000 rpm to get to 725'/s, that might work with a 4 valve head and some expensive hardware, it's not likely to work with pushrods.

The valves and port area determine how much hp you can make. Valve closure type determines the max rpm you can run, stroke length then allows you to pull the tq/hp peak to the design rpm your valves can reliably run at. That rpm and displacement determines the length and volume of the ports and headers.

QKSLVRZ

This is my guiding theory, backed by a lot of software dyno runs on configurations you'd (I) never afford to build.

Bigger bores hold more valve area, and as long as you get port velocity up to the 700'-750'/s port speeds you'll be happy. Conversely longer stroke just lowers the peak tq/hp rpm (which is set by this magic 700'-750'/s port velocity).

What you have to think of is that the engine takes a gulp of air, the bigger the gulp or the faster it takes one in the more power you make. The tq peak is the rpm of best breathing, and even as it takes in less air, rpm goes up faster than the volume/cycle goes down, and you get peak hp at the rpm of most breathing.
If you run a displacement limited class, short stroke 4 valve engines, as long as you can get the port velocity, makes the most hp (think F1). A longer stroke just increase port velocity at that rpm, at 6,000 rpm with the same cam the valve is open the same amount of time whether you're trying to fill a liter cylinder, or a half liter cylinder.
On the other hand, a 4L short stroke v8 with big valves, might need to spin at 12,000 rpm to get to 725'/s, that might work with a 4 valve head and some expensive hardware, it's not likely to work with pushrods.

The valves and port area determine how much hp you can make. Valve closure type determines the max rpm you can run, stroke length then allows you to pull the tq/hp peak to the design rpm your valves can reliably run at. That rpm and displacement determines the length and volume of the ports and headers.