Quickin

Is it just a matter of proper balancing and good parts? Can it safely be made to spin 9,000 rpm? What will ultimately limit how many rpm's it can safely go. Shorter stroke? I'm going 4.155 bore, I could go with a 4.100 stroke...445ci or a 4.00 stroke for a 434....if it will ultimately make more power due to the higher rpm's allowed.

Key words hear.....SAFELY and LONG LASTING.

I want the LS7 blocked 447ci with a 250 progressive shot that I'm having built to spin HIGH but remain reliable. It'll have a Lunati crank, Manley rods and Wiseco pistons. I'm just on the fence whether or not to go solid roller for more peak HP. 50-180mph runs ONLY, no track visits.

I have about 2-3 weeks to make the decision.

I don't need to hear that a solid roller set-up is going to require more expensive heads/parts, I already know that.


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sr71bbjr

iTrader: (52)

well light weight internals is a very big deal..I would use a callies billet crank,howards rods,and a custom wiesco piston.Titanium valves would help alot aswell.I wouldn't go more than a 4in stroke in any setup that your going to spin past 6900..Theres not enough to be gained out of it and the increase in piston speed is going to put alot of unnecessary strain on the motor..434ci is plenty of ci. to make the power.

Old SStroker

More of what sr71bbjr said:

Safely and long lasting and those kind of stroke/rpm combinations don't go well together.

1)Keep the piston speed (PS)below about 4800 ft/min. to keep inertia loads down. (see 2) below)

PS = stroke x rpm /6

PS = 4.00 x 9000/6 = 6000 ft/min.
PS = 4.10 x 8000/6 = 5467 ft/min

or:

Stroke = 6 x PS/rpm

Stroke(8000) = 6 x 4800/8000 = 3.6 inches
Stroke(9000) = 6 x 4800/9000 = 3.2 inches

2) use light weight and very strong parts. Lighter and stronger than LS7 parts.

3) redefine "long lasting". Cup engines spin well over 9000 for a couple of hours before rebuilding. LeMans 6.0L Vettes run 24 hours in anger but nearer 6000 max rpm rather than higher, and they have BIG budgets.

4) build an engine for the torque and power you need and the budget you have. Forget those rpm ranges.

Not what you wanted to hear, I'll bet.

Quickin

I'm already planning on Lunati crank and Manley rods. Whats the difference in price and weight in using the Callies and Howards stuff?

4.00 stroke is fine with me if it'll get me a decent power increase by way of higher rpm's.


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Quickin

So, which will be better for runs from 50-180mph?

4.000 stroke x 7,500 rpm/6 = 5,000 ft/min

or

4.125 stroke x 7,000 rpm/6 = 4,812 ft/min

Should I go with the extra cubes with the 4.125 stroke since the PS is basically the same?


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M6HuggerSS

what is your reason for trying to rev the **** out of your motor?

a super high duration cam will probly run like crap on the low end....

just kepp the power between 3-7K

Quickin

I thought the higher the rpm, the more power, the better for roll races 50-180mph.

If its just not the case, I won't bother. I'll stay around 7,000-7,500 and be safe.


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Luke Duke

you didnt say anything about heads? a motor is only as good as the heads especially at high rpm

slowpoke96z28

iTrader: (2)

i say to not spin the motor as high and just use more nitrous. it'll accomplish the same thing. how high do you have to spin to reach 180 at whatever gear you plan to hit it in? that should help you determine where to want to make peak power. spinning much higher than that is not needed IMO.

TransAminal

I wouldn't worry nearly as much about the bottom end of the motor as much as I would be concerned with the valvetrain. 9,000RPM is a ridiculously high speed for a pushrod valvetrain, they just aren't designed for high RPM operation. Its definitely possible, look at Nascar engines, but it sure isn't very cost effective or worth the effort IMO. One company makes a set of DOHC heads for our motors, which I'm sure would be more suited to high RPM's. But like the other guys said, there are plenty of better ways to make more power without turning sky high RPMs.

Quickin

My builder ports LS7 heads to flow 392 @ .650 lift so I'll be using those from him.


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Quickin

Probably 3:23 gears. 4L80E. 3400 Pro Yank verter.

Got a link to a calculator to figure that out?


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DONAIMIAN

iTrader: (18)

itll be a lot easier if you sold your car and just got a supra.

Quickin

This 447ci is gonna be my N/A/nitrous car going in my WS6, I've got other plans for a Vette, Supras will get killed. hint: NRE Complete quote, package and set-up are in stone, just gotta drop down the deposit, hopefully before years end


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sr71bbjr

iTrader: (52)

I just went out to NRE last week..Nelson is a super cool guy..theres some badass stuff at his place..

treyZ28

money

racer7088

THe valvetrain is what will stop you not the bottom end.

Quickin

I'm flying out to see him in a few weeks with a check (deposit) in hand. Did he tell you about his TT 454ci, its so awesome its just silly

Yeah, he's a great guy, we've been talking in detail for months about what he's gonna do for me, and the price really isn't out of line.

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Louie83

iTrader: (3)

Nitrous likes high RPM's. Nitrous only affects your torque, so the higher up the RPM band you make that torque, the more horsepower you will have. I assume you are going solid roller and dry sump to make this work.

Personally, if I was going to make a highway car, I'd go turbo and never look back.

treyZ28

Odd way of looking at it... what else would it effect other than power and torque?