Any High RPM NA Viper Builds

[dewilmoth]

With all the Viper future value discussions going on lately, I'm ready to read something more technically interesting on the forum. Wondering if anyone has experience with building a high RPM 8.4L, and what went into it. I admittedly won't be undertaking a build like this anytime soon, but if/when I do modify my Viper, it would likely be a spinner.

After running some piston speed numbers and comparing them to the LP560-4, it seems as though the Viper engine leaves quite a bit on the table in terms of RPM. The Lambo has a mean piston speed of approximately 26 m/s at max RPM, vs 21 m/s in the Viper. At 7500RPM, a stock stroke Viper would have a mean piston speed of approximately 25 m/s, which seems very doable with good rods, rod bolts, and pistons. Custom pistons allowing longer rods would be ideal. Shortening the stroke with a custom crank could make 8000+ possible, with the added benefit of a very favorable rod/stroke ratio and lots of dwell. Anyway, just thinking out loud and would be interested in hearing thoughts/experiences on the matter. Thanks!

[donk_316]

I like threads like this...

If the heads and cam / valve train support the higher RPM I don't understand the lower rpm (relatively speaking) of the Viper engine.

The engine seems to wake up at 4000rpm and then red lines just over 6500.

[J TNT]

Bearing speed on the mains of the crankshaft is the issue . A smaller main bearing would be needed , not a simple fix .
7500 rpm is possible . Arrow is your best source for answers .

[dewilmoth]

Bearing speed on the mains of the crankshaft are the issue . A smaller main bearing would be needed , not a simple fix .
7500 rpm is possible . Arrow is your best source for answers .

Interesting, bearing size was never on my radar. How do the Viper main bearings compare in size to say a SBC or the European V10s? I'm guessing Dodge built the motor with larger mains to get the strength they wanted out of the crank?

[Jdmuscle]

That would be interesting and it'll definitely alter the way this motor sounds as well. Combine this with an well rounded cam / heads pkg and it'll be killer. I'm on a quest to a perfect NA build as well. When it comes to gen Vs, turbos and super chargers don't interest me. Typically I'd like to build a bit on top of what factory put a vehicle out with and exploring the NA route is an amazing idea for me.

[PaulP]

Great thread, From talking to a few engine builders the viper struggles with bearing issues and oiling issues as it sits at 6000rpm and 6700, revving any more would only hurt it more or create more issues, If someone where to build a motor and de-stroke it and do the necessary oiling mods, maybe adding a dry sump kit you could rev to 8000rpm like some viper engines are out there, Kevin at exotic engines has built a few and is very knowledgeable in this.

[NT-ACR]

http://driveviper.com/forums/threads...y-sump-engines

[Martin]

This is something that I've been thinking about for 20 years or so. I used to be an engineer, so I did a lot of thinking about what it would take to get these engines to really spin.

The consensus I got from lots of people was that it would require a lot of work. Lowering the rotating mass is just the start. Overhead cams would likely be necessary, and the configuration of the engine would have to be changed to make it an even firing and balanced engine.

I'd love to see a 8000 RPM (reliable) Viper V10, but something tells me that 7k is about the most that can safely get squeezed out of the current platform unless material science delivers on some super lightweight and super strong components. That said, it is definitely a fun conversation and it's fun to research what could be done.

[Steve M]

Application matters...there is a big difference between doing a few spirited runs on the street or at the drag strip vs. sustained high RPM diving on a road course. For the latter, I'd think a dry sump would be necessary.

Check out this thread here:

http://driveviper.com/forums/threads...y-sump-engines

That should provide some insight. LSX guys have been doing high RPM stuff with push rods for years...the question is whether or not you really need it.

[dewilmoth]

You guys make some good points, and I agree it sounds like a complicated project. That being said, an 800hp/7500 rpm NA Viper sounds like the ultimate sports car to me. The specific output would still be quite reasonable due to the cubes. From the sound of it, oiling is the biggest issue with such an undertaking.

And we haven't even discussed gearing yet. That would require some serious changes as well.

And thanks for posting the link to the other thread. Sounds like everything I'm asking about has already been done.

[uberpube]

The next question would be will the synchro's in the transmission handle it? I built a rotary for my old RX7 that I aimed to shift at 10,200 rpm and ignition cut hit at 10,800. It became a transmission eater, the stock transmission synchro's could only take repetitive shifting at 7500 rpm. 25 laps per transmission got kinda old.

[SharpMan]

Might be fun to de-stroke the engine, reducing displacement and reciprocating mass, and through that increase RPM to attain same HP but with a very different character.

[dewilmoth]

Might be fun to de-stroke the engine, reducing displacement and reciprocating mass, and through that increase RPM to attain same HP but with a very different character.

I had very good luck with a de-stroked long rod 4G63 Evo motor several years ago. It was an absolute animal of a motor, and the engine characteristics were phenomenal. I would think a similar premise on a Viper engine would be very fun. And it's not like we're talking about giving up much displacement. I'd have to do some math, but I'm guessing de-stroking to 8.0L and pushing the wrist pins as high as possible in the pistons would result in a spinner. But that still doesn't solve the oiling and valve train issues mentioned earlier. Based on the thread above though, it sounds like those issues have already been solved. It's only money!

[SRT_BluByU]

That's the point of big displacement.. it doesn't need to Spin it's brains out. 6400-6600 rpm its tons for the weight of such a large piston. There's a good reason those lambos and f-cars have smaller displacements and bores.

Would be interesting to see if a Ferrari v12 or v8 would fit between the frame rails..

[biturboamg]

Even 7500 would be nice. A nasty head/cam with 8000rpms would be a blast. Love the 9000rpms of the gt3 and even the gt350 with 8200-8400 is great.

[SharpMan]

F12 V12 would be epic!

That's the point of big displacement.. it doesn't need to Spin it's brains out. 6400-6600 rpm its tons for the weight of such a large piston. There's a good reason those lambos and f-cars have smaller displacements and bores.

Would be interesting to see if a Ferrari v12 or v8 would fit between the frame rails..

Agreed. A nice, fast-spiting, raspy, on-cam monster!

Even 7500 would be nice. A nasty head/cam with 8000rpms would be a blast. Love the 9000rpms of the gt3 and even the gt350 with 8200-8400 is great.

[Viperawi]

Just a small note I would like to add on this subject, reading what Dick Winkles wrote in the (SRT Viper: America's supercar returns):
" I feel the viper engine is at the zenith of a naturally aspirated cam-in-block two-valve engine. You could make over 800 hp if you didn't have to pass emissions, but we do "

So, I second that Arrow have more interesting answers on this !

[dewilmoth]

Just a small note I would like to add on this subject, reading what Dick Winkles wrote in the (SRT Viper: America's supercar returns):
" I feel the viper engine is at the zenith of a naturally aspirated cam-in-block two-valve engine. You could make over 800 hp if you didn't have to pass emissions, but we do "

So, I second that Arrow have more interesting answers on this !

I'm guessing 800 is actually quite conservative. It just surprises me we don't see more NA builds on the Viper. Maybe that will change in the coming years when people start modifying the ACR, which isn't really suited for FI applications.

[uberpube]

I wonder if anyone will bother churning out another aftermarket head for the motor? Some companies are making new heads for dead engines like the B/RB and magnum so maybe there is a chance.

[Nth Moto]

OP, great topic! We've been getting an incredible amount of interest in naturally aspirated builds lately from mild to wild and at the end of the day it's going to come down to how much does a person want to spend vs gains and results realized.

Application matters...there is a big difference between doing a few spirited runs on the street or at the drag strip vs. sustained high RPM diving on a road course. For the latter, I'd think a dry sump would be necessary.

This is a critical point here; nicely said Steve. What a person can get away with in an NA drag application vs an endurance engine are two different things usually. Combine that with not wanting it to be a maintenance headache (not major, even just minor upkeep) or have driving quirks which are inherent as the aggressiveness of the combination continues to go up and you have an increasingly tall order on your hands. Entirely plausible, but challenging.

I'm guessing 800 is actually quite conservative. It just surprises me we don't see more NA builds on the Viper. Maybe that will change in the coming years when people start modifying the ACR, which isn't really suited for FI applications.

800-875HP isn't an unrealistic number if we're talking crank HP. And yes, that will be a very fun/quick car to run around. At that power level they can be made to drive quite well also and not get into the serious geometry alterations, oiling systems, etc.

However, getting there and then going beyond comes at a small rate per dollar very quickly, and that's why you don't see more "big" NA builds in our opinion. While they have clear and definitive advantages/perks over a forced induction build, putting together a well engineered destroked combination like we have done in the past with the oiling system, heads, valvetrain work to support it, intake manifold to optimize it, etc etc can end up costing as much as a forced induction build. Since most people are focused on the end power output the FI build wins out at that point hands down, so only the most die hard of NA fanatics will stick through it, unless there are class and/or use concerns or restrictions.

With all of that being said, the road less traveled has it's own rewards sometimes.

[Antonio@CalvoMotorsports]

destroke, cut the mains down and go for that 8k

[dewilmoth]

The problem with de-stroking is now you're in it for a custom built crank, and that makes an already expensive build become really expensive. After reading the thread link posted earlier, it seems like a 7500rpm stock crank motor that will live a long healthy life is entirely plausible. I'm glad to hear people are starting to inquire about fun NA builds. FI makes great Hp/$, but peak numbers are not what make the car fun to drive. I learned that he hard way with my Evo.

[Arizona Vipers]

Calvo and A&C performance are getting 700rwhp with their heads/cam packages. I think they are redlining around 7K RPMs. That's well over 800 crank horsepower.

[J TNT]

This is not high RPM , but it is High Horsepower .

https://www.youtube.com/watch?v=JWXbsyYR-8g

[dewilmoth]

Calvo and A&C performance are getting 700rwhp with their heads/cam packages. I think they are redlining around 7K RPMs. That's well over 800 crank horsepower.

Just read through your thread, impressive... that transmission and dry sump setup are pure automotive porn. Can't wait to hear your thoughts when the car is finished.