Firebirda7x

I was just checking out the new Lambo Aven-somethings motor. 6.5 liters, 691hp at 8250 RPMs. I know (generally) how to make a motor rev in such a manner, and my question to you engine gurus is has anyone done this to a 350 and had it not destroy itself? Is a flat-plane crank, use of titanium and extreme camming going to yield desirable results? I always wanted a high revving large displacement v8. I am not sure if the limitations are in the block design itself, or if it is possible to any degree.

Edit: The main thing i can think of is balance issues.

TNT_Z28

the limitation is the push rod technology verses duel overhead cam technology the the lambo (as u mentioned) utilizes.

but then again, NASCAR engines are pushrod arent they?
and i know they rev extremely high

midnightfirews6

iTrader: (1)

Any given night at the drags or any Sunday at a NASCAR race there are cars running in that range... you'll want a lightweight rotating assembly and a very good valvetrain with a built bottom end... a short stroke can help as well (like the 302 chevy had)

These cars don't last long running at these high RPMS. TNT_Z28 nailed it, small displacement DOHC engines are designed to scream. Hell, even a 1980's Twin Cam Corolla will spin 7k all day long... they're torqueless wonders though, whereas a v8 has all its torque down low and is designed to stay below about 5.5k but pull like a freight train right from idle. It can and has been done with the right parts, but it won't be cheap and will require a lot of planning and precision in the build... small errors will rip the motor to shreds at those speeds.

Firebirda7x

Oh yea duh....pushrods. Ugh. So even if I had it blueprinted, those rods aren't going to hold up long at those RPMs. Bah....

J.Prock

Find and buy an Lt5 if you want high RPM power

Apeiron

The main thing is cost.

TNT_Z28

Ah yes.... the LT5

This is off topic, but does anybody know of anyone running one of these in third gen? I scene one in a vette once. Sounded pretty mean.

Doesn't seem like the idea caught on with gm since theyve stuck with pushrod tech. (which I like) thru the present day (except for that northstar v8)

J.Prock

GM made a thirdgen with an LT5 in it. I think the paint is ugly tho. LT5's are just so expensive, hard to find, few places can work on them, and you have one transmission choice.


(This is the LT5 camaro)

UnderCover89TBI

iTrader: (25)

I just dont think you need a high revving motor to make power. why rev to 8000 rpms when you can rev to 6500 and make power. Your head ports will have to be so big to make power that high of RPM's that it'll be a track only car and you'll be launching at 5500 rpms...no street manners...seems out of the question.

AlkyIROC

I take my 540 to 7500+ so size isn't the issue. As mentioned above, it's the quality of the valve train.

RPM is how fast work can be done. You can make xxx amount of torque at 6500 rpm but if you can make the same amount of torque at a higher rpm, you will be faster because the work is being done quicker. Moving that powerband up higher makes more work faster however the trade off is the quality of the parts surviving.

NASCAR engines are basically SB2.2 engines and still use pushrods. To survive those high rpms for long periods of times and keep valve train stability, it's not uncommon for them to use 7/16" or even 1/2" pushrods. They also use high end shaft rocker systems.

Shadow Z

iTrader: (2)

A couple of you guys are placing RPM limits on the style of valvetrain, i.e. SOHC and DOHC Vs. OHV. That's just not it at all.

What generally comes into play when trying to build a high revving setup is stroke length, which transfers to piston speed, obviously. Also, the other huge factor was already mentioned, quality of the valvetrain.

As Alky mentioned, he takes his 540 to above 7,500 RPM, which I'm assuming is a very well built engine. No 100% stock BBC could handle that. Then again, this thread is comparing an Italian supercar that is in the hundreds of thousands of dollars, to a run of the mill Chevy 350. Basically it'll come down to, what's the point of wanting to rev as high as a V12 Lamborghini when you can make that power much lower in the RPM range, and what's your budget?

My '01 Mustang is obviously an OHC engine, Ford's SOHC 4.6. However, I don't make any more power after just barely above 5,000 RPM. Stock, they come with a very decent fuel system, good heads although the cams are a bit on the conservative side, there aren't many intake manifolds for them that flow better than stock, and they have a decently flowing 65MM throttle body, stock. So, why? My little 4.6 although being more than a full liter smaller than a 350, has a longer stroke than a 350, and of course I'm running a 100% stock drivetrain.

I have my shift light set to 5,500 RPM right now, and the only reason it's actually above 5,200 is to set myself right around the peak torque range after I shift. So really all in all, OHC Vs. OHV is a fairly annoying, vague assumption that has been repeated over and over. The weight of the internals, bore and stroke, quality of the valvetrain, WAY more important.

This big 6.5 Lamborghini actually only displaces 541cc's per cylinder, whereas a Chevy 350 is at 712cc's per cylinder. There's just a ton of factors that influence the engine's RPM range. Displacement and the valvetrain quality are just some of the main factors.

Shadow Z

iTrader: (2)

Matter of fact, my old dinosaur technology flat tappet cam 350 felt a little better in the higher RPMs than the Mustang does. The highest I have ever revved the Mustang is 6,000, just out of curiosity of how it performs above it's peak power range. It was upsetting. It was like power just immediately shut off after around 5,800.

I actually thought I blew the IROC's 350 from being rev happy, that wasn't the case. Pulled the engine on Sunday, heads were off Sunday night, and it's down to just the crankshaft now. Heads were fine, no visible cracks, internals are perfect. So I don't have a clue what the knock was over. Even the main bearings were fine, rings were fine.

Oh well, had no interest in running a stock 350 anyway. I really want to give up my plan of buying a truck and build a forged 383, now that I have a decent 4 bolt block to work with. Gonna have it magnafluxed, pressure tested, and cleaned up soon just to see if it's good to go.

ASE doc

The NASCAR Northwest guys run small block chevys based on gen 1 blocks with cast iron block, heads and siamesed cylinders that make 700hp at 7,000rpm and run 500mile races. And they survive an entire season running this way. The things that no one mentioned are the dry sump oiling system, rotating assembly balance and tolerances.

sofakingdom

iTrader: (1)

Even more important than anything technical about the engine, is owner expectations.

If you've got somebody paying $200,000 for a car and they are looking for the fastest possible road rocket but don't mind that the motor's lifetime is measured in HOURS and MINUTES rather than HUNDREDS OF THOUSAND OF MILES, then RPM isn't so much of a limit.

Then of course there's that little matter of the $200,000.... given that alot of people seem to think that buying a set of tires depletes their entire life savings (and maybe they're right), it might be a bit unrealistic to expect that for 1% of the cost, a junk truck motor or something can perform equally, eh??

Curious_George

Torque is not a function of how many cylinders a motor has. A 4 cylinder motor can have huge torque numbers, if built properly. V8, V4, straight 6, flat 4, etc can all have good torque if built properly and right off idle.

CG

torque_is_good

would you be so kind as to elaborate a bit more on your above post.

thanks

TNT_Z28

3rdgenmaro

iTrader: (9)

they can be built to do it.

A local gear jammer legend around these parts, Lones Combs and the VA Hillbilly, leaves the line at 10,500. I have no idea on the engine specs other then it is a 283. Just figured Id throw that out there. Very fun to watch on a sticky night. You've got to love the gear jammer classes.

http://www.youtube.com/watch?v=Q_9gmvnLf_U

http://www.youtube.com/watch?v=ZEKFpbNaoIo&NR=1

Curious_George

Torque is a function of filling the cylinder with as much air / fuel as possible. Modern induction systems (intake runners, intake base, etc), variable valve timing, fuel injection (direct injection), faster computers, etc have come a long way and it is these things that are largely responsible for the power output of modern engines.

The Ecotec turbo 4 cylinder engine in the Pontiac Solstice is a good example of this. It puts out more power (overall) than a lot of V8's did 20 years ago.

This is not really a discussion of normally aspirated vs. charged induction, but just an illustration that filling the cylinder as much as you can will result in good torque numbers.

The old wives tale that the Jeep 4.0 liter engine had huge torque because it was a straight 6 is just a joke. No doubt that motor had a good torque curve, but it was not the result of it being a straight 6.

Apeiron

Torque comes from burning fuel. The more air you can get in to burn more fuel, the more torque you make.

sofakingdom

iTrader: (1)

Torque = CID x cyl pressure.

Cyl pressure comes from heat.

Heat comes from fuel and is extracted by compression. (or more accurately, by expansion, in exactly the same ratio as compression)

Fuel can't burn without air.

Air is only available at atmospheric pressure, unless boost is involved.

That's your upper limit on torque, in a nutshell: once you get the cyl 100% full of air by getting the cyl pressure back up to atmospheric before the intake valve closes, and get the right amount of fuel in there with it, and light it on fire, that's all you'll ever get. No way around that.

# of cyls doesn't really matter.

Brand doesn't matter.

FI vs carb doesn't matter.

Ignition system doesn't matter.

OTOH, with ½ the displacement, you'll get ½ as much torque, if all else is equal.

All the "new tech" in the world hasn't changed the torque output of motors by more than 10% in the last 50 years or more. Don't fall for the hype.

None of this matters as to why a super-expensive low-volume high-performance car can turn more RPMs than a truck motor.

Firebirda7x

Yes but having 8 cylinders means more valve area, more piston area for downforce by air/fuel mixture, and a better balanced motor from the firing order. As you were describing volumetric effeciency above, the big V8 will have higher VE than the 4 banger, assuming both are N/A, until the smaller motor starts turning huge RPMs at which point torque is gone. So, technically, most 4 bangers you will see are going to have crappy torque unless they were a huge 4 cyclinder. This is all assuming Natural aspiration.

Also, as we all know the formula for making horsepower, the higher RPMs of smaller motors to make up for the lack of displacement further decreases their torque figures. Those flat plane V8s and V12s still have smaller toque numbers (relatively) compared to our 350 monsters.

Firebirda7x

Um, a modern computer-controlled Direct injection motor will have higher volumetric efficiency due to the precisely controlled timing and atomization of fuel as opposed to a carb setup with runner length tuning to determine it.

Also, my 50k volt HEI ignition pack is going to produce a better spark and flamefront for more even and full burn than a shitty ignition system.

Apeiron

Area is about the bore, not the number of cylinders.

Timing and atomization effects combustion efficiency. Volumetric efficiency is all about flow dynamics.

Orr89RocZ

iTrader: (20)

Volumetric efficiency is highly influenced by head port design/valve size, intake manifold runner design, and valvetrain events. A great motor combination can achieve over 110% cylinder fill. Its an inertia ram effect that allows a motor to fill the cylinder beyond its displacement. Carbed or FI, doesnt really matter


But yes, you can build a pushrod 350 or w/e motor to rev very high. Just takes right parts and attention to detail on the valvetrain side. 8000 rpm in the drag race world isnt uncommon. 9000 in nascar is doable and the example above, that little stick shift 283 or w/e cube it is runs 10-11k rpm!!

sofakingdom

iTrader: (1)

Wrong.

That's a bunch of hype. You just bought into it like the rest of the sheeple.

Volumetric efficiency = the percentage of air that manages to get into the cyl, vs the theoretical max amount that could possibly get in there. It's all about AIR FLOW exclusively. That's taken into account in the "cyl pressure" part of what I wrote.

"Direct injection" has NOTHING WHATSOEVER to do with torque output. All that does, is give better fuel control; less wasted fuel for any given amount of power, not, more power. Torque is still a function of cyl pressure and CID.

Same for spark. Either the fuel burns, or it doesn't. If it burns, it releases its energy. Having a big fat spark means it will light EVERY time, consistently, and you won't have to change plugs as often; but doesn't change the amount of energy stored in the fuel, and therefore doesn't change the amount of energy released by burning it, and therefore doesn't change the max cyl pressure that comes from the heat released by burning the fuel. More hype.

Don't be misled by the hype.

zsmoore68w

use the 350 block and build yourself a beast 302 for the street that feels comfortable at 8000, or strictly for the strip that somehow manages 11000+ rpm

Orr89RocZ

iTrader: (20)

Just use a light weight crank, long rod and custom low compresson height piston to keep weight down. Doesnt matter on cubes really...although like mentioned in here, stroke length has an effect on piston speed but so does rod length. Most of the high reving stuff you will see in the 350-369" range will use 6.125" or so rods with a short piston, realitively short strokes 3.48-3.625. Lightweight parts, a very good rod bolt and strong block are all needed for high rpm operation.

Then you need to work with a good cam grinder that has experience in those applications to get a lobe that you can control at 8000+ rpm. Some lobes are too aggressive and would need alot of spring pressure to work which can really hurt valvetrain life. Spintron use can help analyze cam lobes for those high rpm setups and then a valvespring can be selected. Its critical that you get all that to match then you will need a rigid pushrod and shaft rocker system to make it all work.

Definately doable in a street car although not cheap.

Firebirda7x

I thought that, the better the combustion and more even the flamefront, the better heat expansion you will achieve, because of how fast the engine is moving at high RPMs.

brownstone101

make a 302 if you want an 8k motor. i really want to make one, winds to 8k all day and she will be fine, shortens the life, but yeah i love 302s.

ASE doc

The 302 will rev to 8,000 quite well. But as has been said already in this thread, a 377 can rev to 8,000 too and will make more power at that speed. Another critical issue that I haven't seen mentioned is the block. NASCAR guys, the ones who make the top five anyway, all use GMPP bowtie blocks, or equivilent. For one thing this race specific block accepts a small journal crank like a 3.00-3.50 stroke crank tends to have. Of course they can be line bored to take a large joumal crank if desired.

They also can be bored to 4.165 allowing more cubes with a given stroke. In addition they have more material in high stress areas for increased strength and rigidity. Rigidity is crucial at high revs to support the rotating assembly in a stable manner. The bowtie block is also predrilled for priority, dry sump oiling.

brownstone101

yeah, im in the processes of looking for a chevy 400 block, and a 302 crank... if you can see where im going with this. for a 1979 camaro and a 4 speed. or a 396, but i dont want any old 350 in that motor, unless i really cant find one, or get one cheap cheap then ill build a 350.

ASE doc

The 400 block with the 302(3.00) crank is problematic. The only way to fit that crank in that block is to use main bearing spacers. The spacers retain heat and interfere with the normal cooling of the main bearings. This in turn will lead to bearing failure and an expensive engine failure. Especially if you plan to run this motor at high revs.

On the other hand, the short stroke, big bore 350 you're talking about is a great design. Just spend the extra money and buy an aftermarket block with small main journals and big bores. I believe Eagle? makes one for about $1,300. Cheap for that block.

brownstone101

man awesome! and thanks for the advice on not using the over sized bearings, i haven't figured out what exactly im doing to my 79 gasser themed (NOT Ibeamed) camaro yet. i want a 396, or de-stroke 350. or a stroked 350, haven't decided on the rear end ratio and what its end goal is. all i know is, its geting primed only (over old sealed paint),lexan windows, two seats and a 4speed, and the front fender wells are being removed for fender well headers. its being based slightly on the two lane blacktop 55 chevy, minus the ability not to handle well.(not that solid axle gassers didnt handle) and also i haven't seen many or any of this idea, and shes a crap box with a huge hole in the floor and missing half of herself anyways so why not step outside the box? ill be proud of it when its done though thats all that matters to me.

Firebirda7x

I still have my 305 I was rebuilding before I found the 350. What if I splayed the mains to 4 bolt, and went to town on it with everything discussed here. You can get sleeves to decrease bore size and I can get a new crank to lessen the stroke, right? If I reduced it to like, I dunno 4 liters from 5 and had everything built up for light weight, do you think it would be able to do something like that?

brownstone101

305 has same stroke as a 350. would be the same as running a 350 block with more room basically. i built a killer 305 with a bud of mine, it will be good when its done. im not really releasing specs or what we did. but its what i had to work with and all ill say is we massaged it over a little to make it go faster lol

ASE doc

You may be missing the point. There is no need to reduce CID. If there are sleeves that can reduce bore size, I've certainly never heard of them. The point is, with the right parts and machine work, any size V8 can be a high revving motor.

brownstone101

exactly what he said. RPM is effected by stroke more than CID. the 305 is a long stroke small displaced motor when the 302 is the opposite. 3" stroke 4" bore, 302 would make 400~500hp pretty easy up higher, while the 350 and 305 make theres more in the 1,500~5.500 zone, 302 makes 450hp at oh ill guess, 7,000 depending on cam specs, defiantly would cam that motor for a sweet spot that it can see easy though,

AlkyIROC

I guess nobody wants to even mention the rpm range of an INDY engine

brownstone101

OH yeah, dono much about those, but just imagine what that motor is doing, its incredible really, and sad at the same time that more people cant appreciate the fact you have a cam lobe spinning at 9K rpms and not just self destruct yeah know? not to mention a whole rotating assembly that weights upwards to 30~50lbs or more totaled out, its insane that it just doesnt come apart.

and also there are more factors to affect a motors ability to wind and limiting factors like pushrods, the oiling system, windage, the blocks stroke ability and stroke geometry. the list goes on, but theres a reason that the DZ 302 would wind up too 8k on fueler heads but a 350 on fueler head redline was in the 6k rpm zone.

Firebirda7x

Hmm. I had thought about bore reduction because that way there is less material for friction at high RPMs. I had figured you would want to do that to give as much assistance to longevity of the parts and the work the motor has to do to rev high. I thought you could buy oversized sleeves, maybe that's different than what I'm thinking of though.

Firebirda7x

I believe they are N/A 3 liter V8s and they rev to 17k rpms lol. Not sure if pushrod or DOHC

brownstone101

its because at 17K rpms geared REALLY TALL and being so light they can go from 6k to 16k back to 6k and back to 16k and act like a slot car would accelerate. they go very fast. but you could make a 454 geared right do 200mph but those cars see a pretty good 25/75 cycle of 25% wide out in any straightaway and 75% popping in and out of turns doing 15~70 depending on the style of turn so a 17k rpm motor will give them that response cupled with hell what a 5.11:1 rear end ratio or higher? they need to act like a two stroke dirtbike does in area cross, unlike good old thumper 4strokes on bigger trail style races or hair scrambles.

BTW verry cool fact. a slot car, is the worlds fastest ratio car. as they are what 1/16? scale car. but they did the math and it would be like getting in your fbody steeping on the gas and doing the quarter mile in 1~3 seconds, i forget the specifics? but it would be just INSANE to own a 1:1 ratio slot car doing the same ratio speeds.

ASE doc

The Indy motors are dual overhead cam and represent the most advanced engine design technology. Actually though, the Indy motors of today are a big step back from what they were in the 80s. Today's Indy cars produce 750hp. In the 80s they were bordering on 1000hp but tightening regulations brought power levels down significantly.

The DZ302 was a high revving small block that made use of the short stroke big bore theory to reduce rotating mass and reduce piston velocity in the upper half of the stroke. This allows for better combustion at higher RPMs, and thus for more top end power. Today we have light weight rods, pistons and cranks that allow us to reduce rotating mass in any given bore/stroke ratio. The key to altering piston velocity is rod/stroke ratio. The ideal R/S ratio is 2:1. This would be a 6" rod with a 3" stroke. But we can get very close even with longer strokes. A 6.125" rod with a 3.5" is still in the ball park. The short stroke 350 that was referred to earlier using a 4.125 bore and 3.25 stroke can be built using 6.25" rods making an excellent rod to stroke ratio.

The key to building an engine that will survive at high revs is using high strength, light weight parts, a rigid block, and a very good oiling system designed to operate at high revs. In order to make power at these high revs, you need hi flow ports and valves. In order for this to be streetable you need these hi flow ports to produce good velocity at lower RPMs. That's hard to do. The same ports that will support torque production at 7K+, are not going to produce good velocity below 4K. Then there is the cam. In order to produce high rev torque to support high rev power, you need a cam with high duration and lift. The same cam that supports torque above 7K will not produce good compression below 4K. This low compression leads to poor drivability.

One of the latest and coolest developments, something that a freind and I dreamed up years ago(unfortunately the geniuses at Ferrari were thinking the same thing) is the variable cam. Everyone knows what V-TEC is, every ***** in the world has to have it. V-Tech is half of the equation. The latest advancements in camshaft technology actually allow the cam to vary both lift and duration according to engine demand. Look at the new Ferrari Varicam sometime. This alllows the same engine to drive around town like a toyota station wagon, then turn around and produce 700hp at 8,000 RPM.

Firebirda7x

It all comes back to my favorite part of the 350: pushrod design. I guess I'll just have to save my pennies and buy a Ferarri. (haha I wish)

ASE doc

Actually, thanks to NASCAR and all the great engineers who have worked tirelessly to pull every last HP out of these little engines, the American V8s are very capable of high rev power. Why do I feel like I'm repeating myself? As hot as the new Ferarri is, I would put my IROC with the addition of a NASCAR 373CID push rod small block, running about 720hp, up against one anyday. It would give it a real run for its money.

Firebirda7x

A NASCAR car will not be streetable and is under constant rebuilding. A Ferarri is streetable and doesn't need such meticulous maintenance. I was looking to make a 350 revver streetable.

ASE doc

NASCARs only need constant care because they are run so hard. And with a few changes to the cam and heads, a NASCAR small block can be very streetable. And, used on the street under normal driving conditions, the NASCAR would out last two Ferraris.

You think a Ferrari doesn't need alot of care? They need almost as much care as the NASCAR being raced every weekend. There is nothing cheap about a Ferrari, that includes owning one. I only mentioned Ferrari because of their VariCam. This is the technology that can make a smooth running street engine also produce high rev power. Chrysler produced a variable cam for cam in block engines. They use it in the Viper RT10. It allows them to make 620hp from the same engine that one year earlier made 495hp. All this while maintaining good street manners and emmision compliance.

While less streetable, we do the same thing with small block chevys, using a single cam. It's just a matter of compromise. We give up a little low end torque in exchange for top end power.

Firebirda7x

How does variable length runners work? Do they have like, a valve that redirects air to a shorter or longer one depending on engine speed? Is there a way to make a 350 have such a function? I really like the pushrod design but todays world has gone in such a different direction I wanted to somehow have a turbo'd 350 that can rev high-ish and still be streetable. I know the LS1 fits that role well, not sure what they did differently to allow for it though (engine design wise).

Shadow Z

iTrader: (2)

Do you have a ton of money? If not, just have your 350 make impressive power under 8,000 RPM, like almost everyone else does. There is absolutely no point in wanting your engine to rev higher, just for the cool factor of revving higher.

Sanctioning bodies of racing use those high RPMs to make the power they do, because it's pretty much their only option, due to most being forced to run N/A.

Horsepower = Torque X Engine RPM / 5,252.

So, if you can't make the torque you want at a low RPM to get the big power numbers, figure out a way to carry that torque very high into the RPM range! That is how they think, when they are limited to a certain engine size, and running naturally aspirated.

You're just a private person, in no (I'm guessing) sanctioning racing body. You have no limits other than what the government forces on you. Exhaust emissions, noise levels, that silly crap.

If you want something that revs just for the sake of revving, go buy a Yamaha R6, CBR600RR, Kawasaki ZX6, Suzuki GSXR600. They're little inline 4 600CC motorcycles that all make peak power at close to 14,000 RPM. Heck, they don't even make peak torque until after 10,000 RPM. I'm sure you could build one of them up to hit close to 20,000 RPM and have it be streetable seeing as they hit over 15,000 RPM bone stock, with their little 2.6" bore and even smaller 1.7" stroke.

If you can get a streetable 800HP on pump gas out of a twin turbo 350 without revving it's brains out, why ask for more RPM...?