To me nothing sounds meaner than a super high-performance motor winding out on a straight-away... I've been thinking a lot about vintage road racers and high performance cars and how to apply that technology to a vintage hot rod. Obviously this wouldn't be a flathead-trad rod project but I think you could apply the theory around it to create a real frightening road car. I'd like to explore the reasons for and the how to surrounding building high revving performance engines... First, what characteristics do high-winding engines have that make them suited to Hot Rods? Or what are the drawbacks? I've heard that if you build a high RPM engine, it will inherintly have a short power band. I'm not sure I understand the reason for this. Could you build say a SBC that revved to 10K and pulled from say 3k to 9k? I would imagine that along with having the lightest rotational mass as possible, and perfect internal ballancing, you'd want to have excellent breathing characteristics. What else do you need? This is a pretty open discussion... School me on Winding...
the coolest sounding SBC is one with a flat/180 degree crankshaft, then again any engine with a 180 crank sounds cool, but a 180 crank for a sbc is hard to come by, they used to be used in sprint cars and short track cars but i havent heard one in years, used to be a guy running a 350 in his 4x4 pulling truck with hilborn injection back on the east coast when i was into truck pulling years ago and i`ll never forget that screeming sound, i have looked and looked but cant find one of those cranks. but then again all high reving engines have a short life.
I think that for lightweight hot rods, high reving engine is the way to go. The only drawback that I see is that you usually have to give up torque in the name of revability. You want a shorter-stroked engine to build a high revver out of. Such as a Chevy 283 or a 327.(3" and 3.27" respectively) or ideally the 302 of z-28 fame which shares the 3" stroke of the 283 with a 4" bore of the 327. But if your willing to give up the torque of a bigger inch engine then you can build one screaming engine that will turn 10k in an instant. Roger
the problem you run into is that a cam with correct timing to run good at 9k rpm will not run well at all below 4k rpm. some of the newer high tech engines get around this by having two separate runners and valvetrians with different cam timing, or having variable cam timing.
The reason you'd build a hi-revving engine is to pump more air and fuel into it, and more fuel burned = more power. Aside from forced induction and an increase in displacement, revving the engine higher is pretty much the only way to get more air and fuel into the engine. Since racing bodies often limit displacement, hi-revving engines are the way to go. The reason the powerband is narrow is that they typically have huge cams and massive intake ports that don't flow well at low velocities. As you know, big cams give up low-end torque. Other considerations besides the rotating assembly is the valvetrain. Heavier spring pressures are usually required to prevent valve float, and there will be more friction on the cam as well.
junior johson was the last guy i knew of running 180 a degree crankshaft. ran i think in some monte carlos w/geoff bodine. had a very distinct sound.
I see what you're saying about the cam being suited to a certain range of RPM... So as a theoretical exercise, if you had a SBC with 32 valves (2 intake 2 exhaust) and added a little ratio to the rockers for a pair (1 intake/1 exhaust) of valves per chamber, you might be able to broaden the power curve a bit without running dual overhead cams? What if you run a blower or some sort of forced aspiration? My knowledge is limited but with the motors I've seen, blowers seem to extend the power curve farther up the RPM range... A direct driven blower might want to self distruct with that kind of RPM though, right? Turbos might be better suited for something along these lines, no?
If you try to make a screamer mainly with cam(lots of overlap) and compression it likely will have a narrow power band. To get a wide power band and rpm's you need 4 valves(and ports/cylinder) so that at low rpm your port flow doesn't stall out or experience reversion which kills low end. Maybe others will chime in with more complete explanations. 54chop
My 'experience' with 180 degree cranks is limited to flatheads... With F/Hs, the 180 crank actually limits RPM... It makes for a ton of mid-RPM power but it stops pulling before a regular crank would. They also don't want to idle for crap... So you essentially end up with a much shorter power band. Is it the same deal with OHV engines?
At high RPM, the intake valve is only open for a short time, and you can't depend on "just" the vaccum created by the piston to fully fill the cylinder when the valve is open. A more efficient way to fill the cylinders at high RPM is to create a "ram" effect with a large, dense column of fast-moving air/fuel just waiting for the valve to open to fill the cylinder. That's why big short intake runners and long duration high lift cams are recommended for high revving engines. Those same big runners don't fill the cylinder efficiently at low RPM due to reduced air/fuel velocity through them. There is no ram effect when the engine is using a minimal amount of air/fuel. Also, a cam that has an early opening intake event lets the air/fuel just stall and doesn't fill the cylinder well at low RPM. Sure sounds good though.
airflow is the key. if you can get good flow in and out of the cylinder heads a cam with less radical timing can be used. that is why "double hump" sbc heads are worthless these days. cylinder heads from later model vortec truck engines flow more out of the box than some of the iron bowtie heads. take a look at a build up popular hot rodding mag did called the sledge hammer. they used a custom ground hydraulic cam, lots of lift tight lobe centers, mild duration, made for a broad torque curve, good rpm.
You're really not affecting the powerband of the engine with "more" valves, but increasing the valve surface area will technically let more of a gas pass through for any given valve movement. Superchargers will increase the amount of air into the engine at EVERY RPM range. Different methods of forced induction will do it at different RPM ranges though. A Roots blower will tend to be VERY efficient at low RPMs and good at mid and high, but can heat the incoming air a lot. That can be a big deal at high RPMs. Centrifugal superchargers and turbos are usually set up for higher RPM operation, but that's not always the case. Turbocharger technology is so advanced now that there aren't many weaknesses to them. Turbo lag is minimized by better bearings, compressor and turbines can be fine-tuned for specific applications, boost control is easy to manage, and intercooler options are out there. There are examples of turbocharged 1600hp small Chevys that can be driven daily.
i think so, if i am not mistaken w/180 crankshaft two cylinders fire at once, turning a v8 into basically a big 4 cylinder
pretty much any high end sports car runs a flat crank, mclearn f1, lambos, ferrari, a small block chevy sounds like that and can easly be turned over 8 grand.
Intake and exhaust tuning is also an issue here--an engine designed to run at high RPM's will have short intake runners, for example, which will give you little to no "ram effect" or tuning @ low RPM's. Grab TRJ #33 and look at the intake on that little wedge-shaped roadster--that engine revs to 7000, and the intake runners look like they're about 9" long. Compare that to the old 413 ram induction manifolds used on the Chrysler letter cars--long runners for torque. Many modern engines that spin up get around this by having variable length runners or plenum volumes--when you hit a certain RPM, a flapper opens or closes, and sends the air through a different set of passages. This doesn't mean you can't build a 283 and make it rev and have it be usable in a hot rod--it just means that whatever manifold and header set-up you choose that'll make power on the top end will hurt your bottom end torque. In a light car with a manual trans, that might not be a problem.
you guys are right on with the intake 'ram effect' and the cam timing. assuming for this case that the cylinder head runner/valve size is lumped into the intake limitations...it's intake and cam that are the main limiting factors for the powerband. if you consider the Tuned Port Injection systems of the IROC camaros, they make absolutely outstanding low rpm torque because of the long, ~17" long intake runners, create a 'ram air' or 'supercharge' effect at a certain rpm range...which is why they function very well under 3,000 rpm and are pretty poor above 5,000 rpm. same effect but opposite with a short runner single plane intake...great for high rpm, useless for low rpm. the reliability thing is related to mainly balance, tolerances and piston velocity. balance is affected by a number of things: how well it's physically balanced/counterbalanced, firing order and harmonics. the lower piston velocity the better, obtained by both shorter stroke and longer con-rod length. a pretty common swap for both dirt track and high performance turbo'd gen I/II sbc's is the 4-7 swap, changing the firing order to smooth the harmonics out a little. it requires a different cam but those are readily available. if you're talking sbc's, several years ago I spent a fair amount of time in a 70 chevelle with a destroked 400, to about 377 or a little more c.i.d....little 350 stroked, 400 bore. started making power around 3,500 and pulled hard to 9,000 rpm. nice thing about these is that the shorter stroke and longer rod ratio means the bottom end does not have to be as strong as you would have to have with a traditional setup or even a stroked out setup. sure, you give up some low end torque with the stroke decrease and bump up the redline making more high rpm power...it revs so fast you don't know what to do with it and it sounds SO WICKED EFFING AWESOME. things you run into at high rpms are hitting the resonant frequency of the valvesprings. good springs are a must, I'm a fan of the honeycomb shaped valvesprings as they're proving to work very well over a broad rpm range while keeping the valvetrain weight down compared to a double or triple spring. the lighter the valve, the lighter the spring/spring rate can be and the higher revs you can get before the valves float. rollers are good, hydraulic rollers are heavy, solid rollers are light. you can get light springs that push directly on the lifter body (rev kit) to be able to keep the valvespring light and take some of the force off of the rocker arm pivot. for forced induction...I'd rather have a supercharger than n/a; and I'd just as much if not more rather have a turbo than and s/c...I know there are guys that have the opposite perspective and I'd prefer not to turn this thread into a turbo-vs-s/c thread...that's been beat to death a million and a half times on every forum ever. yeah, even on computer game forums. after owning a turbo vehicle and driving several turbo and s/c vehicles and watching the industry (there are astronomically more turbo'd v8's completely streetable that are running sub-10 second 1/4 mile times than s/c'd v8's.) I've come to the conclusion that I prefer the hairdryer. those things are wonderful and take the awesome sound to a whole new level...and by that I mean a sound more wicked than a screaming demon, high rpm + turbo just makes it sound like it's about to rip something apart, drivetrain included. does any of that answer any of the basic theory? I've said a lot of things before that made perfect sense but were not delivered properly...
in a nutshell... -the rotating assembly needs to be as light and well balance as is feasibly possible. -the valvetrain needs to be bulletproof...light as possible with as little friction/resistance possible (roller rockers, lifters; light springs, light valves) -more important than valve size is the intake runner volume/shape and combustion chamber shape. -obviously, everything's gotta match...the intake/cam/cylinder head range should compliment eachother; the compression ratio is directly varied with the cam size/timing. -engine coatings (piston skirts, bearings) seem to be lending to friction reduction and longevity increases. -tighter tolerances allow lighter weight oil which lends to less parasitic drag. -s/c's = awesome -turbos = more awesomer
Just to keep the record straight, Junior fielded Fords for Geoff Bodine in '90-'91...never Chevys. He may have experimented with a180 degree cranks, but I don't remember that. Junior liked LOTS of cubes, which is why he, Tim Brewer and Geoff were banned for 4 point races after the '91 Winston. BTW, I'm supposed to know this stuff... I'm not certain of the criteria for your roadster's use, but I'm a big believer in torque. I'd rather have a 6K Rpm V8 motor with a broad torque curve than a 9K 'winder". Durability and drivability are two good reasons. Jan
I had a 301(327block/283crank) in my '69 camaro,12@1/2to ones,30/30 cam,long tube headers,etc., came up on the cam at 4500 and made power to 7500, very lame below 3000. Whole bunch of fun!
here's an interesting take on building a higher reving motor. be warned thought it's not traditional in any way shape or form.. http://www.aardemasohc.net/index.htm
pretty simple idea, buckets and shims are a bit of a pain, either you need whole lot of shims or a nice surface grinder to cut your own down, same idea on some jap bikes.
I put a 355 together that spun to 7500 rpm all day with a power band of 4-7 thousand for less than 600 bucks and went 12's in a 3800lb chevelle with a stick. Much more fun than torque ahah!
That overhead cam kit is pretty interesting... But one thing I learned designing, modifying and racing RC cars, it that simple is usually faster than complicated... I may be looking at it with the wrong eyes but it just looks a little busy to me... Lots of good info here. Thanks. Lets bring it back up.
I love reading about this kind of stuff.I hope to figure out what to do with my 63 283 someday. The problem with most people now days is the worship the allmighty 350. Had a guy on a s10 board tell me that if the 302 and 327 sbc were so great why did they stop making them. I then reminded him that they don't put a 350 ci sbc in a GM production car anymore either.
Thinking of pulling the 406 sbc out of my occasional drag car and building a 301 (283 block) for it. That way, I can spend more and go slower. But, I'll have that nasty high rpm small block sound that I loved so much during the 1960's Gasser Wars.
Besides just the motor, one must think about the entire package. A high HP motor needs big heads to flow the fuel/air. Big heads need big valves, and that requires a bore size big enough to fit them, so just a small motor doesn't equal a high winder. A high RPM motor also needs low gears and a high stall converter if an auto. These don't make a fun driver. Big cams also have low vacuum that causes the idle circuits to not function properly, thus causing the spark plugs to foul easily and often. So you need to ask yourself if you want a screaming motor, or a car you want to actually drive.
will turn 10k in an instant RPM reached after X length of time has nothing to do with stroke length or breathing ability. A 2" stroke engine with an 80 lb. flywheel will rev like a John Deere. A 5" stroke engine with a 5 lb. flywheel will rev like a Thimble-Drome. With enough valve spring anything will turn fast, but not for long and not develop any power. RPM limit: the safest limit is piston acceleration, with the best components 200,000 f/s/s can be done but not for long. 125,000 much safer. Piston (mean) speed: stroke X RPM / 6 = feet per minute, 4,000 is a fairly safe figure for good pistons. As Larry Widmer said: "RPM" mean "ruins people's motors"
KILROY...do you have something you're considering building an engine for? yeah, bigger the cam, less 'drivable'...kinda important part to consider. there are two things you can do to deal with this. one is a small vacuum tank with a check valve; if the cam is giant, you can put a small electric air pump on the vacuum tank. and the lighter the car, the more you can get away with a higher power band. it's by no means going to be 'slow' at low rpm, just slow relative to higher rpm. my friend's chevelle with a destroked 400 with a TH-350 was a daily driver, had plenty of grunt to drive around 2-3k rpm and that's not a light car. you don't have to use gigantor heads, on a 350 destroked 2.00"-2.02" intake would be fine; on a 400 bore, 2.02-2.05 is fine, 2.08 is pretty common but IMO is a little overkill for something streetable. I think if you had a lighter car and a 700r-4 it would be fantastic. nice thing about the r-4's is that they can easily be built to handle the power and the lockup tq converter lets you run a high stall but lock it up for highway to get some mileage or at least keep the revs low while you're just driving. some day I plan to put a 377/T56 in my '62 chevyII... someday....
I do have an application in mind but I'd rather not go into it too much here... Let's just say it's an extremely light car with a good stick gearbox. The whole package wouldn't be up to gobs low-end torque but would scream with some upper RPM power. For the purposes of this discussion, lets just focus on how to build a high revving engine for a street car... The fact that a torque monster is cheaper to build and faster down the 1/4 mile is basically a given for most situations. But that's not what we're talking about here. I'm thinking of the sound of a Ferrari as it takes the final turn at like 6-8k and then accelerates down the back straight... But on a SBC budget... Crescendo...
Kilroy - I love winding motors; most every car I've owned has had a winder in it; the higher, the more I like it. In reality, engines are built to a single operating point - that's the point of peak volumetric efficiency. Cam duration, venturi sizing, runner lengths, etc. are all mechanical methodologies to widen the power curve. SBC's and SBF's can be built to take a 7000-7500 RPM peak and still be pretty durable - if you go beyond that, two things happen: 1) the cost to build is waay high - and the motor don't last that long, and; 2) there's a diminishing return as frictional losses 'eat' much of the additional HP. On a SBC, the rate limiting event is usually the valvetrain, on a SBF it's the bottom end. Manufacturers are making good 'kits' of componentry these days which allow for a winding motor with some measure of durability. Hint: The ferrari sound is more a function of firing order than anything else. you can get 'the sound' by fabbing up a set of 180 degree headers - a snake's nest of pipes whereone of the 'lope' cylinders (the cylinder pair which fires sequentially on the same bank, causing V-8 'lope' sound) are piped to the other side. This is what Ford did for the Lemans GT 40's - and they sounded an awful lot like big block Ferraris. The other method? Go buy a DOHC 32V from FRPP; they have a couple of versions - the lesser one is a 4.6 liter mill which makes 305 HP stock and with minimal tuning will put 300+ HP on the pavement while making power to 6400 RPM and a redline of 7K. the other motor - a 5.0 liter mill is more $$, but makes a LOT more HP. the lesser motor is complete and available new for $5K - a homemade intake manifold and some carbies and you've a motor which looks like a Chrysler hemi but sounds like a lot like ferrari when wound tight. and...it's all aluminum, baby! Just a thought, man.
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