I'm thinking about building a motor with a 4" bore and a 3" stroke with 11:1 compression or maybe turbo charge it. My goal is a really high reving race motor for open road racing. Any one have advice or comments? Maybe some one whos built a similar engine?

 

you'll be spending your own money on a bullet to shoot yourself with. high reving is a joke. the major factor in ability of an engine to rev is it's ability to move air in and back out, the more air it moves the more rev and more power it makes.

 

That sounds remarkably similar to the old Chevy 302's...doable, but maybe a 400 block (4.125" bore) with a 350 crank (3.48" stroke) would yield more power and more low-end torque while still being able to rev highly if built properly.
Just IMO....

Pete

 

i don't see why you say this.. what i'm basicly trying to do is copy a ferrari motor, in their 360 spider its got a 3.34" bore and 3.11" stroke and puts out 400 hp at 8500 rpm
maybe i'm missing something but it sounds like a pretty good idea to me

 

Why not just build a SBC 350 with 400hp at 6000rpm?...or maybe I'm missing the point too?

 

Tire Radius, RPM, Rear End Ratio, Transmission Gear Ratio =MPH

I don't see a spot for HP in there.

6000 to 8500 makes one heck of a difference depending on the gearing and when you shift.

having the proper bore to stroke ratio will matter in the end and will be a goofy sounding size until you see it run.

 

alright, i've done a little calculating. i'm going to be using a manual 6-speed trany. with these ratios 3.01; 1.88; 1.46; 1.18; 1.00; .62 and 3.42 rear end gears. with stock size tires (26" Diameter) at 7000 rpm (if my math is any good) that should put me at 255 mph, so what kinda engine combo should i use to beable to hold 7000 rpm without any problems? there are no rules on motors and it will probably be turbo charged

 

I've seen a school's Chevy 302 run on the dyno.

(I think they said it was made simply by dropping an aftermarket 3.00 stroke crank into a 350 block)

The engine had aluminum rods, a solid cam, and some kind of iron race heads, and a single plane, kinda low rise/tunnel ram intake.

That engine would go to 8000 rpm or so.

If I remember right, horsepower was in the 420 range at maybe 7000-7500... wish I'd kept a dyno sheet for that engine.

It was pretty dang awesome, makes me want one!

 

sweet, thats what i like to hear what school was that at? maybe theres a chance they still have a dyno or build sheet for it.

 

it's only a good idea if cubic inch is limited in class racing. waste of money otherwise. even worse if it's a pontiac version. the 301 ponstiac is about as usefull as door locks on a 24 hour store.

 

A high-revving engine would be sweet. However, it may not be that streetable. You'd probably have to have a solid roller camshaft (streetable if you like adjusting valves a lot), and your powerband would be ~3900-up. That would suck on the street. Just my opinion though. Build a badass 406. It would be cheaper and you can make plenty of power to 6k.

 

much better results building a high revving 406.

 

Rage13, it's almost a lost cause asking for help on anything but a 350, 383 or a 406 around here.

 

i'm all up for upgrading what you have, but if you are going to take the time to build one, build the right one. btw, also a 305 fan.

 

ok tell me how 3.34 bore and 3.11 stroke has any coreallation to a 4 bore and 3 stroke. you're build a SBC not a ferrari engine. like i said you're spending your own money on a bullet to shoot yourself i nthe foot with. you're going to more trouble and more expense to make less HP than if you'd stayed with the 3.48 stroke. i'm also willing to bet the ferrari has DHC which would be an asset to producing power and rpms.
evil some people wouldn't reconize help if it bit them on the ***.

 

i'd have to agree with that statement

 

Regarding a high revving 400: And that would be different from any other displacement of small block Chevy that you wanted to make turn high RPMs.... how?

This hobby is all about power per $$$. At least, for most people, that's what it comes down to in the end.

This little tiny motor will cost as much to build as one that produces 50% more power. It fails the most basic HP per $$$ test right there.

Anyone who has ever built a "high RPM" motor would also know that there's a whole lot more to that than just the bore/stroke ratio. All sorts of things have to be set up properly. The valve train is the first place you'll have to spend extra $$$ to get the extra revs; once you do that, all sorts of things you never thought possible will start happening. You do of course realize that if the crank is doing those high RPMs, so is your flywheel; I personally know a couple of people in wheelchairs because their flywheel and clutch let go at high RPMs, which produced a 40 lb load of spinning shrapnel about 6" from their feet, and it took them right off. Another thing that people don't think about is their accessories; I myself had an alternator fan explode one time, trashed a perfectly good hard to replace hood. And the list goes on.

The idea of doing this is proposed all the time, invariably by people who have no experience with it. After being around this hobby for a while, most people come to learn that you can't create yourself that much of a handicap (less CID) and overcome it very easily; it just doesn't work that way. But, some people need to try it, and learn the hard way. Power comes from burning gasoline molecules. The more gasoline molecules you can burn, the more power you can get. The larger the cylinders and the more of them you have, the easier it is to burn more gasoline. It's so basic and elementary I guess it must be easy to overlook.

This fantasy about a "high RPM" motor is just that, a fantasy, in the vast majority of cases. The only really good resaon to build something like that is if you're racing in an organized class of some sort that has a cubic inch limit rule.

But, if the guy wants to build it, let him build it; and I encourage him to report back on his overall satisfaction. Tell us how any other cars you beat on the street, and how much money those other ones had had spent on them in comparison to yours; or how fast it went in some measurable way be it drag, oval, road course, etc. compared to other competitors; or give us dyno numbers; or something.

 

Ask yourself this:
Why do people build stroker engines?
Why would you want to do the opposite of that?
Build your killer 302, swap in a 350 crank and see what happens to HP and torque. Swap in a 400 crank and see what happens to HP and torque. IMO, build the biggest displacement engine you can afford and the best heads you can afford. It's usually easier and cheaper to make power from then on.

 

Go to MUSCLEMOTORSPORTS.com they sell refurbished nascar engines and parts. they have a 650 hp street motor and a 750 hp race motor,those motors should easily turn 8000 to9500 rpm.

 

You are missing something:
3 cams,
16 valves
7 throttle bodies
flat plane crank
...to start with. You can do it, but why? For what it would cost you to build this sbc motor, you could literally go buy a used Ferrari, and enjoy the increadible sound of a small v-8 at 7500 RPM, but w/o all the work!

 

the multi-valve (more than 2 per cylinder) engine has considerably more valve surface area allowing giving it the ability to turn that high. an LS6 is 405 at 6k. why turn it that high if you don't have too. notice the torque difference in the two also.

 

let's look at the march of the small block starting with the 302

302ci

4" bore by 3" stroke.

GM: I want more power

here we have a 327ci

4" bore by 3.25" stroke

GM: MORE POWER

then ubiquitous Chevy 350

4" bore by 3.48" stroke

Hot rodders then realized with little work a 400ci small block crank would fit...

372ci
4" bore by 3.75" stroke

And then the all-mighty easy to build, wonderfully powerful, awe-inspiring 383 stroker... :hail:

4.030" bore by 3.75" stroke

GM sure never had a problem with increasing stroke to increase power...

people stroke big block 454s to 496ci. Cubes, cubes, cubes. I had ideas of building a 4.185" bore by 3.48" stroke 383ci motor for my twin turbo project. Mostly because those turbos are gonna produce hellacious torque, and i'd rather not have it down so low. but I'll probably stick with a tried and true 383 stroker because well, i am not uncle penny bags, and my pockets are well defined, not bottomless, to research and design a weird engine. sure it'd be cool, but may or may not be worth it in the end.

Look at where LS1s and LS6s rev, and their bore and stroke. 3.9" bore by 3.62" stroke. People stroke them more often because you can't bore those iron cylinder sleeves very far w/ out replacing them and boring the aluminum block itself. I've seen 4" bore by 4" stroke LS based engines running around, and they are mean. There are big blocks that rev to like 9 grand out there (while these are primarily racing motors, hehe, i'm using them to show that even monster stroke engines can rev)

Hell, the engine in my Elantra has a 82mm bore by like a 93 or 94mm stroke (not converting to standard, sorry, hehe. just suffice that its like a 3.5, 3.6" bore and almost half an inch longer stroke). It revs to 6.5k (and makes max power at 6k....omfg what a waist, lol, but anyways). DOHC helps, hehe, i admit, but the point is any engine can rev, it doesn't have to just be a big bore short stroke combo (though F1 cars are kings of that formula, hehe)

Personally, I'd stick with what you and everyone else knows works, unless you happen to have money out the a$$, in which case, go nuts, have fun, and let us know your findings.

But if you just really want a 302, go with that, too. its a bad little motor by itself, but by the rules of physics, can never make as much power as a bigger engine.

 

this motor will not be in a street car, its going in an open road racing car.. with the gears i typed before, i'd need to hold an engine speed of 7000 rpm to reach the speeds i want. get it? not going to be a drag type stroker motor... for now i'm going to look for some 4 valve heads.

edit: i plan on using a 350 block and droping a 3" stroke crank in it (maybe a little larger bore for bigger valves tho)

 

Rage: I like your idea about the high revving open road race car. One question though, 255 mph? You'd need upwards of 7-800hp to achieve those speeds. And there's no way you could build a road race worthy suspension that can also go 255 safely, but this is a whole 'nother thread.

I'm interested in this project, you gotta keep us updated. Don't listen to all the people tellnig you not to do it (ede), how did anyone come up with a good engine combo? They tried it first.

 

The build sound solid to me but I would consider one of them hydra rev kits. I really like the idea and design behind them, they should of made it like that factory.



https://www.thirdgen.org/techbb2/sho...76#post1503776

 

The school with the 302 is called Nashville Auto Diesel College (NADC). I doubt you could get any info on the motor over the phone, you'd probably have to talk to one of the HI-Po. instructors personally, assuming you want to drive to Nashville, TN.

Btw, I'm thinking that motor had long rods too, which was another advantage it had going for it.

Basically, your mantra for the valvetrain is "light and strong". You want solid lifters (lighter than hydr.), light pushrods (titanium?), aluminum full roller rockers (maybe even shaft mounted), titanium retainers, keepers, lightweight, sodium filled valves or other. Basically the valvetrain is where a lot of attention needs to go, the shortblock is more basic. Forged crank, aftermarket rods rated for whatever RPM you wanna go, light pistons & wrist pins.

(And like someone hinted, aluminum flywheel and scattershield a must! )

It's truly the classic trade-off of strength and durability versus weight.

The point of using a smaller stroke motor is having the rotating mass of the journal closer to the center of rotation, causing less centrifugal loads and requiring less energy to accelerate.

Oh yeah, and that 420 horsepower 302 I mentioned?

One instructor said that it wasn't even maxed out yet!!


PS: build what you like, don't sweat the pessamists. A small block chevy turning at 8000 RPM is truly an incredible sound!

 

i'd like to hope they can get more than 420hp out of a 302.

 

I'm going to be starting my project after new years, going to start by striping the car of just about everything (ebaying most of the stuff to help my pocket) and putting in the 14 point cage. And will be taking tons of pics to keep track of everything.

 

they're fairly common, shouldn't be hard to do at all

 

If the guy wants to build what he's been talking about, I'd say help him with that project. If it's the wrong route to go, so be it, it's his choice. I'm just get tired of seeing people say it's a lost cause, you'll get more power for less money on such and such engine and so on.

 

Ditto, that one minded thinking of more power for less money has had many a 3rd gen owner jump ship over to ford. Cause the rustang is lighter and cheaper to build. I know at least 5 GM guys who did just that.

It cheaper n faster and girls don't care about brand.
Long as its shiny and goes vroom vroom, it neat.

I love to see someone be different.
Thinking out side the box is good.

 

evil all you say may be true but it's my guess he's not making an informed decision, sort of supported by the "making a SBC act like a ferrari" comment. hell considering none of my cars or truck is powered by a SBC i'd say him and i belong in the same camp. my old car is 402 and my new one is a 266. i buy alot of stuff from snap on and wear a rolex, you wouldn't believe all the "waste my money" comments i got over that, so you're right it's his jack to do with as he pleases.

 

it's not just a money issue. if you put any time into a project you want the best results you can, the same goes if you are helping someone. even if you're just helping you'd like to see it turn out better and that's the point here. it could turn out better without the dare to be different approach. as for it being his project, sure it is, but if he didn't want negative comments, don't post it. putting something on any forum leaves it open for anyone's comments.

 

If you are going to road race with this engine, I assume that a long engine life (you break you lose) and power whenever you stab the throttle will be of a great benifit to you.

I suggest the one thing than no one else covered.

"or maybe turbo charge it"

No matter what engine size you choose, an intercooled turbo charged engine will give you the biggest bang for the buck.

A 302 ci engine at 16 lbs of boost equals around 604 ci inches of air and fuel going through your engine

Build a strong 8.0 to 1 compression bottom end with a cam designed for turbos and add a set of off the shelf (they don't need to be fancy or high dollar) aluminum heads and you will have a race motor with lots of power.

Don't believe the garbage about turbo lag. If you buy a well designed setup you can have 300-400 rwtq at 2000 rpm.

The lower the red line of the engine the longer it will live but if you really must have an 8000 rpm engine the turbo will still work.

I don't remember seeing how much power your looking for, but if you built a strong bottom end on a 350 with good aluminum heads and kept your redline at 6000 (or less) rpm, you could have a dependable 500-700 rwhp & rwtq.

Another bonus: depending on the system you buy, if you need more or less power, you just turn the **** on the dash and adjust your wastegate.

Also keep this in mind if your racing, the more off the shelf parts you have in your engine, the easier and cheaper it is to replace them if they break. Suck a valve on a "4 valve" sbc head your going to be out a chunk of money and if you don't have a spare in your shop, it may be a while before your up and running (so much for a points series)

Just my opinion.
Ken

 

Why do you guy always have to be so hard on anyone how wants to destroke something. Do you guys froget that the Z/28 is famous because of the 302 not the 350 or a 396 or a 454. The original Z/28s didn't have all low end but have made up for it in horsepower. Hotrod or Car Craft tested the Z/28 and said that the 302 was the most responsive american v-8 they had ever driven. Also the 350 and the 302 were introduced at the same time both in the Camaro. You guy are lucky because Ed Cole wanted the 327 to be increase to 350 in bore only which was impossible. Oh by the way if he is gonna road race why doesn't he want the revs. Unless I misread something formula one cars have only have 3L of displacement 12 cylinders make 600 plus horsepower idle at 7000 and redline at 18000. Show me a 383 or 406 that make 600 horsepower and can keep up with one of them.

 

I'd like to see the N/A 302 that can keep up with a twin turbo 3L V12

 

Ah yes, another debate on bigger is better. The guy wants a 302, then fine. Why bitch and moan about it. The 302 in a 5.0 mustang doesnt seem to have a problem beating up on thirdgens with 350's? Why get all bent out of shape? Why dont you help him instead of degrade him and basicly telling him its a stupid idea. Z/28 from 67-69 had no problem making the power, and for what hes using it for, why not? Good luck on the 302 and I hope you have some help. You are gunna need to find a 3 inch stroke that fits the block. Depending on the block being a large or small journal, your are gunna have to find the crank to fit it. I dont know of anyone that makes an aftermarket 3 inch stroke crank, so your gunna have to some research. I think its a good idea and your car can be different in a good way.

What would be cool if someone buitl a 321. 400 block, 283 stroke. It has big bore, short stroke. Bore out the 400 .040 and have a 327.

 

If he needs high rpm, wants reasonable engine life and has to go 250+ mph that bore/stroke combo under a fuel injected intercooled twin turbo setup will most likely be his best bet. Anything he can do to shorten the stroke and lengthen the con rod will be a big help at higher rpm's.

If he has the budget a 3.00" (or less) stroke in an aluminum ZL1 block would really be sweet.

Ken

 

umm... have you found a way to adapt a small block crank into a big block?

 

No, but if the budget is big enough, you can have any stroke dimension you want. Besides that ZL1 block will handle a lot of HP.

4.25" bore x 3" stroke = 340 ci and a lot of room for a long rod.
or
4.25 x 2.5 = 284 ci that, with aftermarket aluminum big block heads, it will rev and handle 25 psi of boost and weigh about the same as a small block.

Ken

 

That is a retarded argument. Youre comparing apples and oranges.

 

Not to mention that ANY 600 hp 383 or 400 would keep up with that 3.0L just fine.

They use the 3.0L because they have rules that force them to. Not so that they can then "rev higher". Since they are displacement limited by RULES, they have to rev higher, as this is the only way to make more power.

A 600hp 400 will keep right up with a 600hp, turboed, V-12 or what ever anecdotal engine you want to dream up. It's just that the 400 will do it at about 6500 RPM, and have low end torque/decent drivability and the "high rever" won't. Ever try to engage the clutch on an engine that idles at 7 grand, and has no flywheel? LOL.

 

The reason the guy is getting so much flak is because this is an obvious newbie / troll / garbage post.

Forget how dumb the 'copy a ferrari' comment was, considering a SBC and ferrari engine have nothing in common.

Let's just go right to the 'I need 7,000 rpms so i can run 255mph'

Outside the salt flats and straight line top fuel there isn't a racing series on the planet that sees those speeds. Even F1 cars won't go near 240. So right from jumpstreet it's OBVIOUS that this kid isn't building anything more than a bench racing machine. Nevermind the fact that you need more than just high engine speeds to push that much air. Like a lot of horsepower. A LOT more than any NA 302 would ever hope to make. So not only is he building an imaginary race car. he also wants to do it with an impossibly small engine, despite the fact that he isn't even competing in a restricted class of any nature.

Everybody in this thread who is attemoting to stick up for the original poster is IMHO being just as big a tool as he is for not immediately recognizing he was flat out dreaming with this ****. Even if it wasn't all a pipe dream, it still doesn;t change the fact that the best advice anyone can give to someone looking for power is more engine. If you want to build some destroked wunder-motor, go for it. If you actually possess the skill to pull it off and not get smoked by every junkyard 350 that car craft built for $150, then you woulnd't be sitting here getting huffy about why noone likes them. Last time i checked, noone in ANY serious organized racing venture even attempts to make do with less than what they are allowed. If destroking and running less inches was the way to make power, don;t you think SOMEONE would have gone to the winners circle that way at some point ni the last hundred years of automobiles.

Damn trolls. The best part is the 'well car craft said that 302s are so great they will give you head while you cruise' part. JFC man, you mean you've never even seen a 302 car in your life, yet you somehow feel qualified to comment on it. Go tell your mom what yuo read in a magazine, most of the guys trying to tell you what's up have actually been there with those cars.

 

Ed, where did he say he wanted to go 255mph? Im not flaming, Im just asking. I stuck up for him because in his original post,that he stated he wanted a 302. Whats so bad about that? He wants to build a engine. It shouldnt matter weight its a stroked big block, or a short stroke small block everyone here should help him. Im sure he knows that the 302 will not make as much power as a similar 350(well at least he does now) but that does not give anyone the right on this site to call his ideas stupid... unless he really wanted to get his car up to 255mph then yeah WTF are you thinking. But if he just wanted a 302 because he wants one why bash and tell him its just a pipe dream? Some of you guys get too carried away.

 

i'm with you there ed. this is part of the reason i rarely post here anymore.

 

.Big Al

 

Thanks Ken. Well if its a 255mph motor you want, call up John Force or Kenny Bernstien. If you wana build a 302 chevy Ill give you my support, but what you want from this engine will never happen.

 

thanks for the name calling... i would have hoped a mod would be more grown up then that oh and heres the race i'm building the car for http://www.silverstateclassic.com/
and i know what everyone is saying about bigger ci for cheaper power, but i want something different (also something i don't have to worry about running out of gas before the in of the race with..), i'm even toying with the idea of putting a rotory engine in, but seeing as how almost everyone flamed the last guy that brought that up i wasn't going to bother...
i know this project will work, i was coming here hoping to find help and other ideas to make it easier (and thank you to all that have done so). and not everything has to have big ci to win, last week my friend handed my *** to me with his stock I-4 MX6

 

Though there are rare cases....the general consensus is you must learn to crawl before walking. Especially before running full speed!

 

I sort of suspected in the back of my mind that this is where this was going..... a bunch of people have posted stuff about running in that race before, and for some reason, alot of them think that this short stroke / small motor stuff is actually a matter of some significance to running well in it. Obviously most of these people have never tried to run a street car at that kind of sustained speed before.

Engine RPMs does not equal top speed. The aerodynamic properties of the car ultimately determine that. These cars, in their stock trim, start becoming giant brick walls at 145-150 mph, and their HP requirement goes up exponentially to get their speed to increase beyond that point. If you take one that has a motor in it that makes (as an example) 250 HP at whatever RPM it takes to push it at 140 mph, it might easily take 300 HP to push it at 145 mph, and 425 HP to make it go 150, and 800 to make it go 155.... etc. I don't know what the exact numbers are, but their proportions are about like that. Shortening the stroke, and thereby reducing the engine's horsepower, doesn't alter that basic fact.

Then there's all the other parts of the car that get stressed, that you never think about. Things like rear end gears (they run rear gear fluid coolers with pumps and electric fans in NASCAR for example); transmission fluid coolers even for manual transmissions; wheel bearings; U-joints; etc. Then there's accessories: power steering pumps, alternators, etc. won't withstand being run at 7000 engine RPM for a very long time before they burn up. Even valve springs will fail from heat buildup during sustained high RPM running. Most of the time, when you see a NASCAR racer or similar motor that blows up, it's a broken valve spring. A short stroke won't do a damn thing about any of that.

The way to make the car go faster is to make it look "smaller" and "slipperier" to the air, not to reduce the engine's power output by removing cubic inches. The way to make it last for long-term high speed operation is to get rid of excess heat that accumulates in all of the moving parts and running gear, not throw away cubic inches.

IMHO if you're contemplating running in one of those races and not just burning up your car all at once in a meltdown from one end of it to the other, you really need to spend less time spanking off about how many RPMs you think you can get by shortening the stroke, and more time investigating the real issues at hand. As if shortening the stroke will really do much for the engine's upper RPM limit.... and as if the engine's upper RPM limit really was the main determing factor to how fast the car can ultimately be made to go for extended periods of time.