No Replacement for Displacement (myth or fact)

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273

273

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I guess I'm challenging the "no replacement for displacement" that everyone likes too throw around, I'm not an expert or anything
my knowledge is mainly through alot of reading about about engines. So far I've just been a Cam, Headers and 4bbl swap kind of guy never built
a full engine until now when I do my 273 build and I'm banking on my theories on "no replacement for displacement" but if I'm wrong I like know
before I spend dollars on my 273. So below is how I understand things which may or may not be true.

Peak power has all to do with air flow (Top End) I'm not saying that engine size does have no effect on HorsePower but it effect is on the powerband and the shape of the curve but not its peak number so much just where it makes it in the powerband.
Torque has all to do with displacement so if you build a 400HP 318/340/360/408 each ones gonna do it at different rpm peaks
but each engine gonna make different amounts of torque at different rpm peaks 318 making the least and 408 making the most so that the 408 makes the same HP and more TQ than the other 3 so the 318/340/360 will always loose to the 408, but that doesn't take in to account the effect that on gears have on torque to the ground. And the other thing I hear alot it takes alot more work to let say make 480hp with a 340 than 410 I don't believe this too be true so i've done a few test on my Dyno and Drag simulators to see how displacement effects power and ET's so I built 3 engines all based on a stock 340 block and bore 4.04, with different strokes 3.31/3.58/4 to get 340/367/410 each engine has the same top end a stock LA eddy's heads, 10:1 CR, Air Gap, 750 Holley, 1 3/4" Headers, Comp cams 20-225-4 284-296 .507-.510.

The results are each engine makes about the same HP but at different peaks as size go's up peak rpm go's down but with torque as size go's up so does torque

340 Red lines 367 Yellow lines 410 Green lines
HP 486@6500 HP 484@6000 HP 471@5500
TQ 463@4500 TQ 487@2500 TQ542@2500

So I stuck each one into 72 duster 3410lbs 4 gear 10" slicks and let the Drag simulator optimise each Launch rpm, shift points and gears
340 has 4.74:1
367 has 4.24:1
410 has 3.99:1

The 1/4 Mile times where pretty close each other
340 10.361 @ 124.6
367 10.407 @ 126.6
410 10.511 @ 124.7
So basically if this is right, if you gear and setup a 450Hp 273 and a 450Hp 440 right they should have similar performance but the only thing if you
don't want to run alot of gear and rpm don't build a small displacement engine. The only time I feel "no replacement for displacement" is right
if you built let say a 318/340/360/408 from 1500 to 6500 each engine will make different HP and TQ levels but it will take alot more Air Flow and Mod's for the 408 than the 318 to make peak power at 6500rpm.

The graph below the top half is HP and the Lower half is TQ
340 is RED Lines, 367 is YELLOW Lines, 410 is GREEN Lines
 

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On the top graph shows flywheel torque over 1/4 mile distance the lower graph shows torque put to the ground over 1/4 mile distance which show gears ratio even out the different torque levels from the 340/367/410.
 

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No Replacement for Displacement (myth or fact)


Ask any woman and they will say it's a fact...


That's what she said....
 
Its Fact - the engine is an air pump,,,more air and fuel you can circulate through the more power you can obtain.

If you are making 450HP out of a 273 then you have a very good top end on it, an equavalent top end put on your 440 will no longer have you at "only" 450HP.
Same topend on either has you choking off the 440. You prove my theory here by putting the same top end on each of your builds.

If there was replacement for dispacement top fuelers and the likes would have figured it out to keep more money in their pockets.
 
Not only do cubic inches provide the potential for more horse power / torque, it as you mentioned provides the ability to give this horse power goal in a more reasonable rpm range against a lesser cube engine. This means less radical engine (less rpm for hp number), less stress on engine components, less cost, more drivability, more reliability and longevity.

The compromise is cost and necessary air flow vs cubic inches which is where the 360 comes in. Considering the required air flow to support a certain advantage due to increased cubic inches you have to consider how much additional co$t in head flow and stroker kit it will take to build and support a deep breathing small block at 410 ci.

Any time you build a stock stroke 360 vs any other small block, you will come out ahead in hp, reliability and torque vs. $$ (if your goal is horse power vs money).

My two cents.
 
So explain the following:

Why is a 426 CID hemi a more powerful motor than a 454 or 460 CID motor?

Why did 5.0 litre motors usually beat 5.7 litre motors in the 80s and 90s?

The answer is...

Efficiency in design.
 
YY1 said:
So explain the following:

Why is a 426 CID hemi a more powerful motor than a 454 or 460 CID motor?

Why did 5.0 litre motors usually beat 5.7 litre motors in the 80s and 90s?

The answer is...

Efficiency in design.
Click to expand...

Correct,,,and if that same effeciency in design is applied to more cubes, the new winner is the larger cube motor.
 
YY1 said:
So explain the following:

Why is a 426 CID hemi a more powerful motor than a 454 or 460 CID motor?
Click to expand...

Its not, it depends how its built.

A guy I know builds a lot of Chevys. He did a iron headed, pump gas, 454 recently that made 550 hp, roller cam, power brakes and grandma could drive it.

I agree, more displacement is the way to go. A milder 360, would whomp on a built 273 all day, And be more fun to drive on the street.
 
Rodzilla said:
Its Fact - the engine is an air pump,,,more air and fuel you can circulate through the more power you can obtain.
Click to expand...

Yes the more fuel and air in a certain amout of time (rpm) makes horsepower, say we build a 273 and a 546 and the 273 would have to spin twice as fast as the 546 since its half the size but it would have the potential to pump the same amount of air in the same amount of time (displacement X rpm = hp) .
 
It sounds like the 546 will last twice as long because of wear&tear.
I like this thread.Makes you think.
 
YY1 said:
So explain the following:

Why is a 426 CID hemi a more powerful motor than a 454 or 460 CID motor?

Why did 5.0 litre motors usually beat 5.7 litre motors in the 80s and 90s?

The answer is...

Efficiency in design.
Click to expand...

I don't know if your agreeing with me since both engines (426 & 5.0) that you say are better than the other bigger engines that you listed but yes efficiency plays a huge role in making HP but larger engines aren't necessarily more efficient at converting fuel and air into HP than smaller ones. If anything the opposite would be true smaller displacement engines tend to be physically smaller so less surface area every where bearing and ring friction more complete combustion than larger bores.
 
Boost throws it right out the window. What is the most you can get out of a stroked pump gas small block? If it is not 900+ hp then it is true.....
 

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Displacement is irrelevant once you know what you want to do. Then it's optimizing the package for what you have to get what you want. The analogy works if you're the "bolt in and go" guy. An even in that case, it's not universal. My 340s used to spank big blocks all the time on teh street. Because I knew how to drive them to get the power I needed.
Once you get talking about a needed result - say - to accelerate a given weight to 150mph in 1320'... then it's easy. It's just math. And you can use 200" and wind it to 15Krpms, or you can use 534" and keep it under 6K. I know of some record setting Ford 302s an 351 Clevelands that only were "fast" because of the rpm ranges they were built to operate in, and put in a package that enabled that power to get to the tires, and the tires to stick. Same thing with cylinder head designs and everything else.
The right package is always the fastest. Doesn't matter how big it is.
but yes, size matters in the girl bit...lol.
 
With Boost you have somewhat of a "replacement for displacement". The ability to shove way more air into a given space, add that much more fuel to keep the ideal ratio going. Its now a precharge to your airpump I mentioned before. More bang for low cubes, still need to have a great top end to flow the air.
 
Yes effiency in design, however turbos are a great equalizer. Import crowd loves em. And this is a catch 22. Reason being that u can take a 2.0 liter displacement 4 banger and give it v8 horsepower, but since its only displacing 2.0 liters u can only boost it so much. Take 5 liter v8 apply the same ideas and get double the power of the boosted 2.0 liter. Or more if using a bigger v8.

Hotrodders have now figured out that 2 turbos on a v8 and a big intercooler equals big power.the big block twin turbo chevelle that was in hot rod magazine a year back thats street driven 900 hp low boost and 1300 hp high boost is a testament to this. Turbo engines use dished pistons, and have low static compression. This is why they idle and drive very docile until you hit the loud pedal.

So i would have to say, there is no replacement for displacement, unless you are using some sort of forced air induction. Be it a supercharger or a turbocharger. Turbos are more efficient in design since they use exhaust power to operate, however nothing looks cooler than a polished roots blower popping thru the hood.

My bet on horsepower would be on a twin turbo boosted 318 over a naturally aspirated 426 hemi. But twin turbo the hemi and its game over for the 318.
 
Darter6 said:
It sounds like the 546 will last twice as long because of wear&tear.
I like this thread.Makes you think.
Click to expand...

Yes I agree the larger engines are gonna be more streetable and to a certain extent more cost effective and most the time the way to go that's not really part of my argument. My point is basically going from a 340 to a 416 is not gonna make you one peak HP more (probably less cause of more friction) with no other changes the 340 22% smaller so it got to rev 22% higher the flow the same amount of fuel and air so and equally prep (same top end) 340/416 will make similar peak hp and if geared proper be equally as fast. The only time "No replacement for displacement" is true if you build to make peak HP at a certain rpm lets say 7000 than yes a 416 gonna make more power and torque than a 340 at 7000 and be faster in every way but its gonna take a lot more to make a 416 to make peak HP at 7000 than a 340. But most people seem to pick a HP level to build too, say like 450hp then everyone tells them a 416 will make that easily where 340/360 gonna take a lot more effort even though its pretty much the same parts list even for my 273, 10:1CR, RHS, 750, Air Gap, .550+lift cam.
 
Your ET/MPH simulations are REALLY aggressive. 480FWHP is going to be lucky to run 10.9x0/121ish at 3400. It's going to need to leave REALLY hard with superior 60' times to get to the 10.9x range.

Read Moper's comment over and over. It's about the overall package.

What works well for a 340 may not and likely will not be good with a 4" arm.

The BIGGEST reason that the "No replacement" comes about is because it's easier to meet an HP goal when you start with a bigger pump. If I want 550 HP, it's easier to get 1.1hp/ci out of a 500" engine than 1.6hp/ci out of a 340. Plus the range is much lower on the 500" engine, easier on valvetrain, etc.
 
back in the day...only thing that out ran cubic inches is rectangular dollars..
 
My belief follows the air pump theory, but some food for thought is the velocity of which you move the air. Sure a 440 moves more air than a 273, but which one moves it faster? I'm a big fan of RPM big bore, short stroke, long rod, short compression height, making for something you can twist the sh** out of. Use the gearing for torque multiplication. If you build horsepower the torque is going to come with it, I was taught to focus more on power than torque unless you're building a tow pig engine. I'm not arguing the fact that there is more potential for big power in a big engine, but personally I like screaming by at 5500 rpm mountain motor at 8500 in a small mill. Sure you have to be a better engineer to do it, and the masses will snicker at you, but who cares? Build what your budget allows, don't worry about what other people think, read and research, go to a national event and talk to the stock/super stock guys and see what they're doing. I feel that the masses flock to popular belief and get sucked into the magazine articles and power block episodes, that's fun an entertaining, but how many of us on fabo have an unlimited budget? Find a good machinist, not one that quit learning 40 years ago and pick his brain. I say build the 273, give it a healthy dose of compression, work the heads, talk to a professional porter and build them for terminal velocity, healthy cam with a narrow lobe separation, aggressive ramps, open the valves faster, hold them open longer, open the exhaust valve before the intake valve fully closes, that'll make it scavenge, get it in and out fast, and squeeze the crap out of it while its there, and it will scream. It might have some street manners depending on your opinion of street manners. Visit www.samracing.com there are some links to magazine articles that one of the instructors did, many of which were done while I was enrolled there. Read them over and maybe that'll shine some light.
 
273 said:
Yes I agree the larger engines are gonna be more streetable and to a certain extent more cost effective and most the time the way to go that's not really part of my argument. My point is basically going from a 340 to a 416 is not gonna make you one peak HP more (probably less cause of more friction) with no other changes the 340 22% smaller so it got to rev 22% higher the flow the same amount of fuel and air so and equally prep (same top end) 340/416 will make similar peak hp and if geared proper be equally as fast. The only time "No replacement for displacement" is true if you build to make peak HP at a certain rpm lets say 7000 than yes a 416 gonna make more power and torque than a 340 at 7000 and be faster in every way but its gonna take a lot more to make a 416 to make peak HP at 7000 than a 340. But most people seem to pick a HP level to build too, say like 450hp then everyone tells them a 416 will make that easily where 340/360 gonna take a lot more effort even though its pretty much the same parts list even for my 273, 10:1CR, RHS, 750, Air Gap, .550+lift cam.
Click to expand...

You are correct, if your going to build a 416 with all the wrong parts, a 340 will come out the winner! ;-)
 
No Replacement for Displacement.

A lot of guys said that to my Dad when he took Grandpas old 73 2180CC VW sand drag car out to Glamis back around 99-02. Big inch V8's were the in thing and people had seamed to forget that weight was king in the sand.

They stoped laughing after he smoked them.


So in the end I would say it depends. Ya sure they had more CID, HP, and TQ but they still lost the race. LOL
 

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