If I change my short block 350 for a 400, keeping the same setup, cam, heads, intake, carb, etc... will it make more power???? how
much of an increase, say my 350 makes 400hp?

[This message has been edited by TransAm86 (edited February 22, 2001).]

 

Well, An engine is an air pump.

the more air you pump, the more horsepower.

A bigger pump is an easy Way to pump More Air.



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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

so, a small increase on bore and stroke on a 400hp engine, I could see a 20hp increase???
or more?

 

HP is a function of torque.
torque is a function of cylinder pressure, piston diameter, and stroke.

Therefore, if you increase your bore/stroke, yes you will make more torque, and thus more HP, ASSUMING your cylinder pressure didn't fall off more than your bore/stroke increase added. Then we're getting to the efficiency of the system, and how well you can get air into the cylinders. It would be possible to have a perfectly tuned set-up on a 350 making x amount of HP, that when dropped onto a 400 would make less power, due to the fact that the 350s induction couldn't effectively move air to fill the larger bore/stroke of the 400. Concpets like efficiency come into play here in many specialized areas of physics...
...ed

 

It's really simple. Each molecule of fuel releases a certain amount of energy when burned. Torque is the measure of that enrgy; horsepower is the time rate of release of it, or in other words, molecules per time, which is another way of saying "flow".

So here's the deal: More displacement = more air; more air = more fuel; power comes from burning fuel; more fuel molecules = more power.

But, keeping the same induction system prevents the above from being true. Let's say your engine stops producing power because the heads' flow capacity is reached. Well, it doesn't matter how big the cylinders are, you can still cram only the same number of molecules through the heads per time, so you will have the same peak horsepower. It's not quite that simple, but I'm sure you get the point.

Here's a simple thought experiment. You have a bucket (cylinder) you're filling up with a garden hose (induction system), and the hose flows one gallon per minute (flow which equals molecules per time which in an engine equals horsepower). How fast will a 5-gallon bucket fill up? One gallon per minute right? Now what happens if you take away the 5-gal bucket and replace it with a 10-gal bucket, how fast does that one fill up? One gallon per minute, right?

So.... if you transplant an induction system from one engine to an otherwise identical other engine of greater displacement, expect the same peak horsepower (based on the flow), but at a lower RPM; and a higher peak torque (based on the number of molecules in the cylinder at one time), also at a lower RPM. Again, it's not quite that simple, but the analogy is instructive. That's why you have to increase the size of the cam, heads, intake and exhaust to take advantage of the increase in CID.

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"So many Mustangs, so little time..."
ICON Motorsports

 

OK... I use all performer rpm components, intake and cam... my heads are camelback heads with 2.02 and 1.6 valves, rated to flow up too 8000 RPM. I have an holley 750 double pump carb. Hedders and all the good stuff. This setup is an easy 400 horses on the motor, according to edelbrock... Do you think they are enough to handle 400 cubes.
Are the 400 SB heads normally have bigger valves???

 

Stock 400 heads are trash. They're 882s usually. The factory apparently never even glimpsed the possibility of using the 400 in any kind of performance trim, I have no idea why.

Your double-humps should be OK. That's what I have on my 400, 186s specifically, with a certain amount of port work. I doubt they flow as well as the RPM heads would though. You can do better than the Eddie cam, I'd suggest a Comp XE274H with 1.6 rockers. You'll need 1.45" valve springs for that combo; I'm using Comp 986. The carb and intake should be OK for that power level.

400 HP isn't really all that much, if you think about it... 1 HP per cu in... it's all in the heads.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Here’s the short answer that I know to be true based on personal experiences. At the very least,,, you may not get much more if any peak horsepower when only the cubic inches are changed in a combination. However, you should end up with both engines delivering similar peak HP numbers,,, but the peak power will be at a lower RPM with the larger cubes. So,,, while your peak power may not necessarily increase due to the cube increase the over all power and torque will,, all at a lower RPM. When gearing, converter, and suspension is utilized to take advantage of this situation,,, the car will be substantially faster while shifting at a lower RPM.

RB,, that garden hose / bucket analogy is,, uhhh,, really bad. I’m sure you know, but for the sake of the other folks,, the pistons pull the air through the induction system. The air flow through the intake system is not constant (like the garden hose example) when you increase bore and / or stroke,, you increase the “pull” therefore increasing over all air flow.

 

look at it this way whateveryou can do to a little motor... do it to a big motor... got turbo civic , then turbo the the big block .. got a supercharged v6?? supercharge the v8

get it??

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1983 CHEVROLET CAMARO with a 1986
305 C.I.D.V8 BORED .030 OVER
HIGH VOLUME OIL PUMP
FLAT-TOP PISTONS
MILD CAM
3" CAT BACK EXHAUST W/ FLOWMASTER MUFFFLER
KEYSTONE CLASSIC WHEELS.
B&M RATCHET SHIFTER
STAGE THREE SHIFT KIT
(she'll spin em into third)

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MUSTANGS SUCK

 

No BadSS, you're wrong. That's one of the main myths in engine design that confuses people. You DON'T increase the pull!!!! That is not possible. The most "pull" you can ever have is one atmosphere, 14.7 psi, no matter how big the engine is, or anything else.

Except of course, nitrous or SC or turbo.

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"So many Mustangs, so little time..."
ICON Motorsports

[This message has been edited by RB83L69 (edited February 22, 2001).]

 

just to elaborate on my above statement, i love it when a turbo civic and thousands of dolars of motor work pulls up next to me in my buick and beats me and laughs about it. think abou it, he took that 1.6 liter motor and bored it and threw in flat tops and turbocharged it and intercooled it and changed injectors and a bunch of other ****

my 91 buick century daily driver has a homeade air intake on the stock 3.3 liter v6 with 125000 miles on it. all i say to them is what would happen if i did the exact same mods to that motor or my v8 in my camao for that matter....that usually shuts em up

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1983 CHEVROLET CAMARO with a 1986
305 C.I.D.V8 BORED .030 OVER
HIGH VOLUME OIL PUMP
FLAT-TOP PISTONS
MILD CAM
3" CAT BACK EXHAUST W/ FLOWMASTER MUFFFLER
KEYSTONE CLASSIC WHEELS.
B&M RATCHET SHIFTER
STAGE THREE SHIFT KIT
(she'll spin em into third)

CHECK OUT MY SITE http://www.fbody.com/members/bigdaddyshawn/


MUSTANGS SUCK

 

Right, the atmosphere "pushes" the air in, if "normally aspired".

Out here, that "push" is 12.0 psi. Imagine what THAT does to power...

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/LB9 block, ZZ3 cam and intake, WP 305 heads ported & polished, Hooker headers & y-pipe, 3" Catco cat).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, 3.08 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

Now you did it five seven. You going to begin a debate as to whether an engine "sucks" air in or air "pushes" into and engine.

I am just going to wash the various answers on this one. I know Smokey's answer.

 

Push,, pull what ever,, I've been wrong before,, but what I do know is a larger cubed engine uses more of the available cfm and a 406 can pull,, push, ingest a lot more air at a lower,, and higher RPM,, all converts into more power. The dyno print outs do not lie.

 

the answer to this one is going to be in the TPI section when I finish that post.