I'm thinking about putting together a bigger small block for a buddy with an older vette. If I've done the math right, wouldn't a 454 cid small block make the same power at 5400 rpm that a 350 would make at 7000 rpm? That's assuming carb, intake, heads, cam, exhaust, and cr ratio were about the same. Seems like the bigger engine could make the same power, with a fatter torque curve, and have much better street manners. I know it wouldn't be cheap, but a 350 with the internals and valve train to live at 7000 rpm wouldn't be cheap either.

1 hp/cid on an aluminum headed 454 small block would make a pretty spicy street/occasional strip engine. To get to that same hp level on 350 cid would make for a set up that would require a higher stall speed converter, and maybe some higher #'ed gears in the back. While I know the small one would have a more menacing sound, I'm afraid it would be too much trouble to deal with on the street.

Anyone put one of these big inch small blocks together? Also wondering how they hold together. TIA.

 

I'm in the middle of a 4-year build on a 427 SBC...expensive. When finished I'll have almost $15k into the motor alone...making approx. 1.7 HP/cu. in. in N/A trim. I'm seriously considering turbocharging it, and making 2.8 HP/cu. in. (or 1200 FWHP on 15 lbs of boost)...insane I know, but nothing a little Thorazine won't take care of...

My current motor is a 355, making 420 FWHP or 1.18 HP/cu. in. I gained 20 HP doing some additional intake work on the last build.

With the right combination, you can make 450 HP easy, and don't need to wind it out to 7000 RPM either. My 355 makes the power all below 6200 RPM. A 383 can get you there with room to spare...

The other side of the big-inch small-block argument is you'll NEVER get there with a stock SBC. You'll need to get some kind of aftermarket block to support both the bore and stroke needed to get you to 454 cubes. And once the motor needs a rebuild you can throw the block away...there won't be any margin for cleanup or another bore. You'll need to sleeve the block or start all over again.

SKI and Jeb have these big-inch smallblocks and thrash them every weekend at the track. They've been holding up quite well, and laying down great power. As for how they hold together, they can't say as every winter they pull motors and tinker to get more power. I've seen some street combinations hold up very well, and are fairly easy on the pockets once you get it tuned.

 

This should get quite a discussion going....

The short answer to your question is 'yes'.
Assuming everything else is the same as the STOCK 350, a bigger engine will have better low-end torque, but less rpm capability(the small carb/cam/intake/etc being the limiting factors). Since horsepower is the product of rpm X torque (basically) the horsepower will be the same.
IC engines are air pumps. Pump more air through an engine and it will make more power. A 350 pumping 500cfm will make the same horsepower as a 427 pumping 500cfm.

Until you narrow the variables in your scenario down to specifics, there is no right answer to your question considering all the possible combinations.
I think you are on the right track, though, with your thinking.

Larry
code5coupe

 

The Motown 455 SBCs weighs more than the 350. Combining weight with the massive torque will require careful application of power for street use.

The best of both worlds is an aluminum 427 SBC.

 

In spite of what some people say, "size matters"! For a daily driver, I think big inch torque rules. It is so much easier on the engine. And part throttle response is so much better. BTW, I am not knocking the 350 SBC engine so I hope I am not affending anyone. It is just that we have many choices for different applications.

 

Yeah, people here can make small 350 CID screamers or 454 CID stump pullers. I agree that low revving strokers probably have more part throttle "umph" and last a lot longer than a high revving screamer.

Screamers if you like circle track racing, AutoX, road racing and stump pullers if you like street manners and trips down the drag strip.

 

Anything special needed in the cylinder head department, or can a set of heads from a stock sized motor work? I realize that I'll need a good flowing set of heads because of the extra cubes, but does the bigger bore create any special problems? Is the deck height on the aftermarket blocks the same as regualar GM small block? I know some of the big block stroker motors have a taller deck height which creates problems with intake manifolds and header fit.

 

The chambers will need to be opened up to match the size of the bore...

Deck height can be had in either configuration...just be sure you specify what you want when you order/buy one. Double check everything...

In today's market, it is just as cheap to get an aftermarket set of heads compared to CNC work on a stock set. By the time everything is over, you'll spend as much or more for the stockers.

Just remember that a 427 NEEDS nearly 1730 CFM at 7k RPM (427 x 7000 = 2,989,000 cu/in / 1728 [cu/in per cu/ft] = 1729 CFM)...@ 6k RPM it needs nearly 1500 CFM...anything less is choking the potential of the motor. Heads are the EASY part...the intake is what you need to pay close attention to. Even a 1300 CFM Monoblade is still 430 CFM shy of what the motor REALLY needs to run well @ 7k RPM...and the choice of intake/carb (throttle-body) will have a huge effect on how the throttle response is on the car.

In this scenario, twin 52MM throttle-bodies will give you better throttle response AND will give you a combined flow rate of 1800 CFM.

Now, get them tuned and working with each other and then I'll call you. I need that much flow on my 427...try adding 27 more cubes to the mix

 

Just remember that our 4 stroke/cycle engines only have one intake stroke per cycle, or every two revolutions. I didn't bother to check your arithmetic, but assuming it is correct, your 427 needs 1729 CFM of air at 14,000 RPMs with 100% V.E. Good luck! I hope that engine has a stout bottom end. A stud girdle may not be a bad idea, either.

RACE ON!!!

 

When you say "older Vette" are you talking about a C3? If so, then just go with a big block. 454 seems to be pushing the envelope with a SBC.

 

I'm not too sure on the math either...

Been a long day and I've been looking at numbers until my eyes can't focus.

Girdle??? I don't need no stinkin' girdle!!!

 

After owning several high revving 350's (which I still love) go for the cubes on a street motor.

 

Subject vette is a C3. Not sure of the exact year, but it's a '68-'72. Won't be worrying about throttle bodies etc. I'm thinking 850 cfm carb on an aggressive single plane manifold. I know a big block would fit, but I like the lighter weight and the extra wiggle room in the engine bay that a small block has. I'd rather replace the "buzz" of a small small block with the quiet and steady pull of a big small block. I like to accelerate at the edge of traction on occasion. You can do that with a bigger small block and not attract too much attention. Not as easy to do with a smaller motor.

Brain fart here. Just figgered out that I should have posted this in the C3 section. Wife's vette is a C4 and you guys have steered me in the right direction before regarding her car. Didn't occur to me 'till just now to post on the C3 board.

 

Your question about bigger heads on the 454 small block is a key question. If you are not going to spin the engine much and are looking at it as a torque monster you won't need a huge head just make sure you select a head that will compliment a big cylinder bore. If you are going to spin the engine some serious rpm's then the high flow race style head will be in order. The Brodix M2 227 CNC Ported is a killer set of heads that will easily support 600+ horsepower on a pump gas setup. Good luck!

 

Always go for CI's I have a 434 and I just saw they came out with the 454 ci sb .Now I wish I had gotten the 454.THe 434 is ok but it only puts out about 670 hp at the flywheel but the tork is 577 ft pounds .
It is real noisy and I have LT4 stock exaust on it.I think it is the CI that
blow more air out the back.The HP peeks at 6700 but it can run to 7200.
With the auto it just spins the tires and most of the time goes no wear.
I think its only putting out about 560 hp at the wheels ,but just the same it is noisey and spinns the tires when I crack the throttle.
I have 11x brodax heads and a 1090 Barry Grant sitting atop a manifold that will never fit under anything but a 4 inch high rise hood
No it doesn't even fit under that hood.I have to get a hood scoop.
The headers are Stahl and 1 7/8 real tight on #3 plug ,have to remove the header to get the plug out.More pains than brains.

 

Actually, the best place to post it might be in engine mods in the general Corvette area. If you're going to have to buy an aftermarket block anyway, why not got with an all aluminum big block? It would seem much more practical in the long run if you want that kind of cubes and it'd still be lightweight.

 

I wish I could remember who it was, but someone on the forum here built a de-stroked 400 (400 block 350 crank) and it made good power (500hp range). But that's an rpm engine for sure.

There's all kinds of ways to make power...

 

That might've been chrisw in Texas. He's got a destroked 400 that's an absolute beast...........a 377 or something

One other consideration is smog compliance. If you stay smog legal then you pretty much limit your choices of intake and heads to a Superram and AFR195s respectively. And.........you limit your cam to something that would pass the sniffer. These limitations all point directly to a torque motor as opposed to an RPM motor

 

"THe 434 is ok but it only puts out about 670 hp at the flywheel but the tork is 577 ft pounds ."

IS OK, just ok? I gotta quit reading these posts. With 670 hp I'd be driving around wearing a full diaper and a sh** eating grin from ear to ear! My local tire salesman would be loving me, I would be painting the towns roads with mysterious black stripes that appear over night. Life would be good.

 

My exact sentiments "only", must be fun I'm strongly resisting building any more motors-but when I built the 64 vette (awesome) what I really liked most-it was a true sleeper looked absolutely stock-no hood mods-like I had to do on my 62. But when I blew the doors off others they always wanted to know what was under the hood I only popped it for a few-mostly I would just tell them sb-God it was hard to keep a straight face-especially seeing the look on theirs-I had no wild loping cam and ran the headers thru stock mufflers-but those who got a peak were impressed-didn't mean to rattle on-but that is why I would build the sb rather than go with big-and in a C3 I think you can do it. Besides-it's great blowing off the bb letting them know you have a sb.