Rewind to the late 60's early 70's

In general where rpm did the big factory hp bbs ( 427/454 ) start to make their power?
Were these big factory hp bb's all pretty radical in camming etc needing high oct fuel etc?

Why did gm kill the 427 and go to 454 for the vette in 70?
When and What changed to give the 454 a rep of being a low hp truck smogger engine?

Fast forward to our modern times,

Starting with a 454 or 427 if you perfer what hp could we see with the constraint of the build being pump gas ( not prem ) and street friendly
In this case I mean it starts making power soon off idle....

 

You can get a lot of power out of either. The popular thing to do is a stroker motor, or change the top end to aftermarket aluminum heads. An upgraded 427/454 can easily get in the 550hp area with plenty of low end torque. A 496 stroker will make 700hp with ported factory heads and 750hp with after market aluminum heads.

I just built a BBC 427 on steroids, lol. A 3.75 stroke x 4.5 bore for a 477. I could have gone to a 4.6 bore for 500ci+-. A 454 has a 4" stroke and 4.6 bore 532s are very popular in drag racing. Either build is not popular because of $$$. The 477 rotating assembly cost much more than a 540 or 565 rotating assembly.

My short stroke motor made 810hp at 7000rpm and 660tq. A 540 with the same top end would have made 810hp at 6000rpm but 800tq+-. I was hoping for tq to be in the 500s to avoid drive train mods but 660 does not require big $$$ mods like 800 requires.

A cost effective 427/454 rebuild plan usually uses afr 265s or Race Rite 270 heads on a .030 over bore. These engines are generally in the 550hp range with a proper cam. There are a lot of these types of builds on the Chevelle Forum. The stroker builds usually use afr 290 or afr 305 heads and make low-mid 700s hp.

 

answers in bold

 

in my opinion I would take a 427 over a 454, 427s have better geometry, rev quicker and make more power down low, 454 unless set up right are kind of pigs.

 

They went to the 454 because they had to decrease compression due to the arrival of unleaded fuel. The 454 was a lower hp engine, but it did make lots of torque, probably why it seems like a truck engine.

 

I built a 427 and 454 with the almost same internals.
The 427 has 781 heads and the 454 has 049 heads. The 454 has the Performer intake and the 427 has the GM aluminum intake. Both have Q jets I rebuilt and set up to Lars' specs(74/41 CH), Comp Cams CL11-601-4 Mother Thumper, Sealed Power L2300NF(060 over) pistons and stock exhaust. The 454 has an HEI with the vacuum can screw turned in 7 revolutions, and the 427 a points style distributor with a B26 vacuum can.
Both engines spin the tires from a 20MPH punch. The 454 feels more torquey at low RPM, but the 427 pulls stronger up to 5500 RPM.
No replacement for displacement!

 

IMO the 454 suffered from poor rod ratios and less ability to breathe. A 6.385" rod on the 4.0" stroke gives nearly the same ratio as the 6.135/3.76" combo of the 427s and the compression height is still fine. A .060 over 454 with the long rods, internally balanced, and a performance top end is a great motor.

Off topic and I'll get flamed for this, but I'm not a fan of anything over 4.0" in a factory BB (or 3.75" in factory SB) or for these reasons. At some point you sacrifice rod angles, oil control or piston stability.

 

Postal 123: I agree with your comments though I probably don't have as much knowledge. The stroker crate motor craze, is an easy way for an engine builder to make hp at low rpm for the purpose of warranty.

The problem for us Corvette owners is we have to deal with an irs that will break with heavy torque. Shorter stroke, higher winding engines are a better option as the same hp can be made with less low end torque.

500hp 383s are very common. There are several build plans for 327s, making the same power with the same top end. The power band will go from 6000rpm (383) to 7000rpm (327). The higher power band is still good for SS valves, no shaft rockers, etc.

A bbc 427 can make the same power as a 496 using the same top end. The power band will be 1000rpm or so higher but not require high $$$ parts like titanium valves and shaft rockers. These builds don't make sense for solid axle, heavy Chevelles. They do make sense for 3300lb cars with an irs and a stick.

 

Jerry,

You're much better versed than you let on. I've followed a few of your posts closely and I'm in total agreement with your philosophy...maximizing hp but trying lower the torque into manageable levels. Your 477 must be an amazing motor. Some sort of aluminum BB haunts me in my sleep (in a good way).

Bats,

The main point I was trying to make is that with some internal changes your 454 can improve angles and reduce friction. And the best part is you won't have to sacrifice compression height to do it. If the rest of the build is done to suit, you'll have a great motor on your hands. Personally, I still like the idea of the 3.75/3.76 stroke, but it seems like anything less than 4.0" cranks for BBCs is high-end race stuff and really pricey!

 

650-700hp pump gas 496" engines are every where, streetable and very reliable.

How many 700hp 427" engines do you see around? Especially on pump gas. Hell you rarely see a true 600hp 427 BBC engines..

No replacement for displacement... Except boost.

The problem with the OEM 454s vs the OEM 427s back in the day were the 454s had lower compression (71' on) no cam, cast iron choked up intakes etc etc.. They were real restricted.. They were high 13 sec cars at best...

Honestly, the 69' 427/390hp cars were not much quicker (stock), if any.

I'd take a 454 over a 427 any day if both had the same level of components. You can spin a stock bottom end 454 to 6500+ no problem... Rods/cranks are fine.. It's the valve train that will limit you.

Now days, unless you're doing a restoration type build and using original parts, there is no reason to build anything less then a 454.. And if you need a crank/rods, then build a 496.
It ain't 1970 anymore fellas, cubic inches is where it's at.

 

Thanks all!
All the comments does engage my mind, what got all this twisting in my head was running across a hipo 427 engine the other day, my high school mentality took over and I started thinking that is just what I need, because it's factory "hipo" 40 plus yo factory but...
I do know I do not need a solid lifter big cammed beast in my street cruiser...


You are the first person I heard say a 427 will make more power down low than a 454 which are known for being low end torque beasts,
A smogger truck 454 running well will still melt the tires off most c3's I can't call that a pig...
But yeah, set up that way 427's are snappy, the problem is all the bb's I have rode in and messed with were fairly high hp builds...I really dont know what the old stock 427's and 454's in vettes did.

For me a "427" has an ingrained place in my mind it's high end bad ***, but that was placed there when I was a teen, times and tech changes, 27 ci extra has to help not hurt,
I really dig what nowhere man says that Zora said about boring out iron...

 

Mark Jones can build a 600hp 427 with Brodix Race Rite 270s and a 630hp 427 with AFR 265s, with both builds hitting peak around 6500rpm. Maybe not everyone's cup of tea but doable and affordable.

Im sure the same or better can be had with a BBC 454. I didn't research a 454 build but Mark does have a 468 crate motor that is an overbored 454, I think.

 

Zora was quoted to say that in 65 when Chevy announced a new 427 was replacing the 396 in Corvettes.

 

Yeah a stock 390hp 427 will definitely have a bit more breath up top then a stock 390hp 454... They probably make the same power but the 454 will peak earlier and nose over faster. A 390hp 454 is done making power at 5000...a stock 390hp 427 probably pulls decent to 5500-5600.

Now if you are talking about the solid lifter 435hp 427s with square port heads, yes they will obviously make more power and much higher in the rev range, and hold on better. If the car is geared to maximize that upper RPM range, it will be the faster car vs. a low rpm 454.

Many ways to skin a cat.

We just built a "restoration" type build on my dad's 65' 396/425hp. We lowered the compression to 10.0 (from 11.25), stock heads with only a good valve job, 237/245* HYD roller... Stock intake/exhaust manifolds. With a way too small 650 cfm carb, it made 441hp/434tq on an engine dyno. Pulling nearly 2" of vacuum at wot, we know the carb was choking it. We figure it's an honest 450-460hp 408" engine now thru stock manifolds.. (Unlike the factory 396/425hp engines dynoed with headers).

I haven't driven it hard yet but I can tell the power is from 4k and up..

 

Yeah Mark has a 9.8:1, 570hp 468" HYD flat tappet combo, a 10.5-1, 620hp 468" solid flat tappet combo, and then gets into the 650hp HYD roller 496 stuff..

Ofcourse he has a bunch of variations of each and will build whatever you want.. Most people just buy his proven combos above.

That being said, Mark makes more power then a lot of other builders out there using the same/similar "parts".

 

This thread got me to looking at 427s, lol. I didn't realize the ZZ427 (480hp version) crate motor is an exact L88 spec engine with the addition of a hydraulic roller cam. The dyno sheet is just shy or 500hp and the pull was to 5500 rpm. The engine is a little pricey but is complete carb to pan. $8900.00

 

I don't agree with some of the things I've read here about 454's.

The factory 454's were not internally balanced, the 427's were. If you have a 454 built up, you can have it internally balanced. Now it will rev like a 427.

Breathing. Buy big block heads with rectangular intake ports. One rectangular intake port will have a cross sectional area that's equivalent to the entire exhaust of a Honda or Toyota economy car. GM says don't use the rectangular ports on a street car because the intake ports are too big...never had any trouble running rectangular ports on the street.

Pig..The 454 shouldn't weight anymore than a 427. For Corvettes, the 1970 454's came out with cast iron manifolds...Arggh! The 69 427's came with aluminum manifolds. You can buy Edelbrock aluminum manifolds for your 454. or a 69 aluminum manifold will fit.

Pig Revisted...If you're building a big block for you Corvette, please buy aluminum heads. It really reduces the gross big block weight. Your Corvette will drive and handle so much noticeably nicer. A big block with aluminum heads and aluminum manifold weighs about the same as the all cast iron small block engine. Edelbrock makes aluminum water pumps for big blocks also.

Poor performing 454 truck engines. They came with the "peanut" cast iron heads. The intake ports were grossly restricted. The intake ports had a u-shaped cross section that some people likened to peanuts.

Building a 454 is yesterday's newspaper. Bore the cylinders out to get 496 cubic inches. Depending upon the block you may be able to go to 502 cubic inches.

.........................
Factoid: The rectangular port aluminum manifolds for a 67 breath a little better than the rectangular port aluminum manifolds for a 68/69, since the 67 hood allows the carb to set a little higher above the engine.

 

I agree, my 468 for my camaro had that stroke and rod length. Motor made 708 hp 622 tq and 1006 hp on the bottle. pulled to 7200 rpm, was a nice motor.

My older 427 made 550 hp and 513 tq with 11.25-1 compression Eddy heads and a hyd 585/ roller cam

 

68/70 Vette: I agree with your comments on the practicality and performance of a BBC 454. A 4" stroke engine is easier and cheaper to build than a 3.75".

I would love to see what a modernized BBC ls6/7 could do on the dyno. Im guessing 650hp+ with a .030+ overbore, ported original top end, bigger valves, roller cam, and maybe efi.

 

Yes, I just went through this while debating what to do with my flywheel. The machine shop said they could install weighted plugs into my crank to increase weight, convert to internal balance. I don't recall the price. I was just in for a clutch replacement so I passed. I don't follow how this increases peak RPM. Isn't this a function of the valve train and stroke? Just asking.

Wonder how many people put truck 454's into Corvettes? Could be where the reputation came from?