curvesman

What is the differance,The new 7.0 427 to the old 427 BIG block

ivan111

Big Blocks are bulkier and heavier......

WhiteDiamond

Bore spacing and block dimensions have not changed from the LS2 to the LS7 427ci engine. The old big blocks had a physical change to just about everypart including a larger bore spacing and physically bigger block.

Todd

Boomer 2

Big blocks have more bore, less stroke, typically less rpm, more torque.
They make more power on the low end. The new small block 427 will make power the same way that GM small blocks always have, at the high end.

DDSLT5

Less rpm? Uhhhh...NO! Less stroke means the motor revs much easier, and thus more rpm. Big blocks make huge torque over the whole power band, lots of cids for torque down low, and with the huge bore, they can install huge valves, so it breathes very well up high for big hp on the top end. If you want ultimate power, NOTHING replaces the big cubes with ultra high flowing heads. The big blocks were called 'porcupine motors' because the valve stems stuck out at all angles to allow maximum flowing heads.

That being said, the new 427 will also make big torque down low, with good power up high, because the cids are the there, and the heads flow extremely well too. But it has taken many years to duplicate the power the old school big block made in its day. Only problem is..... big blocks can be stroked to 631 cids!!!

curvesman

The old blocks where bigger than 7.0?
Thanks in advance!

cbgpe

big blocks are just that bigger in all directions. Taller deck height (distance from the crank to the head mounting surface) wider bore spacing 4.4 to 4.9 inches in the case of the chevy big blocks. They have more bore stroke capability. The LS 7 is at the limit of it's growth. A big block can go to 600 cid.
They also weigh a LOT!!
Overall you will be happier with the small block for this application.
CBGPE

LTC Z06

Yes, the 454 was the standard big block up into the 90s. Also, the Pontiac 454 was not a big block, it was the same size as the Pontiac 350.

kewlbrz

FWIW: There is still a Big Block in use today.

The GM 8.1 Liter 496 Cubic Inch V8 Big Block in the truck line.

LTC Z06

Is it based on the 454?

kewlbrz

Blockwise, yes. It uses Vortec heads. Reverse Flow i beleive.

Technically a 454 is 427 based.

Heres a breakdown for comparison

Big Blocks:
Size - Bore - Stroke
427 = 4.250" x 3.76"
454 = 4.250" x 4.00"
(Vortec 8100) 496 = 4.250" x 4.37"

LS1LT1

True, but it was actually a 455 not a 454.

WhiteDiamond

Its not really based in displacement of the motor. It is based in the other things that have been mentioned.. Increasing bore spacing allows for a bigger bore. Increased deck height can allow for longer stroke. Increasing these things requires that the block become bigger than a same cylinder count engine with smaller bore spacing and lower deck height. You could come up with a very low displacement big block and a very large displacement small block, if you wished.

Todd

Nitrodamus

What a difference 40 years makes!!

I have a 66' 427/450 Coupe that I did a body off on 20 years ago. The engine is a cast iron monster and weighs a ton! I rebuilt the engine because the previous owner had turned it into a L88 with 12.5 to 1 compression. It has a red line of 6400 RPM and will still scream up to there with no problem!!

I can't wait to stick a C6 Z06 next to it!

I'm looking forward to the new small block 427 and hope GM did as good a job as they did building the old big block 427!

tolnep

old hotrod mags called the big block the 'rat' motor and the smallblock the 'mouse' motor. I think the called the 426 hemi the elephant and the big block 460 ford the 'shotgun' ford because the valves where huge.

I think the first big block that I was aware of was the old 396 which went to 427 then 454 and up. Seems like some old caddys had bigblocks with huge displacements stock.

People used to say I and I don't know if it was true, that the big block of choice was the chevy because it held up well. Supposedly the hemi had huge power but it had to be continually align bored and rebuilt.

The motors were/are? iron. But donovan (It think that is/was the company) made an aluminum version that was used in dragsters (still is I think) jet boats, and tractors for tractor pulls.

Using today's technology, turbos, blowers etc it would be very easy to get 1000hp out of a bigblock.

The things are huge though... Years ago I bought an engine crane. A friend had just bought and rebuilt a 454 jet boat and I was thinking of doing the same so I bought a crane with a theoretical 2 ton hoist capability. I think the iron 454 was around 1000 lbs with all the trimmings.

Painrace

Bib blocks were much heavier than small blocks. When you add all that weight to the front of a car the front tires sticks and the rear is loose (over stear). That is what killed the big block in road racing. It was fast as hell in a straight line but you had to almost park it to turn.

Now we have a small block with big block bore so we should have all kind of FUN!

LTC Z06

That's right, as I was typing 454 I knew something was off.

curvesman

Thanks,what was the 409,I remember them in the 63 chevys,seemed like they had problems

DDSLT5

Untrue - the 455 is a big block motor. The 400 cid motor was a small block - the largest version of the small block.

DDSLT5

No - it was 6000 lbs - that's it.