Big block vs Small block
Pope
I'm historically an outboard man but am considering two I/O's. What are
the main differences between the big block engines and small blocks??
Can you have either a big or small Chevy 350?? What is the wieght
difference? Is one easier to care for? What else do I need to know?
Good sources of info on this subject.
Thanks, John
Bill Walker
No, the Chevy 350 (aka 5.7, for metric fans) comes from the Chevy "small
block" family, which traces its roots to the 283 of the 1950s. The "big
block" family began, I believe, with the 427 (not sure about year, but the
motor was around in the late '60s), which later became the 454 (aka
7.4). So the main differences, really, are displacement and horsepower.
The rest is just details. I don't have info on the weight differences,
but those figures are quoted in Mercruiser brochures.
For Merc I/Os, another difference is that the 350/5.7 can be equipped with
the Alpha 1 outdrive and some of the Bravo drives, while the 454/7.4 can
be equipped only with Bravo drives (not counting Merc's
ultra-high-performance drives). Early on, you could get a 454 with an
Alpha, but this combination didn't hold up too well (the Alpha wasn't up
to the horsepower), so it's no longer available. So, if you get the big
block, you're guaranteed (at least with Mercruiser. I don't know about
Volvo/OMC) of getting the beefier outdrive. Bravos shift smoother, too,
since they don't use dog clutches like Alphas.
----------------------------------------------
Bill Walker, QUALCOMM, Inc., San Diego, CA USA
WWa...@qualcomm.com
Gary Anderson
> I'm historically an outboard man but am considering two I/O's. What are
> the main differences between the big block engines and small blocks??
> Can you have either a big or small Chevy 350?? What is the wieght
> difference? Is one easier to care for? What else do I need to know?
> Good sources of info on this subject.
>
> Thanks, John
>
> po...@halcyon.com
--
Chevy small block include the 305/350/400 cid series. Only the 305 and 350
are used in marine motors any more. Big Block chevys are the
396/427/454/502 cid motors. Only the 454 and 502s are used in current
marine engines. Sm. Fords are the 289-351, 302 and 351 cid marine motors.
Big block Ford is the 460 marine engine. Weight difference is only about
100 lbs between a 350 abd 454. The drive has to be upgraded from an alpha
to a bravo with the 454 too. In addition, some other items will add more
weight with the 454, ie. exhaust, engine driven water pump with bravos.
Parts are more expensive for the 454, but the engine may last longer in a
similar boat that has a 350 since it will be stresses less.
Boating rule #1: Always get the biggest engine available. Boat
manufacturers will never overpower a boat, but all too often underpower
them.
Gary Anderson
Internet: GDA...@CCMAIL.MONSANTO.COM
Jorg Klinger
In article <wwalker-2509...@wwalker-mac.qualcomm.com>,
wwa...@qualcomm.com (Bill Walker) wrote:
So the main differences, really, are displacement and horsepower.
> The rest is just details.
> Bill Walker, QUALCOMM, Inc., San Diego, CA USA
The big block I believe began as a 396.
The biggest difference between them is that the small block was designed
for passenger car use, the big block was designed specificaly as a race
engine and then incorporated into passenger cars. Although both engines
are good, the big block is much more durable (this is a generalization
since both motors came in numerous configurations).
I would view a top of the line big block as an investment, a motor you
could pass onto your kids.
--
--
Jorg Klinger CR500 You can't make a pig into a
Arch.&Eng. *** racehorse, but you can make
umanitoba Lost Horizons a really, really fast pig.
george
:No, the Chevy 350 (aka 5.7, for metric fans) comes from the Chevy "small
:block" family, which traces its roots to the 283 of the 1950s. The "big
:block" family began, I believe, with the 427 (not sure about year, but the
:motor was around in the late '60s), which later became the 454 (aka
:The rest is just details. I don't have info on the weight differences,
:but those figures are quoted in Mercruiser brochures.
I believe the weight difference is significant. A 'big block' is
actually a larger block. Incedentally, there was a 400ci small block
and a 39x big block at one time or another, so you see the distinction
really is the block and not the displacement.
I wouldn't be at all suprised to hear someone incorrectly call a
high performance 350 a big block these days though. It certainly
is a "big" block compared to the motor in their honda.
--
george
geo...@mech.seas.upenn.edu
Robert Harris
Big blocks are 454 Chevy or 460 Ford engines, and I believe GM has an
over 500 cibic inch engine out there. The small blocks are either 300 or
350 c.i. engines. The big blocks require a totally different outdrive to
handle the additional torque and horsepower. I've had both, in the
Mercruiser brand. The larger setup was much more reliable, as I put a
lot of hours on the boats. You must however, take into account the fact
that I.O. setups have many more potential fail points that outboards.
-
BOB HARRIS JTH...@prodigy.com N6JUN
S/V Priority Won
ZionHill
You are all missing the important differences between the small and big block
Chevy's. You probably weren't motor-heads in the 60's and 70's, but we won't
hold it against you! (Note that the snip above is not complete and I don't know
what else the person said.)
The primary difference in performance is the _kind_ of power you get from each.
The small blocks are typically peppy higher rpm performers that excel in things
like road racing, etc. The big blocks deliver a low rpm pulling torque suitable
for tractor pulls and the like.
Sure, the big and small blocks can be interchangeable for many applications, but
as mentioned above, you gotta watch the weight factor. For a Yacht application I
would want something like twin diesel 454's that give a lot of low end horsepower
without the wear and tear of high rpm's.
Personally, I lean more towards sail power these days, and only need a motor strong
enough to get me out to open spaces.
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Chuck Jackson
Pope wrote:
>
> I'm historically an outboard man but am considering two I/O's. What are
> the main differences between the big block engines and small blocks??
> Can you have either a big or small Chevy 350?? What is the wieght
> difference? Is one easier to care for? What else do I need to know?
> Good sources of info on this subject.
>
> Thanks, John
>
> po...@halcyon.com
John,
If you want twin I/O's for reliabilty and not speed, then the twin small
blocks (350's) would be the way to go. They are lighter, cheaper, and
usually offer better fuel economy. The 350 is considered a small block.
I believe the small blocks weigh about 150 lbs less (each) than big
block.
If you're looking for speed....go big block. There is no substitute for
cubic inches and there are a lot more performance options for the big
block for marine use.
Both engines would require the same type of maintenance.
Vvmfuno
There are 5 / 5.7 and 7.4 liter V8s. All are fine for the right boat.
Lower UNits however, are nothing but trouble. Get straight inboards or
Outboards.
CruiserMer
There are only a couple of million stern drive powered boats out there.
Daniel Font
Prueba.
LorieLou
i agree if you are talking about omc shit or volvo sweedish want to be
stern drives.however MERCRUISER stern drives are as dependable as the SUN!
LORIE LOU'S HUBBY