[Z06] True big block vs. bored out small block
#1
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True big block vs. bored out small block
If I have any of this wrong please let me know. But what I understand is the new 427 7.0L engine is a bored out ls2. What is the difference between a block cast to be a "big block" motor and a reguler block bored out for big displacment? The only thing I can think of is for increased structural rigidity. But GM would not use the "small Block" 427 if it was not bullet proof.
My snake has a huge block in it, but what is the advantage, if any, of that?
My snake has a huge block in it, but what is the advantage, if any, of that?
#2
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"Ask Tadge" Producer
Originally Posted by MonnieH
What is the difference between a block cast to be a "big block" motor and a reguler block bored out for big displacment?
That said, the main difference to the customer is, plain and simple: mass. Big block motors are, by their nature, BIG. With all that extra metal comes extra mass. Since they are, in fact, larger, they also have packaging contraints that come along with them. You just can't drop a big block into the snout of any car. It might not physically fit.
There have been reasonably successful attempts at cutting down the mass of the big block. Look to the all-aluminum rat motor as an example. The probem is, it's still physically large.
The LS7 is a bored and stroked all-aluminum SBC displacing the same cubes as big blocks have in the past. The reason the SBC was used, mainly, is mass and size.
jas
#3
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Also the LS7 was developed in conjunction with those that developed the 7.0L engine for the C5R... and I don't think that they have ever lost an engine during a race....
#4
Le Mans Master
Originally Posted by MonnieH
The only thing I can think of is for increased structural rigidity.
But, it is the advances in materials, castings, and other parts, that now allow a big block sized dispalcement to be available in a small block sized motors. Just witness the size of racing engines (CART, F1) over the past 25 years. Every year they get physically smaller, and smaller, and lighter and lighter; while producing more power--and now lasting longer and longer.
#5
Safety Car
Originally Posted by MonnieH
My snake has a huge block in it, but what is the advantage, if any, of that?
#6
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Big blocks allow for a larger bore and a shorter stroke to achieve the same displacement. Correct me if I'm wrong but I thought the following is true of big blocks....
Shorter stroke = less internal friction = higher potential HP
Shorter stroke = higher max "safe-operating" RPM limit
Bigger bore = larger max valve size
Bigger bore = flatter torque curve
Overall, I don't believe that the above is enough to offset the increased weight and Rod/Stroke ratio of a big versus small block at the same displacement.
Shorter stroke = less internal friction = higher potential HP
Shorter stroke = higher max "safe-operating" RPM limit
Bigger bore = larger max valve size
Bigger bore = flatter torque curve
Overall, I don't believe that the above is enough to offset the increased weight and Rod/Stroke ratio of a big versus small block at the same displacement.
#7
Safety Car
A longer stroke helps build more TQ .... and a shorter more RPM.
Since HP = RPM X TQ , its probably a tradeoff. Some like TQ , some RPM. Personally ... I like the down low TQ.
Hope Duke gives us his take ... for he explains this from the engineer's perspective.
Since HP = RPM X TQ , its probably a tradeoff. Some like TQ , some RPM. Personally ... I like the down low TQ.
Hope Duke gives us his take ... for he explains this from the engineer's perspective.
#8
Race Director
Originally Posted by MonnieH
My snake has a huge block in it, but what is the advantage, if any, of that?
GOLD72
#9
Le Mans Master
Big block has bigger bore spacing and higher deck height.
In simple terms big block can be bored and stroked FAR beyond 427ci.
That means you could have, let’s say, a 540ci motor, something that can NEVER be accomplished with small block.
There are also factors like bigger valves etc, but it’s not that important.
The conclusion: if all you need is 427ci there’s no point adding more weight for big block.
However small block can’t even dream of competing with big block if you modify both (427ci vs 540+ci – yeah right )
In simple terms big block can be bored and stroked FAR beyond 427ci.
That means you could have, let’s say, a 540ci motor, something that can NEVER be accomplished with small block.
There are also factors like bigger valves etc, but it’s not that important.
The conclusion: if all you need is 427ci there’s no point adding more weight for big block.
However small block can’t even dream of competing with big block if you modify both (427ci vs 540+ci – yeah right )
#10
Get Some!
As other threads have stated the reason the big block was made was because the tech of the time could only get so much HP out of small blocks because of valve size. So a big piston allowed for more flow, etc. Now we don't need the big piston to get the flow. 1.17 HP per cube that is emissions legal and noise legal is awesome!
#11
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Isn't the BIG BLOCK physicaly larger and weights much more then the small block?? and putting the big block into the C5 or C6 take some space alterations in the engine bay?
The C5R & C6R Ketech 7 liter engine puts out some where north 900 BHP unresticted. Even with the quarter size restritor plates in each of the two thottle bodies it is 650 BHP in race prep mode.
With power like that who needs a big block??
The C5R & C6R Ketech 7 liter engine puts out some where north 900 BHP unresticted. Even with the quarter size restritor plates in each of the two thottle bodies it is 650 BHP in race prep mode.
With power like that who needs a big block??
#13
Le Mans Master
Originally Posted by AU N EGL
Isn't the BIG BLOCK physicaly larger and weights much more then the small block?? and putting the big block into the C5 or C6 take some space alterations in the engine bay?
The C5R & C6R Ketech 7 liter engine puts out some where north 900 BHP unresticted. Even with the quarter size restritor plates in each of the two thottle bodies it is 650 BHP in race prep mode.
With power like that who needs a big block??
The C5R & C6R Ketech 7 liter engine puts out some where north 900 BHP unresticted. Even with the quarter size restritor plates in each of the two thottle bodies it is 650 BHP in race prep mode.
With power like that who needs a big block??
I would love to be able to get 700-750rwHP NA in a street motor.
I don't see small block doing it
#14
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Originally Posted by EuG
I do.
I would love to be able to get 700-750rwHP NA in a street motor.
I don't see small block doing it
I would love to be able to get 700-750rwHP NA in a street motor.
I don't see small block doing it
http://www.katechengines.com/index.htm
#15
Le Mans Master
Originally Posted by EuG
I do.
I would love to be able to get 700-750rwHP NA in a street motor.
I don't see small block doing it
I would love to be able to get 700-750rwHP NA in a street motor.
I don't see small block doing it
I have a 605 BB drag engine that struggles to get 915 hp so that kind of power out of a small block is pretty cool
at least the bb is cheap!!
#16
Le Mans Master
Originally Posted by AU N EGL
Well the street virson of the C5R Ketech 7.0 liter LS6 has 585 bph.
http://www.katechengines.com/index.htm
http://www.katechengines.com/index.htm
I could use A LOOOOT more
#17
Le Mans Master
Originally Posted by Rkreigh
I have a 605 BB drag engine that struggles to get 915 hp so that kind of power out of a small block is pretty cool
at least the bb is cheap!!
at least the bb is cheap!!
I’m saying I’m sure LS7 style 540+ci BB would make 700-750rwHP NA in street form.
There no way a street 427ci will make that much NA
#20
Le Mans Master
Originally Posted by JJMalone
The LS motor, hands down.
Heh, well for the throwback feel of the "good old days" of cruising, many would say the old 427s but compared to the new rendition of the LS7 which won't overheat itself or be plagued with other problems that needed maintainence, I'd say technological advances win out on this one.