Just hypothetical musings about max power potential

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Mean416

Mean416

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Okay so I was thinking about this. The "word on the street" is that the max power capabilities of a standard sb block is about 700 ish. People claim the block will split. I'm guessing in the main webbing somewhere?

Anyway. What causes the cracking? It's not just power itself. It must be some combination of factors. RPM. Stroke. Cylinder pressure. Actual load (i.e. weight transfer and traction actually putting load on the engine).

RPM: It stands to reason higher RPM leads to higher cyclical loads on the block. So a lower rpm engine should withstand more power right?

Stroke: It stands to reason that a longer stroke would tend to stress the block more compared to a shorter stroke. Just pure physics. Pulsing loads at a longer stroke is going to create higher amplitude of stress.

Cylinder pressure: it stands to reason that higher cylinder pressure would create larger pulses of energy for the block to absorb. Similar to longer stroke?

Actual load: are you running in a high traction situation at a drag strip? Or just spinning the radials on the street? It stands to reason that the former would be harder on the block.

Other considerations? Anything I've not thought about?

So I was thinking that, perhaps the best strategy for maximum output, would be a short stroke, lower rpm, higher boost engine. Like a destroked 340 with a lot of boost, but tuned to kick in earlier in the rpms. Say max 6000 rpm. What would the power holding capability be?
 
Thin cylinder walls, anything over 500 hp is circumspect. Splits the cylinder walls, hence the name LA as in light A engine.
 
In most cases engines with passenger car blocks making more than 500 hp have the water jackets filled with block filler. The next thing limiting hp is the heads do not flow enough to make more than 700 or so hp. Not enough flow to reach higher rpm’s to make the hp.
 
ch1ll said:
In most cases engines with passenger car blocks making more than 500 hp have the water jackets filled with block filler. The next thing limiting hp is the heads do not flow enough to make more than 700 or so hp. Not enough flow to reach higher rpm’s to make the hp.
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If you add boost to the equation making 700 hp becomes quite easy.
 
Mean416 said:
If you add boost to the equation making 700 hp becomes quite easy.
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This is my working theory also. I have a stock stroke 5.9/360 not an LA and it’s turbo charged. Stock crank, forged pistons and rods. Boost comes on around 3k with a 3500 stall and I shift at 5500rpms. I haven’t turned it up to produce 700hp but I’d say I’m close to 600hp. It’s been reliable at that level for a while. Plenty of street blasts and a handful of 1/8 mile runs. I think my head gaskets would probably let go before the block would if I turned up the boost. Right now I keep it around 10-12psi but have gone as high as 15psi.
 
Conversely I have a buddy with a 5.9 based Dakota that runs low 6s in the 1/8th. That motor has to be producing 700+hp to push that heavy truck through the traps at 110mph. Nothing exotic in his block (no filler or girdle), but it does have nice heads and gets smacked really hard by nitrous and he’s abused that block for years. “500 HP?!!…you’ll shoot your eye out kid!”. Lol
 
Seems like a nitrous hit would be way more violent on the engine than any forced induction
 
**600hp sbm block limit? Or is it bs!!**

Some good reading there. Duner/MadDuner peaks his head in and is one of the Dakota guys who has made 700 reliably for years(136mph @ 4,000lbs). I have his complete build list(he posted elsewhere) and it’s not even exotic; stock head bolts, eq heads. 700 to the wheels by the way. Digging through different forums there are many examples of turbo builds in the 6-700hp range. Dizuster pushed his stock cast crank into the 850(140mph @ 3700lbs) range with lots of boost from a box stock s475. I don’t believe I’ve seen a single turbo block failure so if you know of any please post up info for the community. That would be valuable to me personally.

62E870DF-E595-4A2E-839E-303D851CEEA1.jpeg
 
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Mean416 said:
Seems like a nitrous hit would be way more violent on the engine than any forced induction
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It is, you are adding an oxidizer, as opposed to increasing the density of air.
 
ch1ll said:
It is, you are adding an oxidizer, as opposed to increasing the density of air.
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Well, I was more thinking about the big step change in the power profile. You basically go from small torque to huge torque instantly. Sure is fun though!
 
The blocks break because the flex. More power means more flex. RPM is hard on blocks and cranks. RPM and big power is a block killer.
 
I think you’d pull some more life out of the block if you deburred everything and took all the edges off to prevent the crack from sharp stress risers.

Oh and vibration. You didn’t touch on vibration.
 



These two run 8's no problem with hundreds of passes on a stock block, no hard block filler, no girdle, STOCK. People need to stop with the non sense. Detonation kills blocks. I also ran a 351 Windsor block for over 100 passes with a stock cast crank and hyper pistons on a 350 shot, no controller. It ran low 9's like that. Never broke the block. Both the Duster and the Dart are full steel cars. Dart weighs in at 3400 pounds and the Duster is 3300.
 
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