5.7 Vortec Upgrade Options

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Trenton

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And I feel like this should be noted.

Forced induction is a sure way to kill a stock long block. Your stock iron heads are only good for high 9.x/1 at best. With the stock 9.4 c/r if you ONE pound of boost you're at 10.2~.

This is partially why i never thought about a supercharger before without forged internals. On the other hand, boosting doesn't change the compression ratio, just increases pressure itself in the cylinder. Compression ratio compares the volume of a cylinder at bottom stroke versus top dead center. The cylinder volume or head chambers are not increasing in size. Only thing increasing is cylinder pressure.
 

evilunclegrimace

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And I feel like this should be noted.

Forced induction is a sure way to kill a stock long block. Your stock iron heads are only good for high 9.x/1 at best. With the stock 9.4 c/r if you ONE pound of boost you're at 10.2~.

Adding compression the old fashioned way is safer, will give you a better torque curve, and a helluva lot cheaper

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Are you saying that you cannot run higher than 9.5 -1 compression ratio with stock heads?
 

Trigger_guard

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This is partially why i never thought about a supercharger before without forged internals. On the other hand, boosting doesn't change the compression ratio, just increases pressure itself in the cylinder. Compression ratio compares the volume of a cylinder at bottom stroke versus top dead center. The cylinder volume or head chambers are not increasing in size. Only thing increasing is cylinder pressure.
Adding boost increases the *effective compression ratio*. As opposed to static c/r . I'm sorry I should have been more clear

Regardless. You can only have so much cylinder pressure before you have issues.

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Trigger_guard

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Steelheads are fish.

Vortec heads are CAST IRON. Cast iron has too much carbon to be considered "steel".
Iron + carbon = steel.

However it's irrelevant to his question.
L31 heads aren't aluminum. That's all he wanted to know

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Trigger_guard

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Are you saying that you cannot run higher than 9.5 -1 compression ratio with stock heads?
Not by much,. Iron heads are bad at dissipating heat. Thus they run at a higher temperature than aluminum ones. That higher temperature helps cause detonation. Which can cause many small problems but always leads to catastrophic failure.

Tl.dr. The rule of thumb for carbureted engines is 9.5 on cast heads, 10.5 on aluminum. But having an elecro engine gives you some wiggle room

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b454rat

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I ran 10:1 on a TBI'd 406 with 87 octane. Thing was an absolute monster. Zero issues with the motor. All stock ECM and fueling. Many S/C are designed to run on stock motors, meaning not forged internals. They aren't putting out that much boost.
 

Trigger_guard

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IIRC the 70 LT1 'vette 350/375HP ran 11.5:1
Just wanna say y'all are Killing me

In 1970 regular leaded fuel was 94 octane
Super was 103. And alcohol free.

The lt-1 also had about 50° more duration than the L31

More duration = more bleed = less effective compression

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