L31 intake swap-I am actually doing it not a question.

[dave_erald]

When you're looking at intake manifolds dictating torque curves it comes down to port velocity, long thin intake tubes cause low and mid range grunt because intake air velocity is ridiculously high. But, it runs out of breath topend because the long port cant fill the cylinders fast enough.

LT1 engines with their short short intake are not great bottom end but can wing out topend fairly decent.

TBI truck heads have a large ramp on the intake to promote velocity and swirl but way too oversized. Hence 350 tbi's can smoke off tires but die topend.

Vortec intake and heads did decently well across the range largely because of the heads. Yes multiport injection helped but the heads were responsible for the biggest gains.

Best bang for your buck pre LS motors? Dual plane intake. Multiport fuel injection. Aluminum Vortec heads. 10.5 to 1 compression and a healthy cam.

...after that everything needs to start getting bigger or you need to forcefeed it. Simple simple.

 

[Jrgunn5150]

The average carb dual plane has shorter runners than the average aftermarket injection intake lol.

There is much more to the equation than just runner size.

At any rate, I'm going to go ahead and use my XT intake on my towing truck, you guy's can do whatever you like.

 

[dave_erald]

Carburetion has its advantages in ease of tunability and fuel atomization.

Top end nothing atomizes air like a fuel source a mile away from the cylinder

 

[Jrgunn5150]

Carburetion has its advantages in ease of tunability and fuel atomization.

Top end nothing atomizes air like a fuel source a mile away from the cylinder

Exactly lol.

 

[dave_erald]

JR is right, way more to consider in a engine build than just intake type.

 

[Supercharged111]

The average carb dual plane has shorter runners than the average aftermarket injection intake lol.

There is much more to the equation than just runner size.

At any rate, I'm going to go ahead and use my XT intake on my towing truck, you guy's can do whatever you like.

Marine intake and Whipple.

 

[dave_erald]

@Supercharged111 maybe @Justin S can shed some light on the 454 vortec motor, or @88GMCtruck .

I am going to guess cylinder size (its a big mill already) has something to do with intake sizing deviations.

Remember that the only engine to achieve over 100% volumetric efficiency from factory was a carbed 454 engine. No replacement for displacement.

That being said im going to guess that any intake you put on those things has nill effect till you swap cylinder heads. Big motors like to breath big and factory big block heads dont do it as near as i can tell

 

[Jrgunn5150]

It's not worth that much to me, I have a hard cut off for expenditures where I just go buy a new truck.

 

[dave_erald]

...or cheat and marine intake and whipple


I think we've deviated this original topic a bit...

 

[Supercharged111]

@Supercharged111 maybe @Justin S can shed some light on the 454 vortec motor, or @88GMCtruck .

I am going to guess cylinder size (its a big mill already) has something to do with intake sizing deviations.

Remember that the only engine to achieve over 100% volumetric efficiency from factory was a carbed 454 engine. No replacement for displacement.

That being said im going to guess that any intake you put on those things has nill effect till you swap cylinder heads. Big motors like to breath big and factory big block heads dont do it as near as i can tell

Tough to say on the intake as the exhaust and tune really seem to strangle them in stock form. That said, here's an L29 with a carb and headers on the dyno, not too shabby.

http://www.superchevy.com/how-to/en...r-from-a-junkyard-454-with-splash-of-nitrous/