Marine Intake

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wiscomick

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Sure would like to get my hands on one of these marine intakes. Really seems like the poppet valve injector is the limiting factor in modifying the Vortec 350. Could be a nice alternative to an LS swap, IMO.
 

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L31MaxExpress

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Sure would like to get my hands on one of these marine intakes. Really seems like the poppet valve injector is the limiting factor in modifying the Vortec 350. Could be a nice alternative to an LS swap, IMO.
The spider is not a limitation for a naturally aspirated 350 on anything you would run on the street in these trucks. It is when you start adding cubes or forced air that you need more.
 

wiscomick

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Agreed, but.... IMO anyway, FI or cubes are the only option for anything worth your time and money on these things as well, so that makes addressing the injector situation one of the first things to think about when trying to go faster.

It's a consideration that I've been overthinking for months on my truck and where it's at... Do something substantial with the V350 and find a way to make it special power-wise with the engine it was born with, or do what every other yokel does and hit the easy button by swapping in the 5.3/6.0.

IDK. Overthinking is my specialty.
 

L31MaxExpress

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Agreed, but.... IMO anyway, FI or cubes are the only option for anything worth your time and money on these things as well, so that makes addressing the injector situation one of the first things to think about when trying to go faster.

It's a consideration that I've been overthinking for months on my truck and where it's at... Do something substantial with the V350 and find a way to make it special power-wise with the engine it was born with, or do what every other yokel does and hit the easy button by swapping in the 5.3/6.0.

IDK. Overthinking is my specialty.
Or do what I did with my 99 Tahoe. An 8.1L with Van or GMT400 accessories that have the Vortec compressor high mounted is an easy swap. It bolts to the small block clamshells and falls right in with off the shelf OBS big block headers. The 01-02 GMT400 3500HD air intake and fan shroud fits. I put the factory GM marine HO cam in it that makes 450 hp @ 5,000 rpm and 550 tq @ 3,400 rpm with headers. Use a 4L80E and you can leave the 3.08/3.42 or 3.73 highway gears even with taller tires. In the Tahoe with the 3.42 gear and 32" tall P305/50R20s it still gets 17-18 mpg rolling along at 80 mph. Look at what LT has done with a junkyard 8.1L and boost.
 
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L31MaxExpress

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Never even considered that option. Damn. I'd love to learn more about this.
Its basically a factory stroked 454 with LS style cathederal intake ports and matching intake manifold and LS electronics. The block is dual drilled for the standard old 3 bolt mounting pattern as well as the LS 4 bolt. It can either have a low mounted ac compressor LS style or a high mounted Vortec 350 style. Small block lower radiator hose fits it and I cut the upper hose in half where it crossed the water neck. It was an easier swap than a LS IMO because almost everything needed was either already on the small block, on the 8.1L or available off the shelf for a GMT400 without resorting to expensive swap parts. I used the DBW on the 8.1L with an inexpensive GMT400 6.5/8.1 DBW pedal.

Edit the exhaust ports are also traditional big block but being a tall deck block it did require a couple of header tubes to get a small dent for clearence.
 

L31MaxExpress

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I have the 8.1L shortblock bagged and oiled on the storage stand at the shop waiting for the heads to be finished at the machine shop. I ended up burning an exhaust valve on it a while back. This is a picture grab of an OBS GMT400 3500 HD engine bay with an 8.1. Tahoe looks the same minus the dual batteries, dual alternators, 4" air intake and headers. My 8.1L is setup with a P59 PCM and Flex Fuel.
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Supercharged111

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Its basically a factory stroked 454 with LS style cathederal intake ports and matching intake manifold and LS electronics. The block is dual drilled for the standard old 3 bolt mounting pattern as well as the LS 4 bolt. It can either have a low mounted ac compressor LS style or a high mounted Vortec 350 style. Small block lower radiator hose fits it and I cut the upper hose in half where it crossed the water neck. It was an easier swap than a LS IMO because almost everything needed was either already on the small block, on the 8.1L or available off the shelf for a GMT400 without resorting to expensive swap parts. I used the DBW on the 8.1L with an inexpensive GMT400 6.5/8.1 DBW pedal.

Edit the exhaust ports are also traditional big block but being a tall deck block it did require a couple of header tubes to get a small dent for clearence.

I kept the pedal off of the dually I swapped to gas and sold but forgot to snip the pigtail. Will an 800 pigtail plug in or do I need to get lucky at the junkyard?
 

L31MaxExpress

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I kept the pedal off of the dually I swapped to gas and sold but forgot to snip the pigtail. Will an 800 pigtail plug in or do I need to get lucky at the junkyard?
An early GMT800 might have the right plug. The later ones do not. I think EFI Connection may have the correct connector at a decent price if you strike out. The 96-02 Diesel and 8.1L Express and Savanna vans have the same connector on the pedal although the pedal itself is different. The pedal wiring on the 8.1L van exits the firewall through its own grommet and is about 4-5 ft long.
 
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