I'm new to owning an 8.1L Vortec and was wondering if the marine intake manifold is the same as the truck manifold, whereby it has the internal plate that restricts airflow? Also are the injectors the same size/flow rate? Is the throttle body the same size?

2004 3500 8.1L Allison 5spd, 4.10s

 

I think that yes there is something inside of it you can remove and it will be a bit more efficient.
The injectors are 34LB/hr so yes bigger
Throttle body is a different size I believe but not by much

 

Sorry, I don't know the answer to your questions but, that's a sweet combo in that truck that I've never seen before! I bet it freaking rips!

 

The 8.1 is kind of a rare beast around these parts, we are very LS centric here

The truck manifold allegedly has a more broad torque curve, with the emphasis on low end torque production. The marine manifold is supposed to make better peak HP at "high" rpm, but sacrifices what the truck manifold can make down low. Looks like the gains are disputed, but looking at GM literature, there can be a 35hp difference in motors (340 for trucks and 375 for marine) some of that could
be exhaust, induction and tuning. I wouldn't rush to the polls and claim the manifold alone is worth 35hp

Marine injectors are bigger

 

Dantheman1540 thanks, I've had 454 squarebodies before, but have to say this 8.1L is nicer, feels like a 454 with a cam. Arthursc2 I'm looking to build this truck up a bit (cam, headers, duals) and am wondering if the marine itake would be the route to go? I would like to save having to cut my stock truck intake open (save myself the work).

 

I am really not sure how to suggest you go about that. Raylar Engineering is the only company I can name building 8.1 parts. Maybe we can plagiarize a build plan from them and see what they are doing for HP gains

 

Subscribe to LT's Raylar 547 build.

 

Look in the 8 lug section. most 8.1L stuff is in there.

Here is a discussion on moding the 8.1L intake. https://www.performancetrucks.net/fo...-style-534372/