Engine replacement options

[swathdiver]

L31 in final form made 255 HP and about 335-350 FTLBS Torque. Old school low rpm torquey motors. L33 is ultimate 5.3 Gen III motor, nearly identical to Gen IV LC9. Aluminum block and heads, 310 HP and 335 FTLBS Torque stock. Mileage would improve slightly too.

 

[Squirrelsmith]

How many thousands do you want to spend to get good mileage? I am reminded of the fellas who repowered their boats with diesels, spending $40K+ to pay less at the pump. It's nonsensical to decide that way.

Gen IV LS swap with the 6-speed would give you the mileage with a 5.3. Why not just supercharge your L31? It's a great engine. Put a Gear Vendors overdrive in it for highway mileage.

I see your point but if i spend 5k on a 383 crate and get 5mpg afterwards i would not be pleased and probably wouldnt drive it

 

[swathdiver]

I see your point but if i spend 5k on a 383 crate and get 5mpg afterwards i would not be pleased and probably wouldnt drive it

There's guys on here with 383s, they can tell you what they're getting. I reckon it's the same or at most 1-2 mpg less. Of course, a bad configuration of parts can tank the mileage in anything.

 

[Squirrelsmith]

There's guys on here with 383s, they can tell you what they're getting. I reckon it's the same or at most 1-2 mpg less. Of course, a bad configuration of parts can tank the mileage in anything.

Sounds good thanks

 

[Squirrelsmith]

The tranny has supposedly been rebuilt recently but i have no proof. It does shift hard from first to second

 

[TigerEyz3]

Good advice has been given in the above posts. Regardless of the motor choice, you'll want to make sure that your transmission can handle the new motor.

The 350/383 motors will not be as fuel efficient or have as much top-end capacity as the newer LS motors (design differences). However, the 350/383 motors will have more low-end torque than the LS motors. Given that you're driving an OBS truck, which has a black-box computer limiter of 5800 RPMs, and assuming you're doing "truck stuff" with your truck, your needed power will be in the low-mid range RPM range. The 350/383 crate drop-in will certainly be easier than performing an LS-swap (lots more components have to be changed/replaced for compatibility). That said, an LS motor can cost less than the 383 from a motor-only cost standpoint (based on sourcing). The situation really all depends on what you're willing to deal with and what you're wanting from an end result standpoint.

I went the HT383E crate route because I wanted the low-mid torque and already had many component upgrades that I wanted to reuse.

 

[GregoryD]

I have a 1999 4 x 2 Z56 Tahoe with the Police Package. Its got 101,000 mikes and the intake gasket went last summer and she overheated and is now sitting. I'm saving to get the GMPP 383E Crate engine. https://www.gmperformancemotor.com/parts/19355721.html

 

[Racing4funn]

Hands down.. Durmax swap.. Im going to.. Just got to kill the factory POS one first. U'd get 18+ miles per gallon and with only a programmer Ud out run the supercharged guys while doubling their fuel economy. And Ud have no back tires from the ridiculous burnouts.

 

[Walrusmt]

I'm going down this road as well. Ultimately cost was a factor. I was able to get a 96 vortec 454 - including the harness and all the accessories for $350. The fact that the 454 fits existing mount points is a plus. The electronics that came with the 454 bolt in the same place - no new wires to worry about.

I'm doing a rebuild on the engine (along with the upgraded cam and smoothing / porting the heads) - to get up into that 400 hp range. A rebuild is almost always a great idea when swapping in a new motor. I looked hard into the 383 option, but reliability was a question (and by reliability - I'm talking 100K or more).
I'll be adding the engine to a 4l80e that came with the transfer case ($400). There are some additional items I may need (new radiator), but ultimately I'll get where I want to be for under $1500 and an easy weeks work.