Should I swap a 383?

[L31MaxExpress]

I put a 383 in mine a couple of years ago. And there is no comparison between the two. The stock Vortec fuel injection system is capable of supporting about 400 HP, so I had my stock engine built for 450. Brand new, a Vortec 350 was good for 250 HP. If somebody's telling you that 400+ horses isn't a dramatic improvement over 250, they don't know what they're talking about. I do not do any towing, but the thing hauls ass now. And only lost a couple miles to the gallon as far as fuel mileage goes. The only downside was I did have to replace the transmission and the rear end afterwards (they were just old and tired and couldn't handle that much engine). But I still don't regret going with the 383. An LS conversion would get better mileage though.

I do not see how a LS would get better mileage. Never once have I seen it in the real world, the 5.3Ls tend to drink gas in a heavier vehicle and towing. Towing heavier or even just driving around the 6.0L 2500/3500 NBS trucks are thirstier than the same truck with an 8.1L.

My 383 has gotten the best of 20.6 mpg running 70-75 mph in a 7,000 lbs van. The 383 does not have to rev to move the weight. Even towing 8,000 lbs up a slight grade it is in overdrive. Towing a lighter ~3,000 lbs full loaded utility trailer, I can keep it under 2,500 rpm, still accelerate well, get to speed and roll 80 mph without once getting over 2,500 rpm.

The 383 big gain is not so much the HP. I can build a 350 to make as much hp as my 383, but the 350 is not coming close to the low-speed torque.

I also had a L31 in a factory Mexican NBS Tahoe with a factory 5spd in it. That Tahoe was better on fuel than the 5.3/4L60E equivalent ever thought about being.

 

[langkg]

I have a Smeding Hot Rod 383 in my '94 RCLB K1500. It was dyno'd by Smeding at 425 hp / 475 lb-ft and moves the old gal very nicely with 3.73's and a Detroit Truetrac diff. Transmission is a 4L60E built by PerformaBuilt Transmissions and I'm running a FTI convertor (2300 stall if I remember correctly). I ditched the GM TBI and am running Holley Sniper 1 and using the ECU to operate the transmission. I will likely go to the new Holley Sniper trans controller.

That said, it's a blast to drive but no way would I tow with it with the 2300 stall. I use the truck as a bit of a red neck hot rod for occasional off road, hunting, screwing around, cruising, etc. If I wanted a capable tow beast, I'd just buy a newer 2500 with a stock LS and never look back. I think you'll end up spending just as much money with the route your thinking about and it won't be as reliable as a newer stock truck. So, if you want a toy like what I have then by all means go 383 as it'll put a smile on your face but it sounds like you're after more of a DD / working truck and I'd just upgrade to something newer if I were in your shoes.

 

[L31MaxExpress]

I have a Smeding Hot Rod 383 in my '94 RCLB K1500. It was dyno'd by Smeding at 425 hp / 475 lb-ft and moves the old gal very nicely with 3.73's and a Detroit Truetrac diff. Transmission is a 4L60E built by PerformaBuilt Transmissions and I'm running a FTI convertor (2300 stall if I remember correctly). I ditched the GM TBI and am running Holley Sniper 1 and using the ECU to operate the transmission. I will likely go to the new Holley Sniper trans controller.

That said, it's a blast to drive but no way would I tow with it with the 2300 stall. I use the truck as a bit of a red neck hot rod for occasional off road, hunting, screwing around, cruising, etc. If I wanted a capable tow beast, I'd just buy a newer 2500 with a stock LS and never look back. I think you'll end up spending just as much money with the route your thinking about and it won't be as reliable as a newer stock truck. So, if you want a toy like what I have then by all means go 383 as it'll put a smile on your face but it sounds like you're after more of a DD / working truck and I'd just upgrade to something newer if I were in your shoes.

I tow with a converter that flashes 2,900 rpm without issue. I prefer having a looser converter towing, the tighter they are the worse they tow in my experince.

 

[94_Z71]

I've had one in my truck for a couple of years now and I love it. It has transformed that truck from underpowered to super-powered. The stock Vortec fuel system can support at or a little above 400 HP. So I had mine built for 450. The only downside was I had to replace the rear end and the transmission, as they were both pretty tired components and they just couldn't handle the power of that new engine. Have not had a drivetrain related problem since the first 90 days. I don't however haul any trailers. But I'm absolutely sure it would pull just about anything you wanted to. As far as gas mileage goes, you're looking at losing two miles per gallon. At least mine does. That's if you can keep your foot off of it!

PS You do know you can use the block that's in it, right? It just has to be machined to give the new piston bolts clearance and such. That would keep the truck numbers matching too.

 

[Mbosse]

I've had one in my truck for a couple of years now and I love it. It has transformed that truck from underpowered to super-powered. The stock Vortec fuel system can support at or a little above 400 HP. So I had mine built for 450. The only downside was I had to replace the rear end and the transmission, as they were both pretty tired components and they just couldn't handle the power of that new engine. Have not had a drivetrain related problem since the first 90 days. I don't however haul any trailers. But I'm absolutely sure it would pull just about anything you wanted to. As far as gas mileage goes, you're looking at losing two miles per gallon. At least mine does. That's if you can keep your foot off of it!

PS You do know you can use the block that's in it, right? It just has to be machined to give the new piston bolts clearance and such. That would keep the truck numbers matching too.

Yes but my local shop is very expensive and I’m sure it would end up costing more