8.1 Vortec 496 Gas Or 5.9 Cummins Diesel For A 1983 C20 4 Door Dually With A Turbo 400 3 Speed Auto

[Blackandgold26]

For a 1983 C20 Dually 4 door with a 4:10 Gear Ratio, 454 Carburated engine, and Turbo 400 3 Speed Automatic Transmission. I'm trying to figure out what is the better engine choice out of a Cummins 5.9 Diesel or a 496 8.1 Vortec?



The current engine such as the 454 has a light knock to it which i want to go with an updated engine with fuel injection, or if not a 496 Vortec then maybe a 454 Vortec. Along with decent if not decent MPGs and for heavy hauling.



I know Cummins is the choice however. Althought for less the 496 is the choice and i heard it is simple to swap



I forgot to mention the tire size is 245/90/r16s with 4:10s, i dont drive fast past the speed limit by the way along with being light on the throttle on acceleration, and Unleaded Fuel here in Louisiana including New Orleans is less than diesel

 

[Arkansas_V8]

The 496 doesn’t have much of an aftermarket.

So if you plan on doing more after the swap, then the 5.9 is the way to go.

 

[Frankenchevy]

Keep in mind the engine speed of a stock-stockish Cummins coupled with 4.10s and the 1:1 final drive ratio of the th400(less viscous losses). You’ll be doing 2500rpm just to go 60mph. On a stock 12v there isn’t much rpm past that.

 

[Crispy]

x2 on the trans gearing if you go cummins but the adapter for a gm trans is wasted money imo if its a 2wd. Get a 47rh behind it and budget for upgrades on that. If you are going to haul consistently then the diesel is the way to go. Its gonna cost you more upfront and maybe overall. You will probably never "break even" on the swap but im sure thats not the reason behind it.

Not sure whats involved with mounting a newer 8.1 where a big block sat but the cummins will require a new cross member, maybe some plating of the frame and maybe some other stuff. I looked into it and said screw it, I knew I would never be done getting it in. The cummins should be a simple swap to wire and plumb where the 8.1 is probably more like an ls swap with the fueling and wiring requirements.

 

[bucket]

For cost, simplicity and also good power... stick with a big block, imho. An 8.1 is comparable in power to a stock Duramax. You can compare that to a Cummins however you like, I'm not wanting to start a whole other topic out of this, lol.

 

[jjester6000]

Maybe you should rebuild the 454 and stroke it to a 489 or maybe get a 502. That would probably be the cheapest option if you want a bigger motor than the 454.

 

[Dutch Rutter]

Everything I've read about the 8.1 swap is that it's pretty straight forward for bolting in. Fits the same as a 454. I think they can even use the same headers.

This guy DirtyLarry who is all over some other forums did it and has ALOT of detail on how he did it and things he ran into. He is also running a GM nv4500 and a np205 I believe.

Here is one of his posts. http://67-72chevytrucks.com/vboard/showthread.php?t=298696

 

[bucket]

Maybe you should rebuild the 454 and stroke it to a 489 or maybe get a 502. That would probably be the cheapest option if you want a bigger motor than the 454.

An 8.1 can be purchased for a lot less than a rebuild with a stroker kit. The whole swap would likely cost less than a stroker build.

 

[Vbb199]

As you may already know, the 5.9 you'll need an adapter for if you're going to run the th400.

imo, if you're gonna do the 5.9, look for a Dodge Nv4500 to run behind it. You can have your OD so the motor won't be screaming in 3rd gear with thr th400... Again as you already know, a Cummins has a limited rpm range.

A stock 496 kinda has the attributes of a diesel, low rpm torque curve, falls on its ass after certain rpm range. You'll have to consider the firewall clearance, radiator choice to clear the 5.9 etc etc, and possibly some frame notching to clear one of the accessories on the serp system (I think)

I did some reading into this myself for my k5, it was gonna be a 24v or a 502ci.

I went with the 502ci and have holley efi on top.

The 496 you can find yourself aftermarket heads and cam for and make some decent power.
Around here, seems like a 8.1 and a 5.9 run you about the same for a used engine, don't know what your budget is, but obviously the less work of the 2 is the gasser... But I'm just biased towards gasoline engines anyway

 

[Vbb199]

Might I add, a stock 8.1 is gonna outperform the typical stock 12v. And additionally, with that 8.1, it's simple drop in and go, you can save the money you was gonna spend to make that Cummins work in the truck on a good set of aftermarket heads and cam.... That's all I've got for now.

 

[Craig 85]

I've had numerous 454 trucks and a couple 8.1's. I definitely liked the power of the 8.1. I preferred the Allison behind it over the 4L80 I had in the Suburban. Mileage for the 8.1 was about 12 MPG max with 4.10's. RPM wise, the stock power maxed out at about 4000. With an cold air set up and a chip it bumped to 4500 RPM before it fell on it's face.

It had plenty of power towing my 30' travel trailer. Many times I would find myself gaining speed passing people going up hill.

 

[Catbox]

I would go with rebuilding the 454 to what you want it to be.
There is not much aftermarket stuff for the 8.1 and if you want that size for what ever reason you can still stroke it like mentioned above.

I have a Vortec 7400 big block I picked up from the junkyard and it should be easy to make it a monster for pulling or high horsepower as the traditional aftermarket parts fit it for the most part.

I plan on a simple rebuild on my engine with the addition of a cam from the 502 engine.
The compression ratio is already 9.4 to 1 and the cam is pretty much as big as you can go with the stock heads.
Should be plenty of fun for whatever it gets put into.

 

[bucket]

I would go with rebuilding the 454 to what you want it to be.
There is not much aftermarket stuff for the 8.1 and if you want that size for what ever reason you can still stroke it like mentioned above.

I have a Vortec 7400 big block I picked up from the junkyard and it should be easy to make it a monster for pulling or high horsepower as the traditional aftermarket parts fit it for the most part.

I plan on a simple rebuild on my engine with the addition of a cam from the 502 engine.
The compression ratio is already 9.4 to 1 and the cam is pretty much as big as you can go with the stock heads.
Should be plenty of fun for whatever it gets put into.

The beauty of an 8.1 is they make very respectable power in stock form and getting the tune done should be easy since it's similar to the extremely common LS. Looking at Car-Part.com, you can get them for as little as 1200 bucks. I actually did not realize how cheap they are these days... it's making me want to swap one in myself.

But yeah, there's not a ton of aftermarket support so if the goal is monster power levels, building an earlier big block would make more sense.

 

[80BrownK10]

The beauty of an 8.1 is they make very respectable power in stock form and getting the tune done should be easy since it's similar to the extremely common LS. Looking at Car-Part.com, you can get them for as little as 1200 bucks. I actually did not realize how cheap they are these days... it's making me want to swap one in myself.

But yeah, there's not a ton of aftermarket support so if the goal is monster power levels, building an earlier big block would make more sense.

Your not going to touch a Cummins for $1200 unless it's grenaded! Haha

 

[Shorty81]

I would go with rebuilding the 454 to what you want it to be.
There is not much aftermarket stuff for the 8.1 and if you want that size for what ever reason you can still stroke it like mentioned above.

I have a Vortec 7400 big block I picked up from the junkyard and it should be easy to make it a monster for pulling or high horsepower as the traditional aftermarket parts fit it for the most part.

I plan on a simple rebuild on my engine with the addition of a cam from the 502 engine.
The compression ratio is already 9.4 to 1 and the cam is pretty much as big as you can go with the stock heads.
Should be plenty of fun for whatever it gets put into.

I have old school 496. Makes loads of torque.

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