Building a K20 Burb to do some towing, overlanding, cross country travel, wondering what you guys would build to throw in there? My options are the following;

1. 5.3 or 6.0L with a 2300 or 2650 PD Blower on top.
2. 496 Big Block, AFR headed, fuel Injected 9.1 compression (run on 87oct)

The LS (at least the 5.3) would get significantly better MPG unloaded, probably similar loaded, but requires 93 oct. The LS would probably make the same power down low, but obviously much more power up top.

The 496 should be making 650 ft lbs and 480-500hp, but down by 5500rpm which is fine. The 496 will be completely forged rotating assembly, so I could throw a blower or turbo on it later. I have both the big block and 6.0 in the garage (would need to buy a 5.3, but thats not a big deal). For either LS Id need to buy the blower and my big block right now is a 468, so Id need to put a new bottom end in it.

Id be towing a 21' travel trailer, while only 21' is a heavy girl, loaded out its about 8k. I just towed it cross country with my 19' 3500 Ram w/ Cummins and average about 7.5-8.5 mpg . That being said Im willing to bet both gas motors would be roughly the same in fuel efficiency, but cheaper fuel, especially the big block. Either motor gets a 4l80e behind it, with the LS Id run a Holley to control both engine and tranny, but the big block would need a controller for the tranny, so cost isnt to far off.

Also, not interested in turboing the LS.

So if you were building the Burb, what would you do?

 

Towing 8k with a big block and expecting near 500HP, using 87 octane seems a bit unrealistic no?

 

not really. My 496 puts down about 500-550 hp. But I recommend 91-93 octane. Big blocks love gas. Realistically a built LS will get you there more efficiently

 

9.1 compression, low 30* timing, decent size cam to help with cylinder psi bleed off, aluminum heads with an efficient chamber, no not at all.

 

For a 3/4 ton burb, heavy towing, off roading, I think the low end torque should be the priority over the fuel economy. You can buy more gas when you need it. If multiple tunes is an option, for 87 when just cross country with no load. 91 or 93 when you can use it. Especially if you already have one sitting there. I would think a 5.3 in a 3/4 ton burb would get bad mileage no matter what, and be even worse with torque and mpg when loaded than a BB.

FYI, I'm trying to upgrade from rarely know what I'm talking about to occasionally.

 

Either way I'd run a holley to run the big block or LS and transmission.
Big block would be more simple and probably a decent amount cheaper than a PD blower on a LS? Blower would be 7k minimum?

my brother's 18 cummins got terrible fuel mileage towing before we removed some parts off it. Then it gained almost 5mpg towing the same trailer and 8mpg empty.

But them trucks are expensive haha.
I've towed a bunch with a turbo 6.0 and have no complaints or issues with over 330,000 miles on that setup.

I've tuned some trucks with 454 and 496 big blocks with EFI and they are pretty impressive. But they got terrible mileage empty. The 496 truck we ended up doing a turbo 5.3 and it got over double the mileage and was much more enjoyable to drive.

Have no experience with a twin screw so I'm no help there except if you go that route, carry spare belt and tensioner. Several of my buddys always seem to loose the belt and spring the tensioner at the worst possible time.

What about a 12 or 24 valve cummins?

 

with 9:1 compression, what cylinder pressure are you trying to bleed off? that big block ain't no high-strung boost build.
if you're staying N/A, i'd recommend another 1/2pt compression if you want to run 87 & a stock-ish cam. a bigger cam with a little more overlap can bump it up a little further with the same safety.

from what i understand, it's ultimately the dynamic ratio you want to target when determining your fuel/timing constraints.

mmm... in almost a dozen years with my TVS LS1, i've only shredded one belt - and that's because it was too loose & jumped a couple ribs.

 

5 years never shredded a belt unless my water pump pulley was being a bitch. Lol. I'd go blown LS for reliability and lots of power and efficency.

 

How doesnt Murphy not visit yall?

 

Is the 496 the same as the early 2000s 8.1 Vortec?

What about putting a blower on the 6.0, if you already have it?

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