Agreed, I think low MPG isn't practical in these trucks. If that is the only consideration, a 6.2L diesel might get the best results. Just don't be in a hurry to get anywhere.
100% agree
CK5
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Military Crew Cab Build-Cummins swap.
- Thread starter Cruz89K5
- Start date
100% agree
The pump is an EP381 pump...same one I used. Was for a 97 Tahoe that fits inside a TBI tank hanger (same dimensions of a TBI pump) but puts out the necessary ~60 psi needed for LS or aftermarket EFI
It'll hit 90psi if you have a kinked return line.
It'll hit 90psi if you have a kinked return line.
Haha, I remember you telling me about that. I think I remember Larry said his hit 100 psi cause he had too small and restrictive of a return line on when he first did his 8.1 swap on his K10. Crazy
454Sub
5/8 ton status
One thing to consider is the 6.0 has about 20-30 more HP than a 5.3. The cost differences in them is rediculous considering that.
A cam swapped 5.3 will spank a 6.0s booty raw as a fresh caught fish.
A cam swapped 5.3 will spank a 6.0s booty raw as a fresh caught fish.
NA 5.3's are gutless in a heavy truck.
On the highway 5mpg is a common number and the truck doesnt like 75mph. I drive it a few days a week around town and to work here and there. I have 4 other trucks and a car, so this is just something I drive for pleasure. The long term goal is driver quality repaint, some modern convenience, and a 24v or CR Cummins with a 6 speed for a daily driver. But I think thats at least 5 years off and I'd just like to make it more enjoyable and reliable for short to medium trips now. Maybe even haul the RZR around with it a bit. 10MPG would be nice. Drivability and reliability would be the goal. I do not care for the 8.1, it is not on my list of considerations. Two of my good friends have them, abysmal mpg and not much better running than my 6.0 unloaded. Loaded would be a different story, but I have a diesel tow rig for anything heavy.
Freshening up the big block has been tossed around, and honestly it isnt as tired as I say it is. It does have a mild cam, headers, and an intake. A new carb wouldnt hurt it, but it runs decent as is. I've been talking with a few of my coworkers and they're pushing in the EFI direction over the LS swap and they're starting to sway me. It is much easier to run what you already have.
Of course I'm bias, the LQ4 in my SAS truck has given me over 30k miles of trouble free use on a big tire with a lot of abuse. It's taken me out of state, 11 hour round trip. I've used it for a daily driver. Its taken me 3 hours at 80mph with a quad in the bed, wheeled in the dunes all weekend, and came home with zero trouble. With 184k on the clock I'd drive it anywhere. The 100k mile LS6 in my DD sees at 6k between shifts several times a day without a single complaint. I just turn the key and go.
I'm not sure the old big block could ever be so trouble free, and that's my only hang up with keeping the BBC. Really, the EFI swap isnt the issue. From what I read it seems great. Frankly, I want the old truck with minimal electronics with modern efi reliability. I'm tired of always having to tweak the carb or seal a leak or worry about spinning it 2600rpm on the way to work.
cam swap and EFI
Thanks for the real world info on the sniper, I've enjoyed following your build. The truck had a blazer tank at one time, and I plan to go back to one, so finding a baffled one wouldnt be difficult. I had considered putting my other saddle tank in as well, so that's where the baffled question came in. Mine has a military data tag on the roof, and I believe the curb weight stamped into it is 6800 pounds. It was a 6.2 dually truck at one time. I'll double check the weight and correct if I'm off. I would like scale it one day as it sits to know for sure. I hadnt thought about the fuel system being the same if I wasnt satisfied with the 454. Thanks for making good points, this is exactly the kind of knowledge I was expecting.
Just keep the 454 and do aftermarket EFI on it...from the sounds of it, it will probably suit your immediate needs just fine. At least until you want to do the cummins swap
And just as a side note, I've heard everything under the sun by now of why people hate on the 8.1. 9 times out of 10 I've found it's because the user has unrealistic expectations out of what the motor will give them in stock form (especially in regards to mpg's). It's almost become laughable to me at this point. To each their own I guess
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I'm leaning that direction more and more. I know it'll be much simpler to modify what I already have vs sourcing something else. And I'm not wanting to deal with another part out. Buyers wear me out.
I do not hate the 8.1. I would have liked an 8.1 in place of the 454 in my RV. Cant afford a diesel pusher, and I missed the 8.1 by a year. But for a pickup if I'm going to tow I'm skipping gas, so the LS powerband doesnt bother me for my intended use. The stock LS6 in my CTSV makes 50 ft pounds less than an 8.1 and has a gigantic aftermarket. The 8.1 doesnt make sense for me.
And its the comparison a lot of owners make to diesel power that really turned me off of the 8.1. My Dodge made over double the 8.1 torque with just tuning, and does 14 to 16 all day long unloaded and would haul my dozer at 80 without breaking a sweat. The one ton 8.1 I'm familiar with doesnt like hauling my 6500 lb 32' trailer with a few joints of pipe on it. It is a shame you have to buy a dodge to get a manual trans and a solid axle though.
Honestly, the only reason I used the EFI stuff is cause it came with the engine I bought for my chevelle.
If you're planning on a cummins swap then I wouldn't spend the money on EFI I'd just tune the carb properly, buy an electric fuel pump (for easy fast starts) and do an NV4500 swap. That way you'll already have the trans you need for the cummins and can enjoy overdrive and less RPM for now with the big block.
I was planning a cummins swap on mine as well but I've been eyeing the duramax swap also, and for me they'd be about the same cost cause I'd be using a 6.7 CR cummins.
If you're planning on a cummins swap then I wouldn't spend the money on EFI I'd just tune the carb properly, buy an electric fuel pump (for easy fast starts) and do an NV4500 swap. That way you'll already have the trans you need for the cummins and can enjoy overdrive and less RPM for now with the big block.
I was planning a cummins swap on mine as well but I've been eyeing the duramax swap also, and for me they'd be about the same cost cause I'd be using a 6.7 CR cummins.
Vombrown
Mountain Man
Well known and often lamented that I am a diesel guy through and through.... I always lean to the cummins but sometimes ya just want to do something different. I'm putting a big block in my k-20 and will eventually add fuel injection to it. For me a gas engine is way out of the norm but in my honest opinion the only thing you loose by keeping the big block over a stock cummins is fuel mileage. Torque numbers are close comparing apples to apples. Most stock cummins engines are in the 20 mpg range and a big block with good tuning will see 12-15. However I will say the one thing he big block has over th diesel is RPM. If you need wheel speed (mud, snow, ICE) uphill climbs and stuff like that you'll love that big block again with a mild cam. I have a few diesels around here and the big block will be fun to have around.
Cold weather operation and maintenance costs are also a win with a gasser.
Vombrown
Mountain Man
That's especially true at my place! I have cords running all over for block heaters. Then again I would most likely do it for a gas motor as well. Nothing starts well in sub zero temps.
I’m gonna add my 2cents worth here..
like you I daily a ls powerplant.. the ls is hard to beat for daily duty, get in turn the key boom it starts every time and runs the same all the time.. super consistent..
now the towing or having a heavy rig I believe it would either need to be a big cid ls like a 6.2 to be worth a dang in anything north of 6500 heavier than that would automatically put you into bbc territory, just because of the nature of the torque curve.. you gotta shove a brick and you might as well use a hammer you don’t have to swing fast.. my l29 bbc in the burb I tuned and I am not sure what mpg (was getting 13mpg totally stock btw lifted it now ) it’s getting but it pulls great and with no hesitation will pass everyone on the hills around here 2500 ft and up.
But if you are going to tow heavy,(8500lbs+) id go diesel only if you are going to do that a lot, it doesn’t pay for itself if not, the big block will do it almost as easily and if you efi and cam swap one or boost it (omg who would do such a thing) then you torque offset is so much lower.. crap I am going to boost my 5.3 just for it to be more fun and tow better.
like you I daily a ls powerplant.. the ls is hard to beat for daily duty, get in turn the key boom it starts every time and runs the same all the time.. super consistent..
now the towing or having a heavy rig I believe it would either need to be a big cid ls like a 6.2 to be worth a dang in anything north of 6500 heavier than that would automatically put you into bbc territory, just because of the nature of the torque curve.. you gotta shove a brick and you might as well use a hammer you don’t have to swing fast.. my l29 bbc in the burb I tuned and I am not sure what mpg (was getting 13mpg totally stock btw lifted it now ) it’s getting but it pulls great and with no hesitation will pass everyone on the hills around here 2500 ft and up.
But if you are going to tow heavy,(8500lbs+) id go diesel only if you are going to do that a lot, it doesn’t pay for itself if not, the big block will do it almost as easily and if you efi and cam swap one or boost it (omg who would do such a thing) then you torque offset is so much lower.. crap I am going to boost my 5.3 just for it to be more fun and tow better.
Well we skipped a few steps and drug this home today. 347k, minimal blow by. Gotta figure out the trans situation as this one is an automatic. Probably just tune it up, reseal it and run it.
Nice purchase. It's all the rage.
It belonged to my dad. It spent 2 years in a battle with a transmission shop over warranty repair and unrequested labor cost. He finally got the truck back with a fresh "rebuild" and it wont move. So he text and asked if I wanted it. Hopefully I can find a deal on a 4500 and offset the cost of all of the other parts by selling the big block, 4 speed, and the rest of the dodge.
nice score! I ended up selling a lot of my donor truck and got the motor for free.
