454/TH400 swap for 6.0/4L80 or 6L80. Who's done it? Glad you did?

[bigoilman]

I just bought a 1977 Camper Special C30 Dually. It's freshly restored and has a fresh motor and trans (both stock). I have a complete 6.0 (whole truck minus transmission actually) that I bought, planning to do this swap. Now I'm having people try to talk me into keeping the big block. I can put a 4L80 behind it to help the mpg. A stand alone EFI system would help too. None of that's cheap and I'm not sure I wouldn't be better served long-term by the LS swap.

BTW, IV done an LS install before. My '36 Chevy has a 5.3/4L60e in it.

Please, only respond if you have knowledge of the results AFTER completing the swap and driving it for a while. I do still have to pull my boat with this truck (#8000).

Thanks

[kdh454]

I have a 75 crew cab dually and contemplated the same. I ended up keeping the big block, but converted it to EFI with a Holley Terminator system and swapped the TH400 for a 4L80E. I chose that route not for practicality, performance or expense, but primarily because I wanted to retain as much of the stock look as I could. With the proliferation of LS swaps, hardly anyone takes notice anymore.

In the end, I spent about as much as a decent salvaged 6.0/4L80E swap would cost. Performance and mileage is probably close as well.

Similar to you, I have a Jeep with a 5.3/4L60E. It drives great, has more power than it needs, and was a pretty easy swap. It was just not what I wanted for the truck.

If you have driven or own a 6.0 truck, you should already have a pretty good idea how it will perform, which is very well.

[bigoilman]

Thanks! That's exactly the sort of info I'm looking for. I have a 2005 1500HD with the 6.0. It's lifted and has 35s on it but hasn't been regeared. Gets about 11mpg.

[tucsonjwt]

I don't know about the LS swap, but the only advantage I see is the more reliable FI engine. I have an 83 C20 Camper Special Regular Cab Long Bed with 454 and SM465. My best mpg has been 11 city/13 highway with the stock Qjet. IMHO, once you get into a 3/4 ton or up truck you can forget about good mpg, unless you have a diesel, which brings along other diesel related complications.

[meatwagon83]

I was going to do it, I even had all the parts, but when I read up on the kind of milage I would be getting I changed my mind, I rebuilt my 454 with an eye to efficiency and I'm pretty happy with it, and it was a lot cheaper than doing the ls swap, I'm getting 12.6 put of mine now with a 454/th400/dana 70 HD 373 combo, next weekend the nv4500 swap starts, that should put me at 16 or 17 on the highway

[GRADYS Performance]

I would stay with the 454 and swap to the 4L80E. The towing power of the 454 with the 8000# load would be my choice. You could update the fuel system at any time to FI to help the mileage even more. I did my 85 Suburban 3/4 ton 454 4L80E 3.73 235/85/16 and am very pleased compared to the TH400. I have a post about the swap in the Suburban section.

[bilfman]

I have done and driven my 454 4l80e swap for a few years and will definitely be going to a LS swap. The monitoring of air fuel and timing while towing keeps your beast in a much stabler power curve. Old tech is ok, but the LS has it beat.

[Nodnarb76]

I just completed this swap on my 3/4 Ton 87 Suburban. Truck came with a
454/TH400 Combo and I swapped the LQ4/4L80 into it.
Here is my build thread:
http://67-72chevytrucks.com/vboard/s...d.php?t=693824

The 454 I had in it was tired and worn out. It was way down on power and got horrible gas mileage. I'm getting about 14mph average now and the extra power is great!
My truck is my daily driver, and I put about 70 miles per day on it, so the goal of my swap was bulletproof reliability over power/speed.

[foamypirate]

Not sure if I'm allowed, since my 88' R20 crewcab had a 350/TH400 combo, but I'll chime in anyway...

I have an LQ9 6.0L and 4L80E swapped into mine, and it is AWESOME. Tons of power, good mileage, reliable; it just flat works. I've been averaging about 13-14mpg running around town, and cruising 65-70mph actually nets me about 17-19mpg, which I was NOT expecting at all. I figured I might get 15mpg, tops. I do have 4.10 gears and 235/85/16s, so tall and skinny. It seems to be the sweet spot for mileage between the lower rolling resistance and RPMs. Unfortunately, I haven't yet had a chance to pull with it, but I couldn't be happier with what I've experienced so far.

The primary difference that I can see, is where you make the power. The big block will be more "relaxed" when pulling a heavy load, where the 6.0L will need some RPMs to get it moving. That's not necessarily a bad thing, just different than what some people are used to, and I think it freaks them out a little bit in some cases. Geared appropriately, I don't think you'll be disappointed with the 6.0L/4L80E combo. If you are...well, there is always an 8.1L/4L80E swap.

[bigoilman]

Some great first-hand, real world info here! Exactly what I was hoping for. I'm still not sure which way I'll go but I'm leaning toward the 6.0 since I just got a complete truck for free (after selling what I won't use). I'd have to buy an OD transmission either way so that's a wash. Adding EFI to the 454 will cost about what the stock 6.0 rebuild costs. Plus, this motor and trans only has about 1000 miles on it so I should be able to sell it. I'd really like the original look but you can't have everything. We'll see.

[bigoilman]

Soooo...let's take it a step further. Anyone seen a 6L80e or 6L90e behind either motor in one of these trucks. Or maybe a link to a build thread where it was done?

[bilfman]

I have not heard good things about the durability of the 6L's. Extreme off road did an episode and totally recommended the 4L over the 6L. Ian knows his @"&) so I would put some weight behind his/their suggestion/research.

[GRADYS Performance]

Part of the motor decision depends on what you are doing with the truck. Daily driver and or light towing then the LS series motor would be ideal. If you are just using the truck to pull Heavy loads, which 8K leans more towards a heavy load then the 454 or 8.1L is the motor to get the job done. A daily driver with once in a while pulling 8K then using the LS would be OK. Build it for what YOU want and expect to do with it 90 percent of the time.

[bigoilman]

Originally Posted by GRADYS Performance

Part of the motor decision depends on what you are doing with the truck. Daily driver and or light towing then the LS series motor would be ideal. If you are just using the truck to pull Heavy loads, which 8K leans more towards a heavy load then the 454 or 8.1L is the motor to get the job done. A daily driver with once in a while pulling 8K then using the LS would be OK. Build it for what YOU want and expect to do with it 90 percent of the time.

That's the reason I'm leaning toward the LS. I have the exact same setup in my daily driver now (1500HD Crew Cab 4X4). I pull the boat mostly short distances (less than 5 miles) every other weekend in the Spring and Summer. That's it's only work duty. The rest of the time it's my daily with 250-300 miles/week of driving.

[MalibuSSwagon]

Have you put any miles on the C30 yet to see what it'll do? Be good to get a baseline feel for it before you rip it apart. I specifically tracked down and bought a 99 Vortec 454 Suburban as I wanted something that would not struggle with a heavy load. Seems the 6.0L trucks get similar mileage loaded and struggle more than the big block. Plus I wasn't worried about MPG much as it won't be my DD, I have a 5.3L C10 that gets 20MPG everyday.

[bigoilman]

I've put about 300 on it so far. Made a concentrated effort to drive slow (55 and less) and got 9.09 mpg. There is probably a little mpg to be had with a little tuning but that's the baseline number. It's my DD. If I can just get it better than my 1500HD, I'll be pretty happy. It gets 11mpg.

[MalibuSSwagon]

Ouch yea thats no good. I'm getting 10-12 now with my Sub, but I gotta replace an o2 sensor.

[GRADYS Performance]

The Dually will not get as good of mileage as the Suburban. More weight and rolling resistance.