Anyone have a LS swapped 3+3?

[AaronW]

IMO, assuming carb is tuned properly and the TBI is working properly for this comparison you'll get most of your MPG improvements with the extra gear in the transmission. I personally thing the MPG difference between an properly tuned carb and a properly operating TBI is very minimal.

Thanks for the opinion. I'll pass that on to my machinist fried who rebuilt the engine. Is there another thread here where people have real-world comparison like this? If not, I should start one.

 

[Camar068]

from what I've read, the 8.1 swap w/allison.....you'll have the power, but not any gas mileage. That along with it not being that popular in the after-market community, sorry but good luck. Please prove me wrong, I've got access to both in my price range.

 

[KnockingDiesel]

Only issue I would see with the LS 8.1 is that the engine wasn't around long. Does that impact parts availability at all? Otherwise, awesome choice of powertrain combo

from what I've read, the 8.1 swap w/allison.....you'll have the power, but not any gas mileage. That along with it not being that popular in the after-market community, sorry but good luck. Please prove me wrong, I've got access to both in my price range.

While short lived in trucks the 8.1 had lots of industrial and marine applications so parts are available.

Howell makes a direct stand alone harness for the 8.1/Allison not listed on their site (I called in and asked) for $750-$850 which is the easiest route. It’s 4 wire with the option Cruise Control which is why I want it

Adavance adapters makes a kit for the Allison 1000 to NP 205 $800

For cam options BBC GEN 6 swap in but require a reprogramming of the ECU/firing order. There are 8.1 specific cams available also.

Raylar Engineering makes performance stuff for this engine like aluminum heads and intakes. Although expensive it’s available.

While not a popular option for sure it’s not impossible to fit it in this truck. I could swap a 4l80 behind it and not cut the floor.

I wanted a power train that wouldn’t be near its limit with the truck empty. If it was a 2 door 1 ton or 3/4 ton 2wd 6.0 or even 5.3 would be fine.

This truck with the 454/th400 and 4.56 gears had GCVW of 17,000 so the chassis is stout and though I don’t see towing 10k all day long the 8.1/A1000 had a GCWR of 21,000. So I won’t lose the utility of the truck.

I wanted GM EFI for reliability and usability, the 8.1 had 340hp and 460 Ft lbs stock. Family trips with my 2 young boys and wife would be a lot more pleasant with a vehicle capable of 75 mph at 2300 rpm. I am building a truck I can use instead of buying one for $60k +.

As far as fuel economy, crew cab, long bed duallies with 4wd, suck. I’ve owned lots of trucks in diesel and gas. At 75mph 11-12 mpg diesel and 9-10mpg gas, going from Albuquerque to Denver/Cheyenne/Billings is all I’ve ever got. Slowing to 65mph improves mpg but I’m not interested.

I’d have loved a Cummins swap but noise was partly why I didn’t. I have a 7.3 powerstroke cclb drw 4x4 cost of fuel and maintenance is another.

Over all my engines were the vortec 7400 (gen 6 454), the vortec 8100 (“gen 7” 496) and the L8T. I really thought about the 6.0 L96/6l90 and if I was going for just cruising I woulda tried it. But I was just worried that 380 pounds of torque at 4200 RPMs would have been too high in the powerband (stock 454 was 380 lbs at 1500 rpm).

This is not ”THE POWERTRAIN” for everyone but it’s what I think will work best for me. Well see how it goes but I’m pretty confident it’ll be in there a while.

This is my dream truck so I’m taking my time with it. Progress will be slow but be made. Thanks for reading, happy holidays

 

[KnockingDiesel]

I came across this information while surfing the web

You must be registered for see images attach

You must be registered for see images attach

 

[Old77]

While short lived in trucks the 8.1 had lots of industrial and marine applications so parts are available.

Howell makes a direct stand alone harness for the 8.1/Allison not listed on their site (I called in and asked) for $750-$850 which is the easiest route. It’s 4 wire with the option Cruise Control which is why I want it

Adavance adapters makes a kit for the Allison 1000 to NP 205 $800

For cam options BBC GEN 6 swap in but require a reprogramming of the ECU/firing order. There are 8.1 specific cams available also.

Raylar Engineering makes performance stuff for this engine like aluminum heads and intakes. Although expensive it’s available.

While not a popular option for sure it’s not impossible to fit it in this truck. I could swap a 4l80 behind it and not cut the floor.

I wanted a power train that wouldn’t be near its limit with the truck empty. If it was a 2 door 1 ton or 3/4 ton 2wd 6.0 or even 5.3 would be fine.

This truck with the 454/th400 and 4.56 gears had GCVW of 17,000 so the chassis is stout and though I don’t see towing 10k all day long the 8.1/A1000 had a GCWR of 21,000. So I won’t lose the utility of the truck.

I wanted GM EFI for reliability and usability, the 8.1 had 340hp and 460 Ft lbs stock. Family trips with my 2 young boys and wife would be a lot more pleasant with a vehicle capable of 75 mph at 2300 rpm. I am building a truck I can use instead of buying one for $60k +.

As far as fuel economy, crew cab, long bed duallies with 4wd, suck. I’ve owned lots of trucks in diesel and gas. At 75mph 11-12 mpg diesel and 9-10mpg gas, going from Albuquerque to Denver/Cheyenne/Billings is all I’ve ever got. Slowing to 65mph improves mpg but I’m not interested.

I’d have loved a Cummins swap but noise was partly why I didn’t. I have a 7.3 powerstroke cclb drw 4x4 cost of fuel and maintenance is another.

Over all my engines were the vortec 7400 (gen 6 454), the vortec 8100 (“gen 7” 496) and the L8T. I really thought about the 6.0 L96/6l90 and if I was going for just cruising I woulda tried it. But I was just worried that 380 pounds of torque at 4200 RPMs would have been too high in the powerband (stock 454 was 380 lbs at 1500 rpm).

This is not ”THE POWERTRAIN” for everyone but it’s what I think will work best for me. Well see how it goes but I’m pretty confident it’ll be in there a while.

This is my dream truck so I’m taking my time with it. Progress will be slow but be made. Thanks for reading, happy holidays

You've certainly done your homework. Looking forward to seeing it progress! Please continue keeping the thread updated regardless of how slow progress is

 

[KnockingDiesel]

You've certainly done your homework. Looking forward to seeing it progress! Please continue keeping the thread updated regardless of how slow progress is

I will, I have always wanted a square body cclb drw 4x4, so I’ll take my time to make it exactly like I want.

 

[Old77]

I will, I have always wanted a square body cclb drw 4x4, so I’ll take my time to make it exactly like I want.

Absolutely agree!!! LOVE my 91 cclb drw!! She's a keeper and I'm doing the same as far as making it exactly what I want

 

[MuffinMan]

I'm looking at doing an L8T swap with 6l90 or 8l90 transmission.

Any clearance problems on the C30 front cross member with swapping in a LT engine?
What about tunnel clearance problems with these huge transmissions? I can't seem to find if C30's came with high rise tunnels or not for automatics.

 

[1lejohn]

I'm glad to see that others are finally realizing that the Holley Sniper is one great big ole POS like I have been saying for years. I have posted about my experience with it so I'll leave it at that. On the other hand, I went back to Edelbrock Pro Flo, a true port EFI that uses 100% GM parts except for the ECU. I have been extremely happy with it and had zero issues. Not to derail the topic but I, and others I know, have had similar experience with FiTech. It just seems TBI and the concept of putting the electronics on top of the engine was not the best idea.

The Eddy system has gone up in price about 600 to 700 over the last few years. I was planning on running it, bought a new fuel tank sending unit, and pump. I just can't justify the cost for now.