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Anyone have an 8.1L in your Blazer?

colbystephens

colbystephens

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I am looking at a drivetrain swap right now, as my 200,000+ TBI engine is smoking pretty bad and I doubt I'll pass smog this month. If I can't pass smog, it's not that big of a deal, but I need a long-term plan to get this taken care of.

Russell and I have been talking about making a deal on his 8.1L/4L80E set up, and it is a really good deal that I likely don't want to pass up. So, I'm looking for feedback on what that would be like in my Blazer. Mostly, I'm interested in knowing the fuel mileage vs. a 5.3L swap.

I effectively have 6" of lift with 38" tires, 5.13 gears. When I did the Rubicon last month, I got 12.5 MPG with 4 people, a dog, a spare tire, and all our camping gear on the highway. Not bad for what it is, really. I was dreaming that with a 5.3L I'd end up somewhere around 15 MPG.

Either engine would have a massive boost in power compared to my tired 5.7L. Big block sounds cool, but I'm wondering if it's my best choice. The cost of the swap is similar to what a 5.3L would run me, but if I go with the 8.1L, I have Russell's extensive expertise - which is one of the biggest positive qualities of going to the 8.1L. When I'm finished with the swap, it needs to be factory-quality...
 
Don't get your hopes up too high for comparable mileage if you swap the BBC in. I've never heard of them getting over 10-12 mpg on the highway at all. Most averages were in the 7 mpg range, loaded or unloaded.
 
thatK30guy said:
Don't get your hopes up too high for comparable mileage if you swap the BBC in. I've never heard of them getting over 10-12 mpg on the highway at all. Most averages were in the 7 mpg range, loaded or unloaded.
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I've heard the same thing with the 8.1's. They are a bad A motor that will give you a lot of power and run really smooth, but fuel milage prob wont be there. You will have more luck with your setup with a 5.3 to get those mpg that you are looking for.
 
I'd talk to Larry.

Didn't he do some huge overland trip in his k10 and avg something ridiculous like 11mpg overall? That's pretty dang good IMO.



And I think he was talking about how the stock 8.1 tunes really limit them as far as power and fuel mileage go. And alot more can be had with better tuning
 
thing to remember is with a 5.3, you'll be needing to run it a little bit higher to get up and move the full load (comparitivly, i'm not saying the 5.3 couldn't handle it) where with all the torque of the BBC, it should be night and day. you'll get lower mileage, but I imagine it will stay flatter whether you're loaded and wheeling or driving around or what. I will say, having the big block in my suburban now as heavy as it is, I couldn't imagine going back to a small block in something so heavy loaded.

also, talk to Larry. he is the resident 8100 guru supreme.
 
Deuling said:
I'd talk to Larry.

Didn't he do some huge overland trip in his k10 and avg something ridiculous like 11mpg overall? That's pretty dang good IMO.



And I think he was talking about how the stock 8.1 tunes really limit them as far as power and fuel mileage go. And alot more can be had with better tuning
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Yea, Larry has done one if I recall too. He's in Pueblo West, CO if I recall.

I have the 8.1L in my Yukon XL. My mileage to Idaho towing the boat 7.5 MPG at 75 MPH or so. About a 4,000# boat. Coming back unloaded with just my wife and I (no boat) I hit about 11.5 MPG at 75 MPH. They are not known for being very efficient motors but they pull great!
 
Colby,

The 8.1 is a badass motor, but what do you need the power for? For someone like larry, who IIRC tows a lot, and puts a lot of miles on it, the 8.1 is probably better.

Do you have a need for the extra torque though?

You seem to drive pretty easy, and are concerned with fuel mileage, which makes me think the 5.3 may be a better bet.

Surprised the 6.0L isn't in the running, although, Larry is an EXCELLENT salesman on talking people out of the 6 and into the 8.
 
8.1 motor in a blazer.

Guy and his wife that ride bikes quite a bit. Also have a mileage car

GAS MILEAGE BE DAMNED ITS A BIG BLOCK


Doooooooooooo it :D:D:D:D:D:D:D:D
 
Eric - 99% of the time mileage essentially doesn't matter. There's amazing wheeling nearby, and my in-town work doesn't require more than about 20 miles of driving when I need the truck. So, you're right: between bicycles and our 50 MPG Jetta it doesn't really matter. But, the only real reason that I care about fuel mileage for the truck is that I want to do some 4wheeling in distant places: Alaska, Colorado, Utah, etc. I want to be able to afford to do those trips, and over that many miles a 5 MPG difference becomes fairly significant in cost.

dhcomp - I don't need the extra power, is what it boils down to. Working with Russell on this, both mechanically and financially, is the real reason I have an interest in it. And, if the mileage is similar, then this makes sense. If not, I guess it doesn't make sense. I'm certainly not going to be pulling any big trailers with a short-wheelbase truck with 6" lift and 38" tires...
 
i get 15.6 with the 8.1 allison all stock going 65 with 3.73 gears. at 75 i get 14-13mpg depending on wind.
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Downhill maybe.

I'm all for running a BBC but you do it for either one of two reasons: 1. Towing, or 2. Bragging rights.

I've been doing #2 for 17 years next month with my '85 K30. :waytogo:
 
Colby - I've had both the 5.3 and the 8.1 (silverado 1500 and a Suburban 2500) both 4x4.

I can get as high as 12 at 70 in the suburban with 4.10s with the 8.1 - I've hit over 20 mpg in the silverado with 3.23s.

If you want all the power you could ask for - and bragging rights - go with the 8.1, if you want any semblance of economy, go with the 5.3. I loved the 5.3 and for general wheeling I bet it would be a great choice.

I love my 8.1 for towing my trailer and just for driving around in a giant 3/4 ton suburban - but it is not anything close to being efficient. :)
 
Fubeca said:
Colby - I've had both the 5.3 and the 8.1 (silverado 1500 and a Suburban 2500) both 4x4.

I can get as high as 12 at 70 in the suburban with 4.10s with the 8.1 - I've hit over 20 mpg in the silverado with 3.23s.

If you want all the power you could ask for - and bragging rights - go with the 8.1, if you want any semblance of economy, go with the 5.3. I loved the 5.3 and for general wheeling I bet it would be a great choice.

I love my 8.1 for towing my trailer and just for driving around in a giant 3/4 ton suburban - but it is not anything close to being efficient. :)
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If I round up from my 11.5 mpg, I get 12 MPG too! :haha:

I have 3.73 gears in my suburban though. I will say though, it's a blast to drive!
 
hmmm, the first gen guys are really pushing me towards the dark side so if you pass on this I may have to give russel a holler myself. :)

but don't let me influence your decision. If you want the heavy gas guzzler you should go for it. :D
 
I love the 8.1 but I have nothing to say as far as the 4l80e goes behind it. When I worked at the shop we had an 01 with a 8.1/allison. Its the only automatic trans I actually like in a truck setting. We also had a 6.0/6l80e truck and I hated that trans. As far as the 4l80e goes we had one behind a vortec 454 and popped it twice plowing...
 
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