Anybody have the 8.1 Vortec....or had one in the past?

c good

Original poster
Member
Dec 8, 2011
526
Found a very nice 2003 GMC Yukon XL. 4x4 Original owner. 199 k miles. Excellent condition. What has your experience been with the 8.1? Reliable, problematic, etc?

I'm looking for something bigger than my current Envoy to eventually tow a 6500 lb boat. It would be a weekend and vacation use vehicle only. Not a daily driver.
 

Reprise

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(umm... Mods? When does the snow storm end? While it's a nice change of pace from the usual, it's a little distracting when I'm writing this post... ) :wink:

Well, first... I don't / haven't owned an 8.1. If you can't get past that, maybe stop here... :undecided:


A little while back, I debated (internally) about getting my hands on an 8.1, to replace the 6.0 in my truck, because of the torque potential. I eventually decided... 'against'.

I'll share what pulling 6000 lbs of travel trailer is like with a LWB 5.3 Envoy... you feel it, to the point where you're bumping up the assist on the trailer brake controller. I used it to pull my current trailer from PA > IL a couple of years ago, and even though the Voy was mechanically sound, with all of the maintenance / repairs I had performed on it before starting towing with it, I decided after that trip that it would not be towing that trailer.
Did I get into an accident, or kill anyone? No.

Was I over the rated towing weight? No. Even had another 1200-1800 lb in reserve, per GM's 2003 rating (which governed).

Was I conscious of what I had behind me? Oh, yes.

Did my underroos have skid marks? Not saying, but I did hop in the shower when I got home. :whistle:

Now, a boat is a bit more streamlined than the average travel trailer of that weight range. So it's not like 'pulling a sail'. But -- at that weight and above, I think one is better (and safer) stepping up in capability.
Most people with 6000lb boats aren't towing cross-country, however, so your trips will likely be shorter than mine. But you still have to deal with launch / retrieve. I have no experience with that, but I know I wouldn't want to be embarrassed at a boat launch, if I couldn't pull my own boat out of the water. Or hurt someone / myself, pulling the thing around.

So... I'm voting for the larger platform, which besides larger brakes, heavier frame, etc., also has switchable 'tow mode' which makes use of a second set of shift logic tables for the transmission (and if you go for a 3/4-ton platform, you'll get a heavier-duty trans, as well).

Moving on from platform sizing, we'll talk engine.

The 8.1 is a bit of a 'hybrid'. It's basically a Chevy big block, with the distributor and carburation replaced by LS-style engine controls.

It's a heavy engine, because the heads as well as the block are iron.

The heads, while having canted valves for improved airflow, aren't backward compatible with the old 396 / 402 heads, as the bolt pattern and number are different (so, no direct head swap). GM never made an aluminum set for the 8.1, although at least one aftermarket set exists (and they ain't cheap).

Why do I fixate on aluminum heads? Besides the weight, aluminum also dissipates heat better than iron, and that's especially beneficial in the cylinder head. If I have a choice between an iron and aluminum head, I'm going to almost always side with the latter.

Pros:
- It's a torque monster. The engine develops more at 800rpm (in stock trim) than any stock LS engine. (this is what I was thinking.... 'torque torque torque'). The cylinder heads are a bit part of that, with their canted valves (big airflow).

- GM strengthened the block a bit, and changed to 4-bolt main caps on all 5 bearings (many 'Rat' motors had 4-bolt mains, but only on the inner three bearings).
- You get bragging rights and the claim of something 'rare', if that's important to you.
- If you want to modify it, you can do so. Mild to wild.
- Low compression makes it a great candidate for boost method of choice, if you want it.
- It's not diesel (so no having to learn that architecture / maintenance / repair regimen, if you're not buying 'new').

Downsides:
- Being based on the old big block architecture (which was based on the small block), it's not as robust as the LS. Take the mains, since we mentioned those, above. All LS engines have 6-bolt mains (even the 'lowly' little 4.8). That's just one example. In short, the powertrain engineers started with something very good (SBC), and after they were done, had addressed all of the limitations of that engine, with the LS. 'Very good' became 'great', to the point that 'LS swap the world' isn't just a meme.

- Fuel economy is worse in the 8.1 (and the big block ancestors) than with the LS. Even the thirsty 6.0 does better, both unloaded / loaded. The less you drive, the less this is a factor, but... 'times are a changin'. And they're changing quicker than I imagined, at least. E.g.; what will fuel availability, emissions regulations, etc., be in 10yrs? Longer?

- Aftermarket support, while good, isn't close to what's available for the LS. Cam choices are somewhat limited (stock is around 330 whp and 450 tq, iirc) I'm in that ballpark after doing a cam swap in my 6.0, and there's more to be (safely) had.

- (as far as I'm concerned) You can build more power, with better reliability and fuel economy, cheaper with an LS.

There are other things I haven't mentioned, both 'for / against', but you get the point.

Now... that being said... it could be an excellent project motor, if that's what interests you. It will take some time, a fair bit of coin, and a lot of effort... but you can build something really robust, if that interests you. If I were to get one, it would be with this in mind; keeping one stock (but just catching it up on 200K mi of maintenance) would just be kind of a wasted opportunity, IMHO. In short, you're building it *because* it's such a rare bird.

Bottom line: If you're just looking for the 'best available tool' to pull your boat, and want a minimum of headache... get a 3/4 or 1 ton SRW with the 6.0 (or 6.2, if more recent), and don't worry further. You can always upgrade it later, if you decide you want more.

If the idea of having a real Big Block engine just makes your heart go a-flutter (and one that's not super-rare, like from the 60s, so modifying it won't ruin its intrinsic / collectible status)... then nothing else is going to do.

Since I drive a lot farther, I voted for reliability & fuel economy (marginal tho it may be). If I were doing sub-200 mile jaunts with a boat, on a seasonal basis -- I might go the other way and put an 8.1 under my hood, since I'd have a big off-season to plan mods for (here where I live in IL, boating is very popular, but boats spend 4-5 months in the water, at most)

Hope the above provides some insight, when making your choice. 🤷‍♂️
 

c good

Original poster
Member
Dec 8, 2011
526
Thank you for the excellent info Reprise. I'm not interested in building anything more than stock. I basically want something to be reliable and be able to occasionally tow something bigger than my current Envoy. Right now the Envoy does fine with my little trailer (3000 lbs max loaded) and my smaller 18 ft boat. (Lakes/river only) (not at the same time of course!) :smile:

Sometimes I just car camp in the desert and it would be nice to have something longer that I can sleep in when the wind drives me out of my tent. I have to sleep caddy corner in my Envoy and it gets uncomfortable.

Eventually (in a few years after I retire) I plan on moving up to a bigger trailer(maybe a toy hauler type) and more of a ocean going style boat. Something in the 20-24 ft center console or walk around Cuddy Cabin style boat.

I'm planning on inspecting it tomorrow. It is about 2.5 hour drive away so will report back tomorrow afternoon. Thanks again for the info.
 

littleblazer

Member
Jul 6, 2014
9,265
Friend has a set of 8.1s in his boat. (Not apples to apples) Pushes it around better than any big block ever would and almost as well as my turbo diesels in my boat. They don't wind out much at all (shows over around 4200) but they're pretty bullet proof.

The biggest issue is they existed for a very short period of time. The iron heads while a weight issue aren't a deal breaker on that engine simply because compression is so low for it to really matter. Iirc it's something like 8.9:1. The early 6.0s had iron heads too and they removed them only for weight savings. Iirc the casting was damn near the same.

I would be fine having one. They usually put them in front of Allison 5 speeds I believe which is imo... a fantastic combination. Better flexibility then a regular 80e.

As far as a 6500lb boat, in the 20-24 range that's got to be huge for its size and carry a ton of fuel.
 

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