I was on the GMC site now looking at the GMT 900's and there only appears to be a 6.0 or a LMM... did they do away with the 8.1? any reasoning?

because of the H.O 6.0 i think. it makes just as much as power as the 8.1 but just not at heavy.


well thats my thought anyway I dont know the real reason.

They are coming out with a 7.5L V10 to replace the 8.1.

i think it has to do with the MPG of the 8.1L

They are coming out with a 7.5L V10 to replace the 8.1.

Hey,

Do you have anymore info on this? Sounds real interesting.

Hey,

Do you have anymore info on this? Sounds real interesting.I would like to know also

i think it has to do with the MPG of the 8.1L

I was under the impression that if you get the same load behind the 8.1 and the 6.0, the mpg turns out to be the same. If that was the case why wouldn't they do somthing like a H.O. 8.1? Like they did with the 6.0? Just wondering.

I was under the impression that if you get the same load behind the 8.1 and the 6.0, the mpg turns out to be the same. If that was the case why wouldn't they do somthing like a H.O. 8.1? Like they did with the 6.0? Just wondering.

that was my thoughts......other than that, it has to be emissions that killed it. IDK

On edit: I also think on the assembly line, it would simplify things. You either get the 6.0 with the 6 speed light duty or the 6.6 with the Allison.

The 8.1 is still offered in the medium duty line of trucks and in workhorse platforms for motorhomes and utility trucks. So emissions had nothing to do with it. I emailed chevrolet and a woman called me and said that the complete list of engines for the HD's hasn't been listed yet and to wait until December or January and it will be listed. I guess I'll just wait and see if they offer something different. I think they are raising the specs on the 8.1 because Ford passed them last year in torque in the motorhome market. The new 6.0 isn't even close with the torque compared to the 8.1 and without the allison it isn't really a real trailer hauler.

The 8.1 has/had a lot more potential than they used. Unless it's going to be uprated there's no point in keeping it as an option. IMHO.

If gm dumps the 8.1 and stuffs some stupid v10 into their trucks I'll barf.
v10s suck big time

If gm dumps the 8.1 and stuffs some stupid v10 into their trucks I'll barf.
v10s suck big time

What's wrong with a v10? Gm never built one, so are you comparing it to Ford and Dodge? I don't see much benefit to running more cylinders, other than the motor will be a bit smoother. I don't think the mileage will benefit enough to justify designing an entirely new engine. So why is the 8.1 being replaced??????

So why is the 8.1 being replaced??????

Emissions, that would be why. If you take a 6.0 Gasser, (or a 7.0!!) and add 2 more cylinders, you will have a cleaner running, slightly more powerful engine. I am pretty sure that the larger bore is what contributes to higher emissions, but I am sure others with more knowledge will chime in here.

Big bores are not good for complete fuel burn, there's just too much room for the f/a mix to spread out in. This incomplete burn raises CO and HC levels, not sure about NOX levels.

Med trucks have different emission standards than LD trucks.

Why stop at 10??? Let's shoot for a 9 liter V12, talk about a smooth running engine.

Why stop at 10??? Let's shoot for a 9 liter V12, talk about a smooth running engine.

:exactly:

GM need to bring back the 5.7 as an option. It would do most anything necessary and got good mileage. Had a '97 with that engine. If it had been a crew cab I'd probably still have it.

GM need to bring back the 5.7 as an option. It would do most anything necessary and got good mileage. Had a '97 with that engine. If it had been a crew cab I'd probably still have it.

The 5.7 was a good engine, Don't get anything less than a 5.3L and you will be ok. The new engines are built to run and peak at different rps, from what I have been told. That is the difference.

I had a 2002 Z71 with a 5.3 and it had way more power than the 5.7(350) that was in a 97 chevy.

I had a 2002 Z71 with a 5.3 and it had way more power than the 5.7(350) that was in a 97 chevy.

At high revs or bare truck only. Hook a trailer to it and a 5.7 was a way better rig as Will said the power peaks way higher in the revs

At high revs or bare truck only. Hook a trailer to it and a 5.7 was a way better rig as Will said the power peaks way higher in the revs
Agreed. Few yrs ago, a friend had a new '99 Chev 5.3 (sure its been uprateed for power more by now though) and I had a '90 GMC 5.7 TBI. Ina drag race, he'd take me, but my 5.7 would hold speed much better w/ my 16' cargo trailer than his.

They are coming out with a 7.5L V10 to replace the 8.1.

Chevrolet Silverado: In the 2008 model year a new SS version of the Silverado will come out. It is said to look very aggressive and sport a 500+ HP Small Block V8. A two-mode hybrid Silverado will arrive in January 2008 as well. There is also speculation about GM adding a 7.5L V10 powertrain to the HD trucks to replace the 8.1L Big-Block V8.

This is from http://www.gminsidenews.com/index.php?page=Future_Product_Guide SPECULATION is the key word!!!!!!

Agreed. Few yrs ago, a friend had a new '99 Chev 5.3 (sure its been uprateed for power more by now though) and I had a '90 GMC 5.7 TBI. Ina drag race, he'd take me, but my 5.7 would hold speed much better w/ my 16' cargo trailer than his.


That is probably due to the horsepower/torque range. The older motors had a lower curve. The newer motors make all their power up top.


I like the old 5.7's better too. Exhaust sounds way better on them! :D

When I talked to the dealer the other day he just got back from a seminar. He was saying that they are going to put the 6.2L in the 3/4 ton trucks. That motor has 400 hp, and I believe is all aluminum. Just repeating what I heard. I know this is the motor in the denali's and cadillacs.

I have towed with a 96 Vortec one trip and a 5.3 the next. the 5.3 would run away and hide from the 5.7(NON LSx) truck even with a trailer on it.

As many have said the biggest reason is Emissions. Same reason the old SBC Gen I and II are dead ;)

Big bores are not good for complete fuel burn, there's just too much room for the f/a mix to spread out in. This incomplete burn raises CO and HC levels, not sure about NOX levels.

Med trucks have different emission standards than LD trucks.

Why stop at 10??? Let's shoot for a 9 liter V12, talk about a smooth running engine.


With open chamber heads yes, with modern quench style heads that is not necessarialy true.


The older 5.7's had a sloppier torque conver which helps off the line acceleration. Above 2700, the 5.3 overtakes the 5.7 and never looks back. The 5.7 does sound better (stock).

They are coming out with a 7.5L V10 to replace the 8.1.


The big block finaly died.

Chevrolet Silverado: In the 2008 model year a new SS version of the Silverado will come out. It is said to look very aggressive and sport a 500+ HP Small Block V8. A two-mode hybrid Silverado will arrive in January 2008 as well. There is also speculation about GM adding a 7.5L V10 powertrain to the HD trucks to replace the 8.1L Big-Block V8.

This is from http://www.gminsidenews.com/index.php?page=Future_Product_Guide SPECULATION is the key word!!!!!!
Bring it on!! Sounds awesome.!!

bring Back The Rat Motor Gm

think it is emissions, assembly line(eng/trany) and CAFE regs. have driven DCM and ford V-10's didn't care, think stupid selling point - lot of work done to smooth out Harley bolted on to back of engine. if they are going for more cylinders bite it and do 60degree V-12 small bore/long stroke setup(intercooled/supercharged) mercruiser uses 6.2 also, not bad engine. could go with 7 liter(427 s/b vette engine), Vortec engines turn higher rpm to get out of egr hurting power output. 8.1 has good industrial usage(might be going to a higher comp. ratio) running of propane/natural gas. mercruiser still listing in lineup also. 7.5 more than likely bait of is it 7.5l Duramax (455ci Isuzu/Buick/Olds/Pontiac not 454ci chevy displacements).

Talked to GM at SEMA at length about this subject. The 496 is out due to simple economics. For each new series of vehicle an engine and/or engine-tranny combo has to be certified for emissions to the tune of half a million dollars for each certification. As much as the GMT 900 truck group and GM Powertrain wanted the big block in there, the bean counters didnt feel there was enough buyers for it to make it happen. They think the 6.0 gas or the Duramax will take care of the market. Not for me. I understand their reasoning, but it still wont make me spend $40k on a new truck. I have a 2003 big block as my personal truck, and a 2005 Duramax as a company truck. Both good engines but if I'm gonna buy one, it has to be a big block.

Big bores are not good for complete fuel burn, there's just too much room for the f/a mix to spread out in. This incomplete burn raises CO and HC levels, not sure about NOX levels.

Med trucks have different emission standards than LD trucks.

Why stop at 10??? Let's shoot for a 9 liter V12, talk about a smooth running engine.

id buy one ):h

Liar............ LOL you'd still own a max.

I'd be happy with an Ls7 instead of the 8.1l. Not going to hold my breath though.

Liar............ LOL you'd still own a max.

Haha yea I'd have both! IF I could only afford it:ro)

How odd? I was reading the October Issue of Construction Equipment with a feature article on the class 8 trucks and the incoming DPF. On the GM write up it stated that GM would be offering the 8.1 in the class 8 trucks and noted that they were the only manufacturer to offer a gas engine. Has anyone seen this out the the medium duty side of the GM website?

GM continues to offer the big block in the medium duty trucks since no emission certification is needed.

because of the H.O 6.0 i think. it makes just as much as power as the 8.1 but just not at heavy.


well thats my thought anyway I dont know the real reason.


ARE you saying that the 6.0 and the 8.1 have the same torque ratings?

il take a 8.1 big block over a 6.0 snall block any day

because of the H.O 6.0 i think. it makes just as much as power as the 8.1 but just not at heavy.


well thats my thought anyway I dont know the real reason.
It might make the same hp, but wont come close on tq,just another stupid thing gm has done.

It might make the same hp, but wont come close on tq,just another stupid thing gm has done.

Maybe sales, and emissions had something to do with it? Or maybe something better is on the horizon and this is the transition period at the engine plant. You never know. Personally I think the 8.1 is under powered for its displacement, in the torque department anyway. I am sure better things are on the way.

From the people i know with an 8.1L they all say they get the same MPG's as my truck with a 6.0L does. If i would have known that when i bought mine i would have paid the extra $900 for the big block. it has a mild cam in it so you get the low end torque but still get good MPG's just low HP, all you have to do is put a bigger cam in it and those things will roar, except the MPG's drop but the power makes up for it. I hope they don't put a V10 in the new trucks. I know i shouldn't compare them, but i drive Dodge V10's and Ford V10's for work and they suck, they sound like a little V6 and don't have any go I mean they are Fords and Dodges (junk) but still a V8 is better.

Yeh it is a shame that the 8.1 is gone. Ahh who am I kidding Id buy a duramax anyway:D