What do you guys think would be more advantageous (sp?) in a 2500HD crew cab...

8.1 is 496 cubes to begin with. So there is an obvious advantage right there of 131 cubes.
6.0 is 365 cubes to begin with. It is at a disadvantage.
6.0 to 422 cubes picks up 57 cubes over a stock 6.0 but still lacks the cubes of the 8.1 motor.

Stroker kits are also around $4k for forged crank, forged rods, and forged pistons. Hell even a 4.25 bore x 4.25 stroke LS1 aluminum block (if it can be sleeved that far) is only 482 cubes and would cost an insane amount of money to do. As far as I know an aluminum block can go 4.125 bore x 4.25 stroke giving ~453 cubes.

Now imagine stroking an 8.1. Somewhere in the 'hood of 540 cubes!

Also the compression is lower on the 8.1 making it more blower friendly. If you were to try to stay N/A you could always have the heads decked to bump the compression.

You can do head work to an 8.1 for around $2500-3000. 6.0 head work is far cheaper around $2000 or less depending on amount done. I figure anything done to a 6.0 would yield more power on the 8.1.

The 6.0 only comes with a 4L80E trans too with 4.10:1 gears. Granted it is very strong, it has a 2.48:1 first gear and you can rebuild it with a 2.68:1 (I think that is the ratio). The Allison 1000 has a 3.10:1 first gear and a nice split for the extra gear in 3rd and is insanely strong. Even if the Allison came with a 3.73:1 in the diffs the gears would be lower than a low ratio geared 4L80E with 4.10:1s. Apparently Yank does converters for the Allison now and ATS Diesel has valve body mods too.

An intercooled Whipple on the 8.1 takes its power from 340hp/450tq to around 500hp/700tq!
An non-intercooled Whipple on the 6.0 takes its power from 300hp/360tq to around 400hp/570tq!

When the intercooler is added to the 8.1 it makes another 40hp/50tq. I figure the gains will be around there somewhere for the 6.0, probably a bit less due to the displacment.

Both versions have that huge 10.5" rear axle that would be unbreakable when equipped with an Eaton posi in lieu of the factory G-80 and a stud girdle. Also Eaton's E-locker is available for the IFS on this truck too. Traction should be attainable as well as launches on slicks with assloads of power.

Post up what you think...!

 

The 8.1 has bigger ports.bigger valves,stronger crank and rods.It can make an easy 650hp with relatively mild mods and you can buy a built marine version with over 1000hp.Now for the downside it's heavy and expensive to modify the 1000hp motor will cost about 12-15 thousand dollars.

 

i think you are missing a few things, i am by no means an expert on these things but here is what i think

the ls1 has killer after market support, that forged rotating asembly is suppose to be good for 1000+hp(someone correct me if i am wrong), sure bigger is better but when you are working with forced induction it kind of takes some of that cubic inch stuff out of the equasion. my #1 quesion is wich motor can be built to handle(not make) the most power. with nitrous and/or FI, you can make as much power as you the bottom end can take.

what about the heads, i understand the stock 8.1 heads prety much suck, seems like i have been told the ls1heads outflow them stock and outflow them with a performance job done too.

i am geting ready to do a truck swap so this is an interesting topic for me. i want some 9's!!!

 

Look at the marine products available thru Mercury Marine for use on offshore boats the parts are there.With turbos or supercargers you can buy as much horsepower as your checkbook will allow.If you have really deep pockets 1000hp would be a drop in the bucket.ASM lists a 1000+ motor on there website for $17000.I do think you can get more bang for your buck with the LS1 based motor.If price is no object the Big Block is the way to go just ask the offshore racers.

 

is the 8.1 just a good old fashiond big block, like a 454 or a 502? can aftermarket heads for a 454 bolt on?

bigger is better if it can be built to take the power, can i get the link to the ASM site?

 

It is a Gen IV or VI big block. It is similar to the old designs but with the new basis. The 8.1 for the water is aroun 535HP or something with 8.1L. This motor seems to be just getting better and better the more I look into it.

I have a hard time believing that those heads are that bad. The worst heads I have seen (and still have) are late 80's to mid 90's SBF E7 heads. They flow terrible. Hell Car Craft did just a head swap on a 5.0 roller block went from ~270hp with stock headers and rocker on an engine dyno to just over 400hp with AFR-165 heads, roller rockers, and long tubes! Over 100 hp increase with a head swap alone and emission legal!

www.azspeed.com I think is their website.

 

Parish8 try www.azspeed.com

 

For that kind of money you could have Lingenfelter build you a twin turbo 427 LS1 with 750+hp and install it in your truck.That would get you into the low 11s without nitrous and save about 100lbs.You could probably spray it into the 10s and be emissions legal.

 

I'm of course gonna back the 6.0 and 4L80e set up. The aftermarket for the genIII engines is huge and the quality unsurpassed, Jessel shaft rockers, yella terra rockers, and SLP just as example. GenIII engines have gone to racing in ASA and ALMS endurance racing (C5R vettes) cause of the vettes we know have available JE pistons and Carillo rods otherwise their would have been no need till years from now to make them for GENIII.
The 8.1 oil burning as it does, people on GMfullsize count how much oil they use and add it to the fuel cost its so bad. I'm sure this motor does make some serious power though and I wouldn't doubt it could make more aftermarket sourced power, but with the GENIII engines its almost to the point of nearly every possible mod has been done and can be consulted very easily by hundereds of people on this forum. With an 8.1 your kinda in unchartered water where few have dared to go.