8.1L info

Anyone got some good links for GM's L18/8.1L/496/Gen7 (2001 up bigblock)?

The 496 weighs like 730lbs and makes 400hp@4600/500ftlbs@3200 (on a tune) stock. Cast iron block and heads.
The 364/6.0L weighs like 540lbs and makes 370hp@5600/400ftlbs@4400 (on a tune) stock. Cast iron block and aluminum heads. LQ4 and LQ9 are pretty similar.

It makes me wonder if going with a 496 for a street truck is the way to go as far as dollar for performance (8.1L trucks resale for about the same as 6.0L LQ4 trucks). I'm looking at 2001up (so you get the good 6.0L or a 8.1L) standard cab long box 3/4 tons.

Seems like the only way to make in excess of 500hp on a 6.0L is with forced induction. So, when you get to forced induction you might as well aim for 14lbs or so. Hard to get 14lbs into a BBC but cake with cheap turbos on a 6.0L. Car people's throwaways could be had to build the 6.0L. Can't find used stuff for a 496... especially since there is like no aftermarket parts anyway.

It's still 190 extra pounds on the wrong axle though.

I just sold an 8.1 out at the spring jefferson.

Stock for stock it can't be beat, its a bad ass engine but it has alot of draw backs if you want to start modding it.

Basics of the engine Its pretty much a big block LSX motor. It has cross bolted mains like and LSX, runs on an LS1 style ecm with coil per cylinder ignition, on the LSX firing order not on the old BBC firing order.

So that means regular BBC cams wont work and theres only a few companies making anything after market for the 8.1
Raylar has cams and the only set of Aluminum heads I could find for it. But the heads are about $3000 and I think thier cams were about $500

At jefferson I did run into a guy that said there is a way to make old BBC heads fit on the 8.1 but it requires drilling another hole in the head (8.1 has one more head bolt than old BBC) and it requires a special gasket. I have still yet to find any info or proof that this can be done.

Another thing I found was that the cranks in these engines tend to have issues if you spin them past 5000 rpm. found a few stories of shattered cranks and cracked blocks....

When I get to work during the week I can post up some links to 8.1 info.

My suggestion is go with the 6.0 it will be cheeper and easier in the long run.

500hp can easily be done n/a w/ a 6.0

So, it seems that you can pick up a new crank pretty cheap ($700 or less). So, in theory, you should be able to then spin it pretty quick (or at least to the limits of hydraulic lifters).

The 8.1L has 33% more displacement than a 6.0L but also 30% more weight. So, in theory, it should make 33% more power. Kind of limited by the heads. How bad are the heads? How much horsepower will they support without forced induction or nitrous? Can't seem to find a number anywhere other than GM makes a 450hp version of the 8.1L.

The 6.0L has a bunch of "cheap" parts left over from car guys. And a much larger aftermarket. But, it seems that if you want a torque-infested streetable 6.0L you're pretty much limited to 450hp without spray or boost. LQ4s don't come with the nice rods of the LQ9 until 2004. So that's an added cost.


Seems like forced induction costs the same on either. HPtuners fixes the ECM problem. 4L80e is what I'm looking for as far as a transmission. A 5 or 6 speed Allison would be neat but it costs a lot to fix and weighs a lot. A lot cheaper to build a 4L80e but it has the world's crappiest first gear.


I'm aiming for 10lbs/hp normally aspirated or 6lbs/hp on boost and would like to maintain some sense of decent handling so I'm already leaning away from the 496. But I don't want to regret building a 6.0L because it seems once you get to 650hp it gets exponentially more expensive.

I dont' believe that at all about the 6.0. You can use all the new Hybrid LS7 intakes and heads, aka the LS3 intakes and heads. Vettes are 430 out of the box with those. port that stuff, stick a cam in it and you should be able to get to 500rwhp w/out breaking the bank. Stroker crank is going to push you up to nearly 7 liters anyway if you want to go that route. Then again in a year or two you'll find 6.2 blocks for the cheap.

Fuel injection can make lots of stuff plenty streetable