I've had this dream in the back of my head for a while that I would someday build up a big-inch aluminum LS engine to put in my '02. I absolutely love the low-end torque of my father-in-law's 462ci Buick, and I'd like to have something similar.

I want to do everything NA. Partly for reliability, weight, and stealthy appearance, but also because I already have a turbo car (the GN) and my father-in-law is in the process of installing a D1 on his 462.

I've been doing a lot of reading, and it seems to me that the biggest you can go while still avoiding the inherent reliability issues that occur when the piston comes very far out of the bottom of the bore is a 427ci LS7. An LS3, due to a smaller bore compared to an LS7, won't go much past 415ci.

415-427ci, while big, just isn't as big as I had in mind in this little dream of mine. If I were to pursue this dream, I don't think I'd settle for anything smaller than 454ci. I'd really be happy in the 470-500 range.

An LS7, stroked to 4.125", would give 440ci, and now we're getting close, but everything I've read warns of excessive piston wear (and therefore frequent need for rebuilds, and therefore not appropriate for a street car) with strokes in excess of 4.000".

So, some questions for anyone who is well informed on the subject:

Are my concerns about excessive piston wear on a street driven engine with an extreme stroke well founded? What can be done? I know that Dart will machine a billet block to my specs, and I figure that could probably accomodate 4.500" stroke and beyond, but I also figure that would cost at least ten grand, and probably more, which is impractical to say the least. Is there any other way?

I think I could do it with a tall-deck LSX, but I'm not totally sure; I'd rather not have all the extra weight of an iron block.

Other suggestions welcome.

 

you can make far more power with a LSx than those old dinosaur motor and more tq with less CI, just because it is so much more efficient.

anything with alot of stroke is going to scrape pistons.....

I always like a short stroke big bore for rpm.... if you want the tq then you want stroke, but you have to find the line of where you want to be without pulling it down every year.....

You could always get the high dollar block too and build something big.... I know someone that did a 440 LSX block it made about 900 NA, but it was a race only pc.



How about the new edelbrock heads?

 

The thing is, racing, peak power, etc are all highly unimportant to me. I'll go to the strip maybe once or twice a year for fun (assuming the car is legal without a rollbar), but it'll primarily be street driven, so I'm all about low-end torque. 800-4000 rpm is what I really care about. Anything above that is just candy.

I want to do it all on pump gas (tuned for 91 octane, though I'd most often run 92), too.

900 is WAY more power than I want. I just want to see 500 lb-ft or more at the wheels (through my built T56 and a Dana 60 I haven't bought yet) at 2000 rpm or less. What happens in the higher RPMs is largely unimportant, although I'd like it if it would still spin to 6000-6500. I can't see how that'd be an issue, assuming I went with a quality rotating assembly and valvetrain (which I would).

 

http://ls1tech.com/forums/generation...t-release.html

 

As I said earlier, I don't want the weight of the iron block. Also, I'd have to see a dyno graph (can't see it from work) to see if that thing makes the low end torque I'm looking for.

Maybe someday GM will make an aluminum version of the LSX.

 

If you're looking for lots of stroke with an even larger bore, you have three viable options:

Buy an LS7 block (4.125" from the factory), which is $$
Wet-sleeve an aluminum LS1/6/2 block $$$
Buy an LSX block and go with the 454ci. $

That's about it. Everything else is going to be a 418 or less on an LQ.

You can honestly throw your dreams of a 4.5 stroke motor in the dumpster. That's just rubbish unless you're hauling dirt or building a diesel motor.

Honestly, I don't understand the fascination with big big cubes... I mean have you honestly even ridden in a well-built 408 motor or even a properly setup heads/cam LS motor? Those are seriously torquey like big blocks of the 60s-70s. My heads/cam LS1 setup made the exact power/torque of my friend's 383 225cc LT4 Sold-Roller car.

Take a ride in a 402 or 408 LS that's not overcammed before you make your mind up.

 

I can't wait until I blow this motor up so I can pick up a nice HKE 408.

 

That's impossible. Unless you're willing to go into the diesel truck scene or a 600+ci BBC, you should set more realistic goals. Even 400 lb/ft at the wheels at 2000rpm would be extremely difficult. Furthermore, if you're looking for that kind of low-end torque, you can forget about power over 6000rpm. The cylinder head and intake design just don't allow for that.

 

Exactly.

I think my 408 made 450rwtq at 3500 and 505rwtq by 4700. That was with a mild cam for the size of the motor (238/240 110 LSA) and 6 degrees retarded for more top end power to make up for the size of the cam. If it wouldn't have been retarded, it would have made torque lower, but not even close to 2000 rpm. The only reason those old motors make low low low end torque like that it because they are garbage in design and don't make any top end power... just like most "muscle car" motors from the 60s-70s. 375 horsepower from 440ci isn't worth much in today's world when you can make nearly 550 horsepower with 346ci and drive it around every day with the full interior and AC and run it on pump gas at 24mpg on the interstate.

Mike

 

Anybody with a 400+ inch LS motor want to take me for a ride, or better yet, let me take it for a drive?

I'll take you for a drive in the 462ci Buick (or better yet, maybe in his friend's 540ci Mercury) in exhange, and for comparison.

My nearly-stock 346ci LS1 makes 300lb-ft at 2200 rpm. I find it very hard to believe that with 100+ more cubes and a head/cam combo chosen with these goals in mind, I couldn't get to at least 450.

As I said in post #3, I simply don't care about high RPM power. I'll set up whatever I build to go as high as is reasonable, but my priority is the torque down low.

 

FWIW, the LSX 454 linked above makes 400 at 2000, although AFAIK that's BHP, not RWHP.

 

Believe it.

Ummmm... You just cited a healthy 454 that makes roughly 350 lb/ft of torque to the wheels at 2000rpm. You do realize that's 150 shy of your goal? The only way you can get power like that is to make the engine MUCH bigger, or make it think it's bigger with lots of compression and forced induction.

 

I do.

It can't be done by sacrificing top-end power? 590 is significantly more than I want.

What if I said 2500 instead of 2000?

Suffice it to say that I want as much low-end torque as I can possibly get in a naturally aspirated, all-aluminum LS motor. I'm willing to adjust my goals within the realms of what's possible, but I have a hard time accepting that it can't be done based on examples in which the goal was something entirely different.

A 1970 Buick GSX with a 455 made 510 lb-ft at 2600 rpm. Admittedly, that's gross, not net, but it's also 40-year-old technology.

 

No matter what you do, no LSx is going to do that for you, regardless of the scope of the build. There have been many builds with lots of displacement focusing on low end torque, and NONE have come anywhere close to your unrealistic goal. It would be like setting a goal for your GN to make peak power at 7000rpm.

No head and cam combo is going to increase torque at such a low rpm. And since a stock LS1 makes 300 lb/ft of torque at the crank at 2000rpm (about 250 lb/ft at the wheels), you will need twice the engine to achieve 500. So basically all you need is a 700ci LSx

That GSX examples is a HORRIBLE one! 510 lb/ft net, which would equate to what? 450 gross? Turn that down 600rpm and you'll have much less, 410-420 or so. Measured at the wheels you'd have around 360 lb/ft at 2000rpm, which is right where most of those old big inch muscle cars dyno at.

 

Actually the number I gave for my stock LS1 was at the wheels, so 300 is 300.

I do see the rest of your point; I still want as much low-end torque as I can get.

What sort of goal would you say is reasonable? Let's imagine I have a budget of 15k for a complete motor.