What's the biggest you can go with an LSX street motor?
01-24-2009 | 02:54 PM
#16
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Joined: Dec 1999
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From: MD
01-24-2009 | 07:47 PM
#18
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Joined: Oct 1999
Posts: 3,167
From: Inside Uranus
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.
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.
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
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
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.
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.
Here's the sad sad fact:
The GSX with the 455 made as much power as the LS1 did in 1998... 455ci making 350 horsepower? That's a goddamned joke as is this entire thread
Once again:
****ty heads = ****ty power. Big cubes + ****ty heads = a bandaid for making ****ty power using ****ty heads/intake less ****ty.
No flow = no go and big torque. The engine can't breathe.. OF COURSE that's why it makes big torque down low and no power up high.
DUHHHHRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR!
If you want power down low, I suggest you get into tractor-pulling.
Go moderate the lounge and stop clogging up my Tech section!!
Mike
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