347 vs 370
09-09-2012, 06:43 AM
#22
Is this just a street car? Is your goal an ET?
The reason I ask, is I was in an identical situaiton as you last year. I had a D1SC on my stock motor, took out #5 and #7 piston ringlands, and then needed to rebuild and didn't know how big to go with cubes.
I had/have aftermarket great flowing heads for a 346, so NA power was already there. When I added the blower, it made 1st and 2nd gear useless at any rpm with any kind of boost. Honestly, once the tires start to spin, 500ft/lbs of torque is just as useful as 600ft/lbs.
I kept my compression level at a reasonable value, around 10.3:1 which makes things very fun even out of boost. With 3.73 gears, I have no issues what so ever driving around out of boost.
I really don't think you would need the larger cubes if you don't plan on going bigger than a D1SC. I don't know where you live, but try and find someone with a 6-speed and blower and see how you like it on stock cubes. I love it. The only thing going to bigger cubes would have done for me is lower my psi of boost with the current pulley size. Power would have gone up marginally, maybe more, who knows, but power right now isn't my issue, it's traction, which hopefully the 305/30/19 R888s will solve.
So either try and get a ride in a couple different cars, or save yourself the cash and stay stock cubes for now. If you're NA right now with stock heads, then you are going to look at double the horsewpower which is dramatic. It's not like going from 600-700 horsepower. Going from 400-600 is a huge jump, especially the torque that goes from 350ft/lbs to 500ft/lbs with a well boosted motor.
The reason I ask, is I was in an identical situaiton as you last year. I had a D1SC on my stock motor, took out #5 and #7 piston ringlands, and then needed to rebuild and didn't know how big to go with cubes.
I had/have aftermarket great flowing heads for a 346, so NA power was already there. When I added the blower, it made 1st and 2nd gear useless at any rpm with any kind of boost. Honestly, once the tires start to spin, 500ft/lbs of torque is just as useful as 600ft/lbs.
I kept my compression level at a reasonable value, around 10.3:1 which makes things very fun even out of boost. With 3.73 gears, I have no issues what so ever driving around out of boost.
I really don't think you would need the larger cubes if you don't plan on going bigger than a D1SC. I don't know where you live, but try and find someone with a 6-speed and blower and see how you like it on stock cubes. I love it. The only thing going to bigger cubes would have done for me is lower my psi of boost with the current pulley size. Power would have gone up marginally, maybe more, who knows, but power right now isn't my issue, it's traction, which hopefully the 305/30/19 R888s will solve.
So either try and get a ride in a couple different cars, or save yourself the cash and stay stock cubes for now. If you're NA right now with stock heads, then you are going to look at double the horsewpower which is dramatic. It's not like going from 600-700 horsepower. Going from 400-600 is a huge jump, especially the torque that goes from 350ft/lbs to 500ft/lbs with a well boosted motor.
09-09-2012, 09:14 AM
#23
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Is this just a street car? Is your goal an ET?
The reason I ask, is I was in an identical situaiton as you last year. I had a D1SC on my stock motor, took out #5 and #7 piston ringlands, and then needed to rebuild and didn't know how big to go with cubes.
I had/have aftermarket great flowing heads for a 346, so NA power was already there. When I added the blower, it made 1st and 2nd gear useless at any rpm with any kind of boost. Honestly, once the tires start to spin, 500ft/lbs of torque is just as useful as 600ft/lbs.
I kept my compression level at a reasonable value, around 10.3:1 which makes things very fun even out of boost. With 3.73 gears, I have no issues what so ever driving around out of boost.
I really don't think you would need the larger cubes if you don't plan on going bigger than a D1SC. I don't know where you live, but try and find someone with a 6-speed and blower and see how you like it on stock cubes. I love it. The only thing going to bigger cubes would have done for me is lower my psi of boost with the current pulley size. Power would have gone up marginally, maybe more, who knows, but power right now isn't my issue, it's traction, which hopefully the 305/30/19 R888s will solve.
So either try and get a ride in a couple different cars, or save yourself the cash and stay stock cubes for now. If you're NA right now with stock heads, then you are going to look at double the horsewpower which is dramatic. It's not like going from 600-700 horsepower. Going from 400-600 is a huge jump, especially the torque that goes from 350ft/lbs to 500ft/lbs with a well boosted motor.
The reason I ask, is I was in an identical situaiton as you last year. I had a D1SC on my stock motor, took out #5 and #7 piston ringlands, and then needed to rebuild and didn't know how big to go with cubes.
I had/have aftermarket great flowing heads for a 346, so NA power was already there. When I added the blower, it made 1st and 2nd gear useless at any rpm with any kind of boost. Honestly, once the tires start to spin, 500ft/lbs of torque is just as useful as 600ft/lbs.
I kept my compression level at a reasonable value, around 10.3:1 which makes things very fun even out of boost. With 3.73 gears, I have no issues what so ever driving around out of boost.
I really don't think you would need the larger cubes if you don't plan on going bigger than a D1SC. I don't know where you live, but try and find someone with a 6-speed and blower and see how you like it on stock cubes. I love it. The only thing going to bigger cubes would have done for me is lower my psi of boost with the current pulley size. Power would have gone up marginally, maybe more, who knows, but power right now isn't my issue, it's traction, which hopefully the 305/30/19 R888s will solve.
So either try and get a ride in a couple different cars, or save yourself the cash and stay stock cubes for now. If you're NA right now with stock heads, then you are going to look at double the horsewpower which is dramatic. It's not like going from 600-700 horsepower. Going from 400-600 is a huge jump, especially the torque that goes from 350ft/lbs to 500ft/lbs with a well boosted motor.
09-09-2012, 09:33 AM
#24
My car is procharged now. With a 4.25 pully on the blower it makes roughly 10.5# at 6000 rpm and with 14* timing it makes 581/524 on a dynojet. It is a weekend warrior that spends most of its time getting beat on, on the street with the occasional trip to the drag strip. Maybe 5-10 times a year. I would like to run well into the 10's pretty easily (quite confident it will run a 10.xx the way it sits now). Of course just like you traction is a issue on the street. First is mostly useless and second will spin at the very top at peak boost unless the tires are hot. They are 315 Nitto drag radials. i have a 3.80 gear in my 9" now but will be changing it to maybe a 3.55 when I build the motor. My issue is, I know my setup now without meth and making the power that I am now, it isnt the safest combo in the world. My main reason for building a combo and adding meth is to make it safe/reliable. It just so happens that building a motor opens up the door for more power. With either motor I go with, they will both have the same 3.4 pully on the blower, Same heads (slightly ported 317's with good valvetrain, same custom grind blower cam that I already have, same meth kit and same D1 blower. I just want to know what the power differance will be between the 2 motors with all the above being the same and at that point I can decide if spending the extra money and adding the extra weight of the iron block will be worth it.
I think the major difference between the two displacements is going to be weight, boost pressure, and then power, in that order.
Going with the 370 or bigger, unless you do an ls2/3, is going to mean adding 100lbs to the nose of the car. For me, I refused to do that. The larger cubes means that you're going to see slightly less boost pressure at any given rpm. Don't think that means less power, it just means less pressure, which translates into less heat.
Since you plan to max out the D1, that's the limiting factor in your overall power production. Honestly, I would be surprised if you saw more than a 25-30hp difference between a 370 and a 347 with the D1 maxed. I bet you'd see 20-30 more ft/lbs through the rpm, but is that worth the extra cost and weight, that's up to you.
Maybe I'm wrong and you could see more power, but here's a link to a maxed out D1SC on a 347 in a corvette.
https://ls1tech.com/forums/forced-in...-800-rwhp.html
So is 824hp/717ft/lbs enough? It's up to you.
09-09-2012, 12:29 PM
#25
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So you really are where I was last fall.
I think the major difference between the two displacements is going to be weight, boost pressure, and then power, in that order.
Going with the 370 or bigger, unless you do an ls2/3, is going to mean adding 100lbs to the nose of the car. For me, I refused to do that. The larger cubes means that you're going to see slightly less boost pressure at any given rpm. Don't think that means less power, it just means less pressure, which translates into less heat.
Since you plan to max out the D1, that's the limiting factor in your overall power production. Honestly, I would be surprised if you saw more than a 25-30hp difference between a 370 and a 347 with the D1 maxed. I bet you'd see 20-30 more ft/lbs through the rpm, but is that worth the extra cost and weight, that's up to you.
Maybe I'm wrong and you could see more power, but here's a link to a maxed out D1SC on a 347 in a corvette.
https://ls1tech.com/forums/forced-in...-800-rwhp.html
So is 824hp/717ft/lbs enough? It's up to you.
I think the major difference between the two displacements is going to be weight, boost pressure, and then power, in that order.
Going with the 370 or bigger, unless you do an ls2/3, is going to mean adding 100lbs to the nose of the car. For me, I refused to do that. The larger cubes means that you're going to see slightly less boost pressure at any given rpm. Don't think that means less power, it just means less pressure, which translates into less heat.
Since you plan to max out the D1, that's the limiting factor in your overall power production. Honestly, I would be surprised if you saw more than a 25-30hp difference between a 370 and a 347 with the D1 maxed. I bet you'd see 20-30 more ft/lbs through the rpm, but is that worth the extra cost and weight, that's up to you.
Maybe I'm wrong and you could see more power, but here's a link to a maxed out D1SC on a 347 in a corvette.
https://ls1tech.com/forums/forced-in...-800-rwhp.html
So is 824hp/717ft/lbs enough? It's up to you.
