370 vs. 408...which one and why?
04-27-2008, 12:25 PM
#21
Thanks for all the replies....but...stop this turbo talk!! Haha.
I'll be using a D1SC. My goal is only 550 rwhp and this is a street car, not a track queen. I don't wanna try and make that power on a stock LS1 because it would just be disaster waiting to happen. Right now I'm leaning towards the 370 because it will handle more power than I would want to make anyway and the block would need no additional windage/rod clearance work. TSP has brand new 370 assemblies for 3400 the way I'd want it...Diamond pistons, Callies rods, ARP hardware, and a stock crank. The stock cranks are dependable, I have no worries there.
The car has a Dana 60, chromoly driveshaft, stock M6, Spec 3, two Walbros, and I have 60lb injecors on the way. I'd like to be able to run E85 if I want to but the bottom end needs to handle it.
Any other reasons to go with a 408 over a 370? Yes...it would be cool to say it's a 408...but I don't plan to make insane power and I think the 370 would handle more than I want to make anyway. It keeps some $ in my pocket for other things...like gas.
I'll be using a D1SC. My goal is only 550 rwhp and this is a street car, not a track queen. I don't wanna try and make that power on a stock LS1 because it would just be disaster waiting to happen. Right now I'm leaning towards the 370 because it will handle more power than I would want to make anyway and the block would need no additional windage/rod clearance work. TSP has brand new 370 assemblies for 3400 the way I'd want it...Diamond pistons, Callies rods, ARP hardware, and a stock crank. The stock cranks are dependable, I have no worries there.
The car has a Dana 60, chromoly driveshaft, stock M6, Spec 3, two Walbros, and I have 60lb injecors on the way. I'd like to be able to run E85 if I want to but the bottom end needs to handle it.
Any other reasons to go with a 408 over a 370? Yes...it would be cool to say it's a 408...but I don't plan to make insane power and I think the 370 would handle more than I want to make anyway. It keeps some $ in my pocket for other things...like gas.
04-27-2008, 01:39 PM
#22
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Need to look at the system as a whole and compare that to your goals and how well the system meets your goals.
A 370 is capable of exceding your power goals and will cost less than a 408. Sounds like a no brainer to me.
A 370 is capable of exceding your power goals and will cost less than a 408. Sounds like a no brainer to me.
04-27-2008, 07:38 PM
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I didn't want to start another thread so if the OP doesn't mind a would like to piggy back off of him... I'm in the same situation as he is it's just that I have a different power adder. I have an APS kit and don't know if I should go 370 or 402/408, what do you guys suggest? And money is an object with me and my goals are simple just to max out the hp potential of the kit... Let the suggestions fly...
04-28-2008, 12:49 AM
#29
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I think thats what your girlfriend tells you to make you feel better.
When the boosted list was up you could see there were tons of 408 and 402s running fantastic times. Not sure what happened to it. It was handy to compare mods.
One reason I went to 408 is wanted to go fully forged crank .As said off boost the bigger motor is superior and it should spool turbos quicker be they smaller ones or bigger ones. And if you can use less boost to make same power that might be easier on head gaskets too. And optimum turbo sizing depends on your goals.
Does a guy need more than 1000 engine hp? Can a person hook up more than 1000 hp in a street car, in fact most cars like ours? Pretty much need wheel tubs and giant tires,etc to hook up much past 1000. And of course you need medicals ,full cages etc to run under 10s at most NHRA tracks. So personally think much past 1000 is overkill. Rather set things up at maybe 600 rwhp. Have smaller quick spooling turbos. Have a wider powerband and have bigger motor for better off boost torque and hp. And just feel better with fully forged motor but stock 370 cranks have done think 1000 at least with not much trouble.
Is the 408 worth the extra 1000 or so on a FI motor. Depends...
Is it worth it NA ..no question..Unless you are looking for better mileage or something. That said it was a big jump it seemed to go to 427 or 454. So did stop at 408.
When the boosted list was up you could see there were tons of 408 and 402s running fantastic times. Not sure what happened to it. It was handy to compare mods.
One reason I went to 408 is wanted to go fully forged crank .As said off boost the bigger motor is superior and it should spool turbos quicker be they smaller ones or bigger ones. And if you can use less boost to make same power that might be easier on head gaskets too. And optimum turbo sizing depends on your goals.
Does a guy need more than 1000 engine hp? Can a person hook up more than 1000 hp in a street car, in fact most cars like ours? Pretty much need wheel tubs and giant tires,etc to hook up much past 1000. And of course you need medicals ,full cages etc to run under 10s at most NHRA tracks. So personally think much past 1000 is overkill. Rather set things up at maybe 600 rwhp. Have smaller quick spooling turbos. Have a wider powerband and have bigger motor for better off boost torque and hp. And just feel better with fully forged motor but stock 370 cranks have done think 1000 at least with not much trouble.
Is the 408 worth the extra 1000 or so on a FI motor. Depends...
Is it worth it NA ..no question..Unless you are looking for better mileage or something. That said it was a big jump it seemed to go to 427 or 454. So did stop at 408.
Last edited by tomz28; 04-28-2008 at 01:07 AM.
04-28-2008, 01:06 AM
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Thanks for all the replies....but...stop this turbo talk!! Haha.
I'll be using a D1SC. My goal is only 550 rwhp and this is a street car, not a track queen. I don't wanna try and make that power on a stock LS1 because it would just be disaster waiting to happen. Right now I'm leaning towards the 370 because it will handle more power than I would want to make anyway and the block would need no additional windage/rod clearance work. TSP has brand new 370 assemblies for 3400 the way I'd want it...Diamond pistons, Callies rods, ARP hardware, and a stock crank. The stock cranks are dependable, I have no worries there.
The car has a Dana 60, chromoly driveshaft, stock M6, Spec 3, two Walbros, and I have 60lb injecors on the way. I'd like to be able to run E85 if I want to but the bottom end needs to handle it.
Any other reasons to go with a 408 over a 370? Yes...it would be cool to say it's a 408...but I don't plan to make insane power and I think the 370 would handle more than I want to make anyway. It keeps some $ in my pocket for other things...like gas.
I'll be using a D1SC. My goal is only 550 rwhp and this is a street car, not a track queen. I don't wanna try and make that power on a stock LS1 because it would just be disaster waiting to happen. Right now I'm leaning towards the 370 because it will handle more power than I would want to make anyway and the block would need no additional windage/rod clearance work. TSP has brand new 370 assemblies for 3400 the way I'd want it...Diamond pistons, Callies rods, ARP hardware, and a stock crank. The stock cranks are dependable, I have no worries there.
The car has a Dana 60, chromoly driveshaft, stock M6, Spec 3, two Walbros, and I have 60lb injecors on the way. I'd like to be able to run E85 if I want to but the bottom end needs to handle it.
Any other reasons to go with a 408 over a 370? Yes...it would be cool to say it's a 408...but I don't plan to make insane power and I think the 370 would handle more than I want to make anyway. It keeps some $ in my pocket for other things...like gas.
I didn't want to start another thread so if the OP doesn't mind a would like to piggy back off of him... I'm in the same situation as he is it's just that I have a different power adder. I have an APS kit and don't know if I should go 370 or 402/408, what do you guys suggest? And money is an object with me and my goals are simple just to max out the hp potential of the kit... Let the suggestions fly...
im doing the same thing you are
04-28-2008, 02:24 AM
#31
I didn't want to start another thread so if the OP doesn't mind a would like to piggy back off of him... I'm in the same situation as he is it's just that I have a different power adder. I have an APS kit and don't know if I should go 370 or 402/408, what do you guys suggest? And money is an object with me and my goals are simple just to max out the hp potential of the kit... Let the suggestions fly...
04-28-2008, 05:59 AM
#32
[QUOTE][sounds like you are trying to make your self feel better for all the money you wasted LOL
/QUOTE]
Sounds like you are trying to justify cheaping out...LOL
My 408 cost about 1000 more than a 370. This gets me a forged crank.A good thing to have as may want to hit my motor with some spray in addition to the turbos ,maybe decide to go with upgrade aps turbos althought right now figure don't need to. And the 408 will as said have more torque off boost than the 370 and should allow me to make same hp and torque as the 370 at a lower boost level. It should also give me quicker spooling.
So again the main reasons for going to 408. These are some of the same reasons went to afr heads over stock heads. They have a thicker deck better to make sure don't lift head gaskets. And again should let me make same power as stock heads at lower boost level. Already had fast 90/90 combo and see no reason to sell it off its fine to use up to 20psi or so. APS is using fast90/90 and afr 225 heads on their current test mule with lingenfelter gt 11 cam. I got gt7 cam cheap so giving it a try possibly with 1.8 rocker for a bit more lift.
It is a shame the boosted lists seem to have been deleted. There were many cars running 402 and 408 on there with turbo applications. There were also quite a few running decent times with 370 and some with 346 mostly forged up 346. Stock engines have guess two main weak points. Rod bolts and the hypercrap pistons.
Hypercrap pistons and yes calling them that on purpose as they have weak ringlands. I have several examples of them at home and can take pics ,one from ati lt1 and one from other buddies sts lt1. But same piston as ls1 cars. Hypercrap. Not good to use on boost.
Stock 346 crank is pretty good and stock rods seem ok. So why go 370 then, why not just stick with 346? Well most guys went to 370 for same reason I went to 408. Bigger engine should be better off boost and spool the turbos faster. Iron block supposed to be stronger than the 346 and crank is think stronger than the 346.
Also should need to run less boost on the 370 versus the 346 to make same power and torque again good things from head gasket point of view and lower boost might be better for certain turbos depending on the turbo.
I got this same arguement in my dsm cars. The come with 2.0 and you hear how its perfect for them and why would a guy want to go bigger to a 2.3 or a 2.4. You hear this rod ratio thrown out.How the 2.3 and 2.4 can't be revved that high,etc.
Well I built a 2.4. Thats 20 per cent jump in displacement. Like going from 350 to 427 roughly. And guess what. The car is much better to drive off boost. More torque and hp off boost. Still revs pretty quick. You need a shift light for sure.
Still rev it to 8000 daily and 8500 occasionally. Versus say 9000 for 2.0. And it does what you think .It gives me better spool up and allows me to run a bigger turbo
and get spool up like 800 or 1000 lower than would on the 2.0. Rod ratio and side loading and all that talk is nice theoretical talk. I love my 2.4 for street use and quite a few race cars are turing great times with them. And they are generally needed less boost to make same power and torque as the smaller engines.And my 2.4 is very torquey on boost much more so than the 2.0.Enough to break driveline parts if you don't upgrade them.
So we see again and again the talk of optimum rod stroke ratio. Yet we have just seen JM turn 9.90 at near 140mph on his 402 at only 12.5 psi.! And dyno just about 720rwhp on his auto with 9 inch and 4.10s. Again at only 12.5 psi .
A 370 might have needed 15 psi to get those numbers. A 346 might have needed 18psi. And his spool up and his off boost performance should both be better than a 370 or 346.
Wasted money?LOL Well wasted a grand on forged crank. Insurance ,why buy fored pistons and rods then? Stock might hold. Some have pushed the stock engines pretty far at high boost. OH will only be able to hit 9s with my smaller turbos on a 408..I guess I will just have to live with 9s. DARN! I wanted to go 6's! NOT!
The backpressure and smaller turbo arguements is another very common one I hear. Again in the dsms I see the practice not just theory. Factory put a tiny tiny turbo on the 2.0 2nd generation dsms. Its nicknamed the t too small.It is very tiny and its power limited to about 250 hp from its airflow rating. You push it too high on boost on the 2.0 and it mostly puts out hot air. You would think being very small it would thus have too much backpressure. Well maybe but don't see any big effects of this. The turbo puts out pretty much its rated airflow. And rated power.Gaskets don't blow with it from backpressure. Nothing much happens.Factory uses way too small turbos in many factory turbo cars.No apparent ill effects aside from lower power output levels. Less lag though than bigger turbos.More useable wider street power band. Wider down low where it counts giving up some up top.
You upgrade to bit bigger still likely not optimal for top end and you get say 350 hp from 35 pounds of airflow turbo. You get 350 hp at maybe same boost level you got 250 on the smaller turbo. Its airflow not just boost of course that determines output hp. Now you go up again to 400 hp turbo . You get 400 hp at mabye same boost level as before. You get more top end. You go up to 500 engine, 650 , 750.
Again you gain more potential hp. You gain top end and you gain more lag.Its a trade off .Some guys live with more lag than other guys. Some guys like more top end and more potential hp. But you lose useable powerband down low in normal street driving.
You know need to resort to tricks to get the bigger turbos off the line and to come on at lower rpm. You downshift if you have manuals. You use two steps to get off the line or antilag. You use bigger stalls in the auto cars. And you make excuses about how the bigger turbos save you gas by keeping you out of boost around town and how you don't mind the lag and narrow powerband.Whatever floats your boat.
So would like to see more concrete examples of this backpressure thing. It seems to be a bit of urban legend along with this more favorable bore/stroke /rod ratio urban legend.
SO PLEASE DON"T HATE ME FOR HAVING A BIGGER ENGINE! DON"T HATE ME FOR ONLY MABYE BEING ABLE TO GO 9s at 12.5 PSI IN MY 99% STREET CAR.
And I won't look down on you for running your little 346 and 370s with stock cranks or stock pistons or whatever.
I would have love to go to 427 or 454. Then might or might not have went to the bigger kit. But budget did come into it and don't need a 427 or 454 in my street car. Heck most of us don't need a turbo kit. These days you get thrown in jail for like 30 mph over the speed limit on the highway or the city. We don't even need factory power output levels. But guess thats why we are hot rodders and speed freaks. Some would say any mod are waste of money. Just keep it stock and be happy!
I intend to experiment a bit with this too small aps turbos on my 408. See if can get 800rwhp auto or 850rwhp on my m6 no spray for now.Should have numbers this year hopefully. And will admit if I am wrong and go from there. Won't be taking out my 408 for a 370 ,not a chance of that. But might go up to bigger snails if its proved that will have to.Proved in reality not theory.
/QUOTE]
Sounds like you are trying to justify cheaping out...LOL
My 408 cost about 1000 more than a 370. This gets me a forged crank.A good thing to have as may want to hit my motor with some spray in addition to the turbos ,maybe decide to go with upgrade aps turbos althought right now figure don't need to. And the 408 will as said have more torque off boost than the 370 and should allow me to make same hp and torque as the 370 at a lower boost level. It should also give me quicker spooling.
So again the main reasons for going to 408. These are some of the same reasons went to afr heads over stock heads. They have a thicker deck better to make sure don't lift head gaskets. And again should let me make same power as stock heads at lower boost level. Already had fast 90/90 combo and see no reason to sell it off its fine to use up to 20psi or so. APS is using fast90/90 and afr 225 heads on their current test mule with lingenfelter gt 11 cam. I got gt7 cam cheap so giving it a try possibly with 1.8 rocker for a bit more lift.
It is a shame the boosted lists seem to have been deleted. There were many cars running 402 and 408 on there with turbo applications. There were also quite a few running decent times with 370 and some with 346 mostly forged up 346. Stock engines have guess two main weak points. Rod bolts and the hypercrap pistons.
Hypercrap pistons and yes calling them that on purpose as they have weak ringlands. I have several examples of them at home and can take pics ,one from ati lt1 and one from other buddies sts lt1. But same piston as ls1 cars. Hypercrap. Not good to use on boost.
Stock 346 crank is pretty good and stock rods seem ok. So why go 370 then, why not just stick with 346? Well most guys went to 370 for same reason I went to 408. Bigger engine should be better off boost and spool the turbos faster. Iron block supposed to be stronger than the 346 and crank is think stronger than the 346.
Also should need to run less boost on the 370 versus the 346 to make same power and torque again good things from head gasket point of view and lower boost might be better for certain turbos depending on the turbo.
I got this same arguement in my dsm cars. The come with 2.0 and you hear how its perfect for them and why would a guy want to go bigger to a 2.3 or a 2.4. You hear this rod ratio thrown out.How the 2.3 and 2.4 can't be revved that high,etc.
Well I built a 2.4. Thats 20 per cent jump in displacement. Like going from 350 to 427 roughly. And guess what. The car is much better to drive off boost. More torque and hp off boost. Still revs pretty quick. You need a shift light for sure.
Still rev it to 8000 daily and 8500 occasionally. Versus say 9000 for 2.0. And it does what you think .It gives me better spool up and allows me to run a bigger turbo
and get spool up like 800 or 1000 lower than would on the 2.0. Rod ratio and side loading and all that talk is nice theoretical talk. I love my 2.4 for street use and quite a few race cars are turing great times with them. And they are generally needed less boost to make same power and torque as the smaller engines.And my 2.4 is very torquey on boost much more so than the 2.0.Enough to break driveline parts if you don't upgrade them.
So we see again and again the talk of optimum rod stroke ratio. Yet we have just seen JM turn 9.90 at near 140mph on his 402 at only 12.5 psi.! And dyno just about 720rwhp on his auto with 9 inch and 4.10s. Again at only 12.5 psi .
A 370 might have needed 15 psi to get those numbers. A 346 might have needed 18psi. And his spool up and his off boost performance should both be better than a 370 or 346.
Wasted money?LOL Well wasted a grand on forged crank. Insurance ,why buy fored pistons and rods then? Stock might hold. Some have pushed the stock engines pretty far at high boost. OH will only be able to hit 9s with my smaller turbos on a 408..I guess I will just have to live with 9s. DARN! I wanted to go 6's! NOT!
The backpressure and smaller turbo arguements is another very common one I hear. Again in the dsms I see the practice not just theory. Factory put a tiny tiny turbo on the 2.0 2nd generation dsms. Its nicknamed the t too small.It is very tiny and its power limited to about 250 hp from its airflow rating. You push it too high on boost on the 2.0 and it mostly puts out hot air. You would think being very small it would thus have too much backpressure. Well maybe but don't see any big effects of this. The turbo puts out pretty much its rated airflow. And rated power.Gaskets don't blow with it from backpressure. Nothing much happens.Factory uses way too small turbos in many factory turbo cars.No apparent ill effects aside from lower power output levels. Less lag though than bigger turbos.More useable wider street power band. Wider down low where it counts giving up some up top.
You upgrade to bit bigger still likely not optimal for top end and you get say 350 hp from 35 pounds of airflow turbo. You get 350 hp at maybe same boost level you got 250 on the smaller turbo. Its airflow not just boost of course that determines output hp. Now you go up again to 400 hp turbo . You get 400 hp at mabye same boost level as before. You get more top end. You go up to 500 engine, 650 , 750.
Again you gain more potential hp. You gain top end and you gain more lag.Its a trade off .Some guys live with more lag than other guys. Some guys like more top end and more potential hp. But you lose useable powerband down low in normal street driving.
You know need to resort to tricks to get the bigger turbos off the line and to come on at lower rpm. You downshift if you have manuals. You use two steps to get off the line or antilag. You use bigger stalls in the auto cars. And you make excuses about how the bigger turbos save you gas by keeping you out of boost around town and how you don't mind the lag and narrow powerband.Whatever floats your boat.
So would like to see more concrete examples of this backpressure thing. It seems to be a bit of urban legend along with this more favorable bore/stroke /rod ratio urban legend.
SO PLEASE DON"T HATE ME FOR HAVING A BIGGER ENGINE! DON"T HATE ME FOR ONLY MABYE BEING ABLE TO GO 9s at 12.5 PSI IN MY 99% STREET CAR.
And I won't look down on you for running your little 346 and 370s with stock cranks or stock pistons or whatever.
I would have love to go to 427 or 454. Then might or might not have went to the bigger kit. But budget did come into it and don't need a 427 or 454 in my street car. Heck most of us don't need a turbo kit. These days you get thrown in jail for like 30 mph over the speed limit on the highway or the city. We don't even need factory power output levels. But guess thats why we are hot rodders and speed freaks. Some would say any mod are waste of money. Just keep it stock and be happy!
I intend to experiment a bit with this too small aps turbos on my 408. See if can get 800rwhp auto or 850rwhp on my m6 no spray for now.Should have numbers this year hopefully. And will admit if I am wrong and go from there. Won't be taking out my 408 for a 370 ,not a chance of that. But might go up to bigger snails if its proved that will have to.Proved in reality not theory.
04-28-2008, 10:17 AM
#33
FormerVendor
Both the 370 and 402/408 would work but the bigger engine will have more low end and make more total power if it is cammed right with the same turbo. It will certainly have more power way down low and when you are off boost or at low boost.
The 400+ cube engine will also peak earlier in rpm for sure than a smaller one like people are saying so that only means you don't need as low a gear or loose a converter to make it work the same.
The 370 won't rev any faster either as the parts are the same or heavier depending on what you use for the rotating assembly. Some 6.0 cranks are actually heavier than an Eagle 4.000 crank! Of course the pistons are always heavier on a 370.
The 400+ cube engine will also peak earlier in rpm for sure than a smaller one like people are saying so that only means you don't need as low a gear or loose a converter to make it work the same.
The 370 won't rev any faster either as the parts are the same or heavier depending on what you use for the rotating assembly. Some 6.0 cranks are actually heavier than an Eagle 4.000 crank! Of course the pistons are always heavier on a 370.
04-28-2008, 12:37 PM
#34
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Thanks for all the replies....but...stop this turbo talk!! Haha.
I'll be using a D1SC. My goal is only 550 rwhp and this is a street car, not a track queen. I don't wanna try and make that power on a stock LS1 because it would just be disaster waiting to happen. Right now I'm leaning towards the 370 because it will handle more power than I would want to make anyway and the block would need no additional windage/rod clearance work. TSP has brand new 370 assemblies for 3400 the way I'd want it...Diamond pistons, Callies rods, ARP hardware, and a stock crank. The stock cranks are dependable, I have no worries there.
The car has a Dana 60, chromoly driveshaft, stock M6, Spec 3, two Walbros, and I have 60lb injecors on the way. I'd like to be able to run E85 if I want to but the bottom end needs to handle it.
Any other reasons to go with a 408 over a 370? Yes...it would be cool to say it's a 408...but I don't plan to make insane power and I think the 370 would handle more than I want to make anyway. It keeps some $ in my pocket for other things...like gas.
I'll be using a D1SC. My goal is only 550 rwhp and this is a street car, not a track queen. I don't wanna try and make that power on a stock LS1 because it would just be disaster waiting to happen. Right now I'm leaning towards the 370 because it will handle more power than I would want to make anyway and the block would need no additional windage/rod clearance work. TSP has brand new 370 assemblies for 3400 the way I'd want it...Diamond pistons, Callies rods, ARP hardware, and a stock crank. The stock cranks are dependable, I have no worries there.
The car has a Dana 60, chromoly driveshaft, stock M6, Spec 3, two Walbros, and I have 60lb injecors on the way. I'd like to be able to run E85 if I want to but the bottom end needs to handle it.
Any other reasons to go with a 408 over a 370? Yes...it would be cool to say it's a 408...but I don't plan to make insane power and I think the 370 would handle more than I want to make anyway. It keeps some $ in my pocket for other things...like gas.
Who are you planning on having build the motor? Local?
04-28-2008, 02:56 PM
#38
[QUOTE=MY99TAWS6;9251712] You gotta be kidding me! Cliff notes?
[sounds like you are trying to make your self feel better for all the money you wasted LOL
/QUOTE]
Sounds like you are trying to justify cheaping out...LOL
My 408 cost about 1000 more than a 370. This gets me a forged crank.A good thing to have as may want to hit my motor with some spray in addition to the turbos ,maybe decide to go with upgrade aps turbos althought right now figure don't need to. And the 408 will as said have more torque off boost than the 370 and should allow me to make same hp and torque as the 370 at a lower boost level. It should also give me quicker spooling.
So again the main reasons for going to 408. These are some of the same reasons went to afr heads over stock heads. They have a thicker deck better to make sure don't lift head gaskets. And again should let me make same power as stock heads at lower boost level. Already had fast 90/90 combo and see no reason to sell it off its fine to use up to 20psi or so. APS is using fast90/90 and afr 225 heads on their current test mule with lingenfelter gt 11 cam. I got gt7 cam cheap so giving it a try possibly with 1.8 rocker for a bit more lift.
It is a shame the boosted lists seem to have been deleted. There were many cars running 402 and 408 on there with turbo applications. There were also quite a few running decent times with 370 and some with 346 mostly forged up 346. Stock engines have guess two main weak points. Rod bolts and the hypercrap pistons.
Hypercrap pistons and yes calling them that on purpose as they have weak ringlands. I have several examples of them at home and can take pics ,one from ati lt1 and one from other buddies sts lt1. But same piston as ls1 cars. Hypercrap. Not good to use on boost.
Stock 346 crank is pretty good and stock rods seem ok. So why go 370 then, why not just stick with 346? Well most guys went to 370 for same reason I went to 408. Bigger engine should be better off boost and spool the turbos faster. Iron block supposed to be stronger than the 346 and crank is think stronger than the 346.
Also should need to run less boost on the 370 versus the 346 to make same power and torque again good things from head gasket point of view and lower boost might be better for certain turbos depending on the turbo.
I got this same arguement in my dsm cars. The come with 2.0 and you hear how its perfect for them and why would a guy want to go bigger to a 2.3 or a 2.4. You hear this rod ratio thrown out.How the 2.3 and 2.4 can't be revved that high,etc.
Well I built a 2.4. Thats 20 per cent jump in displacement. Like going from 350 to 427 roughly. And guess what. The car is much better to drive off boost. More torque and hp off boost. Still revs pretty quick. You need a shift light for sure.
Still rev it to 8000 daily and 8500 occasionally. Versus say 9000 for 2.0. And it does what you think .It gives me better spool up and allows me to run a bigger turbo
and get spool up like 800 or 1000 lower than would on the 2.0. Rod ratio and side loading and all that talk is nice theoretical talk. I love my 2.4 for street use and quite a few race cars are turing great times with them. And they are generally needed less boost to make same power and torque as the smaller engines.And my 2.4 is very torquey on boost much more so than the 2.0.Enough to break driveline parts if you don't upgrade them.
So we see again and again the talk of optimum rod stroke ratio. Yet we have just seen JM turn 9.90 at near 140mph on his 402 at only 12.5 psi.! And dyno just about 720rwhp on his auto with 9 inch and 4.10s. Again at only 12.5 psi .
A 370 might have needed 15 psi to get those numbers. A 346 might have needed 18psi. And his spool up and his off boost performance should both be better than a 370 or 346.
Wasted money?LOL Well wasted a grand on forged crank. Insurance ,why buy fored pistons and rods then? Stock might hold. Some have pushed the stock engines pretty far at high boost. OH will only be able to hit 9s with my smaller turbos on a 408..I guess I will just have to live with 9s. DARN! I wanted to go 6's! NOT!
The backpressure and smaller turbo arguements is another very common one I hear. Again in the dsms I see the practice not just theory. Factory put a tiny tiny turbo on the 2.0 2nd generation dsms. Its nicknamed the t too small.It is very tiny and its power limited to about 250 hp from its airflow rating. You push it too high on boost on the 2.0 and it mostly puts out hot air. You would think being very small it would thus have too much backpressure. Well maybe but don't see any big effects of this. The turbo puts out pretty much its rated airflow. And rated power.Gaskets don't blow with it from backpressure. Nothing much happens.Factory uses way too small turbos in many factory turbo cars.No apparent ill effects aside from lower power output levels. Less lag though than bigger turbos.More useable wider street power band. Wider down low where it counts giving up some up top.
You upgrade to bit bigger still likely not optimal for top end and you get say 350 hp from 35 pounds of airflow turbo. You get 350 hp at maybe same boost level you got 250 on the smaller turbo. Its airflow not just boost of course that determines output hp. Now you go up again to 400 hp turbo . You get 400 hp at mabye same boost level as before. You get more top end. You go up to 500 engine, 650 , 750.
Again you gain more potential hp. You gain top end and you gain more lag.Its a trade off .Some guys live with more lag than other guys. Some guys like more top end and more potential hp. But you lose useable powerband down low in normal street driving.
You know need to resort to tricks to get the bigger turbos off the line and to come on at lower rpm. You downshift if you have manuals. You use two steps to get off the line or antilag. You use bigger stalls in the auto cars. And you make excuses about how the bigger turbos save you gas by keeping you out of boost around town and how you don't mind the lag and narrow powerband.Whatever floats your boat.
So would like to see more concrete examples of this backpressure thing. It seems to be a bit of urban legend along with this more favorable bore/stroke /rod ratio urban legend.
SO PLEASE DON"T HATE ME FOR HAVING A BIGGER ENGINE! DON"T HATE ME FOR ONLY MABYE BEING ABLE TO GO 9s at 12.5 PSI IN MY 99% STREET CAR.
And I won't look down on you for running your little 346 and 370s with stock cranks or stock pistons or whatever.
I would have love to go to 427 or 454. Then might or might not have went to the bigger kit. But budget did come into it and don't need a 427 or 454 in my street car. Heck most of us don't need a turbo kit. These days you get thrown in jail for like 30 mph over the speed limit on the highway or the city. We don't even need factory power output levels. But guess thats why we are hot rodders and speed freaks. Some would say any mod are waste of money. Just keep it stock and be happy!
I intend to experiment a bit with this too small aps turbos on my 408. See if can get 800rwhp auto or 850rwhp on my m6 no spray for now.Should have numbers this year hopefully. And will admit if I am wrong and go from there. Won't be taking out my 408 for a 370 ,not a chance of that. But might go up to bigger snails if its proved that will have to.Proved in reality not theory.
/QUOTE]
Sounds like you are trying to justify cheaping out...LOL
My 408 cost about 1000 more than a 370. This gets me a forged crank.A good thing to have as may want to hit my motor with some spray in addition to the turbos ,maybe decide to go with upgrade aps turbos althought right now figure don't need to. And the 408 will as said have more torque off boost than the 370 and should allow me to make same hp and torque as the 370 at a lower boost level. It should also give me quicker spooling.
So again the main reasons for going to 408. These are some of the same reasons went to afr heads over stock heads. They have a thicker deck better to make sure don't lift head gaskets. And again should let me make same power as stock heads at lower boost level. Already had fast 90/90 combo and see no reason to sell it off its fine to use up to 20psi or so. APS is using fast90/90 and afr 225 heads on their current test mule with lingenfelter gt 11 cam. I got gt7 cam cheap so giving it a try possibly with 1.8 rocker for a bit more lift.
It is a shame the boosted lists seem to have been deleted. There were many cars running 402 and 408 on there with turbo applications. There were also quite a few running decent times with 370 and some with 346 mostly forged up 346. Stock engines have guess two main weak points. Rod bolts and the hypercrap pistons.
Hypercrap pistons and yes calling them that on purpose as they have weak ringlands. I have several examples of them at home and can take pics ,one from ati lt1 and one from other buddies sts lt1. But same piston as ls1 cars. Hypercrap. Not good to use on boost.
Stock 346 crank is pretty good and stock rods seem ok. So why go 370 then, why not just stick with 346? Well most guys went to 370 for same reason I went to 408. Bigger engine should be better off boost and spool the turbos faster. Iron block supposed to be stronger than the 346 and crank is think stronger than the 346.
Also should need to run less boost on the 370 versus the 346 to make same power and torque again good things from head gasket point of view and lower boost might be better for certain turbos depending on the turbo.
I got this same arguement in my dsm cars. The come with 2.0 and you hear how its perfect for them and why would a guy want to go bigger to a 2.3 or a 2.4. You hear this rod ratio thrown out.How the 2.3 and 2.4 can't be revved that high,etc.
Well I built a 2.4. Thats 20 per cent jump in displacement. Like going from 350 to 427 roughly. And guess what. The car is much better to drive off boost. More torque and hp off boost. Still revs pretty quick. You need a shift light for sure.
Still rev it to 8000 daily and 8500 occasionally. Versus say 9000 for 2.0. And it does what you think .It gives me better spool up and allows me to run a bigger turbo
and get spool up like 800 or 1000 lower than would on the 2.0. Rod ratio and side loading and all that talk is nice theoretical talk. I love my 2.4 for street use and quite a few race cars are turing great times with them. And they are generally needed less boost to make same power and torque as the smaller engines.And my 2.4 is very torquey on boost much more so than the 2.0.Enough to break driveline parts if you don't upgrade them.
So we see again and again the talk of optimum rod stroke ratio. Yet we have just seen JM turn 9.90 at near 140mph on his 402 at only 12.5 psi.! And dyno just about 720rwhp on his auto with 9 inch and 4.10s. Again at only 12.5 psi .
A 370 might have needed 15 psi to get those numbers. A 346 might have needed 18psi. And his spool up and his off boost performance should both be better than a 370 or 346.
Wasted money?LOL Well wasted a grand on forged crank. Insurance ,why buy fored pistons and rods then? Stock might hold. Some have pushed the stock engines pretty far at high boost. OH will only be able to hit 9s with my smaller turbos on a 408..I guess I will just have to live with 9s. DARN! I wanted to go 6's! NOT!
The backpressure and smaller turbo arguements is another very common one I hear. Again in the dsms I see the practice not just theory. Factory put a tiny tiny turbo on the 2.0 2nd generation dsms. Its nicknamed the t too small.It is very tiny and its power limited to about 250 hp from its airflow rating. You push it too high on boost on the 2.0 and it mostly puts out hot air. You would think being very small it would thus have too much backpressure. Well maybe but don't see any big effects of this. The turbo puts out pretty much its rated airflow. And rated power.Gaskets don't blow with it from backpressure. Nothing much happens.Factory uses way too small turbos in many factory turbo cars.No apparent ill effects aside from lower power output levels. Less lag though than bigger turbos.More useable wider street power band. Wider down low where it counts giving up some up top.
You upgrade to bit bigger still likely not optimal for top end and you get say 350 hp from 35 pounds of airflow turbo. You get 350 hp at maybe same boost level you got 250 on the smaller turbo. Its airflow not just boost of course that determines output hp. Now you go up again to 400 hp turbo . You get 400 hp at mabye same boost level as before. You get more top end. You go up to 500 engine, 650 , 750.
Again you gain more potential hp. You gain top end and you gain more lag.Its a trade off .Some guys live with more lag than other guys. Some guys like more top end and more potential hp. But you lose useable powerband down low in normal street driving.
You know need to resort to tricks to get the bigger turbos off the line and to come on at lower rpm. You downshift if you have manuals. You use two steps to get off the line or antilag. You use bigger stalls in the auto cars. And you make excuses about how the bigger turbos save you gas by keeping you out of boost around town and how you don't mind the lag and narrow powerband.Whatever floats your boat.
So would like to see more concrete examples of this backpressure thing. It seems to be a bit of urban legend along with this more favorable bore/stroke /rod ratio urban legend.
SO PLEASE DON"T HATE ME FOR HAVING A BIGGER ENGINE! DON"T HATE ME FOR ONLY MABYE BEING ABLE TO GO 9s at 12.5 PSI IN MY 99% STREET CAR.
And I won't look down on you for running your little 346 and 370s with stock cranks or stock pistons or whatever.
I would have love to go to 427 or 454. Then might or might not have went to the bigger kit. But budget did come into it and don't need a 427 or 454 in my street car. Heck most of us don't need a turbo kit. These days you get thrown in jail for like 30 mph over the speed limit on the highway or the city. We don't even need factory power output levels. But guess thats why we are hot rodders and speed freaks. Some would say any mod are waste of money. Just keep it stock and be happy!
I intend to experiment a bit with this too small aps turbos on my 408. See if can get 800rwhp auto or 850rwhp on my m6 no spray for now.Should have numbers this year hopefully. And will admit if I am wrong and go from there. Won't be taking out my 408 for a 370 ,not a chance of that. But might go up to bigger snails if its proved that will have to.Proved in reality not theory.
04-28-2008, 03:38 PM
#39
For 550 rwhp a 370 or 408 is overkill with a D1SC IMO. Hell there are guys getting that much power out of a 408 N/A. If your really set on going with a large CI engine over stock, then go with the 370. If it were me and I was looking for 550 rwhp id buy a built 346/347 shortblock, toss on some patriot LQ9 heads, get a decent blower cam, and then push in 10 psi or so for over 600 rwhp. With a good tune and fuel system it would live a long time. JMO.
04-28-2008, 03:48 PM
#40
For 550 rwhp a 370 or 408 is overkill with a D1SC IMO. Hell there are guys getting that much power out of a 408 N/A. If your really set on going with a large CI engine over stock, then go with the 370. If it were me and I was looking for 550 rwhp id buy a built 346/347 shortblock, toss on some patriot LQ9 heads, get a decent blower cam, and then push in 10 psi or so for over 600 rwhp. With a good tune and fuel system it would live a long time. JMO.
Right now I have a stock 30k mile LS1 that I do not want to have forged internals put in. It doesnt make sense. And building a forged 347 is going to cost more than a 370. The only thing I'm really giving up is the aluminum block...
LQ9 heads for sure.