346ci FI vs 408ci FI
Thread Starter
Joined: Nov 2001
Posts: 8,259
Likes: 4
From: Valrico, Florida
346ci FI vs 408ci FI I was asked the other day if the difference in power between a 346ci FI street car and a 408ci FI street car would be worth the extra coin?
Is the bigger cubed motor only good for making more power on pump gas?
Is the bigger cubed motor only good for making more power on pump gas?
It will make more power on pump or race gas. Just depends on how much you want to spend on more power. A 348 will take you up to 650 rwhp with pump gas and if you want more than that your gonna need to add meth or cubes. All depends where you want to spend your money and the combo you want.
The 408 will also make a lot more torque in the lower RPM range because of the longer stroke. This is help make up the difference because of the lower compression when driving around and the S/C has not started to build boost. Plus as stated above, it will make more power 
Keith
Keith
I think it would depend on if you can hook the car up. A ton of torque on street tires is hard to put to the ground. I would save the money and go with a 346 myself, especially given some of the numbers put out by 346 cars lately.
Bruce
Bruce
Originally Posted by 52172
It will make more power on pump or race gas. Just depends on how much you want to spend on more power. A 348 will take you up to 650 rwhp with pump gas and if you want more than that your gonna need to add meth or cubes. All depends where you want to spend your money and the combo you want.
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Originally Posted by 52172
with meth he doesn't do it without. 750 on a mustang is like 820 on a dynojet and that aint happening.
I just looked he hit 700 on a mustang dyno with 93 which is 750 dynojet. He gets some very high numbers. I am stuck with 91 here in Ca and am shooting for 650+ rwhp and a single turbo and large FMIC. I will be very happy if we hit 700 rwhp.
Originally Posted by 52172
I just looked he hit 700 on a mustang dyno with 93 which is 750 dynojet. He gets some very high numbers. I am stuck with 91 here in Ca and am shooting for 650+ rwhp and a single turbo and large FMIC. I will be very happy if we hit 700 rwhp.
i have had both and really enjoy the extra grunt of the 408 when not in boost and just driving/cruising around. 346 was better on gas mileage whn not in boost as well so there is a trade off
If you're in your powerband, they will both accomplish the same goal... 408, yes, earlier torque, but the 346 can spin higher and will end up with a very similar curve in size and shape, just shifted higher on the powerband.
If your rwhp goal cannot be had with the 346, obviously it cannot be a candidate. But if it can, then the choice would be 346 for me for financial reasons... Well, I mean it WAS because that's exactly what I had built.
If your rwhp goal cannot be had with the 346, obviously it cannot be a candidate. But if it can, then the choice would be 346 for me for financial reasons... Well, I mean it WAS because that's exactly what I had built.
Thread Starter
Joined: Nov 2001
Posts: 8,259
Likes: 4
From: Valrico, Florida
My 408ci rev's just like a 346ci. As long as my valvetrain is up to the task I could spin it past 7krpm.. I have always thought the difference is like 1 hp per ci. IN the case of boost it might even be 1 rwhp per ci. The math guys can do the tq calculations... 62rwhp difference between a 346ci and a 408ci..
So if you use my FULL GUESS mode logic then you can run 2lbs less boost to make the same power as a 346ci.
So if you use my FULL GUESS mode logic then you can run 2lbs less boost to make the same power as a 346ci.
I think it comes down to how much money you've got to burn. Bigger motor, bigger turbo, bigger fuel system, tunning equipment etc, it all adds up. Once you determine your goals you'll be able to tell if the 346 will cut it or not. Like bboy, I'm building a 346 based solely on cost.
Originally Posted by VINCE
My 408ci rev's just like a 346ci. As long as my valvetrain is up to the task I could spin it past 7krpm.. I have always thought the difference is like 1 hp per ci. IN the case of boost it might even be 1 rwhp per ci. The math guys can do the tq calculations... 62rwhp difference between a 346ci and a 408ci..
So if you use my FULL GUESS mode logic then you can run 2lbs less boost to make the same power as a 346ci.
So if you use my FULL GUESS mode logic then you can run 2lbs less boost to make the same power as a 346ci.
7k isn't high-rpm. We spun our stock ls1 to near 8500 and that's only medium rpm for a motor that small.
TECH Enthusiast
Joined: Feb 2007
Posts: 686
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From: Seattle area
Yeah since I am not made out of money I will hope that when I go FI that the motor doesn't go boom in a big way and then in go forged internals. I would consider a 402 if the engine did take everything with it.
Thread Starter
Joined: Nov 2001
Posts: 8,259
Likes: 4
From: Valrico, Florida
Originally Posted by LTLHOMER
lol that's some interesting math.
7k isn't high-rpm. We spun our stock ls1 to near 8500 and that's only medium rpm for a motor that small.
7k isn't high-rpm. We spun our stock ls1 to near 8500 and that's only medium rpm for a motor that small.
Originally Posted by VINCE
7krpm is high rpm to me.. I am not talking about my Supra.. Show us this graph of a stock LS1 spinning to 8500rpm please. Do you have a video?
Yea I'd like to see it also. A stock ls1 spinning to 8500 will go KABOOM very quick. If that is medium RPM what do you call high?