Forged 346 vs 388 for a twin turbo setup /w stock heads?
11-06-2003, 09:30 PM
#1
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Forged 346 vs 388 for a twin turbo setup /w stock heads? Apparently im starting over from scratch now because a customer came into the shop today and is buying my complete ls1 from my car that im doing a homebuild Twin T04B turbo setup on.
So now i need to build a new longblock.
My quesiton is this. Im going to be using stock 6.0L LQ4/9 Heads (they flow like an LS6) /w good springs on them.
The turbos im using will support 450-500 each (900hp), and were recommended by the turbo companies i called when i got them for the ls1 im doing.
I can build a forged 346 shortblock for about $1650 (stock crank, eagle rods, forged pistons, machinework) or a 388 all bore for $2500 (can get a bare resleeved block @ cost from local race machinshop @ $1080)
On a stock headed motor, is going to be worth the extra $900 to do a all bore motor ??? I dont think it will give more than 20-30 horsepower and isnt worth the extra money because i plan on just turning the boost up if i want more power...
What do you all think??
So now i need to build a new longblock.
My quesiton is this. Im going to be using stock 6.0L LQ4/9 Heads (they flow like an LS6) /w good springs on them.
The turbos im using will support 450-500 each (900hp), and were recommended by the turbo companies i called when i got them for the ls1 im doing.
I can build a forged 346 shortblock for about $1650 (stock crank, eagle rods, forged pistons, machinework) or a 388 all bore for $2500 (can get a bare resleeved block @ cost from local race machinshop @ $1080)
On a stock headed motor, is going to be worth the extra $900 to do a all bore motor ??? I dont think it will give more than 20-30 horsepower and isnt worth the extra money because i plan on just turning the boost up if i want more power...
What do you all think??
11-06-2003, 10:03 PM
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I think you answerred your own question there. The main purpose for going with a bigger bore is better heads, but if you aren't going to be porting the 6.0's at all then I'd go with the 346
11-06-2003, 10:32 PM
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I would preferr to keep the extra strength afforded by a non-bored block. If anything I would do a stroker crank for extra cubic inches (which will help to spool the turbo's quicker).
11-07-2003, 07:56 PM
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I'm with ChrisB, I don't see the big bore block as being the safe and dependable option here. When I first read the post this morning I thought you meant an iron block bored out a bit. I'd do a 4.060 iron block or a 3.905 stock aluminum block, but a 4.100 bore resleever to me is asking for problems.
But a bigger bore/ bigger ci motor would allow you to drop compression and still make decent power out of boost, or allow you to make more power than a stock ci motor like my 348ci. A 400ci motor will make more power than a 348ci motor all things being equal.
But a bigger bore/ bigger ci motor would allow you to drop compression and still make decent power out of boost, or allow you to make more power than a stock ci motor like my 348ci. A 400ci motor will make more power than a 348ci motor all things being equal.
11-07-2003, 08:45 PM
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more displacement means more power on pump gas. if you are using racing fuels, just up the boost.
if it were me, I'd go iron block 4.00" bore and a forged 4" stroke crank, which makes a 402 CI motor. then boost the **** out of it. I think this motor would laugh at 900 hp as long as you can keep the heads down.
if it were me, I'd go iron block 4.00" bore and a forged 4" stroke crank, which makes a 402 CI motor. then boost the **** out of it. I think this motor would laugh at 900 hp as long as you can keep the heads down.
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11-07-2003, 08:48 PM
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More bore = more surface area
More stroke = more torque
A 454ci BBC will make more engine power than a 350 SBC.
SupraTT's run over 30 lbs of boost to run as fast as we might run with 15-20 lbs of boost, because it's only a 183ci engine.
More stroke = more torque
A 454ci BBC will make more engine power than a 350 SBC.
SupraTT's run over 30 lbs of boost to run as fast as we might run with 15-20 lbs of boost, because it's only a 183ci engine.
11-07-2003, 08:48 PM
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I'd also go with a 4.035 bore iron block and 4 inch stroke crank with bigger head bolts, good main bolts and 6L heads. Will be sick with the twin turbo setup and much less likely to lift heads with the ironblock and bigger headstuds/good gaskets 
11-08-2003, 09:51 PM
#11
I agree with both Scott and Chris. It all boils down to your goals. The bigger motor is not needed, but I would think it would last longer because you could use less boost to achieve the same horsepower levels. The ford guys have set a precedence with using smaller motors to achieve awesome dyno #'s and track times. The bigger motor would require more fuel of course and would need the FAST system for sure to get your moneys worth out of it. I for one was hoping by now the LS1 build prices would come down, but it seems the prices are remaining stable. My goals have always been for a street setup. No track for me. I just want to hunt down some Supras One of our local Supra guys keep challenging us to a 0 to 200mph run. One day I am going to take him up on his challenge.
