Should I build a 346, 370 or 408
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On The Tree
Joined: Nov 2006
Posts: 175
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From: Southwest MO
Should I build a 346, 370 or 408 Ok I currently have a stock ls1 with a f1a. I want to build it up to about 800hp. I was planning on running meth, 91 and Bob's blower cam and stock 317. Should I even bother with that and just start building a new forged motor? What motor should I start to build? The car is a weekend car, I want it for show but I want it to go. Currently it has a M6 but I suck at driving it that I might have to get an auto. Plan on going to the track about three times a year. Any advice is welcomed.
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Verdad Gallardo You are pretty much right. Only way to may a 370 or larger is to re-sleeve it. In fact i have seen at least one build on here that i believe its a 427 re-sleeved ls6 block.
On the stock LS1 motors, you can get up to a 396ci but its not good for FI. The max bore you can take a LS1 out to is a 3.905". There's 3.8", 4.000" and 4.125" stroker cranks you can use but none of them are advised for FI builds....some venture there but they are bold! lol Most 370ci motors come from either LQ4/9 iron motors or a LS2. I've put down 830rwhp on 18psi with my 370/Old F1 combo so far. IMO a 370 is one of the best bang for the buck FI motors you can do. With a 4.030" bore it will help to decrease valve shrouding, increasing flow and it will be very reliable.
oops...My bad. I was thinking the biggest on stock stroke. Actually I have a 3.905 bore myself and you can go as big as 3.908 which will make a 348c.i. with a stock 3.622 stroke and a 383 with a 4.00 stroke. A 3.905 bore with a 4.00 stroke will actually be in the 382 c.i. area FWIW
I don't think anyone takes a LS1 out further then a 3.905" really. It removes to much from the cyl walls leaving them thin and weak, also able to distort easier. Remember with boost, your adding a lot more cyl pressure. With that bore you can use a 3.800", 4.000" (383-ish) or a 4.125" (396-ish) but none of those strokes are really advised. I've been looking alot into oversquare motor (bigger bore then stroke) and that seems to be the best route. Like I said a few guys have done it but myself and others steer away from greatly stroked FI motors....to many issues to arrise.
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From: Detroit, MI - Camp Pendleton, CA
I was on my way to building a 402 or 408 but I've steered away from the 4" stroke as well. Plus, stock cranks have been pushed passed 1000+hp which helps the cost of buying forged ones. Now I'm just waiting for my boy blue to come back from Afghan so I can buy his motor! 
so I am in the process of building mine as well, and this was a question on my mind. So keeping the stock block at 347 with the 3.905 bore will indeed keep my cylinder walls thick and allow me more reliability at 700+rwhp? I will be achieving this with a set of 225-227 heads with a 3/4 deck, diamonds, callies, and katech rod bolts, and studs. this will be a d1 car. not and f1.
Ok I currently have a stock ls1 with a f1a. I want to build it up to about 800hp. I was planning on running meth, 91 and Bob's blower cam and stock 317. Should I even bother with that and just start building a new forged motor? What motor should I start to build? The car is a weekend car, I want it for show but I want it to go. Currently it has a M6 but I suck at driving it that I might have to get an auto. Plan on going to the track about three times a year. Any advice is welcomed.
If so, what kind of power are you making?