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I was wondering g about this I been wanting to build a 370 twin turbo for awhile then I seen a 408 and it was nasty wondering everyone's opinion on this and what they would use turbos sizes and heads valves let's get heads rocking and we say 1000 hp is the goal and torque u name the torque
I was actually in the same quandary as you were, then leaned towards a 408 after researching more and more the snow ball effect rolled in. I ended up ordering an ERL superdeck 6-bolt 427 with PRC 285 heads and topped it with twin billet turbonetics 7575's going on it with the new Huron speed V2 twin kit. I think I overshot my goals by just a little but the new setup should make a pretty brutal street car... you wont decide till you actually order something.
I tell everyone the same thing when they ask this question. Go put your eyes on a set of pistons used in a 408 build Then go look at a set used in a 370. The difference is staggering.
The biggest benefit to running a 370ci motor in my eyes is the retention of factory geometry. Not stroking a motor your about to throw a bunch of boost at always appealed to me as far as reliability was concerned. In the end the goals and more important the weight/type of vehicle this is going into is important. A 370ci motor with a set of twin 62mm and bigger will make some SERIOUS hp. If you drive a tank/dig race/run the 1/8 alot than maybe a 408 is a better choice due to the early on set of torque compared to the 370.
Without more details though its a shot in the dark as far as opinons/suggestions are concerned.
I'm on the fence as well about whether or not going 370 or 408 with my PT8285. I have a LQ4 in the garage and thought about going with a dragon slayer crank, callies billet rods, and wisco pistons. Since i'm wanting to go forged crank I could just bite the bullet and get the 408 stroker setup and slapping my 317 heads and ls6 intake on to see what it can do. Later on maybe do a ls3 top end swap.
OP I think it all depends on whether or not you want to keep the stock crank. They are pretty strong to begin with.
I'd say neither... Factory bore and stroke is best if your trying to get the most out of a OEM block. The cyl walls on a 6.0 aren't very thick to start with. If your going aftermarket on the block, bore and stroke away...
Block will be fine. You'll likely have head gasket leaks before having block issues from stroke. Either will be fine tho imo. I like cubes for less boost which gives you less heat into intake charge, so you dont tax the intercooler as much
theres many different good opinions here, personally i went 416 because with 4bolt heads i wanted as much power on as least boost as possible, and my turbo should spool quick. compared to a 5.3 thatsa lil laggy n 1.5 to 2x the boost to make the same power
Block will be fine. You'll likely have head gasket leaks before having block issues from stroke. Either will be fine tho imo. I like cubes for less boost which gives you less heat into intake charge, so you dont tax the intercooler as much
That's ridiculous in so many ways I don't know where to start...
Bottom line. If your trying to extract the most out of a setup with aftermarket rotating assy the block is the weak point. Leaving it alone is the best bet.
Cracks between the bores are common on 1000whp+ HP 6.0 builds. More so if they have been bored. The material just isn't there for big power on most castings. Some are better than others. Stock48 has sonic tested a **** ton of 6.0 blocks.
Cyls are very thin between cyls. Thrust. Side is always thick .200" + but have seen as thin as .060", and about .150" at the thickest between the cyls at std bore.
Thats why you get a well machined shortblock from ERL or other well known builder that can handle the HP goals your looking for, all those issues are quite a bit less worrisome if you get the right components for your boosted application. If you want to skimp and then get upset when your motor dont hold together is just the risk you have to take.
how is forced induction a replacement for displacement? you can add boost to any size engine. if anything a replacement for displacement is RPMs because generally the bigger you go, the lower you can rev, all else equal.
That's ridiculous in so many ways I don't know where to start...
Bottom line. If your trying to extract the most out of a setup with aftermarket rotating assy the block is the weak point. Leaving it alone is the best bet.
Cracks between the bores are common on 1000whp+ HP 6.0 builds. More so if they have been bored. The material just isn't there for big power on most castings. Some are better than others. Stock48 has sonic tested a **** ton of 6.0 blocks.
Well my two local buds must be doing something wrong then lmao. 1150 and 1050 whp builds. Th400 and 80e trannies. 8.3 et and 8.6 et
That doesn’t prove anything… you can achieve the same numbers with a factory bore/stroke as well. Running lower boost levels to not tax the IC makes no sense. The higher temperature differential across the IC the more efficient it becomes. Shying away from big boost because you’re worried about your IAT’s temps is crazy. If you have the right combo, IAT's won't be a concern.
The bigger engines will make more power per PSI to a point. But the factory bore/stroke engines will be able to exceed that point. If reliability or max effort is the goal, you want to remove as little material as possible on an OEM block… It’s common sense.
You dont need cubes to make power with boost. For example flashs ws6 is only a 364. Youre better off spending the money you would spend on stroking or big cubes and bullet proofing the rest of the car.
Go get yourself a junkyard 5.3 or 6.0 iron block get it machined line honed forge pistons if you plan on just under 1000 the crank will be fine youll have a reliable motor to throw plenty of boost at without having to worry about the block.
03-15-2015, 06:38 PM
370 twin or 408 twin turbo would u build 
