i wasn't sure whether to put this here or in the forced induction section.

i've been reading up on these 408's & i'm impressed. how much boost can they handle?

 

The better question is how much power do you want to make, and how much can you afford.

With a good block + rotating assy you can just about make as much power as you would ever want. 1000+, maybe as much as 1500+, nowadays.

With a factory block its still pretty easy to make 7-800+

Boost is just resistance to flow. good pistons + rods, and as much cylinder head as you can afford usually will get the job done. Dont get caught up in, I want to make XX psi boost. The right combo makes the power you want at the least amount of boost possible, to keep it safe and get long life out of it. Unless you dont care, or have unlimited budget.

 

That's an extremely broad question. It all depends on what internals you use. Typically the iron LQ9 block can handle a crapton of power.

 

what are some common boost setups with 408's?

i did a search but didn't find any

 

Broad question again.

What are your goals? What is your budget? What setup are you trying to replicate/duplicate?

 

You can go anywhere from a 6.0l iron block w some what cheap rods and blower friendly pistons and a z06 cam (not a 408), to an LSx block w a forged stroker crank and big $$$ rods and pistons.

In a price range anywhere from maybe a few thousand to 15k+ for a motor, depending on how much you can assemble yourself. Then top it off with turbo(s), or a supercharger(of various types). almost limitless possibilities and power to be made.

Again, whats the budget? and how much power do you want to make? Is it a hardcore race only setup that needs to be reliable at WOT + high rpm all the time, or is it a daily driven street car that will only see the occasional full throttle blast.

An example. My setup isn't a 408, because my small turbo's are pretty maxed out with 347 ci's. BUT it will still make decent power, especially for a street car.

Its an ls1 block and crank, compstar rods, diamond blower pistons, custom turbo cam, and dart 225 heads w slightly bigger chambers to keep compression a tad below 9:1. I expect to make 600-650 rwhp when its tuned, depending on how much boost I can run with 93 octane. I expect 12-15 psi will get me there. If budget and time allows, I might go alchy injection to make a little more power.

high end build. http://videos.streetfire.net/video/L...-on_168394.htm

 

thx for the replies fellows

no goals & budget just yet. right now i'm just gathering info, i'm still enjoying my 93 LT1 : )

i knew that LS1's made more power but those 408's make WAY more power, Kraest's 408 made almost as much to the wheels as i'm expecting to the crank of my 383 build lol

what sparked my interest is there is a guy that ran a 5.98 at the local 1/8 mile track in an RX7. rumor has it that its a 408 with a turbo, people that saw it run heard the turbo. he won't lift the hood or say much. he also drove it to the track & back home.

 

i enjoyed watching that link, thx

 

Cubes is only about of quarter of the whole picture. You can build a naturally aspirated 346 Gen III motor to assrape a 454ci Big Block. If I were you, I'd be doing more research on the heads/cam/intake for your 383.

Mike

 

i've already picked out a LE2 package for my 383. i got laid off so right now i'm not spending money on a toy. once i become employed again i can finish my 383 build.



i just like 2 look ahead, after i complete my 383 build i just might go to a 408 in something lightweight maybe like an RX7.

IIRC aren't there only 4 head bolts surrounding a cylinder on LS's? does that limit boost?

 

4 head bolts... It does a little bit.... maybe. there have been guys running pretty big boost numbers on 4. over 20 IIRC. Tune is key to keeping it ok. And even then, some of the harcore setups push water between runs, but they live with it. Not good for a street car.

OR you can go with an aftermarket block/heads w 6. Someone might have tapped an oem block for 6, I cant remember if it worked or not.

And then you can do what this guy in sweden? did. Search pyramid rings on ls1 tech or google. formula 1 cars used to run this in the 80's to hold 70+ psi from what I have read.

http://forums.corvetteforum.com/c5-f...questions.html

 

I'm planning to do a 408 with boost as well next year.. But after listening to opinions from local forums a lot of them are saying just go with a forged 370 with GOOD heads and push 600+ to the wheels.. In which the stock crank would be used and you would save a good chunk there that can go towards the top end.. I'm still undecided my self..

*book marks this thread for more info**

 

You don't even need to do that. I was running 514rwhp through an AUTO with a STOCK LS1 block with STOCK crank/rods/pistons on low (less than 10 psi) boost. It's all about setup and how the engine flows. I was using lightly ported stock heads and a baby 212/218 camshaft along with an LS6 intake, so the engine setup flowed decently for what it was -- the more you open the motor up, the less boost you have to run to make the same power -- the same setup on a stock internal motor would have been around 14-16psi I imagine.

For a reliable boost setup, all you really need to build is a 347 (.005 honed stock block) with some aftermarket forged pistons and forged aftermarket rods (depending on how much power you're trying to make) to be able to up the boost and go way over 600rwhp.

Mike

 

Like Kraest said... don't worry so much about a big fancy engine and a certain number of lbs. of boost. My route to 500+rwhp has been a stock-heads/cam LT1 with a shot of nitrous. Yet to be dynoed but I'm sure I'll be able to break that number easily with a 150 shot. Do the 347 and rev it a little higher.