what are the differences in power/ drive ability between a forged 6L running say 20psi, a forged 402 at 15psi or a forged 427 at 12psi, can any of them live without the use of meth or race gas?

 

Take the base HP and add 25-30HP per pund of boost and you will have a rough estimate of final power. They will all be very streetable, but you are not going to want to keep a forged 427 at 12# for long. Race gas, no - methanol, yes. I don't know why people get freaked out about adding it, but it is really hassel free.

 

i agree about hassel free, infact im sort of addicted to the smell of burnt race gas but i would like to beable to drive my car cross county without needing to hunt down 110 or meth

did you mean your statement for the 427 in the sense that that large of displacement weakens the block or that I will want more boost?

im looking for combos to produce 900-1000 rwhp

 

For a safe 900-1000 rwhp that you can drive across country, get a forged iron block LSx454 crate engine(454 cu in). It has forged pistons around 11:1(I think) so you can't add a whole bunch of boost, but a heck of a lot more then a aluminum block LS engine, Besides having a cast iron block(118 LBs more weight then a LS7) it has aluminum heads based on the LS7 head but they are 6 bolt instead of the normal 4 bolt, for serious clamping to hold boost. The crank has to have a new 8 bolt flywheel.

The LSx454 can handle up to 2050 HP. Later on, if you want more horsepower, put in a set of lower compression pistons and up the boost. Plenty on meat in the heads for some serious porting.

http://gmtv.feedroom.com/?fr_story=e...47e&rf=sitemap

 

I would rather have a pump 93 tune and run meth. Meth is boost activated so you will not run out for a while unless you plan to be in boost your whole trip across country..

 

I don't quite follow your reasoning... 11.1 Compression + Boost on 93 pump gas with no meth = Safe?? Uh?
Also, seeing as the internals are what fails on these engines, all the iron block is doing is weighting more; it is no "safer" on an engine that is detonating on pump gas with high compression than an aluminum block would be, since the pistons are what is going to break in that scenario. The iron block CAN handle a lot more power, but what the OP is asking about is not a 2000HP engine; the lower end of his power goal has been reached on stock LS blocks even.
Finally why 6 bolt heads if you've got a huge engine running small amounts of boost; the added clamping is needed when cylinder pressure becomes very high, which is exactly what you are avoiding by going with a large cubic inch motor. The 6 bolt mains are nice, but not required.

A 454 cubic inch motor with a sensible compression ratio (say, 9.8:1 => 10:1) and some boost would be your best bet at 900 - 1000WHP on pump gas. You'd want great heads, all forged internals and a good blower cam. It would be easier to do it with turbos too. The block does not have to be made of iron; a sleeved LS motor, a C5R motor, an RHS block or an ERL Superdeck would all work without the 110lbs weight penalty... Sure, it'll cost more, but I'd pay 2 grand to not have a boat anchor under my hood.

My 2 cents worth.

 

I agree PW my goal has always been a car that is an all around performer so a heavy iron block is a no go just as you said. i have a 900rwhp goal in mind, im thinking a forged 6l at 20psi with good heads and bigger exhaust manifolds (already have a large cam in) should make it. if the price of a forged 427 is reasonable id boost it just enough to make my goal


question about octane: is a motors octane requirement based apon hp or boost or a factor of both? ie would a forged 427 at 16lbs live on 93?

 

No problem with the 427 block whatsoever. What I meant is that you are going to get bored of a 427 at 12# really quick, especially since you can run 20# with pump gas and methanol. It is going to take ~26# on a 6L, ~24# on a 402 and ~20# on a 427 with a race prepped top end.

900-1000hp is a nice goal, but most wind up closer in the 800-900hp because of the additional effort and $$$ it takes to support 1000hp.

Good luck with your build.

 

So how much boost would you have to stuff into a 454 with 10:1 comp ratio, on 91 pump gas, and meth to reach 1000rwhp? Im planning a build like this for the winter and I am looking into my options.

 

It is mainly dependent on cylinder pressure, but it is always possible (in an octane limited situation) to run more boost with a lower compression ratio and make more horsepower than a high comp / low boost combo would make. The reason for it is quite simple: As air is compressed, it heats up. This applies in a turbo or supercharger as much as it does inside the cylinder. Once the air/fuel charge becomes hot enough, it will autoignite and cause detonation. A 13:1 compression engine would detonate on pump gas with no boost. An 11:1 compression engine would detonate at about 5 pounds of boost. With 9:1 compression 20 pounds of boost can be run without detonation:
When the air/fuel charge is compressed inside your cylinder, its temperature rises in direct proportion to the compression ratio. That is also true when the air/fuel charge is compressed by a turbo or supercharger (it will heat up in direct proportion to the amount of boost, plus the efficiency loss of the blower), HOWEVER, when your turbo or supercharger compresses air and it heats up, that air can be intercooled, so you can have an intake charge that is twice as dense as ambient, but only 20% warmer... Since the density of the intake air charge times the size of your engine times the engine determines how much power you can make (very simplified concept here), more boost will always equal more power.

Hope that makes sense, I'm on my second sixpack

 

ehh, I went with the GM LSX376 6bolt, 9:1 compression crate engine, forge pistons.. should be good to go.. running 109 octane.. should be done next week!

 

another captivating post!finally i understand