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Company built LS7 question

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Old 11-30-2011, 03:01 PM   #1
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Default Company built LS7 question

A while ago for my first performance engine I was considering the LSX454 engine, it seemed like such a good choice, but then I started looking round more and it seems that unless I'm pushing well over 1500 horses, iron block is nothing more than wasted weight. I wanted to push max power out of a light enough NA engine for use in common v8 swap vehicle, the RX7. I'm only in the planning stages right now, and my current DD vehicle is a 1997 Buick Riviera, which has a very reliable 3800 series II powerplant. I plan to drive this for a long time as my DD even when I do get the RX7 running. I wish to find a n RX7 FD rolling shell with no engine or tranny for as cheap as possible, or an s2000 shell if I can't find an RX7, I know LS1's can easily be fitted in either car with proper modifications.

that being said, instead of spending 10k on the lsx454 block, I'm looking into buying a built aluminum LS block from a race company.

I'd probably be going NA only to save weight and I really don't need more than 700hp for my application, but it would be nice knowing that later down the road I could boost my motor reliably. What exactly is the difference in their boosted and non boosted engines? for example on their site, what is the difference between the cheaper 427 LS7 and the 427 boosted LS7? and I'm guessing the 440 may be a bad idea to boost because of a thinner cylinder wall? if not, what would a 440CI LS7 block be able to handle reliably with those internals out of curiousity?

that, and I'm guessing that I'd need heads and cam and then it would be a turn key engine given an intake, headers, engine belt accessories, or what exactly else is needed to make this a full crate turn key engine? the site is not very informative lol

by the way, I'm not expecting to just randomly buy an engine and s2000 and lol derp it into a v8 bastard child ghetto car. I just know I want a performance car in the somewhat near future and instead of being like every other corvette or Camaro on the road, I'd like to have either an RX7 or s2000 v8 swap, and there are many things I don't know yet, so I'll try to learn most of the v8 related things here.

one thing I have no idea that I've been trying to find out is: are all the LSx engines the same exact crate size? AKA if an LS1 fits in the hood, an LS2, LS3, LS6, LS7, LS9 will all fit with the same mountings and are very easily interchangeable? like if you tore out the LS1 of a Miata v8 swap, you could easily cram an LSX454 in it too? Iv'e never been sure on that one :3

also, I'm thinking the engine will weigh around 500 pounds or so, basically the same weight as an LS1, and WILL retain damn near perfect weight distribution in an rx7, there are plenty with around 51/49 Iv'e seen on forums, so given that the engine weighs the same, I'm guessing it will be the same exact dimensions, I only raise the question because some guy that seemed to know alot more about cars than me said the LSX block was bigger than the LS1 to me a while ago. basically an LS1 kit would work perfect for any LSx block as well?

I'm almost positive this thread will be treated as a joke because I'm not a professional builder and don't know everything already, but I might get a helpful reply >_>

so I'm guessing the built block from that site+ all other components to make a turn key engine will cost around 10k? honestly I think I'd go with the 440 because the block and a supercharger would actually mess up the weight distribution, and I want the car to handle perfect.
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Old 11-30-2011, 03:30 PM   #2
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btw even if I could never do the swap, like I'll get spammed

I'm pretty sure buying the shell, LSx engine, and a T56 tranny all together would be cheaper than a used corvette anyhow with their turn key build. and I intend to do it anyway.

the question is am I better off buying an LS1 out of a scrap yard or actually putting down big money for a built brand new LS7, because brand new LS1 engines are at least a few grand, if I'm paying more than chump change I might as well get the way better engine for more IMO

one more thing, keep in mind this will never happen soon, it will be a while before I even buy anything for the project I'd just like info so I know everything I need instead of being a chump who spends 30 grand on a brand new mustang GT :3

Edit: I'm figuring it will cost around 20 grand for everything I need assuming I can get a shell car around 3 grand for it, if I pay the company to do it for me, around 25 grand if I use a fully built 700 horsepower LS7 motor, might cost a little more

If I use a crappy LS1 it would cost more like 16 grand as a do it myself project I figure, assuming 3 grand shell car. I'm thinking I'd go the built LS7 route if I could, and it might cost more than I think, not sure, let me know on that.

on another note, it might actually be worth buying a used v8 pre swapped car if I can find one cheap enough actually

btw if this is deemed a bad idea overall, my fallback plan is simply buy a used GTO and either be happy or swap the more powerful engine if the car has a blown engine upon purchase, either way, I'll be extremely happy with my first performance car

Last edited by c0reyl; 11-30-2011 at 05:05 PM.
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Old 11-30-2011, 05:07 PM   #3
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For starters, you are in the wrong section. There is a conversion/hybrids section for your swap and there is the Gen III and Gen IV engine section for LS motors. You are in the Smallblock chevy section.

For what you are trying to do will require alot of money, time and fabrication. Hope you got alot of tools handy or a fat wallet.

If you are bent on putting an ls engine in an RX7 or S2k why don't you start small first and just put a H/C/I ls1 in the car first to get the fabbing part out of the way. A H/C/I ls1 will put a light rx7 in the 10's on the motor alone. Some friends of mine did one and it ran 10.87 and it was cam only. It had a Futral F13 cam in it with a ls6 intake and that was it.

Later on down the road you can either buy or build a purpose built engine of the size you want and all the work to the car will be done so you can just slap the new motor in and go.

To answer some of your questions.

An ls1 is the same size externally from all ls1,2,3,4,6,7's. They are just different internally. An LSX block is still the same unless you get the tall deck block.

A boosted motor compared to a N/A motor are two different animals. A boosted motor will have lower compression and a beefier piston to handle the abuse. LS7 blocks are not too good for boost becasue of the thin cylinder walls and are prone to cracking if detonation rears its ugly head.
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Old 12-01-2011, 03:15 PM   #4
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thanks man =]

you basically answered most of my questions perfectly, and that's why I asked if I should get a trash can LS1 engine to start off with, no way I'd buy a brand new LS1 block to start off with when a few more grand alone would yield a way better engine.

this is not in the hybrid/conversion section because I'm not inquiring as much about the hybrid as the blocks alone. I was thinking the 427 cylinder walls were a bit thin, so 440CI build down the road with proper heads and cam yielding up to 750hp NA seems like a good route. keeps it light, reliable, instant powerband and all. basically I'd go either trashcan used LS1 to start off with cheap to just get it running (a highly likely situation) or all out on the built motor NA. this will not be a drag car, more a street car with weekend track capability, kindof like a corvette or viper's intention.

how cheap can a working LS1 reliable motor be had for used? :o

as for fabricating and whatnot, you can get all the parts required for the conversion for the rx7 for about 3800 bucks, or pay somewhere north of 8 grand for them to do everything and just drive your car there and give them motor and tranny. Luckily this isn't a never attempted idea

I'm curious as to how fast 700 horses would make a 2800 pound rwd car
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