neverstop

hey guys,

So cracked a piston in my MTI built 402ci ls2 (my mechanic is guessing bad tune at this point). Heads were ported 243 so I want to upgrade those. While I need to figure out what happened, I'm now unfortunately in the market for a new longblock

Previous setup made 760/700 on dynojet with a D1SC at ~13psi and dual methanol kit. Car is a 2005 Corvette with RPM built 6 speed and diff, ECS 1k hp fuel system, FAST intake, all the goodies, etc


I'd like to get the car to a pretty reliable 850whp at a bare minimum but would be fun to have something capable of 1,000whp+. Car will be used for a handful of 1/2 mile and standing mile events and I drive about 4-5k street miles a year.

Would love to have input from guys here on what they would do in my shoes. I'm pretty open to anything at this point. I'm considering selling everything and going to a turbo 5.3 or going full tilt with 408ci LSX 6 bolt block

Never built something like this before so would love to have your help/input to help me avoid issues. Trying to figure out what is the best direction to go here while not spending a fortune.

questions

1. It sounds to me like the cost different between built LQ9 iron block 408 and a built LSX is about $2,500. For that $2,500 it sounds like you get 6 bolt heads which allows for reliable 1,000whp on the LSX block where as with an LQ9 you're really pushing it at that level. Once I factor in the work to get the LQ9 block into my C6 corvette properly (knock sensors, accessory drilling/tapping, etc) it seems like a no brainer to go with LSX and I wonder why anyone would use the LQ9 when for like $1,500 incremental cost you get the much stronger/reliable LSX?

2. are all the expensive and fancy crank, rods etc worth the money? it seems like very few engines on here fail because of insufficient rod or crank strength and the billet I beam rod upgrade is $900 while Callie Dragonslayer crank upgrade is another $750. This stuff adds up quick.

3. Anyone on here bad bad experiences with LSX 6 bolt blocks? I've got my eye on a Texas Speed LSX 408ci or 427ci

4. For those of you that have been down this road, what would you recommend in my situation? Is a 1,000whp even "worth it"?
if you guys could do it over would you do the uber expensive forged aftermarket longblock route or would you just get a $500 junkyard 5.3, put some 1/2 head studs and an aftermarket thick deck head with a big single turbo, a bunch of methanol and go for 850whp that way? It seems to me that the cost jumps HUGE in these cars when you go from 800whp to 1,000whp, that 200whp more seems like it costs about $5-8k and I'm not even sure there is such a thing as a "reliable" 1k whp that can be driven on the street 4-5k miles per year for years on end without constant hassle.


6. recommendations on heads and valves? I'll be running standing mile and roll racing stuff so wondering if special intake/exhaust valves are recommended for the heat? any thoughts on runner size? considering the PRC 247cc heads.


Not really sure which way to take the car and would love to get help from other guys that have gone down this route before.

Any thoughts or comments are appreciated.

rkreigh

I have a similar issue and I'll throw in my .o2

the 6 bolt block heads and full boogie stuff will be more expensive than you need for reliable hp of 1k at the tire

the drive train will be suspect at that level too

here's my approach

4.8 build with the short stroke factory crank, good rods and forged pistons

the small bore and stroke is great for turbos

if you want to go blower, put in a bigger factory crank

you can get good aftermarket rods and crank for 1100 if you are patient that's what I paid and it was a very fair deal


so, don't bother with 1/2 studs, overkill again. but arp or china studds if on a budget

don't skimp on the fuel system!!

the small displacement motors will stay together pretty well, are affordable, and make PLENTY of power. the blower or turbo sizes will often be more of the determining factor

I also favor a mild compression and multiple tune levels

you can turn down the boost either way but it's harder to run high compression on crappy gas and boost is

detonation will kill anything, no matter how strong it is

run e85 if you can. its the magic sauce for boost or at a minimum some meth to keep the IAT under control (again tune for ZERO detonation and watch closely for it)

denmah

iTrader: (2)

my friends 403 notch is making 920 on pumpgas and over 1000 on race gas without any issue so far

neverstop

awesome man, thank you.

RKreigh, any details on your current setup with whp output and miles on the setup? or what happened to your last setup? were you putting down a reliable 1k whp for a long time? very curious to hear more


unfortunately E85 isn't really available in my area so I'm stuck with running 91 octane pump gas but I am fine putting tons and tons of methanol into it.

assuming they're ok but my MTI built 402ci ls2 had pretty high dollar Dragonslayer crank and Callie rods so may be able to reuse those although probably cheaper, faster and easier to just order a longblock built by reputable shop

neverstop

any more details on the setup? how many miles on it? street driven? iron block?

ScreamingL

Stock motor will live at 800-900 rwhp all day long in the right hands

Been over 1000rwhp all season on a ly6

With said if you go lsx might as well toss the bank at the build as that's the level where LSX comes into play


Choose wisely along with a good tuner

rkreigh

I was running 800 at the tire for a couple of years, but dialed it at 600 at 11 psi boost for traction

engine is still together and runs great but I've got a low rpm tapping noise

might be a bad lifter, piston, rod, bearing, haven't diagnosed it yet.

but I'm considering an iron block build with good internals and studs to swap out the LS6

stepping up to 1k at the tire will take some driveline mods for me. I've already got an RPM 4l65E build for 800 at the tire, but it won't last with traction for long at 1k

I think a more basic build would meet your goals just fine and save some coin

stock48

iTrader: (17)

For octane limited fuel CI and modest compression is your friend... Id be after 408-427 CI with decent cam and good heads. Thick aftermarket 4 bolt head should hold if things are right. Would be a good idea to put some race gas in it when really beating on it; it's cheap insurance.

neverstop

thanks guys.

what compression you recommend?

my last motor had ~9.3 compression and honestly made a little less power than I was hoping but since it blew up I don't know if that was the low compression or maybe the motor was sick and I didn't know it yet. The 760whp on 13psi was less than I had hoped (similar setups have done >800) on the dyno right before I took it out and the piston blew up.

I will be running the car on 91 pump gas but I have a giant dual nozzle methanol kit on it with huge nozzles and I've read methanol is ~116 octane and I don't mind stuffing tons of methanol down the throat of this motor. THE METH is cheap and easy to get around here.

certainly going to be running race gas on it at the airstrip races for sure, there is a track not too far away that sells all the way up to 116 straight from the pump

RonA

iTrader: (1)

I like your original idea with the LSX block. I expect this to be my last performance vehicle and while I don't have a particular goal, I would like it to be fairly potent and last a while. I opted for the Dart block, magnum crank, Ultra I beam rods and PRC 255 heads. Builder seems to think it will make acceptable power and hold up to the once in a while throttle blips it takes to get the heart rate up. A lot of emphasis on proper tuning, engine management, and boost control seems to be the key to good life expectancy.

neverstop

so got more info from the tuner that did all the work right before it blew up about the tune and then talked to some other tuners and it appears this local shop had 23* of timing on my car, I talked to 5 different tuners from other big name shops you'd all recognize and for my setup they ALL Thought that was wayyyyy too high for a car on pump gas with meth setup for 1/2 mile and standing mile event. It seems the other tuners would have expected to see 15-18* for a conservative tune (which is what I requested)

The local tuner also did all the tuning on the dyno, where as most of the other tuners I have spoken with thought tuning a car that powerful without any street tuning or at least data logging it on the street or track was clearly a bad/dangerous idea.

Just posting this so hopefully some other people can learn from this expensive mistake.