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.

Unreal

I bet it is more than $2500 to go LSX from LQ9. There is a lot more machine work, head gaskets are more, head studs are a lot more, then add the cost of 6 bolt heads.

For 1000 you can run just about any block with a solid tune. I would just do a 376 stock cube stock crank forged ls3, and let the blower do the work.

4 bolt heads are fine at 1000.

If you are talking 1200+ for 1/2 to 1 mile then do 6 bolt. If money isn't an issue do RHS, ERL 6 bolt, or LS Next aluminum.

lt1z

An LQ block can be built to handle 1000 easily. Keep the bore to 4.005 and make it a 402 and spend the money you saved on the block on good rods like a Callies Ultra.

turbotuner20v

Lq9 is gen 3, ly6 is gen 4. I'd recommend ly6 so the engine block design is similar to what you have now.

For 1,000-1,200 I'd do:
Ly6 iron block, callies dragon slayer crank and ultra h rods, wiseco pistons. LSA heads with ls9 gaskets and arp 625 custom age studs.

That's pretty much what I have with a 3.622" stroke lunati crank and regular arp hardware

lt1z

You pretty much described my motor to a T except for the block where I used an LSA

neverstop

awesome. This is the first I've heard of the Ly6 block, my mechanic was saying Lq9 would require a bunch more work with some sensors and tapping that would cost a bunch more money but if there is an iron block that will bolt straight into my C6 corvette that would be great.


Turbotuner, what whp are you putting down and how many miles do you have on the motor? interested to hear more as this seems like a pretty attractive way to go.

Unreal

I would go LSA/LS3 block for those numbers IMO like LT1Z has. No need to add 100lbs if not needed.

turbotuner20v

I made 937 for a year + and then recently 1,026. Lots of roll racing and maybe 4k miles. Only issue I've had motor wise is my Melling oil pump bypass spring broke and lost oil pressure

breecher_7

Kind of the same combo here:

LY6 Block, Main Studs, Pinned Mains, Main girldle
Callies DS Crank
Ultra I Beams
Diamond Pistons
Worked LSA Heads with Ferrea Hollow stem intake and Inconel Exhaust valves
LS9 Gaskets
Regular Pro Series Head Studs

1000hp all day long, coming apart for new rings this winter.

staticki

I ended up picking up this block for my build for my 06 base corvette
http://www.summitracing.com/parts/sum-150105-30

Would anyone suggest o-ringing the block for boosted applications. I figured if I am going to be spending the cash, might as well make it last. Plan on either running a YSI or TT kit (ttix or dkt with 6266 turbos).

Unreal

No need to oring for anything under 1700+rwhp.

neverstop

I have been calling shops and the incremental cost to go with an LSX block is just not that much more, seems like it's about $2,500 more, and at this point seems worth it to me to know that i have an invincible bottom end in there I won't need to pull out again. So looks like I'll be going with LSX block at this point. I know it's absurd overkill for what I'm doing now but I like knowing that as I continue pushing the car when at some point in the future I want to put a giant turbo on there or something, that I don't need to worry about the motor.

just got off the phone with all the reputable builders, LME, HKE, TSP, etc and they seem to all think the Q9/LY6 iron block would work fine but if you want to make more than 1k whp you'll be limited where as with an LSX block the sky is the limit essentially. Plus I've heard that the LSX block will likely be more reliable at 1k whp since it is just so much stronger, 6 bolts heads, etc.

So still working on this but it looks like I'm just going to "go for broke" and go with LSX Block and all the goodies.

anyone in here running vacuum pumps on the crank case? I have been doing more research and some guys seem to do this at 1k whp but others never do it so just wondering what setup you guys would recommend and if even necessary.

Really trying to just do this right the first time. Thanks for the help guys.

breecher_7

The strongest bottom end in the world doesn't save a thing if you spin a bearing or something silly like that..

You do not need a LSX block for your goals, it is a gross waste of money. Get a iron 6.0 and have the mains pinned along with main studs.. You will be fine.

Unreal

$2500 that could go towards other stuff is silly. If you have no budget, then hell yes go for it, in fact just do the RHS.

Did you factor in the added cost of headgaskets, studs, 6 bolt heads, etc? That adds up quick. Just the short block I could see being $2500 extra, but when you get a running long block it adds up.

The money would be better spent on fuel system, tuning, meth, clutch, drivetrain, etc.

turbotuner20v

yea, don't just throw money at it for the hell of it... I think your PM said your were doing a D1SC w/ 150shot? Just buy a big blower with the money you save.

neverstop

hey Unreal,

I'm doing more research all day (when I should be working. damn this site) and came across some comments from you and a couple other guys stating that "if you could do it over" you'd not shoot for the 1,000-1,100 whp but instead would just stick to 800whp-ish which seems to be the "sweet spot" for the C6 platform.

you still feel this way?

1,000whp is a fun goal but if it costs 2x as much with 4x the headaches to get that last 150-200hp then maybe this is actually not a great idea for me.

My last car was ~450whp h/c/i C5 so this setup I have now that I'm rebuilding is 2x as nuts as any corvette I've had before

neverstop

I was originally thinking that it would be worth the $2,500 on the bottom end just so that if I ever wanted to put a huge turbo, big nitrous, etc on it and go for 1,400whp or something crazy, I'd already have the foundation to do that.

The more research I do though it seems like stuff gets exponentially more expensive above ~900whp (if you want to be reliable) so I'm kind of second guessing my plan here and wondering if I should just build this for the a slightly lower goal and just enjoy that. Even "just" 850whp is still a $hit load of power for what is primarily a street car.

neverstop

since I am going to buy a longblock the incremental costs of the head gaskets, heads, etc isn't super crazy.

the quotes I am getting from HKE, TSP, etc look like ~$10k for a fully forged Lq9/Ly6 longblock and if I step up to the LSX block that pushes it to a little over $13k so all-in it looks like about $3k more. That's a lot of extra money and I'm not a rich guy but in the grand scheme of things if that means I get something 2x as reliable that I don't have to ever worry about or pull back out, etc then I'm ok with that.

turbotuner20v

call schwanke engines in MN and get a shortblock from them for ~$3,600. Best bang for the buck and that motor looked great after hard use ~930+whp

Unreal

Yes, I still think 800rwhp is sweet spot, unless you live in Texas, or have mile/half mile events to do monthly.

Basic stock block forged motor, ECS Ti trim at ~800rwhp is what I would do if I could start over.