ArabVette

01 c5z. Trying to reach 700rwhp with the least amount of upgrades, but still reliable. I’d like to stay with my LS6. I do not drag/circuit race. I only WOT when rolling at 30mph or above. Upgrades I would like:

Built LS6 (stock cubes and cam)
Stock 243 heads (upgraded valve train but no porting)
Stock intake manifold and TB
A&A blower kit
Headers, x pipe, stock TI exhaust
Meth kit
McLeod twin disc clutch
Pfadt motor mounts and Diff brace

Questions that I would like answered please:

1. How much would this cost? Under $15k?(New parts and I’m not doing the work myself)

2. How much boost could I run safely and reliably?

3. Would I be able to reach 700rwhp safely and reliably?

4. What kind of cooling upgrades should I include?

5. Is this a build worth pursuing or should I be doing something different? (ex: ported heads, cam, more cubes, newer gen LS motor)


Thanks for for all the help!

gimp

Do you have a goal beyond a peak horsepower figure and the bragging rights that entails?

ArabVette

i do not have any goals beyond weekend driving. However, I would like it to be a reliable build all while staying true to the original 346 ci.

neutron82

add a cam to the mod list you have above and you can easily hit 700rwhp, the boost number to get there will differ depending on the blower but don't get hung up on that

ArabVette

Would it be difficult to hit my power goal with out touching the cam and heads? (aside from valve train upgrade)

I kind of want the car to be a sleeper lol. Not a big fan of the sound and drawbacks that would come with a cam. Also, any insight on the other questions i listed?

gimp

You can get a cam that doesn't sound big and lumpy. Get a cam and valvetrain package specifically designed for a centrifugal supercharger.

The thing is that 700 rwhp is over 800 crank horsepower ... those are really big numbers to be pushing for a stock LS6. Without improvement in airflow, without improvement in cam profile, you're going to be seriously bottlenecked. Remember, PSI boost is a measure of restriction, not airflow; you can get big boost numbers without the accompanying horsepower increase you want; on the flip side, with a high-flowing head, you will see bigger horsepower figures and smaller boost figures.

How much boost you can run safely and reliably depends on the rest of the engine setup, the fuel you're running, how long you plan to run at various power levels and RPMs, etc. Your tune can accommodate just about anything but it may be hard. On a stock block, back of envelope estimation says you're basically talking about 15 PSI and good airflow, which is frankly going to be hard to maintain safely for any sort of time.

As far as cooling goes, again, it depends on usage. A drag car that only runs a quarter mile at a time can have no coolant whatsoever. On the flip side, a road course car that is lapped at high heat needs a great amount of cooling - usually, for the engine, this means a far radiator and a fat oil cooler, with good airflow, fat fans, etc.

If I were to estimate your cost or price it out I'd hesitate to even put an estimate down running 15 PSI on a stock bottom end. LS6 engines are great, but they're not that strong. They'll last a while but they will pop eventually under such use. There's a reason that a large number of the 1000 horsepower builds that run in the neighborhood of 15 PSI will use the 6.0 iron block, not the 6.2 or 7.0 aluminum blocks. And I may be understating that (read: it might be damn near all of them that go iron.)

But if we ignore some things we shouldn't ignore:

- Cam and valve train, $1000 in parts and labor
- Heads, high-flowing to support that much PSI, can be $3000 in parts and labor
- Katech timing chain, add another couple hundred in parts and another couple hundred in labor; you'll want this
- You almost certainly want an upgraded throttle body and intake manifold, which can easily hit a grand in parts and labor
- Radiator and fans, $1000 plus a few hundred for labor
- Clutch kit w/ bleeder, $1000 in parts and $1500+ in labor
- Drivetrain R&R during clutch job, expect nearly $1000 in parts and labor for things like torque tube bearings and couplers, fluids, etc
- Trans/diff brace while the rear is down; that's around $400 in parts plus probably a hundred in labor (much easier)
- Probably some sort of engine mount upgrade to control this much power, expect another $500 here
- Upgraded axles, people talk highly of the 300M ones, those look to be something like three grand parts-and-labor with the matching uprights? Not sure about this.
- Built rear end, expect a couple grand parts and labor
- Built transmission, expect a grand or so of parts and labor
- Brakes, so that you can stop; cheapest decent setup is probably C6Z and even buying used parts that's at least a grand, labor is extra if you don't DIY; more expensive setups can easily be three or more grand, the most expensive hitting five-six
- If you plan on sustained power output even close to the peak, you'll need oil cooling; a good kit to do that will include the thermostat ($200 improved racing), hoses ($500 worth of hose, fitting, firesleeve, etc), cooler ($600 for a big ol cooler), misc mounts and brackets (~$100), plus labor (easily $500 if not more), which totals a little under two grand

All that doesn't even touch the supercharger kit, the meth kit, etc.

If we do a quick tally, we're talking $1000 + $3000 + $400 + $1000 + $1300 + $2500 + $1000 + $500 + $500 + $3000 + $2000 + $1000 + $1000 + $2000.

That's somewhere around $5400 in engine parts and labor, $1300 in coolant cooling, $1800 in oil cooling, $3000+ in clutch expenses and drivetrain R&R, $500 for the brace, $500 for mounts, a possible $5-6000 for driveline strengthening, $1000 for brakes. Just over $18k without even installing the supercharger, if you buy new.

How much can you DIY?
You can save some ~$1500 on the engine build. You can drop another ~$500 on heads to get slightly less awesome ones.
You can DIY the radiator and save $300ish, you can DIY the oil cooling and save $500.
You can DIY the clutch and save $1500-2000. DIY the trans brace and save another $100. DIY the mounts and save another hundo maybe.
Skip the axles if you promise like a good boy to roll onto the power and avoid the temptation to get sticky tires, that's like two-three grand saved.
Okay, now we're down to a more reasonable figure, but still ten grand worth of stuff, plus the supercharger kit and meth kit. I suppose that could fit within $15k if you DIY everything.

Your stock bottom end engine is still not gonna last too long at those boost levels unless you avoid hitting them for more than about three seconds every three months, though ... there's a reason that everyone going for these power levels has a built bottom end.

ArabVette

Thanks for taking the time to include that info Gimp, it really helps! I didn’t expect the price to skyrocket so fast, but I do understand quality and reliability is not cheap. One thing you may have missed in my OP, is that I would intend to build the bottom end.

I’m not the most knowledgeable about FI, but basically what i was thinking about doing, is to forge the bottom end and upgrade the valve train to handle a bunch of boost to try and reach 700rwhp. The only supporting mods that I was thinking to include were meth kit, headers, x-pipe, clutch, motor mounts, diff brace, and bigger radiator/fans.

I was trying to avoid porting/replacing heads, cam, TB and intake manifold. After reading your post, I see that it make more sense to upgrade all of those items and to take into account other things as well. I will plan for oil cooling, braking, and misc items. Thanks again for all of the input!

gimp

Oh, I did miss that, my mistake. Yes, a high quality forged bottom end, with rings designed for the level of boost, is a must-have for that much power!

Rkreigh

Gimp is right

here is a cheaper "recepie" iron block 4.8 stock crank, gen 4 rods, wiseco pistons (rehabbed a "wounded piston") short block cost $1250 and will support 1k hp

use stock heads ported on cnc shop around cathedral heads are cheap

stay with a stock cam (cheap) spend the money on fuel system and tuning!!!

the "lil thumper" receipie is what I posted on my TT build you can sell the ls6 for more than the cost of the iron block and it's much happier at high hp with sealing the cyl pressure with the small bore

no one wants these motors so I have them stacked like cord wood. Don't worry too much about the weight, the hp overcomes it and if you want more you can go all forged but the short stroke cranks are actually pretty strong

I don't see anyone breaking the gen 4 rods under 1k hp at the crank either run e85 and let it eat!!!!

nullpointer

I disagree that you need an aftermarket intake manifold and throttle body. Also you do not need upgraded axles. Knowing from experience, you only need axles if you are digging the car a ton. Intake manifold + throttle body are a waste of money at those power levels.

neutron82

I agree, stock intake and tb are fine and even stock port 243 heads but I still think a cam would be a good idea... as stated above it doesn't have to be a radical cam but something to help get the extra air out of the engine and make it a little more efficient

ysb02

The rods and pistons are probably the biggest issue getting into that power range. The gen3 items are not as stout as gen4. I'd just do a t-trim, cam + new springs + retainers, and rods/pistons.

TBH I'd stay away from meth and just run a CR that is safe on 93 pump gas.

Naturally Vain

Jam Cam is what you need!

Got mine in the mail today! I am building something similar to yours. However, the Jam Cam will surely make an incredible sound which was huge with my decision.

FourG63 97GST

I'll def risk it at that power level, odds lean a bit more your favor, even though you're over the threshold of the stock bottom end. general limit rule is 650whp for the GenIIIs, 750-800whp on the genIVs
Just keep in mind they can let go before or well after that threshold. Centrifugal blowers are less aggressive with the power and torque, compared to other power adders. i'll give it a shot before forging a motor.

Stock heads casting are rough, you do not have to go exotic on porting them for an F/I build, I personally went with a hand port on my build, mainly because my OCD couldn't stand looking at the rough casting like that, even though the power adder doesn't care that much, clean up the casting and bumps at minimum if you're diving into it.

Focus on fueling, and the tune/timing, especially in the peak torque area, keep it conservative there, you can ramp it back in on the top side if needed be.
if I was in your shoes, i'm not building anything. cam, clutch, fuel, boost, tune and be merry. it's easy to get carried away with what If situations. next thing you know, you're 20k into you 700hp build
keep it simple.

Pekka_Perkeles

Find a decent tuner first, then go after all necessary hardware and you'll get reliability as well.

Naturally Vain

This seems more in line with all the research I have done. Many people seem to be running this setup with and without changing the pistons just fine. I see RWHP figures around the 650 mark with your above mentioned set up.

Naturally Vain

I like the way you think!

69GTO96Z

I make just shy of 800 rwhp on a stingy dyno with a 347, ported heads, cam, stock ls6 intake, and a ysi with 3.33” pulley.

Pekka_Perkeles

How long, if I may ask?

3 seconds WOT on a dyno or 30 seconds WOT during standing mile?

Or maybe several laps on a race circuit?

Not forgetting 93 octane, perhaps with meth, or race gas, or E85; it all makes a difference..

Anyway, 800 rwhp with stock bottom end is nice!

ysb02

~650-700 is probably where reliability takes a hit on these cars. There was someone here running a stock LS6 with just cam/valve upgrade at 900+ rwhp. It did eventually grenade though. One methanol failure can be enough to lose the entire motor though. I see more shops wanting to do 93 pump or e85 now, no meth.