Guys. Please forgive the ignorance if its detected. Just looking for some guidance.
My son and I want to build an LS. I have a 2004 lq4 thats in good shape. I'd like to do the following:

STAGE 1 (bottom end done OFF of vehicle - want to open the field for future hp) (400-450hp when done)
1. Bore the 4" ID to 4.065" to get from 6.0L to 6.2L. (bigger is better....right/wrong?)
2. Replace the dished pistons with flat top (shooting for the lq9 benefits). Buying new pistons anyway. I know the larger bore will affect the compression ratio too.
3. I'd like the compression ratio to be near the lq9 (10.1+?) if possible so if I need to shave the 317 heads to get it please let me know. I'm open to 799 or 243 heads if someone can convince me but would like to leave for later upgrade.
4. I will put a cam in it but I don't want anything obnoxious, soooo 224/230 - .580ish lift - 113ish for lsa. comments/advice? It will be a manual transmission and a weekend/grocery getter. We want a stealth street fighter (not a brute) but we don't want to nullify the benefit of a cam by being too conservative. Interested in HP not LOUDNESS unless its required.
5. We will possibly get 300-400$ car intake so we can fit it under the hood.
6. We will upgrade the injectors as I'm pretty sure we will reach their limits.
7. We will get exhaust headers but we want to wait until we see the vehicle we are putting it in before we do that. I'm willing to go pretty radical for exhaust flow. (If room permits)
8. Drive by wire and stock throttle body for now. (I know the stock TB limits flow)

STAGE 2 (done ON vehicle) (hp....who knows?)
1. Once the engine is in the car we can swap and/or port heads if needed
2. Upgrade to better intakes (FAST?) I know $$$$ but stock TB
3. Think about boost

The point here is to give my kid a good education/experience building an engine. He has always been a car guy since he could walk and I realize he will grow up and be gone soon. This could be his ticket to leave the smart phone addict world and learn something useful.

Again, noob here so please be respectful. Built engines back in the old days but not the LS......I'm alot older than the LS

Starting build during holidays when he is off of school

 

1) Can be done but the block will have to be sonic tested to see if it can be bored that much.
2) Go with a forged bottom end if your planning on throwing power adders but at least do forged rods and pistons.
3) I would suggest going to rectangular port heads such as 821' or 823's as they will make more power but if dead set on cathedral then 243/799 will work.
4) I'm not cam guru but that doesn't sound like a bad cam profile for a street car.
5) LS3 intakes can be had for that price range
6) Injector depends on what you choose for a fuel but for pump gas a 600cc injector should fit the build.
7) 1-7/8" headers should be adequate.
8) 2010 Corvette has an LS3 with a 90mm TB and is DBW.

My advice for building LS engines would be to get your hands on this book for starters:

How to build and modify LS engines by Jason Potak

 

It's actually Joseph Potak

 

1) I read in many places block can handle 6.2 bore. I got the general approval from the shop but I'll ask shop again. Obviously if block is flawed then it will be a "no go" in any case. They have not looked at the block yet.
2) I'll look at forged pistons/rods. I have read everything else is good to about 650-700hp. I don't see us ever doing that and if so a rebuild would be in order anyway.
3) I will look into the 821/823. I have been on cathedral but am open to the rectangle type. I have read they flow better. Just don't want to break the bank in stage 1.
4) Thanks for the input on the cam. I'm no guru but hours of research (with some frustration) has me close to the one I listed.
5) LS3 intakes can be had for that price range where? Used on ebay?
6) 600cc injectors noted
7) 1-7/8" headers noted
8) I'll start looking for a 2010 Corvette 90mm TB. That's greatly appreciated!!

Will order book tonight.

Any comment on the likely hood of getting 400hp from stage 1 mods? I know reality can suck but engines are like fish stories. Never as big as you want them to be.

 

You don’t need to add cubes to a 6.0 to hit 400hp. I’d just do a normal overbore to a common size piston and shoot for 11:1 compression. Then almost any set of ported heads and consult a vendor for cam profile for your needs. Texas speed, Lloyd Elliot, there’s a ton of good vendors to help with an LS build.

 

Hell man, you don’t need ported heads to make 400fwhp. A set of 243 heads and a mild cam will do that easily. I’ve recently talked to Lloyd about a 6.0 build to make over 500 and even that’s super simple.

 

^^^
If 400'ish flywheel HP is your target then keep it simple. Heads/cam and you're already above your goal. With my limited knowledge of the LS you should be able to do that with a set of unported 243/799's and a decent cam.

 

Also LS3 Intakes aren't cathedral port

 

Exactly, even 500 doesn't take a ton of money or effort, just wise selection. Ported 243's and the right cam plus a compression bump and you're good to go.

 

All,
Thank you for the input. I was suspecting the overbore to 6.2 was NOT netting me much in the way of HP but looking at the numbers of similar LS engines is what my reasoning comes from.

1. Replacing dished pistons (in LQ4 typ 300-330hp) with flat pistons will act like an LQ9 (typ 345hp) so I should see LQ9 HP with that upgrade alone. The consensus is this is the only difference between LQ9 and LQ4 designs (compression increase).

2. 6.2L Corvette is typical 400-430hp-ish so I figured boring from 6.0L to 6.2L, I'd have an iron block version of an aluminum LS3/L99. Yea, I know the vette heads/intake are a huge portion of this 400-430hp but how much? I'm not sure but I would suspect its a lot noting the characteristics of the vette 821/823 heads with their bigger valves/throttle body vs my truck 317's/TB.

3. I read where cams can add 50-70hp so asking for mild sounding street cam should get at least 30-40hp. (guessing/wishing/no data to back this up)

4. Exhaust headers add hp too. I don't know how much though. (15-20?) (guessing/wishing/no data to back this up)

Point is, just comparing the similar geometry of past LS designs and conservative hp comparisons I would figure I could hit 400-425hp BEFORE I spend money on heads and intake upgrades which (I would guess) could send me to 500hp or north. IF someone here can convince me that the extra 0.065" bore (6.0 to 6.2) is a small increase and not worth weakening the design then I would be appreciative. This convincing would not be hard to do because I'm already suspecting it from the comments above and my own research. I am concerned that once I bore it out to 6.2L the option to turbo or supercharge goes out the window or becomes dangerous to block life. I would rather sacrifice 20hp now and keep it a strong 6.0 and have the option of adding 100-200hp later by adding forced induction. By that point the crank/rods/pistons are reaching their limit anyway. I seriously can't imagine ever going to 600-700hp but (as I'm sure you veterans can agree) you always want a stronger fix once you're hooked.

Again guys, thank you for your input. Super excited to build with my son. We are tearing the LQ4 apart this weekend so we can get it back from the shop during the holidays. Makes buying son's (and my) Christmas presents easy.

Please comment and feel free to shoot holes in my reasoning, especially the 6.0 vs 6.2 thing.

 

That's awesome that you're working with your son on it. If it were me, I'd cam it, do some head work (shave to bump the compression), which you would bump your static compression and save you the money of replacing the pistons. Also throw some headers on it. That should get you up to 420 or so.

 

The first thing I’d do is get the mods to move this thread over to the LS section, you’ll get much more knowledge over there than here in the LT section.

The cost of changing pistons is huge, and completely not worth it at all if it doesn’t need to happen. It’s not just the cost of pistons, it’s the overbore, the rebalancing of the rotating assembly, and the reassembly, your talking well over $1000 for maybe 10hp. If that short block is ok, then just swap rod bolts to katech or ARP and run it. Do heads and cam, long tubes, keep the truck intake if it will clear your hood, or LS6 intake. You’ll be well over 400rwhp there, and that’s already honestly too much for a 16 year old.

 

I think it would be a bad idea to throw boost at a max bored block but I'm sure there are many boosted 370's and 408's. No doubt you could make 400+ fwhp without touching the bottom end but if your plans are to boost then forged is the way to go.

 

Quote: "You’ll be well over 400rwhp there, and that’s already honestly too much for a 16 year old."

He may get to drive it (with me), possibly have access to the car at a later date (early/mid 20's) but I'm not going to cut a 16yo loose with that kind of power unsupervised. I would like to see grand kids one day and his momma would terminate me if I let him get hurt. He is our only child.

He loves power (who doesn't) but really geeks out on the technical aspects. He wants to be a mechanical engineer and has been into cars since he was 3-4. Hopefully once we get started I'll see that "spark".....but teenagers are unpredictable.

 

Ben, call and talk to Lloyd Elliott about what you'd like to do and just be straight with him about your goals. Lloyd is the most down to earth cool guy and he's a total wealth on all of these platforms. I can promise you if you do as he says word for word and you invest in what he tells you, you'll end up well beyond happy with your results and you and your son can still put it together... Together.

 

Thank you for the advice Vicious

 

Yessir, you値l be steered in the right direction from minute one, you値l know exactly what you値l need even down to the part numbers and you値l know exactly what to expect from the power and the overall character of the engine.

 

Why is this thread still in this section....should be in the LS section

 

Because I think we just wanna help this guy, an engine is an engine and nobody really cares that it's in the wrong section. Helping and having fun man.

 

I get that...but I知 sure he値l get a larger response in the correct section...jmo