Corvette0096

What's the way to go? I hear the LSX block is a 100 LB heavier than the aluminum block. I don't want it to be a border line build like I have now. LPE 346 forged with a stock crank. 1000 at the tire is the goal. Also will a stage 1 ECS fuel system keep up?

Turbo-Geist

There isn't an easy way to step up to the 427. Which turbos do you have now, 57s or 62s? Are you staying with the TTiX kit? Are you sticking with the 4L60?

neverstop

I have LSX block 427 and honestly If I was going to do it again I'd have gone with a forged Ls3 stock cubic inches with 1/2 head studs or at most an iron block. I think if you want >1,100whp or something then LSX block is important but I'm at 900whp which is way more than plenty for a street car and you certainly notice the extra 100+ lbs in the nose, and lots of guys on here making 1k hp without LSX block and seem to be reliable.

the thing with smaller ci that I did not anticipate fully is that you can rev them higher and at 1/2 mile you can possibly avoid the shift into 5th gear which makes the car dramatically faster.

my d1 runs out of steam on my 427 at like 5900rpm

I run ECS stage 2 fuel system with dual meth and rock steady fuel pressure all the way up to 175mph at the track.

ysb02

How much higher would you rev a stock stroke/bore motor?

I'm looking at doing a LS2 or LS3 for me to hold ~850rwhp and not incur the 100+ lb weight penalty of the LSX/LQ9. I thought doing a 402/416 would give me better low/mid-range before the centri starts hitting hard.

Corvette0096

Buying some 6265 when I can find some. Yes staying with the TTIX and 4l60.

Turbo-Geist

427 Option
Ok, I personally wouldn't pair the 6265s with a 427 engine. If you really feel the need to go that route, I would make sure to run free-flowing 3" exhaust and 3" downpipes. Boost control with the 427 will be an issue unless you put a waste gate on the intercooler and that has its own issues. I would also look at upgrading the intercooler to something less restrictive.

346 Option
You can make the desired 1000rw using the 6265s, but I recommend 3" downpipes and full 3" exhaust. Boost control might be an issue depending on the exhaust system used but it will be better than with the 427. Once again, you could put a waste gate on the intercooler but I’m not a fan. You already have a forged 346, so I would just stick with it unless there is an issue.

Depending on how much you use the 1000rw setting with the 4L60, it could need to be refreshed every season.

C5 Pete

Curious, as I've not built a turbo setup - yet... What's the downside of a wastegate on the intercooler?

Turbo-Geist

One downside is the air gets compressed and heated up and then sent to the intercooler for cooling. Instead of being used by the engine, a portion of this cooled air will be continuously vented to the atmosphere. In my opinion, this could cause higher intercooler temps. A BOV opens and closes to equalize pressure, the wastegate would be constantly open during the entire run if it was being used to lower the overall manifold pressure. I'm talking about this 427 twin turbo combination with 6265s specifically. It probably wouldn't matter in the quarter mile or if you are just driving around on the street. I think it would come into play during back to back pulls and half or full mile runs.

If you want to talk in general with different turbos, a different turbo kit, air to water intercooler, etc., then the dynamics will be different.

Drewstein

That's easy, my 6.0 makes 1100rwhp ish on E through a TH400 and 9".

I used to have a big cube turbo vette and I ran into a problem that the turbos have to be way bigger to make the same power. There's no reason a 6.0 can't handle the power at 20ish psi if build right.

My local shop has a C5 making almost 1200rwhp with a little motor and LSA heads on E. No need for the big cubes. He's a sponsor on her, Cordes Performance.

ysb02

I followed his build thread and I really his setup. I was planning on reusing my 243 heads + ls6 intake to keep the cost down or I'd splurge on a LSA longblock.

The only reason I'd go stroker/big bore is to get more low down torque. I don't know if that would give me much more over a stock stroke/bore though.

neverstop

this exactly

"I used to have a big cube turbo vette and I ran into a problem that the turbos have to be way bigger to make the same power. There's no reason a 6.0 can't handle the power at 20ish psi if build right."


with a stock ls3 cubes a normal street blower (d1, f1a, ysi etc) can rev to 7k which means you can pull 4th gear and are likely much faster in mexico and 1/2 mile runs since no 5th gear shift. just depends on what you're doing with the car.


i think generally with FI setups you make so much power that wheel spin is the issue and typically it's not the cubic inches that dictate the power anyway.

Cordes Performance Racing

Thank you for following OP I can easily put together a solid setup that will do what you want, my car drives smooth as silk, makes the power and runs the times to back it up.

stevieturbo

Screw the extra weight, and go slightly smaller and use an LS3, LSA, or LS9 block.

The latter already using larger studs which will be helpful ( unless you get the others drilled for 1/2" studs )
And oil squirters which are good for longer duration runs like 1/2 mile or more.
Although the LS9 blocks are quite expensive compared to the others. I think they already come with pinned billet main caps too though ?

For only 1000 though, no need for iron at all.

TTBlueZ06

LSX Block, 4.125" Bore, 3.622 Stroke, 388ci and spin that bitch!

Drewstein

This seems a little bi-polar as big cubes are on the high end of the cost scale where you're trying to use 243 heads and LS6 intake.

You're not hitting those numbers with those heads and intake so spend the money there.

Cordes Performance Racing

I'm 11:2 compression on 25 psi. My centri car makes gobs of low end. At peak it made 1005 rwtq and at 3800 rpms I'm at 750 rwtq lol.

ysb02

My thoughts on that were a 402ci LS2 shortblock is ~$6k while a full longblock w/ intake would be $10k+. Using a stock ls2 crank over the compstar stroker one would just be a little bit cheaper. I don't think you can machine the 243 heads for a 1/2" head bolts though?

I was trying to split the top end / bottom end cost. The heads / intake is something I could tackle in my garage but I don't think I have enough room / tools for an engine swap.

Drewstein

You will have issues cramming 243 heads onto a 402 either way. You don't need trick flows etc, heck I have LSA heads and I used LS3 heads from AI in the past.

Get a smaller cube block which saves money as well, spend that on some not so garbage heads. You only need a larger manifold like ported LS3, nothing crazy. Then feed it a ton of boost.

At the power you're talking it's going to hit hard regardless of TQ and you may have traction issues through 100mph either anyways.

robert miller

If you are looking at any aluminum block look at doing a cradle to help the crank from moving around as bad.

MVP'S ZO6

there are definitely lots of different answers and opinions as to how to achieve your goals.

I think you're heading in the right direction. there are common threads or agreeances in here.

1. Iron though heavier is stronger than aluminum.

2. There are methods of helping that weaker aluminum block out but in the end unless you spend more coin it will never be as strong as the iron block. I know everyone does it (makes 1,000 wheel now days) but it's still a lot of power and there's a lot of stuff going on inside that engine at extreme power levels.


I actually have an Alimimum LS2 that's just about ready to pick a rotating assembly for.


I also have a 6.0L iron block that's ready for me to run through its paces on some machinery. Can also get an LSx or an aluminum block that's ready for a 4.125" bore.

Hit me up with a pm or give me a call. I'd be more than happy to discuss the aforementioned with you.

Eight 5 8 two 4 9 eight 8 2 7 is my cell.

Mike