Advantages of LSX block for twin turbo application?

[broken1234]

I'm in the planning stage for a twin turbo 8/900 hp 70 Camaro project.

Being new to forced induction, I'm curious about folk's thoughts and suggestions on just how strong I need to build the bottom end for this HP set-up.

It has been suggested that an LSX block with additional head studs, and an appropriate set of heads, would be a worthwhile investment.

Can someone comment on their experience here and suggest some parts combos that will get me where I want to go without overkil or breaking the bank?

Thanks,

Brad

[ironworks]

There is no such thing as a 900hp twin turbo budget engine that will last.

The LSX block is awesome, it is heavy but super strong. GM says it can handle 2500 hp. A billet LS block will do the same for about triple the cost.

As far as that the engine will be expensive to make it last, unless it's a one hit 900hp wonder.

[Rybar]

Brad a good buddy of mine is building a 427 LSX and he's putting twin T76 turbo's on it. This is for a Drag Car but I believe he's going with 6 bolt heads/studs and fully forged internals. Brand names I'm not sure.

[badmatt]

A stock studded 6.0L iron block will take that no question.

[broken1234]

Well, the clearer story is this; I want about 700 hp at the rear wheels. I'm told that I'll lose about 15% in the driveline (T56 and a Ford 9"). I will have access to an engine dyno.

It's been suggested that my biggest concern is internal pressures, thus the LSX block and it's extra head stud. Obviously all forged stuff in the bottom end. Is this valid?

What else am I missing here?

I don't expect to regularly run the engine at high boost levels. This car won't be a regular racer or autocrosser, just a street car that occasionally hits the track...

[camcojb]

I've seen many 700 rwhp+ LS engines with the stock aluminum or iron blocks. The LSX block is a great platform, but not required. Where it comes into play is if you'll be running high boost, like 20 psi+. If it takes that much boost with your combo to make 700 rwhp, change your combo............ :lol:

Easy to make big power with a forced induction LS engine. The TT 402 in my last car made well over that with a 4L80E and 9", and the boost level was at 14 psi. At that boost level you do not need the extra head bolts. Never got a full pull due to it shutting the dyno down around 4800 rpm due to excessive torque, but I'm confident in saying it was over 700 rwhp. :yes:

http://www.camcojb.com/temp/malitude%20772.jpg

[broken1234]

Thanks for the reply... might I ask what turbos you were running and what sort of heads and bottom end pieces you had in your 402?

[71RS/SS396]

This guy is the "man" for boosted LS engines http://www.kurturbanperformance.com/

[camcojb]

This guy is the "man" for boosted LS engines http://www.kurturbanperformance.com/
Thats where I got my engine parts.
He has an offset piston for the ls that quiets the strokers a lot.!!!!

[gnx7]

If you need a NorCal machine shop I have S&S Automotive in San Leandro, CA build all my motors. Ex-NHRA guys. They did my Buick GN turbo V6 stuff back in the day and now LS motors. They ship worldwide and know their sh*t.

In a nutshell the LSx block is overkill... plus is a fat pig. An LS alum block is around 80lbs. An iron block is another 80lbs or so heavier (160lbs total approx). The LSx block is yet again another 40-50lbs heavier than the production iron block.

If you want 700rwhp you can get a 2005+ engine that has LS2 rods, upgrade the cam/springs/pushrods, LS9 head gaskets, ARP studs, turbocharge it, install bigger injectors, upgrade the fuel system, tune it and you are good to go. No need to build an LS motor with only 700rwhp. The limit of 4 bolt style production heads is around 1000rwhp safely. You can certainly make more.. but the head gaskets will eventually let go. Thicker deck aftermarket heads help at the big HP levels for head sealing. There are a number of cars with forged bottom ends and stock LS3 heads/intake making 1000rwhp+.

If it does pop.... then build it. With the proper tune and quality fuel you shouldn't have issues. For extra measure you could open up the ring gap on the pistons and install rod bolts.

I'm building my car with an '08 alum 5.3 (stock shortblock) with ported 5.3 heads (not needed), LS9 head gaskets, ARP head studs, LS6 intake (not needed), small 225/223 cam, ported throttlebody (not needed), with a medium size TC78 turbo and shooting for 750-800rwhp on e85.
Most of the time I'll putt around with 550-600rwhp and turn it up when needed :thumbsup:

If you have the extra money run an LS2 or 6.0 iron block, stock LS crankshaft, some good forged rods (CompStar), and JE/Wiseco/Diamond forged pistons. That will handle 1000rwhp+ with a good tune.

My buddy has a forged LS3 with ported LS3 heads/intake running a GTS76 turbo on e85 and makes 620rwhp on 3.8psi. 750rwhp on 6psi...960rwhp on 14psi. No issues with his setup and he runs a stock LS3 block/crankshaft.

Here is my engine bay awaiting turbo fab.

[gnx7]

The general rule of thumb is that every 1 bar (14.7psi) of boost will double an engines power output. Meaning if naturally aspirated it makes around 350rwhp.... with 15psi it should put down 700rwhp or so. Obviously you need a turbo that can flow that much to support the power.

Smaller cubic inch engines (5.3) will be able to run smaller turbos more efficiently and not "choke up top in the RPM range." due to not having as much back pressure as a larger one (6.2) simply due to the amount of exhaust that needs to be removed by the turbine housing of the the turbo. A turbine wheel/housing can only remove so much exhaust as the wheel can flow. For example my little TC78 on a 5.3 will pull nicely to 6500rpm or so.... the same turbo on a 6.0 or larger will stop making power probably at 5,000rpm due to the backpressure spiking and the turbine wheel not being able to exhaust the required amount.

[broken1234]

Ok... so I think I'm somewhere in that gray area because I want to do it right the first time, and plan for the possibility that I turn up the boost at some point.

So assuming a 6.2 engine as a starting point, what is a specific pair of turbos to run? I'm still trying to understand how to select a particular component...

[LS1NOVA]

For what your looking for Id put forged pistons and rods in the 6.2 your looking at and use a pair of Precision 6262's. Capable of around 1000rwhp but will still perform very well at lower boost and 700rwhp.

[gnx7]

Lets start with your budget..... Twin GT35R's will spool like mad and make 1000rwhp easily. Beyond what a stock 6.2 will handle reliably. If you aren't building the turbo kit yourself or have a hookup..... it won't be cheap.

A stock 6.2 block/crank will handle that power..... but forged rods/pistons as mentioned should be on your list too. LS9 MLS head gaskets and ARP head studs with some good heads (LS3 or even better yet some thick deck LS9/LSA/TFS/AFR/MAST if you can afford them) will get the job done. Stock LS3 heads flow nearly 330cfm intake and work fine for a street car.

For a dedicated race car get the aftermarket heads.

[MaxHarvard]

http://www.camcojb.com/temp/malitude%20772.jpg

My god look at the angle of those dyno curves :unibrow: