All these twin turbo threads got me real bad. And with the tax returns coming soon, I think I'm gonna do it.

I want a 750-800 RWHP on a bullet proof, reliable motor pushing at most 12-14 lbs. I want a install it and forget it deal. The only thing I want to be changing is engine oil. I know it seems like I want too much.

I know that I will have to spend some serious $$$ on Fuel System (my Z06 has the new pain in the a** fuel system), differential, clutch, transmission if I want a real install it and forget it deal.

I would appreciate it if the FI gurus we have on this forum can jump in and give some advice and answer some of my questions.

* What kind of a longblock do I need to achieve these numbers and be safe?

* Which Twin Turbo kit can get me there? (I'm leaning heavily to the TTI Stage X side these days)

* Can the TTI Stage X kit support 750-800 RWHP on 12-14 lbs of boost?

* Do I need to O-ring my heads and turn the boost even further to get to these numbers?

* If O-Ringing the heads is such a great thing, why is everbody not doing it? Why am I hearing O-ringed heads leaking water? What are the problems with O-Ringing the heads?

* Would a Forged LS2 402 work in my case or is it too much pain to make it work in my Z06? Should I just go with an Iron block instead?

That's a lot of questions but better to ask now, then later.

Thanks.


ART

 

What is so important about only running 12-14 lbs of boost?

Mark

 

I don't want to lift heads and I've read and heard that 14 lbs is the limit. I think I want a boost supported motor rather than a boost dependent. So, I want to keep the compression ratio around 9.1:1 to 9.3:1

 

Art,

The TTi will support that power level. I made over 700rwhp on 13psi on a scrawny 348cui motor. I have attempted 18psi and busted up the drivetrain again even with every trick in the book. So, its will support more boost and airflow.

What cylinder heads? We sucessfully run 18psi+ thru virtually every stock casting the only problem childs are the perimeter bolt patterned 97/98 heads..

That compression level 9.1-9.3 is a great target level, what fuesl do you have available. Forged rods,pistons and stock crank will take more power than we will make .

Phil

 

Doctor Phil,

I was thinking of going with either a 402 CID LS2 or 408 CID Iron block. All with Mahle dished pistons, Lunati crank, Lunati Pro Billet rods, Lunati rings, Clevite 77 rod and main bearings. Although LS2 block will save me 60-70 lbs compared to the iron block, I will have to change to LS2 Front cover, Timing set, Cam sensor, Front cover, Front seal & gasket, Valley cover. And, trying to use the knock sensors on a LS2 is another problem. I am not sure if I want to deal with the unknowns of the LS2 block or go with the frequently used, good old iron block. What do you think Phil?

I'm thinking of using custom ported AFR 225's with upgraded springs. I'm not sure if I want to use Cometic head gaskets and call it a day or O-ring the heads. If O-ringing was such a great thing, why is everybody not O-ringing their heads? What are the potential problems with O-ringing the heads?


ART

 

I would have to recommend that you stay away from the LS2 block. The sensors are external, and requires too much additional effort to work in a c5 IMO. For turbos smaller displacement is actually better for drivability. Larger displacement motors tend to make more power/ torque than can actually be put to the ground, so you have to turn down the boost to make it drivable. It will however make an awesome dyno queen.

I would say a forged LS1 block, with forged internals at 9:1 compression. AFR 205 heads. Dont worry about O-ringing the heads, I think you are asking for trouble. On 12# boost you will see the numbers you are looking for with the stage x kit. If you truely want 700 RWHP then you will have to change to a rail regulated fuel system. On any FI car its all in the tune. Spend the money on a boost controller and all the accessories to do it right the first time

 

[QUOTE=INSOMNIAC][B]I want a 750-800 RWHP on a bullet proof, reliable motor pushing at most 12-14 lbs. I want a install it and forget it deal. The only thing I want to be changing is engine oil. I know it seems like I want too much.

I know that I will have to spend some serious $$$ on Fuel System (my Z06 has the new pain in the a** fuel system), differential, clutch, transmission if I want a real install it and forget it deal.


At that kind of power level, reliability does not exist. You will be looking at spending at least $30K, probly closer to $40K for that kind of a setup. Once you start, its hard to stop because you start thinking of all the potential problems that could go wrong and you proactively start adding the parts. Reliability in a motor is not hard to achieve... it comes down to the tune and the quality of the setup. Good fuel system... Xtreme built me a good one. Trans, clutch, Diff... depending on what you need the car for, you may need to upgrade. Remember, Turbo cars provide a hp/tq ration that favors torque. You will more likely see more tq than hp. So, If you want 7-800 hp, you WILL see 8-900 tq.

 

I'm not 100% set on the LS2 block either. The knock sensors can be implemented but I think they will need to be tapped into the block and there is definitely some additional work there. Also, I will have to change to LS2 Front cover, Timing set, Cam sensor, Front cover, Front seal & gasket, Valley cover. I don't know how durable and reliable the LS2 Timing chain set is. On a LS1, LS6 or Iron block you can use Rollmaster double roller timing chain set but not on LS2 as far as I know.

Is anybody doing a FI LS2 402?

Why AFR 205 but not 225? I don't think I can put down 800 RWHP on 12-14 lbs of boost on the setup you recommend. Phil put down 700 RWHP on Forged 346 at 13 lbs of boost with no cats. And regarding traction and unnecessity of 800 RWHP, I enjoy 4-5-6th gears as much.

What is the deal with O-ringing the heads? Why would I be asking for trouble? Would somebody tell me the whole deal with O-ringing the heads and the problems associated with it?

ART

 

You have an awesome ride. Xtreme pulled an excellent job on your car from what I've seen and read in CF.
You are absolutely right with your comment. I will have to upgrade to a complete high Hp fuel system like the ones Xtreme, FLP and Optic has, upgrade transmission, change clutch and the differential. The list goes on and on as you try to achieve a complete system that will work. But it's like building my own car for my own needs. You can't buy a car like that from a showroom.

ART

 

AFR 225 have a 4.0" bore, AFR 205's have a 3.9" bore. If you are going to build the motor you may as well lower compression via the pistons not the heads. Just a FYI, your lsx block is a 3.9 bore. Phil made 700 RWHP on 13# but he also running 6.0 heads, not AFRs. AFR 205 heads have a thicker deck and disapate heat better, so you can crank the timing up resulting in more horsepower. With the right cam and the 205 heads you should be able to hit 750 RWHP and about 850 RWT. At that level you will need a tranny that can hold the power, a DTE tranny brace, and hardened parts in the rear. Even with over 3-5k in upgrades to the drivetrain you can still brake parts with that much torque.

 

You are right. NEEDS are important .

My heads are o-ringed. Think of o-ringing the heads a an added level of seal beyond the gead gaskets. Remember, your head/motor design is missing a head bolt compared to other chevy V8 designs which means the heads are more likely (although unlikely at the boost level most people are running) to lift under higher boost applications.

A groove is cut around the chamber in the head and the block. A ring is placed in the groove and the heads are bolted to the block. Although more complicated than that, I have not heard of anyone having problems with o-ringed heads. I have heard more people having lifted a head than people having with o-ringed heads.

It just really depends on how much boost you want to run... if you cap at 12, I think you may be ok.

 

IMO FWIW assuming ARP studs,
If the o-ring process is setup right and a good gasket is used (not copper or MLS)... there should be no worries for leaks on the street. There are folks pushing 14+ psi of boost. Some GM heads stay down with MLS gaskets and some lift. So, some have good luck and some don't. This tells me that the performance level has met and/or exceeding the physical capabilies of the GM GenIII heads to stay down considering their 4-bolt pattern. The AFR castings, with their 3/4" deck, are currently, the most desirable head to have in forced induction with power levels exceeding 700rwhp. I have heard talk of 1/2" studs... but am openly concerned about removing material in the head bolt bosses as they are engineered and casted for current head bolt sizes. I know a good engineer will always overengineer for strength and reliability but wonder if 1/2" is approaching those limits. Although this may be a good idea... I'm not so sure its the solution because of the perceived weakness of GM castings and 4-bolt pattern under incredible cylinder pressures. Also, I have not seen any data that supports factory sized ARP studs actually stretching... would be nice to here one way or the other.
As far as LS2 goes... I was going to do an LS2 for King_Pin but without concrete data showing a relocated LS1/LS6 knock sensor would work effectively and sufficiantly we opted the safe route and chose to stick with an LS1 block. I'd like to see some naturally aspirated 6L AL motors out there with some tuning feedback (from folks with external or stand alone knock monitoring capability) to see how well a relocated LS1 knock sensor performs before force feeding...

Bill

 

What is a good gasket to use for O-ringing the heads? I've heard about the 1/2" ARP Studs and I think couple people in this FI forum are using it but I don't feel great about removing material either. I might need to up the boost to 14 lbs or more to achieve 800 RWHP and I definitely don't want to lift the heads.

There are couple people using 402 LS2 N/A strokers in the LS1tech forum but I don't know any that is using a LS2 402 for FI application. Hell, there are couple people running LS2's in F-Bodies without any knock sensors. I remember eading that LS1/LS6 knock sensors can be tapped into the LS2 block to make it work but I don't know how reliable and efficient that would be. I would really like to have a 402 LS2 but if I can't find a way to make it work, I can go with the good old 408 Iron Block.

ART

 

Felpro graphite head gaskets... machining for the wire o-ring to bite on the outer half diameter of the fire ring in the head gasket...

Yes, there are extra bosses on the outside of the LS2 block... or perhaps drill/tap existing LS2 knock sensor boss. The 03-04 Cobra does not have knock sensors... from the factory. They seem to get along... although when pushed by a novice tuner even with their factory forged pistons they can melt down quicker than you can lift. So, remaining analog inputs become much more critical, especially in FI, IMO.



Bill

 

70lbs is the difference .
.7sec in the 1/4 and all the weight over the nose..does it matter much for us..not really..
A lot of potential negatives with O-rings..Brinelling the head & block surfaces, Over stressing the head gasket material on top of the fact your altering the load distribution to transfer clamp load from other areas. This is the usual culprit that causes the coolant leaks.

Phil

 

Well, it's more than just 70 lbs. What is the weight of the TTI Stage X kit with the large intercooler, wastegates, pipes, manifold, turbos, etc? I like drag racing but I would rather road race any day. I would go little extra to make a well front-rear balanced car but not the whole 9 yards.

So, this what I understand. Do not O-ring if you don't need to which is if you are not going to hit 14 lbs of boost or more. And if you are going to O-ring use quality gasket and have it done by an experienced mechanic/shop.

ART

 

Himmm. Why reinvent the wheel?? Maybe, I should go with the good old 6L Iron Block.

 

I think Phil runs LS1 heads that have been slightly worked over to open up the cc's.

Cheers,

Mark

 

Hey Phil,

Which gaskets are you guys using right now?
TIA!

 

How do you hold the heads down on 14+ lbs of boost without O-ringing then? Is it just the lbs of boost that lifts the heads or is it detonation? Would Alky injection help?

ART