What's the most power LS1 can withstand more or less reliably?
I have forged LS1 (2004' block) - Eagle crank, Eagle H-beam rods, Probe Industries pistons, ARP head bolts, Patriot Stage 2 heads, 9.2:1 compression. What can I squeeze out of this motor? Preferably do it reliably I'm going to switch to E85 for safety and cooler combustion too.

 

It's hard to put an exact number on it, but if everythig was machined, and assembled right you should have no problem maxing out a TC78, and maybe a PT88 from time to time if it wants more. Also the tune is the most important part.

 

Yes, certainly bad tune can kill it at 500whp...
I'm talking about good tune, and moderate build quality.
I guess I should have called thread "How many 900whp+ LS1's are out there"
What would be weakest part in my setup - block, or lifting heads?

 

Piston rings and rods are usually the weak links

 

There are enough to show it can be done. My guess is you would lift a head first if everything else is right. Light rotating assembly, and keeping the RPM down will also help it live.

 

yeah but I meant limits of LS1 block, not stock internals

 

Even with ARP bolts? Hm, how could I help them clamp?

 

9 Bazillion.

Really there are far too many variables to make a statement like this. The internal components are what will dictate a limit. I mean look at it like this: If you are going to spend $XX,XXX on superior internals, heads, and intake are you really gonna put that in a stock LS1 block?

 

1CAMWNDR, I would not want to discuss some crazy stupid cases like $100000 internal components with stock LS1 block. I want to understand what LS1 with normal forged internals would handle. Specifically, with my components/heads that I specified in first post

 

I have a similar setup and am at around 700 rwhp, don't no that i would like to push the ls1 block much further.

I think heads lifting or cylinder walls splitting would be the main areas of failer to watch.

 

Come oooooon, AutomagicLS1 pushed LS1 to 1140whp recently, so 700whp shouldn't be a problem for the block

 

Then push it to 1500 run a few 1/4 mi passes and report back

The studd would be a little stronger 190000psi vs 170000psi arp bolt but the head will likely flex befor you streach the bolt. The stud at the same tq will clamp the head tighter due to the fine thread vs corse.

 

Is there anything that can be done to help those Patriot heads?

 

I dont think it is required to do any more to your heads. Stock 317 heads with good valves and valve job have made over 1000rwhp. I would talk to whoever built your 383 and see if they think it needs anything. At a minimum I would change to ARP head studs. Do you have an actual goal in mind? I bet you could make a pretty reliable 800rwhp. Do you intend to keep the TC78 or get something a little bigger that flows better?

 

What about this head lifting and flexing that many talk about? You think Patriots will be OK at say 1000whp? P.S. Actually I bought this car 4 years ago from member here, it was already built (at least I believe so). So can't really talk to the 383 builder.
I have ARP bolts now, are studs any better?
Well... Actually I'm reconsidering my build limits right now. Initially I planned to get TC78 and stop with it. So 900-1000HP build (flywheel; I don't quote WHP because at that time I had T56). But now I realised I might actually be very close to the fastest cars in my country (Audi at 9.0 and Mitsu Evo at 9.5). I expected T56 to brake very soon past 700whp so I sold my T56 and now ordered 4L80. I've decided to go reliable and invested in good expensive converter from Circle-D, and 1000HP-built 4L80E from Jake. So with TC78 and good tranny I actually might be close to at least 9.5s if I perfect this setup. With such a lot of money invested in tranny, having forged LS1 and 12 bolt rear, and being so close (probably) to the fastest here, I'm scratching my head trying to understand limits of my LS1, and hoping to get maybe 1000-1100whp (with bigger turbo). BTW I'm going to run it on E85.
Sorry if it was too long, but your answers were technical and useful so I tried to give the most info too

 

One thing I fail to understand is this head lifting/flexing/whatever problems. In Nissan Silvia world, we don't have ANY aftermarket heads. So some guys run upto 600whp on stock head (record is 700whp). I personally ran around 360whp on stock head, bolts, paper headgasket, ignition, intake. Remember, this is from 110ci engine.
So I can't understand what's going on with heads on LS1, each head only handles half the power, so why can't LS1 run 1000-1200whp? Slightly longer distance between studs perhaps?

 

Deck thickness of the head, the overhead cam style heads tend to be bulkier.

 

The problem with lifting heads comes from the LS1 never being designed from the factory to run big boost (15psi+). So it has a fairly thin deck. Also there are only 4 head bolts per bore.
To run more boost reliably you need either an aftermarket head with a thicker deck, or the LSX block that has 6 bolts per bore (Which will require aftermarket 6 bolt heads).
And yes, the studs are quite a lot better than the bolts.

Since you went with a built 4L80 you need not worry as much about breaking a tranny. I'd step up to a larger turbo that will not choke on the exhaust side. Like an S80 or S85 .

 

800-850 rwhp

 

OK so if I improve clamping/flexing problem somehow, I'd be able to put down a little more power? Those people who has done 1000whp with stock heads, did they do anything extra to the heads to help them stay?
Yes I keep in mind slightly larger turbo, that would help the heads stay too I think.

Lastls1, recently someone posted dyno with 1140whp LS1 So 800whp seems too underrated