I thought LS’s were easy?

...I say that partially tongue in cheek, but compared to a 12:1 H22 build my dad and I did a few years ago, this is turning out to be a royal pain in my behind. Since he's not here anymore to irritate for advice I'm turning to y'all for help. I may cross post this on LS1Tech as well but I don't have an account there yet. Thanks in advance! 
 

Context is here; TLDR washed up ASA chassis being repurposed for a Trans-Am SGT build on a grassroots (yo) budget. The car already has a stock C5 LS1 in it, with a nice observation hole in the side of the block where I can see not only what's supposed to be a piston but also the cam... So I'm not hopeful I'll be able to use anything off of it. I already picked up a first year LS1 short block so I'm at the really fun part of setting money on fire; that's where y'all come in. I'll start off with my class limitations and then go into what I have in mind on ordering. For what it's worth reliability>power but hoping for ~500rwhp to overcome having to weigh 3300lbs.. 

Starting from the inside out: Block size limited to 358ci, with a bore limitation of 0.047" over and sleeving allowed to repair cylinder walls. Compression is free, but we have to run Sunoco 260GTX & they recommend a max comp. of 12:1. Crankshaft has to be the same materials as OEM & no change in angle or stroke distances of throws. Connecting rods must be same materials as OEM, otherwise free. Pistons are free. Camshaft lift max @ .600". Heads are O.E. or commercially available equivalent, with machining for valve train allowed. Everything else in the head is free provided it's metallic. Intake & exhaust porting on heads allowed as well. Intake is free, and can be port matched, but I have to run a 650cfm carburetor. I also get to rock a restrictor plate with 4x 1.125" bores. ECU is free but LOL b/c carb. 
 

Where I'm at: My LS1 block is married to it's 3.898 factory bore. I can have my local machine shop hone it to 3.902 max, because I have an early LS1 block detailed here. Compression I'm thinking 11:1 or 11.5:1 because I don't want to build a hand grenade, but as it stands I don't know how to get there without shaving the head down and/or different sized head gaskets, and that's a delicate balancing game of not putting extra stress on the gaskets. I was thinking I could pick up a set of high compression pistons like I did with my H22, but I haven't been able to find any online. Since I can't play with the crank size to get displacement higher than 346ci, I'm leaning towards a forged Eagle crank and rods. Camshaft I'm torn three ways- safe option of a Howard's .525 ASA cam, WS6's .600 lift ASA cam (detailed here), or Texas Speed Performance's MS3 Cam (not a big fan though due to hearing it's hard on valve train components). Heads I'm hitting the easy button and shipping off a set of 243's to Texas Speed for their Stage 2.5 porting, because #budget (that also starts us out at 10.5:1 comp rate as well before any head shaving or playing with gaskets). Intakes going to be a Edelbrock Performer, carb a Holley 650DP and a MSD 6014 timing box. Beyond that... I'm open to (begging) for thoughts, opinions and how I should go about this build as my Google searches from the last two weeks has hit a dead end. Again, thanks guys!

500rwhp? Going to have to get the fairy dust out for this one I'm afraid. Screw compression, you going to need a snail I'm afraid.

https://ls1tech.com/forums/generation-iii-internal-engine/1963750-500rwhp-n-ls1-build-discussion.html

Olemiss540 said:

https://ls1tech.com/forums/generation-iii-internal-engine/1963750-500rwhp-n-ls1-build-discussion.html

Part of the issue I have with LS1Tech, and another reason why I haven't posted over there yet, is all the responses were focused on the streetability of the car after hitting 500whp and that's not a concern of mine. Other big differences is my transmission is similar to a T101A (4 speed dog box basically) with a Winters quick change rear end. 
 

I don't think 500 is out of the realm of possibility, there's a regional SCCA stock car only class called GTA which let LS1's race under a lot more restrictions (stock 243 heads w/ beehive valve springs, spec'd GM ASA Cam, no porting, same 650cfm carb & edelbrock intake I'll run) who've had cars spit out 480whp before, with an average around 430-460. I was tempted to build my LS1 to those specs (the Eagle crank & rods were actually required for GTA) but if I can go wilder with the build and still afford it I may as well. 

I should probably add here, that 500whp isn't a need but just a goal. My needs are to make sure it's reliable and is reasonably competitive against a 8.4L SRT V10 with dual 50mm restrictor plates 

Do they define the inlet/outlet shape of the restrictor plate or could you, say,  cut a 28mm Weber venturi in half and stick the top of it on the restrictor and bottom of it underneath it?

SpeedRacer41 said:

Olemiss540 said:

https://ls1tech.com/forums/generation-iii-internal-engine/1963750-500rwhp-n-ls1-build-discussion.html

Part of the issue I have with LS1Tech, and another reason why I haven't posted over there yet, is all the responses were focused on the streetability of the car after hitting 500whp and that's not a concern of mine. Other big differences is my transmission is similar to a T101A (4 speed dog box basically) with a Winters quick change rear end. 
 

I don't think 500 is out of the realm of possibility, there's a regional SCCA stock car only class called GTA which let LS1's race under a lot more restrictions (stock 243 heads w/ beehive valve springs, spec'd GM ASA Cam, no porting, same 650cfm carb & edelbrock intake I'll run) who've had cars spit out 480whp before, with an average around 430-460. I was tempted to build my LS1 to those specs (the Eagle crank & rods were actually required for GTA) but if I can go wilder with the build and still afford it I may as well. 

On the flip side, the LS1Tech crowd isnt dealing with restrictor plates, .600 lift max cams, etc, etc. 

Having built (and currently tracking) an LS1 hitting 400whp/wtq, I was just stating the obvious it would take a lot of effort (re: $$$) to get to 500whp without boost. Heck, our LS2 build is lucky to get to 450whp without a trick manifold. All these have upgraded headwork, high lift cams, etc etc. Excited to watch your journey so keep us updated!

Patrick G was helpful in guiding cam specs to meet our goal and even got us a discount on the cam itself (although you pay a small sum for the advice). 

You're correct in much of the info on tech wont apply for you. I wouldnt worry about chasing a couple extra cubes, that just means its harder and more expensive to repair if you have a failure or need a refresh. 

Most of the off-the-shelf cams are going to be geared toward a specific use case, which isnt what you are looking for. Id start with a call to Pat G and tell him what heads and cubes you are running and what specifically you need, let him spec you a cam and make a recommendation on compression. Like you said compression is free, so dont give anything up there, but I also wouldnt just rely on them telling you 12 to 1 static compression ratio is the max. 12 to 1 with a mild cam and no overlap has vastly different octane needs than 12 to 1 with 16 degrees of overlap.

Personally I wouldnt be too concerned with the bottom end, ive seen quite a few SBE LS1s hold together under track use if lubrication was addressed. Not saying they dont let go, but they are pretty strong and in my experience crank and rod strength are rarely the cause of failure. If you could go lighter while maintaining or adding strength that may not be a bad idea.

As far as pistons, there are a lot of shelf options and if you cant find one, JE will make you whatever you want.,

I would ask TSP how much they think can be taken off the heads and what size chamber will result.

If its still around Pat G was one of the first to do 500whp on a stock bottom end LS1, i remember some weird things like he had to get away from all the off the shelf exhaust options because the Y pipes are a restriction, might be worth a quick read.

Overlap doesn't affect compression tolerance nearly as much as intake valve closing.  That is why you can get such a big midrange boost with a tighter lobe center and the same or even longer duration, you're closing the valve earlier to keep all that compression in.

One place where overlap can hurt is on a restrictor, the more overlap the less the engine tolerates intake manifold vacuum, and a restrictor will have you under vacuum at WOT.

In reply to Pete. (l33t FS) :

Youre right, but all of these things are related you dont just change one variable without affecting the others, and on a high rpm motor (IIRC) you generally want a later IVC. What im trying to say is pay somebody who does this all the time with a proven track record, and he will look at things like your use case, engine setup and fuel, and youll end with something that actually takes advantage of all the octane you have instead of the rough guestimation of 12 to 1.