Pulling the engine out of my car to do a winter motor build. It has 80% leakdown on #7 cylinder. This is the 3rd time #7 has given up in this engine. I have been running 16psi on the stock bottom end with no timing and enough fuel to roll coal like a Duramax. The location of the wastegate wasnt efficient enough to hold boost any lower than that. I will also be changing that so it will control boost better.

Here is a rundown on the setup:

1999 LS1 w/ 853 heads milled .025
T56
Turbonetics TC78 (78/68)
Home made log manifolds
2 1/4 hot side piping
Full 3" exhaust
4" turbo inlet
4" cold side plumbing
25x12x4 IC

My goals:

I wouldnt say this is a "budget build", I'm looking for some proven good parts but dont need the best out there either. The car is street driven, pretty much my daily driver when its not broken. Hoping to make 550-600 at the tire on pump gas (93) only, no meth at this point. Hoping to make that happen with somewhere between 12 and 15psi. Would also like the car to be capable of 700whp if i wanted to throw a number up at some event or something.
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The questions:

-Compression. Stick with the 853's or get a set of 317's? Could also use dished pistons to lower compression. I'm worried about lower compression and daily driving.

-Pistons. Considering Weisco forged

-Rods. Callie's?

-Cam. Any opinions?

-Head Gaskets. I am going to put ARP studs in it this time as well. There are a pile of options on headgaskets. Many have mentioned using LS9 gaskets. Even if its doesnt make any difference at all, I dont love the gasket having a larger dia than the bore. Was considering a pair of Cometic's

-Bearings. Unless something has changed, the crank was completely standard size, no machining has been done. I always put the cheap bearings in it. Are any specific bearings recommended with my goals in mind?


Some pics of the car and engine:

 

How are your steam ports setup? Heat from blocked steam ports is a pretty common reason for #7 failure.

If you're swapping pistons, then there's not much reason to swap heads unless they are a major flow upgrade. Swapping them for chamber volume would be pointless.

 

First 2 failures were with blocked steam ports, this last one I had all 4 ports open with a factory "tube".

Thanks for your input. I'm sure the 317 flow a little better than the 853's, but for my goals, I dont know that the flow is a big deal.

 

I think a 317 is a step in the right direction. Even with the standard dish your compression will be to high with your shaved 853. 317 flows more and can be found for around $100. For pump gas only at your desired boost levels And future goals, id shoot for around 8.5:1

 

This has turned out to be false as there are many people with the new steam port setup that have still had #7 fail on them (and #5 as well).

 

meth would have saved it. call me an old fart but 16# on a stock ls1 and 93 fuel alone is asking for trouble.

no sense in not putting a forged piston in it, pretty much anything will get you a lot further than you were.

gm and felpro gaskets are probably the most affordable option for 5.7/6.0 bore I wouldnt go more you want the ebossment staying up on the liner.

had you been looking at backpressure? I like how you did the wastegate but still makes me little nervous.

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The tune becomes a questions after this many failures, although 16psi is up there w/no meth.

What's the tune look like in terms of AFR and timing??

 

took me a solid two mins to find your turbo lol. very nice location.