School Me on LS Motors

[BeXtreme]

The L92s are aluminum block and command a premium, so they're out of consideration.

I don't know about that. I got an L9H(L92 with flex fuel injectors) from a 2009 with the burnt up 6L80 still attached, wiring, and ECM for $1500 a few months ago. It should be done getting cleaned up and checked out at the machine shop by the end of the month. It ran good and still looked almost brand new inside when I took it down for a freshening up.

 

[Erik the Awful]

I did a little playing around with a compression ratio calculator and Summit's LS spec chart. The LQ4 and LY6 have the same dish on the pistons. The difference in compression ratios is all in the heads. With L92 heads they both have a 9.67:1 compression ratio. The LQ9s are flat-top and 10.0:1 compression with 71cc chamber heads. With L92 heads they jump up to 10.4:1 compression. If we can be assured of finding at least 93 octane wherever we go, that might be a hot ticket for making 650 hp.

Now I'm wanting to find a buildable LQ9 to put in WCJr, but I already have too many projects.

 

[BeXtreme]

I did a little playing around with a compression ratio calculator and Summit's LS spec chart. The LQ4 and LY6 have the same dish on the pistons. The difference in compression ratios is all in the heads. With L92 heads they both have a 9.67:1 compression ratio. The LQ9s are flat-top and 10.0:1 compression with 71cc chamber heads. With L92 heads they jump up to 10.4:1 compression. If we can be assured of finding at least 93 octane wherever we go, that might be a hot ticket for making 650 hp.

Now I'm wanting to find a buildable LQ9 to put in WCJr, but I already have too many projects.

My 2011 LC9 equipped Suburban has 9.6;1 and I run 87 Octane in it all the time... even when towing sometimes. It has no issues. A stock L92(or L9H) sits at 10.5:1 with the flat top pistons and 823 heads. You can still run 87 Octane, but the computer pulls TONS of timing to keep it happy. 93 Octane makes it very happy.

 

[0xDEADBEEF]

I think you're going to find the NA limit more like 550 hp.

 

[Erik the Awful]

It'll depend very heavily on what is decided for a rev limit. I'm wondering if we could have a 7000 rpm rev limit, but if something goes wrong and we have to lose top gear, limit the rpm for hanging in gear to 6500 rpm. Of course, drivers never really listen when you tell them rev limits.

The serious flow of the L92 heads plus a 10.5 compression ratio would probably get us close enough.

I spotted an '05 C2500 Express Van with a 6.0/4L80 on Public Surplus, but the bidding rocketed up to $2600. Ugh. Truck prices in Oklahoma... Meanwhile there's an '00 K2500 Suburban with rust issues in Pennsylvania that the seller can't get rid of for $2500.

 

[0xDEADBEEF]

Consider the LS7.

7 liters, high revving, great heads (except for the valve guides), titanium this and that ... 505 HP on the stock cam. You could see over 600 with a max duration cam and intake, maybe even 650.

Not trying to dissuade you. Come over to the rpm darkside.

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[Erik the Awful]

Dude, we're considering a 6.0 because we can't afford a 6.2, and you're talking LS7? Find me one for a cool grand and I'm in!

 

[0xDEADBEEF]

Dude, we're considering a 6.0 because we can't afford a 6.2, and you're talking LS7? Find me one for a cool grand and I'm in!

You missed my point ... 650 HP is about the max for an LS7 with stock heads. You ain't gettin' there with less displacement and worse heads.

 

[Erik the Awful]

The goal is an engine that can survive producing 650 HP all day long, and without requiring a rebuild after every event. For reliability we'd like to produce that much power under 6500 rpm.

You missed my point ... 650 HP is about the max for an LS7 with stock heads. You ain't gettin' there with less displacement and worse heads.

It's a goal, it's not set in stone. We're still in the spit-balling and research phase. If we can't get there, then we can't get there. We'll take 550 hp before we spend our 401ks on an LS7.

 

[0xDEADBEEF]

Is FI against the rules? You could throw junkyard 4.8s and 5.3s at it all season long.