L92s on my LQ9
Sep 16, 2011 | 06:26 PM
#21
Man Motor club
Joined: Jun 2007
Posts: 2,623
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From: Sunniest city on Earth
Exactly. Couple that with an engine that supposedly has a better powerband, and GM must just be TMing away every last bit of improvement they've made with the combo. I've literally nearly gotten stuck in almost nothing in a 2008 HD in 4wd; they won't even try to spin the tires. I've done the same things in 2006 HDs and it's been a non-event. I've logged thousands of hours both on and off pavement in 6.0 HD GMT800 and 900 trucks set up to identical specs otherwise, and can tell you that the 900 gets embarrassed by its older brother every time, even though it has the better array of hardware. The only area I notice the improvement is fuel efficiency.
Sep 16, 2011 | 06:52 PM
#22
It's a newer truck, more de-tuned from the factory so they make it pass their 100k warranty etc etc. Of course it's going to feel weak. They have so much more de-tuning that make these newer engines a dog. It's not the "intake" port that makes them feel like this.
I remember when I first got my 2004 RCSB 5.3 Silverado it was the slowest thing I'd had ever driven. A tune later it still was the 2nd slowest thing, but really woke the truck up.
For example: My LQ9/LS3 Silverado pulls really hard down low in the rpms with the converter locked in OD. I can cruise at 2000 rpm (Where these L92/LS3 heads supposedly lack all this torque) at around 70 mph I barely get into the throttle, so the converter doesn't unlock and it pulls like a freight train. I've had a 1000lb+ load in my bed going up the Cajon Pass which is a 6% grade (total weight 5500lbs) with the truck in OD crusing at 80mph and the truck will never unlock the converter. It just keeps pulling. If I get into it lightly while keeping the verter locked I can easily speed up to 100+. You can't say these L92/LS3 heads have no low end torque and you definetly can't blame it on the intake port design.
I remember when I first got my 2004 RCSB 5.3 Silverado it was the slowest thing I'd had ever driven. A tune later it still was the 2nd slowest thing, but really woke the truck up.
For example: My LQ9/LS3 Silverado pulls really hard down low in the rpms with the converter locked in OD. I can cruise at 2000 rpm (Where these L92/LS3 heads supposedly lack all this torque) at around 70 mph I barely get into the throttle, so the converter doesn't unlock and it pulls like a freight train. I've had a 1000lb+ load in my bed going up the Cajon Pass which is a 6% grade (total weight 5500lbs) with the truck in OD crusing at 80mph and the truck will never unlock the converter. It just keeps pulling. If I get into it lightly while keeping the verter locked I can easily speed up to 100+. You can't say these L92/LS3 heads have no low end torque and you definetly can't blame it on the intake port design.
And a RCSB is not a valid comparison to a Yukon or 2500HD, given weight differences of almost 1 ton or more, which has a tremendous effect.
The 1st gear of the of the 6l90 is a tremendous advantage over the 4l80e, because I know just how massive of a difference going from the 4l60 to 4l80 is right off the line.
Sep 17, 2011 | 12:51 PM
#24
To comment on something Dezert1500 said earlier about same(stock) camshaft / different head swap. If the Cylinder head was, in an installed state (considering intake manifold and exhaust), able to flow more CFM at any given lift vs. the previous head, the engine should be generating more torque. Provided fueling table is modified to take advantage of the additional air in the cylinder.
Ideally what we really need here is an Infinitely variable (within an acceptable range) duration (160-250)/lift (.000-.625) lifter design with independently variable I/E cam center-lines. The .000" lift would allow for built in cylinder de-activiation. That would allow a custom cam map for each segment of RPM and Load on the engine.
Last edited by ForcedTQ; Sep 17, 2011 at 02:19 PM.
Sep 18, 2011 | 02:31 AM
#25
Stock for stock, the LQ4 makes more torque down low than an LY6, which is essentially what you would be building. I've talked to guys who have ported the exhaust on the heads and cammed the engine differently so they can get more down low, but that's a lot of work to make a setup that isn't optimized for torque a torquey setup. I drive LY6 trucks at work every day, and we switched 90% of our fleet from LQ4 trucks (the rest were 8.1s). I can tell you that the LQ4 rigs offered more down low and the LY6 trucks like to be revved. It makes for a bit of a pain in a truck that large. My DD is a 6.2 L92 Silverado, and it's a riot, but if I could change one thing it would be bottom-end torque. Once I give it some revs, it gets really fun, but it doesn't give you the off-idle torque that the more truck-oriented 317 combos do. Plus, as Dezert1500 is saying, you could sell your L92 components and put that money into your ride and you'll come out ahead anyway.
Sep 18, 2011 | 08:12 AM
#27
Imo if your looking to do a head swap id do the 243 heads gettem milled about .030 to bump up the compression to 11.1 cause with the l92 heads you can't mill them to get over 10.5 with out fly cutting cause the exhaust valve is so Damn big. My setup is a stock LQ4 AI ported 243s milled for 11.1 AI custom grind 228/230 600/605 111lsa stock truck intake I've yet to run it on the dyno but I'm hoping for over 400Tq and HP
Sep 20, 2011 | 08:31 AM
#30
