5.5L LQ4 or LQ9?
Thread Starter
TECH Enthusiast
Joined: Sep 2010
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From: North Central Ohio
5.5L LQ4 or LQ9? I see alot of press about 5.3L to 383 strokers & LQ4/LQ9 bored to 370 CID.
What about a LQ4/9 block bored to 4.03 with forged rods & low compression(8.7-9.2:1CR) pistons & a 4.8L(3.26 inch stroke crank) with ported LS3 heads.
A 2.8L or 3.6L KB twin screw blower to boost TQ & HP at a sane RPM range.
What do you folks think?
What about a LQ4/9 block bored to 4.03 with forged rods & low compression(8.7-9.2:1CR) pistons & a 4.8L(3.26 inch stroke crank) with ported LS3 heads.
A 2.8L or 3.6L KB twin screw blower to boost TQ & HP at a sane RPM range.
What do you folks think?
TECH Resident
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From: In the moment...
Im pretty sure his post says LQ4/LQ9 block. Reading is fundamental bro. You would be able to spin that thing to the moon destroked. With forged rods, good rod bolts, and some high flowing ported LS3s, I dont see why 9000 rpm would be a problem. The TQ hit would be lower. I would rather turbo an application like that if it was going to see some rpm. A billet wheel 76mm turbo would FLY.
the 4.8 cant have ls3 beads they require a minimum 4" bore.
If you're using the block only and building it with aftermarket rotating assembly, then it doesn't really matter which of the LQ4 or LQ9 blocks you use. They are basically the same, except the 4 came with dished pistons vs. flat-tops in the 9. There are a few other differences between the gen3 vs. gen4 blocks, but it is very minimal and it's not like gen3 blocks are outdated and useless.
I dont see why 9000 rpm would be a problem.
Why give up all those CI capacity? What's the reason. The shorter stroke will allow for slightly higher piston speed, but not anything to re invent the wheel, it takes a lot more than just a shorter stroke to build and maintain very high RPM. At least for it to hold together.
Teching In
Joined: Dec 2008
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From: Anaheim, CA
Why give up all those CI capacity? What's the reason. The shorter stroke will allow for slightly higher piston speed, but not anything to re invent the wheel, it takes a lot more than just a shorter stroke to build and maintain very high RPM. At least for it to hold together.
Thread Starter
TECH Enthusiast
Joined: Sep 2010
Posts: 580
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From: North Central Ohio
Why give up all those CI capacity? What's the reason. The shorter stroke will allow for slightly higher piston speed, but not anything to re invent the wheel, it takes a lot more than just a shorter stroke to build and maintain very high RPM. At least for it to hold together.
Last edited by N2OBaby; Jan 11, 2012 at 02:17 PM. Reason: If I could spell
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TECH Apprentice
Joined: May 2009
Posts: 323
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From: NW AR
The original poster should just use what he can get cheap, stock LQ4 cranks are just fine. A different piston/rod combination or head selection would be able to get the compression low enough to safely make a shitload of power. Doing something unusual is cool too though.
I've thought about this as well. Would like to see some input from the gurus. Maybe I'll actually do it.
EDIT: I was thinking about a rev-happy high compression N/A motor, not boost
EDIT: I was thinking about a rev-happy high compression N/A motor, not boost
Destroking for RPM in this application is silly. You can turn a 4.00" crank 9000rpm. You are just giving up both avg and peak power by destroking. The piston speed of a 4.00" stroke is manageable and has been done for years. All the top all motor LSX shootout cars have 4.00" cranks (Although they are all probably CCW billet pieces). Like was already stated the most critical thing that demands attention is the valvetrain.
Big bore AND big stroke, have your cake and eat it too!
Big bore AND big stroke, have your cake and eat it too!
Last edited by JS01; Mar 8, 2012 at 11:36 AM.
