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LQ4 & LQ9, What is the differences between the two

Old 01-24-2011, 11:01 AM
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although my engines of choice are the old school BBC. I recently fell into a 2007 6.0(U)LQ4 out of a 3500 express. Spun 2 rod bearings but still running. All 85000 miles of interstate driving. Anyhow, when i pulled the first two rods they were floating bushed/rods. Pistons had a wearable coating on skirts and the tops were very small dish with two valve reliefs diagonal from each other, one at about the 2:00 o'clock position and the other at about the 8:00 o'clock position. Just thought this might help some people out a little.
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Old 08-13-2011, 05:11 PM
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and people wonder why the search feature's dont get used. this is a prime example of why. now if didnt know any better already in which i do thank god. i could have been totaly screw'd from reading this. who ever reads this. your not going to get a good answer by posting a thread on here ask for the info. becouse to many people think they know what going on and don't every person in this thread had good and bad facts. there intent was good but wrong.

next time someone post up something that looks like a repeated question think back to this thread before you rip there head off.
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Old 12-02-2015, 07:49 AM
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Originally Posted by Tuffguy610 View Post
If I am not mistaken an LQ4 is a 5.3 engine. The LQ9 is the 6.0. I am sure somebody else can elaborate.
The LQ4 is a 6L along with the LQ9. The LQ9 is a slightly larger displacement and has a stronger powerband. Also the lq4 has dished pistons as where the lq9 has flat top pistons. So yes, you are mistaken.
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Old 12-02-2015, 09:01 AM
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Originally Posted by Taft Green View Post
So yes, you are mistaken.
And you felt the need to point that out 7 years later?
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Old 02-08-2016, 05:16 PM
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Originally Posted by 12secSS View Post
Wow, a lot of misinformed responses. A quick search would have netted you the correct answer, but to clear the air with facts:

LQ4 and LQ9 are Gen3 engines, not Gen4 (like the LS2, LS3, L76), due to the location of the cam sensor and knock sensors.

LQ4 debuted in 1999
Displacement was/is 6.0L
1999-2000 had iron heads
1999-2000 had a crank adapter to mate the LQ4 with the 4L80 trans (not LS1 compatible)
Compression ratio was 9.5:1
Bloack was Iron

In 2001 the LQ9 was introduced
Both the LQ4 and LQ9 shared the iron block and new 317 heads (similar as the 243, but with larger 76cc chambers), hence both are 6.0L
The LQ9 had 10.4:1 compression ratio, versus the LQ4's 9.5:1
No longer did either 6.0L require the crank adapter for the trans, now works with LSx applications.
In 2004/5 6.0L recieved improved rod design

In 2005 the LS2 block was introduced
It is essentially the LQ9 with an aluminum block
LQ9 still offer with an iron block.

There is no difference between the two except the pistons. the lq4 has dished pistons, creating lower compression than the lq9, which has flat top pistons, creating more compression.
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Old 02-08-2016, 06:05 PM
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ALL LQ9's have floating rods, so the LQ9 and LQ4 are a little different in that sense.

FWIW, my 02 LQ9 has the floaters. My 04 LQ4 had the pressed rods.
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Old 01-18-2017, 01:12 AM
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Originally Posted by 12secSS View Post
That is because you were lucky and had a later 2001 and newer LQ4. Although not a good image, it does show the 1999-2000 LQ4 flat flexplate used with the longer crank (adapter) to mate up to the early 4L80 transmissions. The newer 2001+ 6.0Ls used the LS1 flexplate, which is not flat and curves outwards to the trans, to have the torque converter align properly with the trans pump splines.

You are welcome, and any 1998-2002 Camaro/Firebird V8 trans will work with your 2007 LQ4. The only issue you will have with an LS2 is the cam sensor is in the back-top of the LQ4, where as the LS2 has it on the front timing cover. Also the knock sensors are on the valley cover between the lifters, where as the LS2 has them on each bank, just above the oil pan rail (like TPI, LT1 motors). Otherwise everything bolts up.

So if I have a '99 LQ4 I will have issues mounting up an LS style T56 6spd transmission? I'm going to do a bunch of searching but this is the first time I'm hearing of this. Sorry for bringing a thread from the dead lol but this is important because I'm getting close to tearing this motor out of my 99 Chevy 2500K...
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Old 10-26-2018, 12:28 PM
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Old thread but new question. Which versions of the iron blocks have both bosses for the f body alternator? I have a 5.3L and it has the top right alternator boss (needs to be drilled and tapped) and it has the bottom hole, but it doesn't have the boss/ear for the middle bolt that goes through the fbody bracket to right next to the timing chain cover. Looking at pictures online I seen that some iron blocks have that additional boss while others don't. Does anybody know which ones have it?
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