Quote:
Originally Posted by mikels
There really isn't a 'bad' LS 6.0L out there. There are several options and differences though.
LQ4 - Fe block / Al cathedral port heads / 24x crank
LQ9 - Fe block / Al cathedral port heads / 24x crank
LS2 - Al block / Al catherdral port heads / 24x (2005 Corvette / 2006 Trailblazer SS) 58x after
L76 - Al block / Al rectangular port heads / 58x crank
LY6 - Fe block / Al rectangular port heads / 58x crank
The early LQ4 / LQ9 engines were (and still are) very popular for building boosted motors as the iron block withstands considerable power before becoming a liability - and was available long before LSX block and other 6 bolt head blocks were available. Weak point is 4 bolt heads once >~1200 HP as head gaskets lack clamp load to withstand.
Aluminum block options are much more appealling from a mass perspective, but newer and more costly to puchase.
As far as the 24x vs. 58x crank signal - if building the engine, is not an issue and can make whichever you prefer (there are advantages to later 58x software / controllers).
Cathedral vs rectangular port heads - same thing - if you are changing heads, doesn't matter. If not, rectangular heads lack capability to reach airflow limits that rectangular ports can.
Since you mention a '99 - I assume it's either an LQ4 or LQ9. Only differences are the compression ratio (and calibration). LQ4 was 87 oct engine / LQ9 was premium. Both are great engines.
Bottom line - there are no bad choices - just depends on your goals and budget.
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Just to add a couple notes:
the LQ9 6.)l didn't start production until 2002, so any earlier one will be the LQ4
The 99' & 2000 engines came with a iron block AND iron cyl. heads
Another difference in the pre 05" 6.0L is the LQ4 did have lower compression as mentioned before, but also has lighter duty connecting rods w/ press fit wrist pins
Where as the LQ9 came with the higher compression and heavy duty connecting rods w/ floating wrist pins, crank is alittle heavier due to the added rotating mass weight also
I say "pre 05' ", since 2005 - up, the Vortec series engines came equipped with the stronger bottom end with heavy duty crank, connecting rods and floating pistons w/ coated skirts