Plum Crazy LQ4 6.0L


After the disappointment with the 4.8L in the first LS swap project for the website.  The 4L60E has been worked over to hold pretty much whatever I want to throw into this truck.  I had put a good 50k miles on that 4.8L though and ran well but the low end torque is just pitiful in those things.  Also, the project nitemare truck certainly lived up to its name and I managed to kill the LQ4 in that truck so its now sporting a 408ci stroked LQ4 and I took the old LQ4 and worked over for this truck.  Since I don’t have an unlimited budget, I decided to work this truck over in stages.   I rebuilt the LQ4 and required boring the cylinders .020 over to get them nice.  I had replaced the heads on project nitemare with 225cc procomp heads which lead to the death of that supercharged motor so I can’t really recommend these heads but again not wanting to spend even more money but want more power than the 4.8L offered.   I purchased a Howards 190295-12 camshaft which is very similar to LS1 hot cam but MORE lift.  This is a 218/224 duration  with .604/.604 lift and 112 LSA.  Those procomp heads, I had upgraded the valve springs to some quality Lunati springs for the supercharged truck so I knew they were good for the lift.

The rest of the engine is pretty much all the components right off the 4.8L engine.  i was a little concerned that the injectors wouldn’t flow enough fuel to support the motor but right now its fine.   So how did it do.  Torque and low rpms power is DRASTIC improvement over the 4.8L  The final numbers were a little disappointing though.   If you click on the dyno pictures you can view them larger.  308rwhp and 317rwtq. which is actually LESS than the project nitemare truck pulled with this 6.0L with stock 317 heads and LS1 hot cam.  I know I am not running long tube headers and true dual exhaust but the 4.8L intake is the SAME as the 6.0L.  I was stunned that the 225cc heads which honestly have a good looking CNC intake runner didn’t do enough better to compensate for a little exhaust differences.





So perhaps we will get to explore how to fix this problem with lower than expected dyno numbers.  Since I have dyno numbers for a stock LS3 Camaro 6spd car on the website done on the same dyno  that was my goal for this truck. 366tq and 372rwhp.  so we are not even close right now.  Both peaked just shy of 6000 rpms though.

comparing the 2 engines.  My 6.0L being .020 over bore is now 368ci rather than 364 stock bore and a 6.2L is 376ci so not a significant difference there.   the procomp heads are 64cc and I just used stock Lq4 dish pistons and stock .052 head gasket thickness which calculates out to 10.3:1 compression ratio which is closer to the 400hp L99 Camaro engine than the 10.7 of the LS3 so that will affect that number some.   Procomp lists the head flow of these 2nd generation 225cc heads in chart below.

2.02″ / 1.55″ 8mm Stem Valve Sizes
64cc Combustion Chamber
225cc Intake Runners


.100      67.9       54.0
.200     139.0     113.0
.300     201.1     157.6
.400     255.7     183.2
.500     286.1     197.6
.600     291.5     203.3
.650     293.3     206.6

versus LS3 heads

Stock LS3 Heads
Lift 0.100 0.200 0.300 0.400 0.500 0.600
Intake 66 151 208 256 294 316
Exhaust 59 111 152 174 183 189

I really don’t think there is a enough difference in the heads to make a significant difference, that is why I chose them on the project.

For now i am just going to enjoy the truck for a while and save some money up and then I will start with the exhaust and hit the dyno again.

GM fuel injection for the average guy