LQ4 799 heads or cometic gasket 317s to raise compression
03-13-2016, 02:20 PM
#1
LQ4 799 heads or cometic gasket 317s to raise compression Building a 6.0 for my Suburban that I regularly tow around 6000 lbs with. Fuel will mostly be 87 octane i'm sure. 9.4:1 like the factory LQ4 seems pretty weak even with 87 octane. Will be running a 160 degree thermostat. I'm thinking 10:1 is good? So get 799 heads or run thinner gaskets with the 317s? I will be putting a cam in as well since its out...something good for towing but still pick up some power in passing gears. I do have an 02+ LS6 cam sitting in the garage but thinking something a bit larger. Thoughts?
03-13-2016, 03:29 PM
#4
You should not be towing with any cam that would potentially have PTV clearance issues. You did not mention what gears or transmission you have. I owned a suburban with an L29 (efi 7400) and 4L80 with 4.10's. That first gear is surprisingly steep when pulling a load. 4L60 is a little better, but that drop between 1st and 2nd can be a bear.
Compromising torque anywhere on the low end for a vehicle that "regularly tows 6000 lbs" is a bad idea. There are truck cams out there that will work with the stock stall, provide more than enough PTV clearance, and gain power everywhere. Stay in the 208 to 214 range of intake duration at 0.050" lift to maximize torque. Use the 799 heads and cometic gaskets and you'll have a great towing package.
Lastly, I would be careful with the 160 T-stat. You may find that heat soak is an issue, and the coolant doesn't spend adequate time in the radiator to cool. Add to that, modern engines and cooling systems are designed to run at 195* for emissions and longevity. Run it too cool and the oil temps never reach a point to boil off contaminants.
Good luck with your build!
Compromising torque anywhere on the low end for a vehicle that "regularly tows 6000 lbs" is a bad idea. There are truck cams out there that will work with the stock stall, provide more than enough PTV clearance, and gain power everywhere. Stay in the 208 to 214 range of intake duration at 0.050" lift to maximize torque. Use the 799 heads and cometic gaskets and you'll have a great towing package.
Lastly, I would be careful with the 160 T-stat. You may find that heat soak is an issue, and the coolant doesn't spend adequate time in the radiator to cool. Add to that, modern engines and cooling systems are designed to run at 195* for emissions and longevity. Run it too cool and the oil temps never reach a point to boil off contaminants.
Good luck with your build!
03-13-2016, 03:48 PM
#5
3.73 right now. 4L60E. May install 4.10s soon. 285/75/16 tires. Only time I ever drive it is towing a 20' enclosed cqr trailer with our Camaro or when I have 5+ people with me. The emissions I don't worry about around here. However, oil containment burn-off is always a concern. But when I do drive it its always 10+ miles.
