Project Ultimate TOWBEAST

I am not a big fan of diesels, especially their repair bills so I am going to make modest diesel like power using a LQ4 6.0L gas motor.  I chose the Yukon denali because 1. it rides great. 2. came wired for electric trailer brakes and 3. has on board compressor with air shocks to level the thing up once i put the trailer on it. 4. I really like the LQ4 motor for boosted applications.  LQ4 is only 9.4:1 compression ratio which is really too low for aluminum heads although still makes decent power and shocking how much torque it made after programming on it.   Stock these are rated 320hp and 370-380tq.  Made with the 75% drivetrain efficiency for AWD made 320hp and 380 tq stock with that correct factor.  With electric radiator fans it made 333hp and 393 tq so that mod was worth every penny.  I used the factory twin fan setup from a 2005 5.3L truck which dropped right in and yukon even had the bolt holes for it.  i just added the trigger wires to the PCM to control the fans.  I have the PCM wiring diagrams on my website that lists the 2 pins needed to add to the computer to trigger the relay.  I used the GM AC Delco relays D1786C GM part number 19116057.  I initially tried the universal relays but they would fail after a few months.  These seem to work much better and I have them stuffed under that underhood relay fuse box and I have my main power there as well.  Those ECM pins connect to pin 86 on the relay.  Pin 85 and 30 I connect together and I use a 40 amp breaker hooked to main power.  I find these fans use a lot of power when they run but yukon never gets overheated.  then 87 powers the fan.  I use separate relays for each fan and separate breakers that way one can fail and your still ok.  With the old relays, I would notice that the motor got about 20 degrees warmer while at a traffic light or something and I knew I had a relay out.

Now with programming here is dyno graph.

I was really stoked to see it pull that much torque.  that isnt much less torque then my 1991 454SS project towbeast made on my website.  For a 364ci motor that is still stock exhaust and everything that is a strong number.  I actually thought the programming would have yielded a little more horsepower but in a tow vehicle trade horsepower for torque any day.  Plus the dyno pull was made on 87 octane fuel.   These engines arent exactly great on gas mileage so to give them an advantage on the diesel I want to stay on 87 octane if at all possible.  Since most areas diesel is 15% more expensive than 87 octane, my Denali gets 14 in town and 18 on the hwy and 9-11 depending on how much weight I pull.  15% increase means the diesel has to achieve 16 and 20.7 and 10.3 to 12.6 towing which most modern diesels can achieve but just barely.  We wont factor in cost of diesel maintenance versus maintenance on this LQ4 as that gets complicated.

another comparison a 24v Cummins 5.9L diesel makes 235-325hp depending on year and configuration and 460-550tq.  Stock 6.0L powerstroke 325hp and 560tq.  sure you can chip these things but reliability really starts to suffer but we are also only getting started on this project.


I am not going to dyno between each of my upgrades as my health issues, I can barely pull off this project at all so i am going to do all at once and post final dyno result.

However my first recommended upgrade is that camshaft. The cam used in these motors is just terrible.  I am going with a BTR stage 2 truck cam with 213/218 duration @ .050″ with .551/.551″ lift on a 113 LSA with stock LS3 valve springs GM part number 12499224.  this should be good for 50hp and 20tq as the torque is going to be harder to improve upon.

next if you search ebay for CNC 317 heads you will find some nice Thompson motor sports CNC ported 6.0L heads and you can get them with those blue LS3 valve springs which are just fine for the cam I listed.  If I were going more for horsepower then I would choose the PAC valve springs with a BTR stage 4 truck cam but this is project towbeast.  I am also going to run a set of  hardened 7.400″ pushrods while they arent technically required, I feel better about doing that with mine and for around $100, not expensive piece of mind.   but heads will gain you another 50hp and 20tq.  also on that piece of mind kick, I am installing some head studs to better bolt those heads down for this next upgrade.

Now for the ULTIMATE part, the third upgrade to this setup is going to involve installing a single turbo kit from  as I get closer to ordering the kit as I am not made of money either, I will update the page with what kit I intend to use.     With the camshaft upgrade its going to help make this engine a little less octane sensitive as I am going to tune this setup to still run on 87 octane fuel.  I could make the same final horsepower with the stock heads and more boost but then I would have to run 91 octane fuel all the time so I am going to run the cnc ported heads and only 8psi of intercooled boost.  That low level of boost wont shorten the life of this engine and easily give me a 50-55% power gain.  So this motor with heads and cam upgrade should make around 450hp and 500tq should make around 675hp and 700tq with 8psi of boost.  Also, I am going to run some 60lb/hr injectors and I am using a quantum 340lph fuel pump upgraded sending unit from

GM fuel injection for the average guy