Break the engine in & tune the Holley fuel injection

Mighty Mouse chevy 383 stroker engine build

Mighty Mouse, Part 4 of 5

“I jammed the gas, which promptly pinned my melon to the headrest and the FJ lurched forward with angry vengeance.”

We are almost to the close of our five-part do-it-yourself series on building a 400+ horsepower rock-crawler engine. So far, we’ve shown you our build plans, engine preparation and machining (Part 1), how to build the long block / lower end (Part 2), and how to assemble the top end of the engine (Part 3).


With our engine now fully assembled, it was time to break the engine in, tune the Holley fuel injection software and see what this bad boy would produce. Before we get started, here are some highlights of the engine we built:

Mighty Mouse chevy 383 stroker engine build Engine Highlights: 

  • GM Performance Parts 383 Stroker Block, 1-piece rear main seal, 4-bolt main – part # 88962516
  • GM Performance Parts Serpentine Accessory Drive System w/out A/C – part # 12497697
  • Lunati fully balanced rotating assembly
  • Lunati “SledghammerSledgehammer” Forged steel stroker crank
  • Lunati “Voodoo” cam, roller rockers, push rods, double-roller timing chain and lifter set
  • Holley Stealth Ram multi-port fuel injection system – Part #: 91603211
  • Holley aluminum 2.02 heads – Part #: 300-552-1
  • Holley billet aluminum high-performance distributor
  • Pro-Tru aluminum flat-top pistons
  • High Performance engine bearings
  • MSD Ignition 8.5 mm super-conductor plug wires

 We happened to have access to an engine dyno at ATK Performance Engines and we made good use of it. A quick trip to this Holley-certified engine builder allowed us to put our engine on an engine dyno, program our Holley commander software and break in the engine. After a few days of tuning, programming and some engine adjustments, our engine took its first deep breath of air and turned over producing a beautiful, deep rumbling tone. This was an exciting moment Mighty Mouse chevy 383 stroker engine buildindeed. The engine ran for its predetermined break-in time and then we were able to crack the throttle and see what this bad-boy could produce.

As the technician rolled the throttle lever forward, our built small block changed its tune from a deep rumble to a loud, screaming roar, turning the heads of several engine builders and drawing the attention of a few other employees. The technician ran our GMPP stroker motor that was adorned with a Lunati rotating assembly and Holley fuel injection through its paces like he just stole it. Admittedly I was a bit nervous as he took the engine to a screaming 6,000 RPMs. After a few runs on the dyno, the technician rolled the engine down to idle and printed out my HP/Torque sheet.

He handed the printout to me with a quirky smile and softly said “Check out THOSE numbers.” Like a proud new father, I quickly looked at the power chart and smiled back. I think I felt a tear welling up in my left eye, or it could have been a sty. Either way, this little engine just reliably produced 433 horsepower at 5200 RPM and 467 lb/ft of axle-twisting torque at 4600 RPM. Most importantly, it produces 405 of that 467 lb/ft of torque at 3,000 RPM – perfect for a 4-wheel drive. Convergence happens at about 5200 RPM.


Engine Installation

Mighty Mouse chevy 383 stroker engine build For those of you that don’t have access to an engine dyno, you will now have a completely built engine now sitting at the ready on your trusty engine stand, it is now time to borrow, rent, buy or steal an engine hoist and get busy stuffing it into your vehicle. Before you can bolt it right up though, there are a few more things that you will have to do.

First, make sure that your engine has been recently oil-primed and that it is freshly lubricated on the top-end. If your engine has set for more than a few days, it is highly advisable that you re-prime the engine. It’s a bit of a pain, but it will NOT be wasted effort.

If you haven’t already done so, you will need to install your main seals and oil pan. You will need to install your flexplate (you can’t do this on an engine stand). If you have a small block Chevy, it is internally balanced (all of them are, unless you built one that is specifically NOT internally balanced) and you will need a flexplate designed for this. Bolt and torque your flexplate to the rear snub of the crank shaft.

Mighty Mouse chevy 383 stroker engine build Mighty Mouse chevy 383 stroker engine build Installation of your new engine into your truck or SUV will differ from vehicle to vehicle, so suffice to say, make sure that your engine bay is prepared to receive its new engine. Some people may choose to mate the transmission to the engine first, and install it all at once. I prefer to leave the transmission in the cradle, under the vehicle and install the engine by itself, especially when you’re dealing with the large front axle of a four-wheel drive.
Mighty Mouse chevy 383 stroker engine buildGlide the engine into the engine bay and nestle it carefully into the motor mounts and transmission. Bolt the engine into place where appropriate (e.g. transmission bolts, motor mounts, etc.).

Lastly, start hooking up fuel lines, heater hoses, electrical, starter and so on. Each engine / vehicle combination will be different so we won’t go through the details here.


First Firing / First Drive

Chevy 383 stroker buildFor our application, we needed to flash the Holley CPU and load a “base map” onto it for our specific engine, in order to give the fuel injection and electronic timing control system something to work with. Once this was accomplished, we could now start the engine for the first time.
Mighty Mouse chevy 383 stroker engine buildOK, so it’s now the moment of truth. Before you turn that key, there are a few things to think about;

  1. Double check all of your fuel and electrical connections.
  2. Have a fire extinguisher or two nearby. I prefer to have one in the driver’s seat and one next to the engine. Having a small burst of flame come through the top of the engine isn’t uncommon if your engine’s timing is off or a few spark plug wires crossed.
  3. Have a friend nearby to time the engine while you keep it running.
  4. Your engine will likely run like crap until you can get a base tuning set on the engine. It will take one person to feather the throttle and another to set the timing.
  5. Once you start your engine, you shouldn’t shut it off unless you have a fire, mechanical problems, severe overheating, or its running so horribly that you risk ruining your engine. The first start is always the hardest on the engine and you should run your engine for 20 minutes after you get it running if all possible
Knowing this, it’s time to turn that key. If all was assembled correctly, you will only have to do some tuning to keep the engine running. Fire that bad boy up, tune it, and enjoy the sound of the horsepower that your new engine is creating!
Mighty Mouse chevy 383 stroker engine buildSince our engine had already been broken in and tuned, it was time for us to take it for a test drive. A turn of the key produced that same engine growl that we were looking for. Cautiously I shifted into reverse, then felt and heard a short bark of the tires – nice! I eased the FJ down the driveway and into the street and headed for an area where we could pin the go-go pedal to the floorboard. Shifting into first gear, I jammed the gas, which promptly pinned my melon to the headrest and the FJ lurched forward with angry vengeance. 433 horsepower flowed through the engine and drivetrain quickly and pushed my body back into the seat nicely. This engine runs like a champ.



Chassis Dyno

 We also had access to a chassis dyno, so we trailered our rig to the Horsepower House in Bowling Green, Kentucky (right down the street from Holley’s headquarters) to see what power it was making at the rear wheels. If you’re ever in need of quality engine building, give the guys at the Horsepower House a call – they do fantastic work.
We strapped our FJ onto the chassis dyno and gave it several runs, pinning the throttle to the floor. Our tests indicated a very respectable and head-snapping 311 horsepower and 336 lb/ft of torque at the rear wheels. Remember, there’s a lot of parasitic loss with the drivetrain.



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