The day finally arrived when our 467 ci of pure Pontiac would be bolted to the Stuska dyno at RaceKrafters. Its machining and assembly, along with the parts sourced from Summit Racing and Butler Performance, would be on trial—the jury being the Depac data acquisition system, and the verdict read as horsepower and torque.
Since we needed to get a lot done in one day, both Bob and Craig tag-teamed the Mule engin
Our test Mule is a nice mill but it isn’t exotic. It’s a standard bearer of what most readers would build for a street/strip Pontiac: 9.1:1 compression, ported 6X cylinder heads, along with a stroker crankshaft. The most exotic (for lack of a better word) part of the engine is the hydraulic roller camshaft, and even it is being used more regularly in hobbyist buildups.
The Mule’s conservative DNA will be a starting point for our long-term objective of using this engine as a test bed. Thus, we set a realistic goal for power. Though it is not admitted, anyone who goes to a dyno with an unknown combination always has a number in mind. Anything below that and they will be disappointed. If it is higher, they are ecstatic. Our goal was just over 467 real horsepower, or one pony per cubic inch on pump gas.
The word real as a description of horsepower was chosen for a reason. One of the many motivations to work with Bob and Craig Wise was the accuracy of their dyno cell, along with their engine building and machining skills. Accurate and repeatable testing is the essence of this project as it moves forward. A dyno cell or operator that unintentionally introduces a number of variables into the testing would skew the data and, for the most part, make it worthless. If HPP is going to qualify and then quantify parts and modifications, we need an accurate test cell. RaceKrafters has one.
The dyno controls are a combination of mechanical parts, human interaction, and computer f
Since we covered the requirements and function of a dyno test and test cell in the primer that preceded this story, now we’ll discuss the power that our Pontiac produced, along with the tuning decisions.
Before HPP arrived at RaceKrafters, the Mule had been already bolted to the dyno, test run, and partially broken in. You always want to run a fresh engine with a varying amount of load (not full load) to get all of the parts seated. The crankcase was filled with Brad Penn 30W break-in oil.
The Holley mechanical secondary 750-cfm carburetor (PN 80528-2) came with No. 73 jets all around and a 6.5-inch of Hg power valve. An MSD Pro-Billet Ready-To-Run distributor also had an out-of-the-box advance curve setting with two heavy silver springs along with the blue bushing. The mechanical advance was to be all in by 4,000 rpm and the total timing was set by Craig to be 34 degrees BTDC.
Craig adjusts the timing while discussing the tuning with the author. We began testing wit
Our Mule started immediately and ran beautifully with excellent oil pressure and built coolant temperature evenly. Prior to HPP arriving, Craig made some partial pulls and with everything looking good, shut it down, and waited for us to show up the next morning.
When we arrived at the shop, it was exciting to see the Mule attached to the dyno brake and ready to rumble. With it fired and idling around 1,000 rpm (to build heat quicker) we anxiously awaited for the oil and water temperature to rise. Once the water hit 151 degrees F and the oil 128 degrees F, the time of reckoning had come. The fuel cell was already filled with 92-octane gasoline from a local station. The Pontiac was going to have to show us its mettle against the stout Stuska water brake.