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Every component matters when building a high-performance engine like Project Mighty Mouse, a small-block 327 destined for 500 horsepower. While the spotlight often shines on big-ticket items like the pistons, camshaft, and heads, the fasteners that hold it all together are equally critical. That’s why we turned to ARP for our 327’s connecting rod and main bolts.
ARP Main Bolts
The main bolts are extremely crucial in a high-performance engine build. For your average 350 cubic-inch small-block build, finding a replacement crankshaft isn’t the end of the world. After all, they are nearly a dime a dozen. However, the small-journal 327 has a factory-forged steel crankshaft that Chevrolet only produced from 1962-1967, so it doesn’t have its older brother’s nearly 35 years of mass production. Finding a replacement and getting it machined takes more time and a good chunk of change. Plus, this crankshaft is now a “custom” crankshaft, as we had the machine shop drill and tap it for the sake of bolting on a harmonic balancer and removing the untrustworthy, factory press fit.
The ARP main bolts (P/N: 134-5002) are a key component in the Mighty Mouse engine. They are forged from 8740 chromoly steel and are specifically designed and intended for use with small-journal crankshafts, like the one in our 327.
With the forged steel crankshaft being securely held in place with ARP bolts, I don't have to stay awake at night worrying.
ARP’s 8740 steel bolts have a tensile strength of 180,000 psi, making them a vast improvement over the factory main bolts. Their increased strength ensures the main caps remain secured and the crankshaft is properly supported, even under increased loads.
Always make sure your main caps are facing the correct direction (note the arrow pointing toward the front of the engine). Also, mark your bolts after they have been torqued to prevent missing a bolt.
In terms of the structural integrity of this crankshaft and shooting for 500 horsepower, we have dotted as many i’s and crossed as many t’s as possible. The machine shop Sonafluxed for cracks, balanced, and ground the main journals of the crankshaft for proper tolerances.
Sonaflux vs. Magnaflux
The decision between using Sonaflux or Magnaflux for your inspection needs depends on several factors, including the type of material, the kind of defect you’re trying to detect, the shape and complexity of the component, and your budget. Magnaflux is ideal for inspecting ferrous metals, such as engine components like blocks, crankshafts, and camshafts. It excels at detecting surface and near-surface cracks or defects, making it a great choice for catching stress fractures and other issues that may be visible on the surface of parts. Additionally, Magnaflux is well-suited for simpler shapes where applying the magnetic particles is straightforward. One of the biggest advantages of Magnaflux is its cost-effectiveness; the testing equipment is typically more accessible and affordable, making it a great option for basic engine inspections.
On the other hand, Sonaflux offers more versatility due to its use of ultrasonic waves. This allows it to be used on a wider range of materials, including both ferrous and non-ferrous metals. Sonaflux is particularly useful for detecting internal defects because the ultrasonic waves can penetrate deep within the material, making it the preferred choice for identifying subsurface issues in thicker or more complex engine parts. Its ability to work on more intricate shapes without requiring particles to adhere to the surface is another advantage. While the equipment for Sonaflux may be more costly due to the advanced technology involved, it provides a more comprehensive and detailed analysis than Magnaflux. If you’re primarily inspecting ferrous engine parts for surface cracks and are on a budget, Magnaflux is often the sufficient and cost-effective choice. However, for detecting deeper, internal defects, or for inspecting non-ferrous materials, Sonaflux provides a broader and more detailed analysis, making it worth the investment.
ARP Connecting Rod Bolts
For our connecting rod bolts, we went with ARP’s factory-replacement option (P/N: 134-6001), designed to provide exceptional strength and reliability to the connecting rod’s big end. These bolts are made from ARP’s proprietary 8740 chromoly steel alloy, which offers superior strength compared to the factory rod bolt material. The ARP bolts are designed for use with factory-style connecting rods on small-block Chevy engines like our 327.
After installing the crankshaft, installing the pistons is the next step to get the connecting rod bolts torqued.
As the 327 is becoming more “outdated” by the day, replacement parts aren’t hitting the shelves as fast as they used to. We are using the factory-forged steel connecting rod connecting rods. They are original to this 327, with a length of 5.700 -inches that have been Sonafluxed and reconditioned, as well as upgraded with the aforementioned ARP rod bolts.
As for pistons we are using Icon Forged Pistons. We ordered one of their complete kits (P/N: IC793KTD.060), which includes pistons, rings, and wrist pins. The forged-steel connecting rods will be strong enough to handle our horsepower goals, and the forged aluminum pistons will happily handle the 7,000 rpm engine speed. The forged-steel connecting rods and forged-aluminum pistons make for a perfect combination that is strong and lightweight.
For Project Mighty Mouse, the upgraded ARP bolts provide the confidence to push our engine to its 500 horsepower goal. With a tensile strength of 200,000 psi, these bolts offer a substantial safety margin over the OEM fasteners. Their superior fatigue life ensures they’ll withstand the rigors of high-RPM operation. We know that we are staying naturally aspirated, for now, but we still wanted the option to change our minds down the road. We made sure that they could also handle the increased cylinder pressure that comes with forced induction or nitrous.
A secure short block has never looked so good.
Fastener Lubricant And Torque Specs
Torque specs are one of the most important aspects of assembling an engine and removing inconsistencies from the equation is a must. The ARP Ultra-Torque Fastener Lubricant is included in every ARP kit and is recommended to be used exclusively on ARP fasteners. Engine oil, as well as lubricants designed for other purposes, can lead to higher friction on bolts and inconsistent torque readings compared to a lubricant designed specifically for engine fasteners. As explained on ARP’s website, increased friction can initially prevent fasteners from reaching their optimal preload. The correct lubricant guarantees consistent and reliable preload performance across all fasteners. ARP not only includes their fastener lubricant in every kit, but they also include the torque specs. If your kit requires incremental torquing, they include reminders for that as well. ARP takes things a step further by including the instructions for each kit on their website, so don’t worry if you lose the paper copy.
Reliability and Performance
By upgrading to ARP bolts, we’ve eliminated a potential weak link in the engine. The OEM bolts are adequate for a stock engine, but leave little margin for error when the power output is increased. The ARP bolts, with their superior materials and design, offer a substantial safety margin that allows us to focus on tuning the engine for maximum performance. Be sure to keep an eye out for our next step, where we cap off the top of our engine with free-flowing heads and intake.
