There is certainly a time and place for pulling an iron-block 5.3 out of a pickup truck or a work van and throwing it into your beater along with a low-buck turbo of unknown origin you found on eBay. The bottom-dollar ethos is a cornerstone of hot rodding, and that should never go away.
But sometimes you want to push a few boundaries.
Drag racing is all about exploring the boundaries when it comes to how far you can push engine parts to maximize speed, even if that means occasionally blowing up. But you can’t win championships if you are scattering your connecting rods across the track too often. So, if you are into the science of building rockets that consistently cross the finish line ahead of your opponent, quality and precision become pretty dang important.
Since retiring as a full-time Pro Stock driver, drag racer Jason Line has been building JLine Performance, manufacturing high-performance blocks and cylinder heads. This is one of JLine’s newest aluminum Chevy big-blocks, a no-holds-barred race block optimized for performance, featuring O-rings, super-high-quality sleeves, and, most of all, head bolt holes perpendicular to the deck of the block to work with Wilkins’ 484 Max cylinder heads.
If you are into bracket racing, especially on the East Coast, then you’ve probably heard of Sandy Wilkins and Wilkins Racing Engines. He specializes in big-inch nitrous engines and is especially strong in Top Sportsman, Top Dragster, and other bracket classes. Wilkins makes no bones about the fact that he builds a premium product, and he told us straight up that his entire business is targeted for racers looking to win championships.
So, no corners are cut. Ever. Wilkins, who has built everything from NASCAR Cup, to top-level off-road, to drift engines, has such a strong dedication to perfect engine assembly he regularly fabricates his own checking tools. His attention to detail is off the charts.
We understand that most of our readers assembling engines in their home shops won’t go to this level of detail, but we thought you might be interested in seeing just some of what Wilkins Racing Engines does as a part of building one of their bracket racing big-blocks. Every engine is built with the intention that it can win track championships, which means it has to reliably run a full season of practice laps, qualifying, and racing all the way to the final rounds without a rebuild.
Because, as Wilkins says, “Doing it right the first time might be expensive, but it’s still a heck of a lot cheaper than multiple rebuilds.”
Zack Thomas gently lowers the Callies Magnum series crankshaft into the bearing saddles. The crank has 4.875 inches of stroke, and the main bearings Wilkins is using are from Mahle with a Calico coating.
We joined Wilkins for a 648ci big-block build that will race in bracket classes with a quick 4.50-second eighth-mile index. This build uses one of JLine Performance’s new aluminum blocks and a set of Brodix head castings CNC-ported with Wilkins Racing Engines’ own 484 Max head design. There’s also a simple nitrous setup that Wilkins says is mostly there to help tune the engine to hit the index when the track conditions or weather changes.
On the dyno, this proved to be a high-revving combo, thanks to the free-breathing 484 Max cylinder heads. It put up peaks of 1,022 lb-ft of torque at 6,600 rpm and 1,394 hp when Wilkins pulled back on the handle at 7,700 rpm—and that’s with no nitrous and burning VP Q16 race fuel thanks to the 16:1 compression ratio.
Since this is a competition engine, Wilkins wants to keep a few of the specifics, like the cam specs, to himself. He’s invested quite a bit into R&D, so we’ll respect his wishes, but there’s still plenty to learn. Follow along and check out this unique build and the incredible amount of detail that goes into making sure it can punch consistent timeslips lap after lap.
To improve sealing so that the dry-sump oil pump (and the vacuum pump) can produce more vacuum in the crankcase, Wilkins uses a unique rear main seal. The two-piece seal is held in place around the rear main journal by a band, and then the entire assembly is clamped between the block and the main cap.
Undercut main studs are more difficult to manufacture, but they even out the clamping load from cap to cap, and in this case the main caps have been cut and sit lower to the block, and the nuts cannot jam against the root of the threads and give a false torque reading.
We can tell you the camshaft is a 60mm solid roller that Comp Cams has helped develop with Wilkins specifically for this type of engine. Because this is a race engine, Wilkins prefers to keep the cam specs to himself, but he did say that the total valve lift is less than the height of the Statue of Liberty but taller than a bullfrog’s butt.
A Jesel belt drive setup will link the cam to the crankshaft. Wilkins knows exactly how much camshaft endplay he wants and uses a dial indicator to determine how many shims he needs before installing the rest of the belt-drive assembly.
The distance between the crankshaft and camshaft centerlines can increase significantly as an aluminum block reaches race temperature. So, it is critical to get the right belt length. If the block expands and the belt gets too tight, you can kill bearings. Wilkins uses a special tool that uses sound waves to measure belt tightness. By flicking the belt, the pickup measures the oscillations and gives a very accurate reading. No guessing what each engine needs.
Wilkins’ cam timing setup is one of the most advanced we’ve ever seen. He’s fabricated a mounting plate that positions the dial indicators over the intake and exhaust lifters, directly in line with the lifter angle, and modified a pair of lifters with flat tops so he knows his readings are exactly the same every time. He also uses a solid pointer that bolts to the block, eliminating the potential for movement from a wire, as most engine builders use. That giant degree wheel provides much greater resolution when you are trying to be accurate within a 1/2 degree or less than a cheap 12-inch-diameter wheel.
A dial indicator is great for checking piston-to-valve clearance, but Wilkins is looking for more information than just that one measurement. So, he goes old-school and uses clay to check both piston-to-valve clearance and the radial clearance around the valve pockets because he’s looking to dial in just the right amounts. Too little clearance and you risk bending a valve, but too much is just giving away compression and horsepower.
The connecting rods we are using are Callies Ultra Enforcer steel I-beams that have a twisted cap for extra cam clearance in a stroker build like this. The pistons are from Diamond and have a diameter of 4.600. This is a slipper-skirt design with inboard wristpin bosses to help cut weight in both the piston and the steel wristpins.
When checking rod bolt stretch, most builders zero their stretch gauge against the rod bolt, then measure the stretch after it has been installed in the rod. Wilkins prefers to zero against a standard and measure the rod bolt length both before and after installation. He does all 16 bolts this way. It is more work, but this method allows him to recheck bolt stretch during rebuilds to see if the bolts have stretched during operation.
With the short block complete, attention turns to the dry-sump oil pan. This is a two-piece pan that’s nice and wide to both reduce windage and to allow the drag race team to quickly and easily change out a burned piston at the track. There’s no oil pan gasket used here. Wilkins says since this section won’t be removed, a simple bead of silicone is more reliable.
The bottom section of the pan seals with an O-ring to make removal and reinstallation as simple as possible.
Each pickup features screens to ensure no trash can make its way through the oil pump. Also note that every fitting on the oil pan as well as the block is an ORB fitting with an O-ring to provide the seal. Pipe threads like those on most AN fittings taper, so if they are over-tightened, they can crack the block, leading to leaks.
Wilkins has his own multilayer steel head gaskets made to his specs by Cometic. One change versus typical off-the-shelf head gaskets is that the holes that allow coolant to pass from the water jackets in the block to the cylinder heads are sized to meter the correct amount of flow specifically for this engine.
Each valve is checked and marked for valve drop. The valves in these 484 Max cylinder heads (named for the 4.840-inch bore spacing) are titanium. The intakes are sized at 2.550 inches, while the exhausts are 1.810 inches. You can also see that the combustion chambers have been softened by tapering the quench area to a very mild extent, creating wider, milder combustion chambers. In high-performance nitrous engines, this is important to reduce the chances of detonation.
Up top, the springs are from PSI Springs and held in place by custom titanium retainers by Wilkins Racing Engines. The valve stems are maybe bigger than you might think for high-end racing at 5/16 inch for the intakes and 11/32 for the exhausts, but the thicker stems are necessary to keep from bending with the large valve diameters and also help move head from the valve through the guide and into the water jacket into the cylinder heads. Also, notice the hole in the head in the upper right-hand corner that extends into the intake port. That’s necessary to access one of the head studs.
Here is an angle looking through the intake port. With these heads, the ports are given priority over everything else. So, when some of the intake ports want to be in the same spot as the head studs, you make it work. Since almost all the air and fuel flows over the top half of the port, a slight disruption in the floor of the port doesn’t hurt anything.
O-ringed plugs are fabricated to fit the holes and perfectly match the port profile, then welded to the underside of the rocker arm stands.
The rocker stands complete with port plugs drop right into place.
Here’s a look at the roof of the port with the plug in place. The hole to the left will be filled by the rocker stand bolt.
The intake ports also affect the pushrod routing. The steel Jesel rocker arms use a variety of offsets and angles to straighten the pushrods as much as possible and clean up the valvetrain geometry.
A very tall billet intake manifold from MBE can route an absolute ton of air and fuel to the cylinder heads. There is no water crossover. Instead, hoses route coolant from both the front and back of the heads to a water manifold at the front. You can also see the nitrous system that has been set up.
A quick look down the throat of the intake manifold shows an impressively straight flow path from the carburetor right into the combustion chambers.
The dominator-sized four-barrel carb from Get’M Performance is rated for 1,700 cfm.
The dry-sump oiling system will pull vacuum in the crankcase, but in drag racing more is always better, so Wilkins also plumbed up a vacuum pump.
We ran the engine on the dyno on fuel only, peaking at 1,394 hp and 1,022 lb-ft of torque. Wilkins says the nitrous will likely only be used when weather or track conditions are poor and they need just a touch more to make the 4.50-second index.
Zack Thomas gently lowers the Callies Magnum series crankshaft into the bearing saddles. The crank has a 4.875-inch stroke, and the main bearings Wilkins is using are from Mahle with a Calico coating.
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