Dyno Video: Mike Saiki’s 23-degree Small-block Makes 806 Horses

It’s not every day that a true, traditional 23-degree-headed engine makes 806.7 horsepower and 611.5 foot-pounds of torque, and Mike Saiki along with Bryce Mulvey of Dr. J’s Performance have put an absolute ton of work into this bullet to make those numbers possible. Saiki competes in the West Coast Hot Rod Assocation’s Limited 10.5 class with a 1968 Camaro SS that’s been fully-prepped to withstand the rigors of class racing.

“It’s a 427ci nitrous motor using our 23-degree Airwolf 265 cylinder heads. The engine uses a Dart block, Eagle crank and rods, and custom CP pistons. We’ve run it for quite a bit in this car, and it actually holds the WCHRA record for the Limited 10.5 class. You have to run a 4150 carburetor, a nitrous plate with no nitrous controller and a -04 AN line. You can run a 275-wide radial or 10.5 inch slick on the car. So far, Mike has been a 5.28 at 133.74 MPH back in July, which set the record,” engine builder Mulvey explains.

Mulvey designed the Airwolf 265 CNC ports to achieve the maximum airflow possible given the envelope. His Brodix-manufactured castings have the water jackets modified for better port performance. Big springs and paired shaft rockers control the valves.

DSC00595Don’t think the engine is all high-rpm power and no torque, though. From 5,000 through 8,100 rpm, it never produces less than 512 lb-ft of torque.

The powerband ramps up hard from the 5,000 rpm recording start on the dyno, jumping 168 horsepower between 5,000-6,000, 91 horsepower from 6,000-7,000, and another 113 before reaching the peak at a relatively-low (for a race engine) 7,600 rpm max. Put the hose to it on top of that and you’ve got one heck of a performer.

How do they achieve those stunning numbers, you ask? Dr. J’s Airwolf 265 cylinder head is based on a Brodix casting that Mulvey works his magic upon, resulting in a killer set of cylinder heads that don’t have raised runners. “It’s our own CNC program that we run through the heads, and we feel that it’s probably the best conventional 23 degree head you can buy. We also hold the record on a 275-wide tire with Tim Rigby’s Corvette with those heads – Tim’s car has been a 4.92 at 141 MPH with them,” says Mulvey.

Check Out In-Car Video of Saiki’s Camaro  Securing The Limited 10.5 Class Record With This Engine!

Brodix produces the head castings with a different water jacket location in order to provide room for Dr. J’s port program, and the results speak for themselves. They’ve also got an intake manifold modified by Mulvey atop the monster designed specifically to work with the cylinder head and carburetor package. Camshaft, as always with a class-style car, is a completely custom grind.

Rotating assembly consists of a prepared Eagle crankshaft and rods along with CP pistons. Copper head gaskets are used to keep the water out of the cylinders.

Head castings are produced from A356 aluminum and use standard small-block Chevrolet bore spacing. Intake valve size specs out at 2.15-inch, while the exhaust valves come in at the traditional 1.60-inch size. They use bronze valve guides and a regular old Fel Pro 1209 intake manifold gasket.

DAt 28 inches of water on a 4.155 bore, the heads top out at 372 CFM on the intake side and 269 CFM on the exhaust side at a whopping 1.000 inch of lift. Don’t think that they are simply a race cylinder head, though; they still flow 332/236 at .600-inch lift and 348/249 at .700-inch lift.

Building competitive race engine – especially when limited by class rules that are very specific – is no easy task, but Mulvey and his team seem to have it figured out, as evidenced by not one but two record-holding engines using these cylinder heads. As they say, airflow’s the name of the game, and Dr. J’s Performance appears to be dictating the rules.

About the author

Jason Reiss

Jason draws on over 15 years of experience in the automotive publishing industry, and collaborates with many of the industry's movers and shakers to create compelling technical articles and high-quality race coverage.
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