Video: Borowski Builds Bill Milz A Darton-Sleeved 427 LS1

EngineLabs.com Exclusive Video - Darton MID Sleeved 427 LS1. from Borowski Race Enterprises on Vimeo.

Bill Milz and his 427ci LS1 engine.

Bill Milz and his Borowski-built 427ci LS1 engine.

Road racing is tough on parts, especially when they haven’t been engineered to perform in that challenging environment. Over the last couple of years, Illinois road racer Bill Milz has found out just how quickly an engine can decide its lifespan has reached the limit. The half-hour-long track sessions push the oiling and cooling systems of his 2000 Camaro SS convertible to the breaking point.

“The car had just a stock LS6 in it when I started racing. I went through the stock engine, replaced it with a brand-new LS6 crate engine from GM, then that one blew on me last year,” says Milz.

At that point, Milz had a decision to make. The chassis had been overbuilt for the engines he was using, and the shop that maintains the car suggested he step up the powerplant to something that would be more in line with his desires – a stout bullet that could take the abuse of multiple track sessions per year without leaving him in the lurch before events.

Using Darton's MID sleeve system, Borowski final-finished the bores to 4.125-inch and stuffed them with a set of Racetec's pistons.

That’s where Ken McCaul and the team at Borowski Race Engines comes into the picture.

“I ran into Ken at a show here in Chicago, and we discussed what I was looking for. After speaking with him a few times, I was comfortable enough to go ahead with this build. He had a block at the shop that was a good fit for what I needed. We discussed what I wanted to do with the car, what type of budget we had to work with, and from there this is what we ended up with,” Milz explains.

Borowski selected a GM LS1 block that’s been decked to 9.200-inch and outfitted with Darton‘s MID sleeve system to finish with 427 cubic inches of displacement for this engine. Final dimensions are achieved through the use of a 4.000-inch forged crankshaft from Scat Crankshafts along with a set of Scat’s 6.125-inch forged H-beam connecting rods.

Bore dimensions check in at 4.125-inch, and a set of Racetec‘s forged pistons are used. The 451-gram pistons were selected for their light weight, which will allow the engine to get up into its powerband quickly and provide excellent performance at the track.

Total Seal rings set to .019-inch on both top and second rings were used. Clevite connecting rod bearings and Clevite main bearings were also used.

(Left, Left Middle, Right Middle) The LS1 block was clearanced in all the right places to accommodate the long-arm crankshaft. (Right) The Scat 6.125-inch rods, Clevite bearings, and Racetec pistons awaiting assembly.

A view of the intake valve through the cylinder head and carbureted intake used for the dyno texs.

A view of the intake valve through the cylinder head and converted carburetor-style EFI intake used for the dyno testing. Milz’ FAST intake was subsequently installed onto the engine.

The engine has a set of L92 cylinder heads on top that have been given the full CNC treatment at Borowski, and as part of the build, Milz elected to upgrade the induction system to take advantage of the engine’s new deep-breathing capabilities.

The FAST LSX-R 102mm intake manifold was chosen with a complementary set of FAST’s fuel rails, and one of the company’s 102mm Big Mouth throttle bodies to match.

Helping the engine to achieve the necessary powerband is a hydraulic roller camshaft from Howards Cams. McCaul notes that the company uses Howards products in many of their engine builds, and in this particular instance, the company offered a grind that was exactly what the doctor ordered for Milz.

Intake and exhaust valve lift spec’d out at .612-inch across the board. The camshaft actuates the valves through a set of 1.70:1 GM rocker arms with the COMP Cams roller trunion setup that does away with the GM needle bearing design.

Engine builder Dave Livesey at Borowski set the camshaft with the intake centerline at 109.25 degrees, and the camshaft was ground on a 113 degree lobe center. By spreading out the lobe separation angle the camshaft acts larger than it really is, which helps the high-rpm operation at the expense of low-rpm performance. In this application, that was deemed acceptable as the vast majority of the road racing Milz will do is of the higher-rpm variety.

H-beam soldiers all lined up and awaiting service.

H-beam soldiers all lined up and awaiting service.

The engine will be installed into his Black Dog Speed Shop-prepared Camaro SS. The car has been completely upgraded with a rollcage and other suspension pieces; so far Milz has had it on the track at Gingerman Raceway, Road America, and it’s even made a trip to Road Atlanta among others.

But it’s not just a track machine, as it also sees some time on the street so that Milz can get the most out of his investment. “It’s a very fun street car. It’s loud and it’s a little different than what you’d expect,” says Milz.

The Howards Cams hydraulic roller was dialed in using one of Cloyes' Hex-A-Just timing sets.

The Howards Cams hydraulic roller was dialed in using one of Cloyes’ Hex-A-Just timing sets.

He’s also upgraded the suspension to a complete coil-over setup, and there are plans to also upgrade the factory k-member and control arms to aftermarket pieces. The T-56 six-speed transmission has also been updated to Stage 5 Viper specs for strength.

Other views of the engine.

Final dyno results - a solid powerband throughout. The engine maxes out at 633 horsepower and carries well over 500 lb-ft torque from the beginning of the test through 6,500 rpm.

Final dyno results – a solid powerband throughout. The engine maxes out at 633.3 horsepower and carries well over 500 lb-ft torque from the beginning of the test through 6,500 rpm.

So many enthusiasts gravitate towards the dragstrip, but Milz took a challenge from his brother-in-law a bit too seriously, and headed down an unexpected path.

“My brother-in-law had a 2004 Mustang Cobra, and we were just kind of BS’ing around about each other’s cars, so I suggested we head over to Gingerman and have some fun to see what we could do. After that day, I was hooked,” he says.

“It didn’t happen overnight, but every year, something needs to be replaced and upgraded, so now I’ve got this modified 2000 Camaro SS that I have too much money into,” laughs Milz.

As this car is a modified street car, there’s one challenge in particular Milz faces every time at the track – playing with the real racecars.

“Everyone is very competitive, and I find myself pushing the car beyond what it can do – that’s where I’ve gotten in trouble with the engine part of it. That’s where Ken and Borowski have come into the picture, by building me an engine that’s stronger than what I had,” he says.  “Obviously he can’t prevent driver error, but the engine should be installed in the next week and I’ll be ready to race.”

The engine was tested using a converted carburetor-style manifold with the engine’s EFI system on top simply for ease of use; McCaul says that final engine power once installed into the car will not vary much at all from what was recorded by the dyno. Check out that dyno sheet – this engine makes boatloads of power at lower rpm, great to pull the car through the twisties and provide Milz with solid all-round performance.

Bill's convertible in action. Photo courtesy Bill Milz.

Bill’s convertible in action. Photo courtesy Bill Milz.

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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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