Tony Bischoff and his team at BES Racing Engines are all about making power, and they proved it at the 2005 Engine Masters Challenge. Tony has been a professional engine builder since the age of 22, and a competitor for longer than that. When asked how he liked the competition, he joked, "I liked everybody but Lennart," referring to Lennart Bergquist, who walked away with the top spot. A three-time competitor, Tony is always playing to win. On a more serious note, Tony related that one of the best parts of the Engine Masters competition has been getting to know the other builders, "All the people there are really good, so I really enjoyed that part of it." Tony's BES Racing Engines has been in the competition for the last three years, and their big-block Chevy entry came home in the runner-up spot with a 1265.67 score in the finals, making as much as 838 hp at 6,200 rpm. That's pretty astounding, and made us want to go in for a closer look.
Racers and engine builders aren't too quick to spill their hard-earned speed secrets, and Tony was no exception, but he was more than willing to elaborate on the detailed aspects of his build--after we twisted his arm pretty hard. The toughest part for Tony is managing the day-to-day duties of the business, and working in enough time for adequate testing. This year, the engine was finished only a week before the contest. Tony says, "You don't necessarily start it that late, but end up finishing it that late." Tony doesn't subscribe to a grandiose philosophy when it comes to a combination for the overall engine configuration, "You can get theories on bores and strokes that go both ways, and they're just theories." Tony continued, "I've never done a real small-bore, long-stroke combo. Of course, those are the guys who keep winning, so maybe that's the best way to go, but I'm not really convinced that that's the case." Tony built a bigger bore engine, with a 4.421-inch bore and a 4.140-inch stroke. According to Bischoff, the bore and stroke was arrived at because he already had the crank.Tony does believe that a relatively short rod versus the stroke is a good thing, especially down low at 2,500 rpm.
Tony explained, "I think the rod angle helps torque on the bottom; then there's the thing about the dwell at TDC being faster so it doesn't detonate so bad. I don't know if that's actually true or not, but I do know it makes more torque down low." Tony utilized a 6.300-inch Eagle rod, and conceded that he would have gone with even a shorter rod, but the added piston length and weight can be a problem. Tony pointed out, "It would pull the pin so far to the bottom of the cylinder that short of sleeving the block and hanging the sleeves down lower, it will hurt more than help, so I didn't want to go any shorter."
Bischoff believes the real secret to the competition is getting done with everything you want to do in time and testing extensively. Because the engine was completed so close to the deadline, Bischoff felt additional testing could have made a difference. "Ideally, you'd want to try a bunch of different cams and intakes, but as the timing worked out, we didn't have a chance to try a lot of different parts, and just worked on the tune-up."
The compression ratio was pretty stout at 12.5:1, and that may have been pushing it. Bischoff disclosed, "It may have been a mistake. Lennart was smart enough to test with 89 octane, while I was really thrilled when I was testing, since the engine didn't rattle at all, but that testing was on 93 octane. When we put the 91 [octane fuel] in it in New York, we had 5 or 6 degrees less timing in it than in testing." In the qualifying tune-up period the BES crew worked to dial in the timing for the local conditions and spec fuel with extensive tune-up pulls. Tony relates it can be difficult to tune within the time limitations of the competition: "It's tough to see the gains you're going to get with one- or two-degree changes in timing during the tune-up period of competition, since the (engine) temperature can change."
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Pop the lid on Tony Bischoff's 508-cube big-block Chevy and start the hunt--there are custom touches everywhere, but don't expect Bischoff to voluntarily give up his game. Look, find, ask, and Bischoff will start to divulge his secrets. The fire slots in the pistons are easy to spot; the relocated deck dowels are more elusive, and it takes an accurate ruler to notice the 0.100-inch milled decks. |
Tony custom-crafted the chambers to create a dual-quench pad, substantially filling the plug side of the chamber. The plug was moved over toward the apex of the valves. Tiny plugs were used to minimize the potential of breaking into water during the surgery. |
A closer look at the Ross custom pistons reveals a mirror image of the Brodix head's chamber, and the scrubbed burn pattern gives a hint of the tight quench clearance. Compression rings are 1/16-inch, due to lack of availability of thinner rings for the odd bore size. Tony compensated with a serious back-cut. |
A look into the chamber with the valves out reveals the hand-ported bowls. The porting was done in-house at BES. Tony ordered Brodix head castings normally used for CNC finishing, and cut them to his liking. His aim? Make it flow as much as possible without making it too big. |
The heads were re-located on the dowels to move them 0.100 inch inward, to align the valves closer to the bore's centerline. |
On the exhaust side, Bischoff regrets not going bigger with the port. Bischoff relates, "These ports came really small, and we probably didn't take them out far enough." |
The intake ports carry epoxy work in the floor, a move to dial in the port cross-sectional area. Tony disclosed about 3.9 square-inches when pressed for a number. |
This big-block shares the rod journal diameter with a Honda four. Bischoff disclosed that it is to reduce the bearing speed, which reduces drag. Bearing clearances are tight; Bischoff puts it at "under 0.002," which at least narrows down the general range. |
Reduced bearing diameter follows through to the mains, which is harder to accomplish than at the rods. The clever Bischoff started with big-block Chevy mains, which were installed and line-bored to 400 small-block size. Then 400 Chevy main spacers were installed and line-bored to take 283 Chevy bearings for a final size of 2.300. |