Big-Block Bruiser -- Engine Masters

POWER PARTS
Competing in an event like the Engine Masters Challenge demands that the total combination is working optimally for the rpm range. Tony was quick to point out that much of the development of his engine was directed at producing power down low, while keeping out of detonation. Here, Tony applied some conventional techniques, as well as some unusual tricks. The fire slots on the pistons were something Tony had little previous experience with, at least that he would admit to. Tony laughs, "I have no idea what they do, this is the first motor I've put together like that, and it wasn't tested before and after, so I don't have any idea of whether it helped." We did note that the engine did not detonate, and upon tech inspection after the competition the pistons and rings didn't show any signs of scuffing.

On a more conventional front, to help control detonation, Tony went pretty tight on the quench clearance, about 0.035 inch, which was about as tight as he was willing to cut it with the weight of the pistons and the stroke length. An area Tony would have liked to explore further is the use of thermal coatings. Pressed by time constraints, there was a worry about getting the parts back in time for the competition. Some thermal management techniques were employed, basically trying to keep heat away from where it hurts, and keep it in where it can help. Here again, the thermal coating would have been a useful tool, but some other tricks were employed. The lower valley tray of the intake manifold was cut out, and a divorced valley plate was substituted to try to keep the heat out of the manifold. As is usually the case, Bischoff had more ideas than time, "I wanted to make some phenolic spacers for it but didn't have time to get it done. I know that stuff works."

The heads, needless to say, are extensively modified, with the work performed in-house at BES Racing. Starting at the chambers, the sparkplug side was filled in to produce a squish zone on both sides of the chamber. A noticeable modification was the use of a very small diameter sparkplug. Bischoff explained, "I moved the plug closer to the center of the chamber, and Brodix runs coolant around their plugs; without knowing exactly where the water is, the smaller plug let me remove less material when moving the plug from one side to the other." Filling out the chamber were large 2.300-inch intake valves and 1.800-inch exhaust valves.

Bischoff saw some room for improvement with the valves, "I originally had Manley No. 424 springs in it, and just before shipping the motor, I took the centers out of the springs. I knocked a bunch of spring pressure out of it, taking the load from 290 closed and 675 open to 220/500. It picked up my score a couple of numbers, so I left it that way, but if you look at my dyno sheet, I believe it was going into valve float at 6,400 or 6,500 rpm. I wish I had put in lighter valves, maybe put 5/16-inch stems in it and it might have let it carry the higher rpm. Peak power changed from above 6,600 to just 6,300 after taking out the inner spring." The Brodix-4 heads were fully ported at BES, but Tony saw more potential there, too, "I think my intake port was a little too big, and the exhaust was way too small; I just left it too small." The final size of the intake port was given as 3.9 square-inches. Asked about what it takes to cut a good intake port for the competition, Bischoff replied, "Make it flow as good as possible without making it too big."

The intake manifold and induction configuration is another vital aspect of a competition engine. Tony finds that the operating rpm range used in the competition adds a level of difficulty to getting the ideal combinations, "What works at 2,500 in the manifold is exactly the opposite of what works at 6,500. All the work we did on the manifold hurt peak horsepower a little, but at 2,500 we picked up 50 to 60 ft-lbs." The BES racing dyno is equipped with individual Lambda sensors for each cylinder, which helped to dial in the air/fuel ratio. Tony continued, "The work we did on the manifold may not have helped or even hurt the top-end. The end cylinders at 2,500 are really lean, and at 4,500 it would cross over and everything would go the other way. Basically you need a lot of air speed to keep the fuel in the air suspended, and at low speed it gets separated. That's why you need to try to direct the fuel where you want it to go. We dammed the center runners at the floor with epoxy to richen the end cylinders at low speeds. The end cylinders were dead lean that low; the air/fuel ratio was in the range of 16 or 17:1. As rpm went up they would even up; it was just at the low-end. Interestingly, the dams were originally just crudely put in there at the four center runners, making a rough 1/8- or 3/16-inch ridge, and that helped the score a bunch. Then I took the manifold off and polished it all out and made it real nice, and it actually hurt my score a couple of numbers. The HVH spacer helped the low-end numbers too, but didn't really make much difference at the top."

To make the most of the induction and heads, the camshaft is a critical component. Here, experience is the key. Tony used a custom 256/268 Comp roller cam with 0.846-inch lift. When selecting lobe profiles, Tony revealed that he was after high intensity: "We looked in the Comp book and found the quickest lobes we could find, and put that in it. I've never seen a quicker cam not make more power everywhere. They may make some faster ones, but that was the quickest one they had in the book." The quick lobes were linked to the valves with Crane 1.8:1 rockers, while a Jesel belt drive provided the spin. Speaking on the cam's timing, Bischoff elaborated, "Originally the cam went in at a 102-degree intake centerline; I would have liked to try putting it in a little more advanced, but it didn't have enough valve-to-piston clearance. Advancing and retarding did exactly what you'd expect; retarding would pick up the top-end numbers, but cost down low."

An extensively modified Eagle crank was the main player down at the bottom end. We asked Tony about the small journals, and how they fit in with his plan. Tony replied, "Oil control is important, but I never use scrapers. I'm a firm believer in controlling the flow of pressurized oil. You have to set the bearing clearances for the oil viscosity you are going to run. The small journals bleed-off less oil with tight clearances, and also help with the slower bearing speed. The roller cam bearings were used primarily to control oil. Restricting the oil to the top end is a big help. I like to spread the drainback though the whole motor instead of putting it all in the front or the back. Unless you can get it completely away from the crankshaft, dumping it all on top of the (No.) 7 and 8 cylinders isn't such a good idea. If your oil is restricted enough to the top end, keeping just enough to keep your pushrods in, there will be very little drainback anyway. The trick is to restrict it right.

Bischoff's big-block carried tricks and custom touches practically everywhere we looked, and probably a few we missed. That's this racer's edge. Most of the modifications were learned with hard work by the builder and his team, and done in-house at BES. You've got to respect the competitiveness of a man willing to work that hard for that little bit of an edge. The BES racing crew's performance at the Engine Masters Challenge proves the point.