Showing his Hand
Inside Lennart Bergquist's Winning Big-Block Chevy
From the February, 2009 issue of Popular Hot Rodding
By Steve Dulcich
Photography by Johnny Hunkins
What does it take to bring home the gold in the Jeg's Engine Masters Challenge? If you try to pick up clues from a casual look around Lennart and Birgitta Bergquist's 509 cubic-inch Chevy big-block, you might just be left puzzled. After all, this is the engine that put down a crushing 1,288 score to eclipse the output of all other contenders, delivering an unheard of 851hp at only 6,400rpm, on pump gas. Equally impressive was the torque, bending the strain gauge to record as much as 750-lb-ft in the finals. That's a specific torque output of 1.47-lb-ft per cube for the Autoshop Racing Engines entry, a level that is seldom seen. At an offhand glance, the engine could easily be mistaken for a typical bracket-race mill, but as we have come to find out, Lennart's ways are much more about the details than the outlandish. Lennart confessed, "There's more than meets the eye, you know, when you first see this motor it looks like a crate motor from the mail order."
In general terms, Lennart's overall philosophy was about three ingredients. As he put it, "Number one, you have to have a good air pump; you have to push the air in and out of the motor effectively to make horsepower. Secondly, you have to have a good air/fuel mixture to put in there, and thirdly, you have to have very little friction, as little friction as you can build. For the friction part, you have to go to some lengths to make sure that there is very little friction. For example, I made a tool out of a fish scale that I could hook up to the camshaft and rotate it. I had adjustable pushrods so that the length could be adjusted and determined the exact length that took the least effort to turn the cam around. I just experimented with it until I found the best geometry. Similarly, I made a tool to adjust the link bar between the roller lifters to find any binding. I kept tweaking on the link bar until there was nothing but smoothness." Basically Lennart fine-tuned the details to an amazing degree.One of the major sources of friction in an engine is the action of the pistons and rings on the cylinder walls. Here Lennart did the same thing, trying different rings and honing techniques, and pulling pistons with a scale to gauge friction. Lennart told PHR: "Believe it or not, the least friction and best ring seating technique was to have a fairly rough stone to hone the cylinders with and then using a brush to knock the peaks off the honing cross hatch. When we ran really fine stones we didn't improve anything as far as friction but lost all the oil control. The hassle is getting low friction with good oil control. You can have a low-friction motor, but with no oil control, and you don't want to do that. After the brushing, the cylinders have good texture and cross hatch to seal the rings, but feel as smooth as glass. If you feel the exhaust ports and they are a little wet in there, it's a lack of oil control; mine were absolutely dry." During the tear-downs, we did notice the beautiful condition of the bores after the competition, with no scuffing or signs of distress at all. A custom set of CP pistons was made for this application, keeping the compression ratio at a modest 11.5:1, with the aim of avoiding detonation. The compression rings are SpeedPro, with moly 0.043-inch units gapped at 0.022 inch at the top groove, and like-sized iron second rings, gapped at 0.028 inch. The oil rings are 3mm, also from SpeedPro. The ring seal is optimized by gas ports in the pistons, while the overall package exhibits very low friction. Evidence of this was the mere 12-lb-ft of torque required to spin the completed short-block.
The same level of attention to detail continued into the crankshaft. Lennart explained, "You need a good quality crankshaft, as light as possible, with as small a counterweight diameter as practical, and it has to be as stiff as possible so it stays straight and doesn't flex when you put a load to it." The crank is a custom billet piece by Sonny Bryant, with the counterweights cut to clear a 6.300-inch rod length, even though the rods used actually measured 6.350-inches. The balance was made up with heavy metal. The crank weight is just 52-lbs, a flyweight for a 4.500-inch stroke big-block crank. Further reducing friction and oil flow, the crank was cut with 1.88-inch rod journals, and the main bearings were narrowed. Lennart figured if the aim was to win, he needed something a little extra, and friction reduction was one of his areas of greater focus.
Windage control followed the theme of doing as much as possible to keep the engine from working against itself. Lennart pointed out, "Windage is another reason to have counterweights as small as possible; the smaller the counterweights, the further away from the block and bottom of the pan they will be. I didn't want to have any oil drainback at all over the rotating assembly, so I used roller cam bearings and blocked the oil to the cam journals and blocked the drains in the valley so that the oil would drain at the front of the crankshaft. We had to run five quarts of oil, and I took the time to figure out where that oil will be during a run, and did what I could to put it where I wanted."
Friction abatement and oil control are measures to prevent power losses, while cam and compression, heads and induction are what Lennart refers to as the air pump. "The air pump in general is how much you can pull through the carburetor, the intake manifold, and head, and how good you can move it out of there again." Obviously, the goal was to make this system work efficiently. Lennart reports that he had tried other cylinder heads that were better on the flow bench, but they were not as efficient in this rpm range when run on the engine. The Brodix heads were ported with relatively small bowls, and quite a bit of attention was paid to cross-sectional area all the way through the ports. Lennart told us, "The head shrinks, getting smaller from the port opening to the shortside turn, and then stays pretty consistent from there to the seat." The port throat is sized to 90 percent of the 2.300-inch intake valve major diameter. The final port volume is relatively small, 296cc on the short runners and 301cc on the longer runners.
One of the challenges was to make the engine operate efficiently over the competition's low rpm range. In testing, Lennart found that if a parts combination on the dyno did not make good torque at 2,500rpm, the engine never really recovered, and would be down all the way up to the top of the range. The aim was to get a combination to make over 600-lb-ft right from 2,500. That was the trick to this portion of development, finding the combination of heads, cam, and induction that would be effective over the full rpm range. Interestingly, this dyno development was done at Lennart's Florida shop running 89-octane fuel. The idea was to avoid detonation with the 91-octane fuel in the heavier air at the competition in Long Island. The most unusual aspect of the "air-pump" combination was the use of a 4150-series carb, a Taco-modified Holley 1000 HP. Ironically, Lennart's engine was the only one in the competition not to run the larger 4500 Dominator-style carb. One of the things that caught our eye after the competition was the condition of the spark plugs-they looked like new. Lennart attributes that to air/fuel ratio: "It's not as easy as it sounds to get a flat air/fuel mixture in this rpm range from 2,500-6,500rpm. I kept it within a few tenths of a ratio. That's part of the trick, to have it fuel correctly to produce power at the bottom of the pull. Lots of guys want to run it fat down there to help cool it down a little, but then you lose power, and the engine will never really recover. Distribution also plays a part, getting it right from cylinder to cylinder. To do it, everything is exact, the carburetor, the manifold, the porting, even the air cleaner." Judging by the results, we'd have to say that it appears as if Lennart did just that-got everything exact. Those are the qualities in an engine build that are a little hard to pick up on at first glance.
The Autoshop Racing Engines'...
The Autoshop Racing Engines' 509-cid big-block Chevy put down numbers that were hard to believe and few expected: 851hp on ordinary 91-octane pump gas. The basic appearance of the engine belies the attention to detail hidden within.
At the front of the engine,...
At the front of the engine, we see a collection of top-notch aftermarket parts, but nothing that can be considered one-off or exotic. The Jesel belt drive allows the cam phasing to be fine-tuned for the best average power, while the Meziere water pump prevents a power loss from driving the cooling system mechanically. The TCI Rattler damper helps the lightweight crank live under the abuse.
Lennart found that there was...
Lennart found that there was power to be had in the air filter case. The domed profile is contoured to aid directing flow into the carb throat, and there was a definite improvement recorded, especially at above 5,000rpm.
Lennart equipped the big-block...
Lennart equipped the big-block with an ignition system composed of all MSD components. In the Engine Masters event there is no room for error in the ignition and this system performed flawlessly.
One engine builder chose to...
One engine builder chose to run a puny 4150 carb in a sea of Dominators and King Demons, and it happened to be the builder that made the most outright power. Lennart attributed the great fuel distribution and ratio curve to the carb, a 1,000 HP Holley, modified by Taco. He related that after changing jets and air-bleeds and trying other tuning, the best setting turned out to be as it came from Taco.
Does this look like a plug...
Does this look like a plug that has survived more than a dozen 850hp dyno pulls? The ACCEL plugs looked practically new, thanks to excellent mixture control, a lack of detonation, and outstanding oil control.
The Brodix intake manifold...
The Brodix intake manifold is actually designed to run a 4500-series carb, and the spacer is actually an insert that adapts the smaller 4150 carb. The unconventional stepped transition where the spacer meets the runner roof is intentional. Lennart employs the step to dampen reversion pulses, in a manner somewhat akin to a sheer plate. Note the porting in the plenum and runners, credited for aiding distribution.
There was considerable attention...
There was considerable attention paid to the size and shape of the runners of the matched race oval-port Brodix intake and heads. Notice the epoxy work to reduce a dead area on the upper long turn of the intake manifold runner leading to the head.
The cylinder head port saw...
The cylinder head port saw the same attention to detail. The cross-sectional area was carefully sized throughout, and though these heads were not the highest flowing units Lennart tested, at about 380-cfm peak they made the most power. Lennart pointed out that on the flow bench they sounded dead smooth and quiet.
The chamber side reveals the...
The chamber side reveals the small bowls under the valves. The sizing was intentional with the constraint of the test rpm range determining the shape. The large 2.300-inch intake valves work with a 90 percent throat under the seat, helping create a venturi. The valve seat angles are conventional.