Project Murderous Overkill 455 - Advanced Engine TechPosted in Project Vehicles on November 14, 2007 Comment (0)
If you're the type to sneak a peek at your Christmas presents early or flip to the back of the murder mystery while still on the first chapter to see whodunit, then you'll love the fact that we're publishing the dyno numbers for our Mondello Performance Products-built Olds big-block destined for installation into Jp's Project Murderous Overkill before we even show you the engine buildup.
Normally, we wouldn't play it this way, but because the info fit so nicely in this issue's "Top Tech Secrets" section, we figured the buildup could wait until next month. So follow along as we rub elbows with Steve Brul and the others at Westech Performance Group to see, with real-world numbers, how certain engine theories and generalities play out in the flesh. And be sure to check back next month to see all the parts, pieces, and planning Mondello Performance Products put into making this Olds 455 one of the most durable, well-assembled Pro Street engines around.
We covered the full break-in procedure for a new engine in the story "The Evil Truck Revisited, Part I" in the July '07 issue. E-mail our Web geek, Jason Gonderman, at firstname.lastname@example.org if you want him to put the story up on www.jpmagazine.com.
We always run straight 30W for initial break-in. When compared with 10W-40, which can have either the properties of a 40W, a 10W, or anything in between, depending on temperature and other factors, the straight viscosity of the 30W ensures good protection for moving parts without going too thick or too thin. It's also a good idea to add an engine oil additive such as Comp Cams Engine Break-In Oil Additive to help protect vital components.
Whether you're dealing with a $3,000 or $13,000 (or more) engine, consider contacting a facility like Westech Performance Group for the initial break-in and to get the tune right. Westech has done the initial run-in for literally thousands of engines, and experience goes a long way in preventing damage, properly seating rings, and knowing when to shut down and investigate if something sounds off.
With our 468ci Olds broken in, Brul made an initial pull with the Performance Distributor HEI dialed in to 32 degrees and the 850-cfm Edelbrock Q-Jet bolted as delivered to the Torker and a set of 2-inch primary tube headers. The power numbers told their story, but Brul was more interested in the oil-pressure numbers, which began to fall off around 5,000 rpm.
If the crankcase is too full, the crank and rods can aerate the oil, resulting in pressure loss. It also creates a parasitic drag on the reciprocating assembly. Brul says he's seen a 7hp increase by simply removing 1 quart of oil. Our engine was equipped with a full windage tray, so we knew aeration wasn't a problem-our pressure issues are caused by the Mondello high-pressure/high-output oil pump sucking the stock 5-quart pan dry. We'll swap to a larger-capacity pan in the future.
Power levels generally go up as oil temps rise and the oil thins. We went one step further and drained the crankcase of its break-in oil and refilled it with Lucas 10W-30 synthetic oil. On the next pull, we banged out a recorded 514 hp and 552 lb-ft of torque, adding 3 hp and 7 lb-ft to the previous tally.
It's a general rule of thumb that for each point you raise compression (between 8.0:1 and 11.5:1), you can expect a 15hp gain. The upsides are increased throttle response, more power, and higher volumetric efficiency. The downside is a need for higher octane fuel. For a street engine destined to live on 91 octane, you can usually get away with a full point of compression more with aluminum heads over cast iron. There are a ton of other factors to consider, such as cylinder pressure, combustion-chamber shape, flame propagation, and so on.
However, for our purposes in this brief space, we ran this engine in its old form with iron heads, 9.75:1 compression, and 94-octane Sunoco fuel with minor detonation under heavy load. Conversely, the aluminum Edelbrock heads, with their better thermal shedding properties, tight quench chambers, and relocated plug position for better flame propagation allowed 10.75:1 compression with 91-octane fuel. Granted, our cam specs are way different and the new engine was on a dyno and not in a chassis, but the comparison is there.
Big cubes make big power, but more to the point, a long stroke makes huge grunt. For an off-road mill, you can mitigate the tradeoff in low-end torque associated with a big cam and a single-plane manifold by using an engine with a long stroke-like the Olds 455. Compared with a 350 Chevy's 3.48-inch stroke, a 454 Chevy's 4.0-inch stroke, a 455 Buick's 3.90-inch stroke, and even a 500 Cadillac's 4.060-inch stroke, the Olds 455 enjoys a monster 4.25-inch stroke. To duplicate that with most other brands means stepping into an aftermarket stroker crank.
What's it translate into? According to Mondello's general manager, Lynn Wellfringer, "You just can't duplicate the torque curve of an Olds big-block with any other brand." Brul indicated that our dyno curve was akin to that of a similarly equipped Chevy 454, only our numbers appeared 1,000 rpm lower. That's outstanding.
The key lies in that monster stroke. As the piston travels down, down, down, it draws huge amounts of air/fuel mixture over a longer period of time. Providing the valve hangs open long enough to accommodate that huge draw, a ton of velocity is created. This tunnel ram effect within the intake ports forcefully fills the cylinder and gives a lot of turbulence within the chamber, which helps to light off the mixture, even at low engine speeds with a big cam. The lazy, slow-speed drawbacks inherent in other engine families don't apply to the same degree as with an Olds 455 built like ours.
As we stated, to make the most of our stroke and to complement the modifications to our Edelbrock heads and intake by Mondello (tune in next month), Mondello spec'd a truly ludicrous camshaft for Comp Cams to grind. The solid roller has a whopping 268/276 duration at 0.050 and 0.640/0.649 lift, ground on a 110-degree lobe separation angle. We were scared at first, but the monster cam nicely complements our engine package, proving Mondello really knows its stuff. While there's a chop to the idle, the engine isn't as uncivilized as we had feared. So why does such a monster cam work so well for an engine destined for street and nonrockcrawling off-road duty?
First, the larger the engine, the larger the camshaft can be. A Comp Cams 280 Magnum camshaft may lope like a race car when installed in a Chevy 283, but it will seem like a stock cam in a Chevy 454. Our 468ci engine slightly calms the effect of that much duration and lift.
Second, the lobe separation angle (LSA) of 110 degrees is actually somewhat conservative in a camshaft this large. LSA determines how much overlap, or time the intake and exhaust valve are opened at the same time, there will be. The tighter the LSA, the more overlap and the choppier the idle. The wider the LSA, the smoother the idle. The tradeoff is that an LSA of 106 will make more overall power and higher peak power than a cam with an LSA of 114.
Third, the fact that it's a mechanical (solid) roller allows for the fastest valve event of any camshaft type: hydraulic flat tappet, mechanical flat tappet, hydraulic roller, or mechanical roller. Because the points of contact on a roller cam are round instead of flat, they're able to hold the valve on the seat longer, then snap it open at the last moment more quickly, resulting in more power.
Finally, our camshaft works with, not against, our induction system. The valves open wide and hang a long time to allow the 2.07-inch intake valves to suck in as much air/fuel mixture as possible and to let the 1.685-inch exhaust valves expend the gases.
Brul rattled the walls to the tune of 515 hp and 552 lb-ft of torque with an 850-cfm Edelbrock Performer RPM Q-Jet we had on the shelf. Because Q-Jets work so well off-road, we thought it deserved a shot. Our air/fuel ratios for the dyno pull hovered right around 10.9:1-11.3:1, indicating a rich condition. Brul could've monkeyed with swapping metering rods to lean it out, but Q-Jets are pretty complicated to work on, and dyno time is dyno money.
Instead, we went for the jugular and bolted on an 850-cfm Barry Grant Race Demon. The Race Demon is a full-on performance carb that doesn't mess around with choke horns and pedestrian niceties. It offers features like billet aluminum metering blocks, removable boosters, high flow, concentric venturis, a billet base plate, and a host of other features. Barry Grant automatically recommends the Race Demon for any engine with a cam as large as ours, but Brul suggested we could've gone with the company's Mighty Demon carb to save a bunch of coin with little to no loss in performance because our power levels weren't exactly in the stratosphere.
We were shocked to see the power rocket to 533 hp and 563 lb-ft of torque with an air/fuel ratio right on the money at 13.1:1 with the Race Demon bolted on as delivered. Brul then advanced the timing from 32 degrees to 34 degrees BTDC, and we were rewarded with 541 hp and 569 lb-ft of torque. That's and extra 26 hp and 16 lb-ft with just a carb swap! Even though both carbs theoretically delivered 850 cfm, the difference in the Demon's more efficient fuel atomization and superior metering system really delivered the goods. Aside from adjusting the idle air screws, we did no other tuning to the carb.
To make life simple, we called Performance Distributors and sent in our engine and camshaft specs. The company sent us a DUI HEI distributor and a set of Livewires. The mechanical advance curve was so right that we didn't have to crack the cap. Because we didn't need to worry about the ignition timing, we turned our attention to setting the valve lash.
On a hydraulic camshaft, there's a plunger inside the lifter that takes up the lash, or slack in the valvetrain as the pushrod interacts between the rocker arm and lifter. On a mechanical camshaft, you've got to set the valve lash yourself. Once the engine was broken in and warmed up, Westech set our valve lash to Comp's specified 0.020 inches. Some guys may fudge the valve lash a little to affect the camshaft characteristics. Loosening the lash will make the cam act bigger, while tightening the lash will make it act smaller, but the results can be poor idle quality and noise if the valves are too loose, or bent or broken parts if they're too tight. It's always better to go with the manufacturer's specs.
Mondello employed several tricks like installing its Posiflow swirl polished and backcut valves and CNC-preparing the Edelbrock heads and performing its Mondello blueprinting to the Torker manifold. The CNC mods add 35 cfm capacity to the heads, bringing the flow numbers up from roughly 278 cfm intake and 179 cfm exhaust at 0.500-inch valve lift to 313 cfm intake and 214 cfm. The good flow numbers combine with the ports' shape and the manifold mods to maintain a high port velocity and a tunnel ram effect.
We then swapped on the Victor manifold and made another pull with all the parameters as before. After checking everything to make sure we hadn't missed a step and advancing and retarding the timing, we were surprised to muster a best of only 532 hp and 552 lb-ft of torque. To see why we were 9 hp and 17 lb-ft off our best numbers with the Torker, Brul installed an air meter hat over the carb to check airflow with the Victor and made another pull. We then put the Torker back on and recouped our lost power.
The air meter showed the Victor and Torker were moving the same amount of air, but the larger ports and longer runners of the Victor resulted in slower air velocity. The air just plain got lazy with the Victor. For an engine of our size, trading velocity for volume just didn't cut it, so the Torker stayed on for the rest of our testing.
Nitrous is everybody's friend. You've just gotta know how to handle it. Brul's suggestions were simple: get with a good system in the first place, don't exceed a nitrous shot in excess of one-third the engine's total power output, and pull 2 degrees of timing out of the ignition for every 75 hp of nitrous.
The Zex system we chose is of the highest quality. We installed the Zex billet perimeter nitrous plate (it spays the nitrous/fuel mixture through evenly distributed small holes around the inside of the plate's inside perimeter) and made another pull without the nitrous to see what effect the 3/4-inch plate had. Normally, you pick up a little power with a spacer, but as a testament to how dialed-in our manifold/head/cam combo was, we only saw a best of 544 hp and 567 lb-ft of torque, picking up 4 hp and losing 1 lb-ft (as compared with no spacer).
Brul then pulled 4 degrees of timing out of the picture, filled the fuel cell with 100-octane Rockett Brand racing fuel, and with the engine at 4,000 rpm, hit the button. We nailed just shy of 700 hp with a best pull of 698 hp and 765 lb-ft of torque. In case you're a little slow with the math, that means the Zex system actually overdelivered on the power, giving us 154 hp from a supposed 150hp shot. Way impressive. We could've messed with bottle pressure to eke out a little more to claim 700 hp, but Brul asked, "Why not just go up a jet size for a 175hp shot and shoot for 725 hp?"
However, even though Mondello is confident this engine will suck a 200hp shot all day long, we decided to play it safe. We're happy with the knowledge that nearly 750 hp and probably close to 900 lb-ft of torque is on tap with a simple nitrous jet change.
Mondello calls it a Pro Street engine, but it's really not the wild beast the name conjures up. Granted, you're not going to want to rockcrawl with an engine like this, but for our project's intended purpose as a Glamis sand rig, Ocotillo hillclimber, and maybe even a quarter-mile screamer, it's bang on the money.
The air/fuel mixture and exhaust travel in gaseous balls through the engine known as pulses. By maintaining velocity with moderately sized intake ports of around 300 cfm and efficient exhaust ports, in conjunction with a camshaft that opens the door (valves) accordingly, these pulses are able to stack more closely together to create fat torque lower in the curve and deliver a very high brake mean effective pressure (BMEP). The BMEP is an indicator of how efficient an engine is and allows a comparison of its performance evenly to another engine of a different type with different characteristics. For example, our 468's BMEP came in right at about 170 psi. As a comparison, Brul says most of the normal 91-octane engines he sees are in the 160s. A dead-stock '70s Chevy V-8 may be in the 140s, and a NASCAR V-8 may come close to 200 psi.
|Dyno Run 1: Edelbrock Torker, RPM Q-Jet|
|Dyno Run 2: Edelbrock Victor, Race Demon|
|Dyno Run 3: Edelbrock Torker, Race Demon, 3¼4-inch Zex nitrous plate|
|Dyno Run 4: Edelbrock Torker, Race Demon, 150hp Zex Nitrous|