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Project Off Road Buggy Small Block Chevy Engine - Dream Machine Power

Posted in Project Vehicles on September 1, 2005 Comment (0)
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Photographers: GM Performance Parts

I told you last month that Project Fun Buggy has got to be just that-fun-so like any red-blooded American boy I went out hunting a proper engine for peeling out. I wanted an engine that could chug over rocks and up wooded trails, but still get allfour tires smoking or huck giant roosts in sand or mud. Mileage is important, but not as much on a dedicated trail rig. This one's called Fun Buggy, after all. And finally, it had to look cool under the hood and give off a rumble that would scare the yuppies down the street.

So what to use? Four-cylinder engines are great for economy and putt-putting around. I've seen many awesome rock buggies with Toyota, GM Ecotec, and even Subaru engines that can crawl and still get jiggy across the sand and mud, but when tires get above 40 inches, a four-banger is getting worked.

1. Long-stroke engines are known for their torque, and when turning big tires off-road, you want torque. That's why we are always so concerned with going to lower gears for torque multiplication. The stroked ZZ383/425 engine package comes from GM Parts Performance (GMPP) with a modified four-bolt main engine block, a 3.80-inch stroke 4340 crankshaft, heavy-duty powdered metal rods, and the one-piece rear main seal. It is also ready for an automatic transmission with a 12.75-inch flexplate, and comes with stamped-steel valve covers that we replaced with Scoggin-Dickey's fabricated aluminum versions. It does not include a starter or front accessory drives.

The straight-six Jeep engine is a torquey little anchor and the GM or Toyota V-6 is great for almost any lightweight rig looking to haul a person or two around, plus it can be dialed in for serious smoke shows on steep rocky ledges.

Then there is the question: Why not go diesel? The 6.2 diesel V-8 in my '86 Chevy is fine, but isn't all that impressive, and the Cummins diesels are just too heavy. All the other diesels are either weaker than what I want, too heavy, or not offered in this country. I would love to explore them more down the road, but Fun Buggy needs some steak-and-potatoes power while keeping on the salad side of weight. So no four-cylinders, no diesels-maybe a V-6. But then again, why leave out those extra two cylinders? V-8s are cool-they are as American as mom, apple pie, and mud-wumpin'. They sound cool, can make big power and torque, and just seem right for a 4x4, especially one on big tires. So it had to be a V-8, but which one? The new Dodge Hemis and Toyota V-8s are hard to get-very cool, but hard to get-and there just isn't that much stuff for the Nissan V-8 yet. So old-school Dodge, Ford, or Chevy? Since Feature Editor Jerrod Jones is the Dodge guy, and a good buddy of mine is running a Ford, I started thinking Chevy. You gotta have something to argue about over the camp fire. Plus this is 2005, and 50 years ago some engineers at General Motors designed a V-8 engine that has stood the test of time. Yes, it's gonna be Old Faithful, a small-block Chevy.

Even when I decided on a small-block GM I still had choices to make. In my country-boy logic I saw 40-inch tires and 40-spline axleshafts (see last month's axle build), so I figured I needed 400 horses and even more torque. Of course, the junkyard or classified ads are the first stop for many folks looking for a good engine, but if I was going that route, I would be hard-pressed to come home with a 400hp rat motor. In fact, only two small-block Chevys ever came from the factory with over 400 horses, and both were in exotic Corvettes. If I was going to go with a junkyard engine, I would choose the late-model Gen III 6.0 like Tech Editor David Kennedy put in his Blazer (June '04 and June '05). What I ended up powering this tube car is not cheap, but it will make the tires turn and I'm trying to show the coolest dream parts I could get my hands on that are still anchored back to what the average guy could start with. I know many of you might think this means a big-block or an LS1 aluminum Gen III small-block. Sorry to disappoint, but I'm going with a GM Performance Parts ZZ383. The big-block is still too heavy, and though the LS1 is lightweight and an awesome performer, I decided to push the classic iron block. GM claims 425 horses and 449 lb-ft of torque, but that is based off of dyno tests using a carburetor, and I want fuel injection for steep climbs and off-camber wheeling. So further research brought me to Scoggin-Dickey Performance center in Lubbock, Texas, and its ZZ383EFI. Follow along as we build a crate small-block ready to scare old ladies and fat wallets. It ain't cheap, but it sure is sexy.

2. The difference between the ZZ383 and GM's entry-level stroker, the HT383, is the aluminum Fast Burn heads. The GM iron Vortec heads found on '96-'99 trucks have a reputation for great performance, and the aftermarket Fast Burn heads take that design and expand on it, getting even better flow out of slightly larger 2-inch intake valves and 1.55-inch exhaust valves. Plus, the intake runners are slightly larger as well. If you have a '55-'00 GM V-8 and want to go to an aluminum Vortec style head, you can get them through GMPP as well as many aftermarket companies such as Edelbrock, who offers similar E-Tec heads.

3. The two common styles of fuel injection are throttle body injection (TBI) and Tuned Port Injection (TPI). TBI is similar to a carburetor in that there are injectors (usually two) situated at the top of the intake manifold, and the fuel is atomized in and flows through the intake to each cylinder. But unlike a carburetor, the fuel is injected (duh!) under pressure and is more controlled. TPI (also referred to as multiport injection) usually has an injector for each cylinder and sprays fuel directly above the intake valve. This ensures that each cylinder receives a proper charge. I decided on the aftermarket ACCEL DFI Super Ram system that is designed like a TPI but offers many options for tuning. Since the engine is stroked, Scoggin-Dickey recommended 30-lb/hr injectors.

4. The ACCEL system is designed to replace carbureted engines or TPI engines, but none of these ever came with more desirable Vortec style heads. Instead the Vortec style heads only came in trucks with some goofy Central Port Injection (CPI) that utilizes eight injectors and tubes that run down to each intake valve. Luckily Scoggin-Dickey has developed this Vortec/TPI intake manifold to allow Vortec Fast Burn heads to be run on TPI engines, and since the ACCEL system is a TPI design it allows the better airflow characteristics of the Fast Burn heads without disturbing the optimum charge from the fuel injectors. The ACCEL system usually comes with a lower intake, but we requested a kit without it.

5. Another benefit of the Fast Burn heads is that they are equipped with 1.5:1 roller rocker arms, and when combined with hydraulic roller lifters and a 0.509/0.528 lift steel camshaft that equals 222/230 degrees of intake/exhaust duration measured at 0.050-inch lift. So what does all this mumbo jumbo mean? As the cam rotates (it's turned by the timing chain attached to the crankshaft), its lobes raise the lifters which in turn raise the pushrods that then pivot through the rockers and cause the intake or exhaust valves to open and close, and all this has to happen multiple times every second. The hydraulic roller lifters have less friction and can handle steeper cam lobes (more lift with less duration), which is good for allowing more air in or out. These lifters also require shorter pushrods, which are less likely to deflect so they are more stable and stronger. Then the 1.5:1 rocker arms multiply the movement of the pushrods even more to get longer duration of airflow into or out of the cylinder. Being roller rockers, the friction is again reduced.

6. One small issue we ran into was when the ACCEL Super Ram upper intake runners were bolted to the TPI/Vortec intake manifold, we had to clearance two bolt heads and runner tube slightly for a perfect fit. The crew at Scoggin-Dickey split the difference between the two to guard against any leaks.



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10. We also mocked up the ceramic-coated Sanderson Headers that were recommended for the Fast Burn heads because of the thick mounting flange and exclusive D-port inlets that match the exhaust outlets. I chose a block-hugger design since I'm not sure how the exhaust will end up being built. Finally, before heading out to break in and test this torquer, we installed a set of MSD 8.5mm Super Conductor Plug Wires. They come as a set, but are not at complete lengths so that you can cut them to your desire. These wires have a Copper Alloy conductor with less than 50 ohms of resistance per foot. Plus they have a High EMI suppression, which refers to the electromagnetic interference that radiates from plug wires and can interfere with onboard electronics and computers. I will show you the MSD 6 off-road ignition-control box and blaster coil when they are installed in the chassis.

11. We finally hooked up the ACCEL engine control module (ECM) and its wide-band O2 sensor. The ECM and wiring harness is simple for initial installation, and it also comes with various fueling strategies such as sequential, bank-to-bank, batch, or staged batch. The O2 sensor is installed in the exhaust and measures the oxygen so the computer can determine how much fuel to inject for the desired air/fuel ratio. A wide-band O2 sensor not only tells the controller whether the engine is rich or lean, but also how far from optimum it is so that the computer can more accurately fix the problem. This is especially useful if the computer is put in a closed-loop program, where the information from the O2 sensor is recorded and the ECM adjusts the fuel ratio automatically. Once on the dyno stand at Sunset Racecraft, I began to feel like Dr. Frankenstein. Here was this beautiful engine with all types of hoses and wires running all over it so that Tracy Dennis, the owner of Sunset, could monitor what was going on and tune the ACCEL computer for maximum performance. An engine dyno is a fixture that puts a load on the engine in order to see how much power and torque it can turn at certain rpm. Dennis and his crew are used to building big-block engines for drag racers that push around 1,000 hp, so my little monster was not gonna scare them. Since the engine runs a 9.7:1 compression ratio, we could still test it on pump gas, but we were sure to run premium 92 octane.

12. After hours of assembly, it was finally time to start the engine. We set the timing and calibrated the dual-sync distributor, hooked up the fuel, spark, electric dyno water pump, and exhaust. With Dennis at the controls, it was fired up and rumbled to life. What happened next was a complete whirlwind to me as Dennis dialed in the ECM. The goal was to get an optimum air/fuel ratio and spark timing. This is done by monitoring the manifold pressure, throttle position, intake air temperature, engine coolant temperature, manifold surface temperature, and exhaust gas oxygen and then by adjusting fuel, air, and spark accordingly. To simplify things, the initial setup is done by inputting basic known features of the engine such as compression ratio, displacement, camshaft specs, and fuel pressure into a Windows-based computer. Then the ACCEL software will determine a base-line program for the ECM that will get the engine running. After that it is up to the tuner to dial in the best program. This crate engine from Scoggin-Dickey comes with a base program that should be roughly 405 hp and 480 lb-ft of torque. Then once it's installed in your vehicle you can turn the key and drive. If you want even more, just take it to one of the many Engine Management Installation Centers (EMIC) across the U.S. and Canada where ACCEL/DFI has trained technicians who can always help you. Or you can get a Windows-based laptop computer, load the software, and begin making adjustments on your own. Since the program can be saved on your ECM or laptop, you can always return to those initial settings.

DYNO RESULTS*
RPM Horsepower Torque (lb-ft)
3000 262.3 459.2
3200 283.6 465.5
3400 301.8 466.2
3600 328.5 479.3
3800 355.8 491.8
{{{4000}}} 373.7 490.7
4200 388.2 485.5
4400 401.7 479.4
4600 410.4 468.5
4800 413.4 452.4
{{{5000}}} 410.1 430.8
5200 406.1 410.2
5400 400.7 389.7
5600 392.5 368.1
5800 386.5 350.0
*Peak values are shown in yellow

Dyno Mighty
Our first dyno pull on the computer-written program gave us 395 max horsepower and 473 lb-ft of max torque. Not bad for preliminary testing, especially since we expected the horsepower numbers to be lower and torque numbers higher than GM's carbureted 425/449 catalog digits. Since I was trying to learn all the available options for the program, as well as what all could be adjusted, Tracy Dennis took the time to run 13 different dyno pulls on the 383. And since the laptop could record the different results of each pull, he was constantly adjusting numbers to try and get more power. I followed along and, by the end of it, was catching on, barely. We eventually surpassed even Scoggin-Dickey's claimed numbers on this crate engine with 413 hp at 4,800 rpm and 491 lb-ft of torque at 3,800 rpm. Better yet was the fact that the torque curve was flatter than the military haircuts my dad gave me growing up. In fact, we couldn't even get the dyno to adequately brake the engine under 3,000 rpm since there was so much torque. Check out the numbers below and you will see that this engine should pull hard and still peel out with the big dogs. Now that sounds like fun.

Sources

Chevrolet Performance Parts
Detroit, MI 48232
800-577-6888
www.gmperformanceparts.com
Sunset Racecraft
Lubbock, TX 79411
806-747-2700
http://www.sunsetracecraft.com
Sanderson Headers
www.sandersonheaders
CVR Products
www.cvrproducts.com

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