It used to be that power-hungry hot rodders would stay up late working in their garage, assembling an engine under the glow of a dangling light bulb. With advice gleaned from friends, magazine articles and even stuff overheard at drag strips, guesswork was as much of a contributing factor to performance as was camshaft selection.
Today, however, with the advent of crate engine packages, the only guesswork is what day the box full of power will show up at our driveway.
Don't get us wrong. We're big supporters of the crate engine, as it has given enthusiasts access to proven combinations and prices that would be almost impossible to beat if the parts were purchased individually-this is especially true of GM's line of crate engines. But the crate engine trend also has spawned another twist in the hobby-the install-it-and-close-the-hood syndrome. Besides, say, adding different valve covers and the obligatory air cleaner, most enthusiasts simply drop their crate engine in place and hit the road.
We rarely see one that's been modified to make more power, which seems a little odd. Certainly, the foundation is already in place for even greater power increases.
That's exactly the reasoning behind Martin Motorsports' recent GM Ram Jet 502 engine project, which was initiated by a customer with a street/strip vehicle who leaned a lot closer to the strip. He already had the engine, but figured it needed more power to be competitive.
One of the reasons for starting the project with an already-assembled crate motor was beca
"The owner also wanted the engine to stand out in the crowd," says Harold Martin, of Martin Motorsports.
In a nutshell, the engine was disassembled and rebuilt to enhance its breathing with a new cam and port work. The assembly was also blueprinted and a wet-flow nitrous system was added. A FAST controller replaced the factory computer because of its capability to control timing and fuel on the higher-horsepower engine. It also allows for wide-band tuning.
Off the bottle, the bolstered big-block cranked out 580 hp and 583 ft-lb of torque on the engine dyno; an increase of nearly 80 horses over the crate engine's stock 502 rating. Torque is up almost 20 ft-lb over the stock 565 rating, too. When sprayed, the giggle-gassed Rat's output jumped to 861 horsepower and just under 900 ft-lb of torque. This is terrific output, especially for an engine the owner insisted will see street service.
Crate RebuildAlthough it seems incongruous-and expensive-to take apart and re-assemble an engine that was already built, Martin says the long view of the project points to overall savings.
"The Ram Jet 502 is a great engine to start with," he says. "All the bottom end parts-the crank, the rods, the pistons-are forged. It also has good cylinder heads."
True enough, but most of those parts are available separately. Martin, however, says the economic advantage lies in the details.
"By starting with the crate engine, you also get all the ancillary items that would nickel-and-dime a ground-up project to death, especially all the fuel injection parts," he says. "The injectors, wiring harness, sensors, etc.-they're already included."
With a factory torque rating of 565 ft-lb at 3,200 rpm, GM builds the Ram Jet 502 with a t
Opening up the crate engine, then, should pay significant dividends. That seems to be the case with this 502, which jumped about 80 horses with the following upgrades:
*Cam changed from .527/.544 lift and 224/234 duration to .566/.566 lift and 296/302 duration, with a 110-degree centerline.
*Comp Cams 1.7-ratio roller rocker arms (stock does not include roller arms).
*Comp Cams #924 valve springs; dampened two-spring design with 115-pound seat load and a 322-pound open load.
*"Cleaned up" heads, including port-matching with intake manifold.
"The modifications simply allow the engine to push more air," says Martin. "They also allow the engine to rev a little higher, but not much. It's not an RPM motor."
Actually, it's not the valvetrain or reciprocating assembly that is the 502's effective rev limiter; it's the throttle body.
Like the crankshaft, the factory-installed forged steel rods and coated, forged aluminum p
One of the changes made to the Martin Motorsports Ram Jet engine was replacing the stock c
The stock aluminum cylinder heads were retained for the project. They boast big, 2.25-inch
Martin Motorsports did a little grinding the stock heads. They cleaned up the ports and po
"Its limit is simply less than the engine's capability," explained Martin. "The engine would definitely make more power with a bigger throttle body."
Nevertheless, the breathed-on 502 comes alive with the wet-flow nitrous system, plumbed into the intake runners on the Ram Jet's tunnel-ram-style intake manifold. The wet-flow design is more complex than a simple dry-flow system, but it allows for increased tuning flexibility at the racetrack.
Controlling the nitrous system, and the related fuel and timing deliveries falls to the FAST controller. It's a speed-density-type system that is more programmable than the Ram Jet 502's stock controller.
"We could have left the stock controller in place if we used a dry-flow nitrous system," says Martin. "But the Fast controller gives more tuning flexibility with trimming fuel and timing."
Surprisingly, the Ram Jet 502 does not come with roller-tip rocker arms. Martin Motorsport
It also allows for wide-band tuning, so oxygen sensors were screwed into the headers. The additional tuning capability of the FAST ECU gives the engine an incalculable edge in long-term performance-and Martin says longevity was definitely a priority.
"This is a street/strip engine that has to last the customer a long time," he says. "It's not something that's going to be torn apart after every run, let alone after every season."
Indeed, Martin Motorsports' tuning and dyno testing delivered some impressive numbers with admittedly conservative parameters. The non-nitrous dyno pulls were made with 92-octane pump gas and 36 degrees of timing. When sprayed, timing was dialed down to 12 degrees and 110-octane gasoline was used.
"It makes great numbers and should last a long time," says Martin.
The nitrous system and blueprinting-type rebuild of the engine were the biggest chunks of the cost of this engine project, which added roughly 50 percent on to the cost of the Ram Jet 502's over-the-counter price.
As always, value is in the eye of the beholder, but we think this modified 502 represents a comparative bargain when judged against custom-built racing engines.
The modification of crate engines might just take steer the hobby in a slightly new direction.
Dyno sessions with the revamped Ram Jet 502 saw a 78hp normally aspirated jump over stock, from 502 to 580. Torque increased to from 565 to 583 ft-lb These numbers were made on 92-octane fuel and 36 degrees of total advance. Tests with nitrous were performed with 110-octane racing fuel and a very conservative 12 degrees of timing, resulting in 861 hp and 898 ft-lb of torque. This performance can at roughly a 50-percent premium over the cost of the base Ram Jet 502 engine package.
Air is drawn in to the 502 through the same L98-style throttle body that comes stock on th
The 502's Ram Jet manifold was plumbed for a "wet" nitrous system-a system that introduces
To accommodate the wet-flow nitrous system, the Ram Jet manifold was drilled to accept bun
Because the engine's new FAST controller allows for wide-band tuning, oxygen sensors were
Although the Ram Jet 502's stock electronic controller probably would have handled the eng
Another item retained from the basic crate engine package was the HEI-style distributor.
|Martin Motorsports Ram Jet 502 |
|Engine type ||OHV V-8 with iroblock; four-bolt main bearing caps |
|Bore x stroke (inches) ||4.446 x 4.000 |
|Displacement (ci/liters) ||502/8.2 |
|Crankshaft ||Forged steel |
|Connecting rods ||Forged aluminum I-beam |
|Pistons ||Forged aluminum |
|Compression ratio ||9.6:1 |
|Camshaft ||Hydraulic roller; .566/.566 lift; 296/302 duration; 110-degree centerline |
|Cylinder heads ||Aluminum; oval-port design; 110cc chamber volume |
|Valves (inches) ||2.25 intake, 1.88 exhaust |
|Valve springs ||Comp Cams #924 |
|Rocker arms ||1.7-ratio roller-type |
|Fuel delivery ||Electronically controlled port fuel injection |
|Ignition ||HEI-type |
|Electronic controller ||Speed density with wide-band (closed loop) capability |
|Power adder ||Nitrous oxide "wet" system |
|Horsepower without |
|power adder ||580 |
|Torque without power adder ||583 ft-lb |
|Horsepower with power adder ||861 |
|Torque with power adder ||898 ft-lb |
55390 Lyon Industrial Dr.
GM Performance Parts