One of the really cool things about magazine engines is that we continually get to "revisit" them and monitor their progress. One such project was first seen in our June '01 issue, called "A Stroke of Genius." It involved the buildup of a 391-cid small-block using an effective, yet unconventional, offset-ground crankshaft and rods with the small 327 journal size to yield the extra cubic inches. We followed the buildup over the next two issues and finished with a dyno flogging at Vrbancic Brothers Racing Engines in the August '01 issue.
Then, we revisited the 391 once again in the November '01 issue where we abused it on the dyno in an attempt to see just how much nitrous we could pump into a street motor before it blew up. That test revealed some interesting results. The most important thing we got out of it was that nitrous motors really need some high-octane race gas to live with anything above a 150hp shot. Due to our insistence on running only 91-octane fuel, the engine broke and was summarily shelved for several months until we could figure out a cool approach for its next story. That begins now.
We pitched the idea of setting up the "Genius" stroker to test some Holley street EFI equipment to its original builder, Hye-Tech Performance in La Puente, California. They agreed that it would be a cool idea and began rebuilding the engine near to its original, pre-nitrous-destruction specs. That means a new set of 10.4:1 JE pistons were hung off the original C.A.T. Power 5.7-inch rods with a new Total Seal gapless ring set replacing the damaged pieces. Clevite supplied some new rod and main bearings, and the bottom end was complete.
Hye-Tech Performance rebuilt the long-block using all the same components as before, inclu
Since EFI is currently the hot ticket when it comes to making everyday-reliable street power, we thought we'd add a new Holley Stealth Ram to this stroker to see what it's made of. One thing that had to be changed to work best with the new EFI system was the cam because the solid nitrous grind we had in it before just wouldn't do. So a call was made to Lunati for one of their hydraulic roller EFI grinds, since that'd be a cool way to cruise. With the new cam in the block we tackled installing the Holley Stealth Ram kit. After reading the Holley instruction manual, figuring out where each of the multitude of wires plugged in was fairly simple. Then, to see what this thing could do, we trucked it back over to Vrbancic Brothers Racing and bolted it onto the DTS dyno for its third flogging.
There's another benefit to building magazine test engines. When the people that make the parts we're testing, Holley in this case, want to be sure that we get the best results possible, they'll send a representative out to "supervise" our test sessions. We love that because it means we've got another more-experienced soul in the dyno cell to bounce questions and ideas off of, and if we run into problems, they'll have a much better chance of getting them corrected back at the shop than we would on our own.
For this test, Holley's Doug Flynn came armed with his mighty laptop and was able to tune some impressive figures from our otherwise docile Mouse. The thing to remember with the Stealth Ram kit is that it's not designed to make gobs of power. Rather, its sole purpose is to give its owner smooth cruising, reasonable economy, and easy tunability, all in a package that anyone with a toolbox and a laptop could install and tune. Don't get us wrong; at first this thing was a bit hard to figure out, but once we got all the wires plugged into their correct spots and fired it up, Doug showed us that dialing it in was a piece of cake.
Installing the Stealth Ram intake manifold was no more difficult than installing a regular
The injectors get pushed into the cast-in bungs on the intake manifold, and the fuel rails
The plenum box sits on top of the runners and needs to have this vacuum hole plugged if yo
This is the power we made using a relatively small hydraulic roller cam with 1.6:1-ratio r
The twin throttle body gets bolted onto the plenum next and the Idle Air Control Valve (IA
Note how the horsepower smoothly kept climbing until it peaked and, even then, just barely
Two gaskets are supplied to seal the plenum to the base. Don't use any sealer on them. Jus
The cool thing about tuning an EFI motor is that you do it while the engine is running. Also, the perfect tune-up is usually just a few keystrokes away, but it may take a while to get there if you're not careful. That's because it's just as easy to go way off base with your fuel map as it is to get the thing right in a matter of minutes. Holley has gone to great lengths to supply what it feels will be a reasonable fuel map for each particular EFI kit, but just like with a carburetor, there's always some power to be found with tuning somewhere. However, unlike tuning a carb with traditional jets and air bleeds, tuning EFI takes only seconds, and the results can be felt instantly.
In the end, this stroker Mouse made some great power, and the fact that it idled incredibly smooth at just around 600 rpm points to its being a great daily driver.
The throttle position sensor (TPS) goes on the side of the throttle body and tells the com
|ENGINE SPECS |
|Bore/stroke/cid: ||4.030/3.832/391 cid |
|Crank: ||C.A.T. 4340-steel |
|Rods: ||C.A.T. 4340-steel 5.7" |
|Pistons: ||JE forged 10.4:1 |
|Rings: ||Total Seal gapless |
|Bearings: ||Clevite "H" series |
|Camshaft: ||Lunati hydraulic roller PN 50156 |
|Cam Specs: ||232/242 degrees at .050 |
| ||290/300 degrees advertised |
| ||.510/.525 lift |
| ||110-degree lobe separation |
|Oil system: ||Milodon stroker pan and |
| ||HV pump |
|Heads: ||Holley Street Avenger |
|EFI: ||Holley Stealth Ram |
|Ignition: ||Holley Annihilator |
The Holley ECU monitors coolant temp as well as both ambient and manifold air temp. It can
Before randomly trying to figure out where each wire goes, sit down and read through the e
Not only does EFI have lots of electrical connections, there are also lots of vacuum conne
Sitting to the left is Holley's EFI expert, Doug Flynn, who flew out to California to help
Even though the Holley ECU controls the timing advance curve, you still have to set it fir
We had to try one old hot rodder's trick to see if we could squeeze out more power. We swa
|RPM || TQ || HP |
|2600 || 401 || 199 |
|2800 || 424 || 226 |
|3000 || 439 || 251 |
|3200 || 444 || 271 |
|3400 || 444 || 287 |
|3600 || 441 || 302 |
|3800 || 445 || 322 |
|4000 || 455 || 347 |
|4200 || 461 || 368 |
|4400 || 463* || 387 |
|4600 || 461 || 403 |
|4800 || 457 || 418 |
|5000 || 449 || 427 |
|5200 || 434 || 430 |
|5400 || 429 || 441 |
|5600 || 416 || 444* |
|5800 || 401 || 443 |
|6000 || 383 || 438 |
|Avg || 436 || 356 |
|Max* || 463 || 444 |
C.A.T. Power engine parts
345 Cloverleaf Dr., Suite C
Lunati Cams A Holley Performance Products Company
4770 Lamar Ave.
Holley Performance Products
1801 Russellville Rd.
Bowling Green, KY 42101
13912 Valley Blvd., Unit A
Vrbancic Brothers Racing
1463 E. Philadelphia