Subscribe to the Free

Holley EFI System - A Stroke Of Efi Genius

We Test The Hye-Tech Performance 391 Stroker With Holley's New EFI

Nov 1, 2002
Sucp_0211_01_z Holley_efi_system Throttle 2/17

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.

Sucp_0211_03_z Holley_efi_system Port 3/17

Hye-Tech Performance rebuilt the long-block using all the same components as before, including the same Valley Head Service-ported Holley aluminum cylinder heads. The only component changed was the Lunati cam.

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.

Sucp_0211_11_z Holley_efi_system Seal 10/17

Two gaskets are supplied to seal the plenum to the base. Don't use any sealer on them. Just four stainless steel bolts are needed to hold the top down.

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.

Sucp_0211_12_z Holley_efi_system Throttle_adjustment 11/17

The throttle position sensor (TPS) goes on the side of the throttle body and tells the computer how far the throttle blades are open. This can be roughly translated into how much power your foot wants the engine to make.


JE Pistons
Huntington Beach, CA 92649
Holley Performance Products
Bowling Green, KY 42101
Vrbancic Brothers Racing
Total Seal
Phoenix, AZ
(800) 874-2753
Hye-Tech Performance
La Puente, CA 91746
C.A.T. Power engine parts
Baldwin Park, CA 91706



Connect With Us

Get Latest News and Articles. Newsletter Sign Up

sponsored links

subscribe to the magazine

get digital get print