This was a lot tougher than we thought. A long time ago, Speed-O-Motive built a test engine for us whose only purpose in life was to live on the dyno and test our hair-brained ideas to make more power. While being a very tough little brute, its size was nothing of interest, just 355 cid. Kinda' just like you'd find under the hood of many hot rods today. What made this mule different from all the rest was the sum of its parts. The toughest in the land they were. It was built to take tons of abuse and live through thousands of dyno pulls before finally being laid to rest.
Up until the time we wanted to see just how much nitrous we could throw at it, it stayed pretty healthy. The little 355 had made as much as 585 hp with a Weiand Hi-Ram and 700 hp with an ATI blower and Accel DFI. But now it was going to be a 12.5:1 compression pushing-the-limits pump-gas-burning motor using only bolt-on parts. By that we mean that none of the parts we installed had ever been modified to work, fit or make more power. In other words, every part in or on this baby came right off the shelf and right out of its box. That's not too bad when all things are considered. But could we make 1,000 hp with squeeze? Or how about 900, or maybe just 800 hp? There was no way to know unless we tried, so we called up the crew at Edelbrock and had them send over one of their very trick double-crossbar nitrous plates worth some serious horsepower to see if we could hit the sky.
BUILDING THE MINI BEAST
First, in order for this little nitrous beast to live and make power, a few things needed to be installed. In addition to the tough rotating assembly, including a forged Lunati crank, billet Lunati rods, and custom domed pistons, the iron four-bolt Mowtown block meant we wouldn't have to worry about the bottom end coming apart any time soon. A complete Moroso oiling kit also helped ensure our Mouse would live. Up top we asked COMP Cams to grind a custom nitrous roller cam with lots of duration and lift and a 4/7 lobe swap to enhance power a little further (actually, COMP made an even bigger cam for us to try but it wouldn't fit because valves hit the pistons). But other than the really big cam we special ordered, all the engine's parts came right out of Jeg's catalog.
When running high-power nitrous in a motor like this, there's really no need to run a small carb and/or small intake manifold. So we asked Edelbrock to also supply its Super Victor intake setup for a Holley Dominator carb. Then the guys at The Carb Shop screwed together a nitrous-specific Holley Dominator (PN 9375) that would flow about 1,100 cfm. All of this was bolted on top of a pair of Edelbrock's 215cc Victor Jr. heads wearing COMP Cams 1.6:1 Magnum roller rockers. Armed with our mighty motor, a little 91-octane pump gas, and lots of 114-octane race gas, we headed over to Speed-O-Motive's DTS dyno to see what we could squeeze out of it.
While it can be noted that on a bigger engine, or perhaps one even more highly specified for nitrous use, more power might've been made. But we're here to tell you that 800 hp is possible from an otherwise pump-gas-using 355 small-block. It's not easy, and it's definitely not cheap, but it can be done. And the coolest thing about all this is, like we said before, all of these parts are true bolt-ons, so if you can torque a wrench, you can build this brute. Of course, the key to our giant power was by far the Edelbrock N2O plate with its four solenoids and twin-crossed spray bars; it's capable of making tons of go. But, use caution whenever you're trying to squeeze so much power out of such a small package or you'll suffer a fate you may never care to see.
The Edelbrock Victor Jr. double-crossplate...
The Edelbrock Victor Jr. double-crossplate nitrous system is very effective at evenly distributing the fuel/N2O spray pattern across the intake plenum.
Check out how the N2O spray...
Check out how the N2O spray bar's holes are angled down (top bar) and the fuel holes shoot straight out. Also note what we would have liked to address had we not insisted that all parts for this test come right out of the box. The Edelbrock Super Victor manifold has a cloverleaf plenum shape that may interfere with the outward most spray patterns (see arrow).
In order to build an engine...
In order to build an engine to survive over 300 hp worth of nitrous we added the best-of-the-best, including parts from AE Clevite, ARP, COMP Cams, Edelbrock, Lunati, Mr. Gasket, MSD, Moroso, Total Seal, and World Products to this little 355-cid mule.
We pulled out all the stops...
We pulled out all the stops in order to make the most power possible without the nitrous first because that's how we feel is the best way to build an engine. This Moroso 4V vacuum pump added around 15 ponies.
Royal Purple synthetic 10W-40...
Royal Purple synthetic 10W-40 oil was used due to its high temperature tolerance.
Oil temps can skyrocket on...
Oil temps can skyrocket on a dyno test like this since there's no air moving across the oil pan to cool it. We plumbed a Flex-A-Lite oil cooler with built-in fan into the Mouse through Earl's -10AN lines; this kept temps below 200 degrees.
The Carb Shop-prepped Holley...
The Carb Shop-prepped Holley list 9375 Dominator needed a few jet adjustments to optimize power.
This industrial bottle warmer...
This industrial bottle warmer kept our Nitrous supply bottle up to temps, which equalized supply pressure for every pass. Our trusty Raytek temp gun helped us monitor things.
Speed-O-Motive's DTS dyno...
Speed-O-Motive's DTS dyno runs an MSD Digital 6 ignition, which gave us the ability to program in up to 9.9 degrees of ignition retard when we hit the N2O button. Any additional timing we wanted to pull out came from the distributor.
One of the things we really...
One of the things we really liked about the Edelbrock plate is that it's only about 1/2-inch-thick, making it easier to fit under hoods. Most plates at this power level are around 1-inch-thick.
To keep things under control...
To keep things under control when we hit the button, an Edelbrock Digital nitrous controller was employed, softening the initial hit to go easy on the engine components.
Edelbrock's clearly labeled...
Edelbrock's clearly labeled connections on the N2O plate make swapping jets easy. There's good access to all the fittings too, even though the thin plate makes things just a bit tight.
Timing is everything, and...
Timing is everything, and we monitored the amount of retard on a "dry run" without nitrous before going for the gusto.
Naturally Aspirated power 91-octane pump gas
To properly evaluate the benefit of the big Edelbrock nitrous plate we first had to evaluate the performance of our little motor on its own. So we tuned it Naturally Aspirated (N/A) on the DTS dyno first. It worked well, but we really thought we'd make 600 hp without the squeeze. Oh well, still pretty damn good for a bolt-together 355-cid pump-gas Mouse.
|RPM ||TQ ||HP |
|3,000 ||376 ||215 |
|3,500 ||395 ||263 |
|4,000 ||405 ||308 |
|4,500 ||423 ||362 |
|5,000 ||443 ||421 |
|5,500 ||460 ||482 |
|6,000 ||453 ||517 |
|6,500 ||445 ||551 |
| || || |
|MAX ||461 ||563 |
|AVG ||427 ||411 |
EDELBROCK NITROUS POWER
114-octane race gas #54 fuel and #54 nitrous jets
When it came time to hit the squeeze, we stayed on the conservatively wild side for safety. After all, we were only looking to make 800 hp and we just got there with this hit. Note the lower initial power before we hit the N2O button. This is a result of us retarding the distributor 4 degrees. To augment the max 9.9 degrees, the MSD box could pull out, giving us a safe 14-degree total retard when we hit the squeeze. Also notice how the extra N2O power gradually ramps up starting at 4,000 rpm when we hit the button on the Edelbrock progressive digital nitrous controller. This is to save the bottom end of the motor from the incredibly hard hit with the dyno fully loaded and would also indicate good traction control at the track if this setup were in a car.
|RPM ||TQ ||HP |
|3,000 ||368 ||210 |
|3,500 ||388 ||259 |
|4,000 ||410 ||312 |
|4,500 ||596 ||510 |
|5,000 ||746 ||711 |
|5,500 ||741 ||776 |
|6,000 ||698 ||798 |
|6,500 ||646 ||799 |
| || || |
|MAX ||750 ||800 |
|AVG ||580 ||573 |
|ENGINE SPEC SHEET |
| || |
|Bore / Stroke / CID: ||4.030 / 3.48 / 355 cid |
|Bearings: ||Clevite |
|Block: ||Mowtown iron four-bolt |
|Cam: ||COMP custom roller (265/278 at .050, 293/308 adv, .688/.696 lift w/ 1.6 rockers, 115 LS |
|Carb: ||Holley (PN 9375) built by The Carb Shop |
|Compression ratio: ||12.5:1 |
|Connecting Rods: ||Lunati billet 5.7-inch |
|Crank: ||Lunati forged 3.48 stroke |
|Dampener: ||Fluidampr |
|Distributor: ||MSD |
|Fuel: ||Shell (91-octane N/A, 114-octane w/ N2O) |
|Head Gaskets: ||Mr. Gasket MLS |
|Heads: ||Edelbrock Victor Jr. 215cc (64cc chamber) |
|Headers: ||1 3/4-inch Hooker dyno headers |
|Ignition: ||MSD Digital 6 |
|Intake manifold: ||Edelbrock Super Victor (PN 2970) |
|Lifters: ||COMP solid roller |
|N2O System: ||Edelbrock Victor Jr. |
|Oil System: ||Moroso kit |
|Pistons: ||Lunati forged |
|Plug wires: ||MSD |
|Pushrods: ||Manley 3/8-inch |
|Retainers: ||COMP Cams Ti |
|Rings: ||Total Seal gapless top |
|Rockers: ||COMP 1.6:1 Magnum |
|Spark Plugs: ||Autolite (PN AR3923 motor, AR3932 w/ N2O) |
|Valve Springs: ||COMP Cams (PN 999) |