Installing The GM Ramjet 350

When it comes to research, engineering, and design, few aftermarket companies can match the resources of an OE manufacturer, especially General Motors. When the General wants to, it can really put on a show by dipping into its enviable parts bin and combining tried-and-true components into a kick-ass package. A case in point is GM Performance Parts’ Ramjet 350 crate engine—the first turnkey electronically fuel injected crate engine available from a Big Three performance division.

The Ramjet has been on the market for a couple of years now. We got this Ramjet more than a year before this story was written from Scoggin-Dickey Parts Center, one of the nation’s largest GM Performance Parts distributors, which sells them for just under $4,500. Since then, Scoggin-Dickey’s Nicky Fowler says Ramjets have been flying off the shelves and into the engine bays of everything from street rods to classic pickups to musclecars. With a rated output of 350 hp at 5,200 rpm and 400 lb-ft at 3,500 rpm, it may not be the rowdiest, highest-revving, street stomper you can imagine, but it’ll move even our 4,000-pound ’65 Biscayne along at a steady clip. It also starts, idles, and runs like you’d expect a factory engine to perform, which is nice in everyday L.A. traffic. The Ramjet’s MPFI-3 fuel/spark management system is based on the marine L31 engine and uses many of the same sensors as late-model Vortec-equipped GM C/K pickups, so service parts are available at any GM dealer or auto parts store.

Engine Installation

Installing the Ramjet 350 is as simple as swapping any other Gen-II one-piece rear-main–seal small-block into a GM car. Headers, motor mounts, and most other accessories from a traditional first-gen small-block will bolt right up. The Ramjet is shipped with a flywheel that accepts up to an 11-inch clutch, which is exactly what we were running, so that part of the swap was a breeze. We bolted our Hays clutch, GM bellhousing, and Richmond Super T10 four-speed up in minutes. If you intend to run an automatic, you’ll need a flexplate designed to work with the ’86-and-later one-piece main-seal– style crankshaft. Our motor mounts and headers also bolted right up, so we had the engine swapped into the car in a few hours after yanking the old small-block. The rear-sump oil pan that comes on the engine is designed for truck and marine usage, but easily cleared our Biscayne’s crossmember. GM recommends using the ZZ4 oil pan (PN12528916) in applications where the supplied pan doesn’t fit. Neither of these pans will fit ’62-’67 Novas, however, which may require a custom oil pan.

We did run into one odd problem, however, when we tried to swap our short water pump in place of the long- style pump that comes with the engine. Late-model Gen-II small-blocks use an O-ringed composite plastic timing chain cover that is attached to the block with shouldered bolts. One of the bolts interfered with the casting body of the pump, preventing it from bolting down against the block. We had to file the head of the bolt down quite a bit and grind a minor clearance into the pump itself to make it fit. This is a problem that applies to any small-block using the plastic cover, but is not an issue for any ’69-and-later long-water–pump application. Other than that, all our existing brackets and pulleys bolted on and lined up.

Plumbing the Fuel System

The Ramjet instructions recommend adapting the in-tank electric fuel pump for a Vortec truck or an LT1 Camaro or Firebird. That’s a great idea, except neither of those gas tanks will “bolt in” to a ’65 Impala, or probably any other musclecar for that matter. There are several good options for building an EFI-compatible fuel system, some of which are discussed in other articles in this issue. Basically, what you need is a system that provides some sort of sump or internal baffle inside the tank so the fuel pickup doesn’t become easily uncovered when the fuel level is low. You also need a way to return the fuel that’s bypassed by the regulator back into the tank. Then you simply plumb the lines for supply and return. For the Ramjet, we chose what we believe to be the simplest and least expensive option: installing a sump in the stock tank and running an external electric fuel pump. This was appealing in part because the Biscayne’s original tank had no less than seven puncture repairs and still leaked like a sieve, so it needed to be replaced anyway. We ordered a new replacement tank from Classic Industries and sent it off to Aeromotive to have a baffled sump installed. When it returned, we took it to a local welder to have an AN bung welded in for the return line. Bolting it into the car took about three minutes.

To supply fuel to the engine, we enlisted Aeromotive’s PN 11106 EFI inline electric fuel pump, which is capable of supplying up to a 700hp engine. This is far in excess of the minimum 35 gph at 45-55 psi required by the Ramjet to operate, but overkill is usually a good thing in an electric fuel pump as long as it is still capable of running in continuous duty on the street. Dirt and grit is a major cause of malfunction in electric fuel pumps and injectors, so per the company’s recommendation, we ran a course 100-micron filter on the inlet side and a fine 10-micron filter on the outlet. We plumbed the rest of the fuel system with braided stainless hose and fittings from Goodridge.

Wiring

Wiring the Ramjet engine controller harness is simple. Only four wires need to be hooked up: A power lead to Battery positive, which we wired with an inline 30-amp fuse to protect the circuit; a 12-volt keyed ignition source run from the fuse box or ignition switch; fuel pump power; and fuel pump ground. A tachometer lead is supplied if the car is equipped with one. Additionally, the harness itself must be grounded to the back of the cylinder head. The harness has built-in ignition and fuel-pump relays that can be mounted out of the way on the firewall. After a few minutes cranking to prime the electric fuel pump, the Ramjet fired right up and purred like a kitten. There was just one problem—it wouldn’t shut off when we switched the key off! See the “It Keep Running” sidebar for an explanation and the easy 59-cent solution to this puzzling problem.

Conclusion

Converting to electronic fuel injection can be a daunting proposition for a first-timer unsure of the intricacies of this “newfangled” technology. With its supplied computer and wiring harness, the Ramjet is a true turnkey, plug-and-play EFI crate engine. It fired up and ran flawlessly right out of the box with no tuning required. However, the Ramjet’s computer control, developed for use in boats, is a completely sealed unit, and it’s not easily reprogrammable. This means you can’t go in and change the cam or heads or add nitrous or a blower and reprogram the fuel and spark curves. The Ramjet is what it is and that’s that, which is a great crate package for anyone who wants the convenience and drivability of EFI without major cost and hassle.