[w72]

Sniper EFI, Performer RPM intake, shaker hood. Unholy trifecta? Has anyone made this happen?

I'm about to do this on a virgin 1978 W72 4-speed car. I plan to put all the valuable vacuum hoses into carefully-labelled boxes so that when I'm dead, another person can obsess over Quadrajets and pretend to enjoy 220hp. In the meantime, I need a Trans Am that can outrun my wife's Subaru.

Any advice on fuel system plumbing, air cleaner abuse, where to run lines and harnesses, where to mount ignition stuff to avoid RFI issues, etc... would be helpful.

Even if you've tried this and failed, or looked into it and decided against it, please share the reasons.

[Steve C.]

https://butlerperformance.com/i-2445...tegory:1234772



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[78w72]

Originally Posted by w72

In the meantime, I need a Trans Am that can outrun my wife's Subaru.

sorry i dont have any advice on that combo... but just an efi & rpm intake is not going to give a stock 78 400 much more power than the q-jet & stock intake. can make a lot more power for a lot less money with some other more common upgrades. will take some other changes to beat your wifes subaru!

[Skip Fix]

Measure the height on the TB then compare to Qjet/Holley height. RPM is supposed to be something like 1 1/4 taller?

I'll agree it will take a little more than that to beat the Subaru esp if it is a WRX. My 78 orinignal 180 HP motor with a cam change was just in the high 14s.

[Steve C.]

"but just an efi & rpm intake is not going to give a stock 78 400 much more power than the q-jet & stock intake"

"I'll agree it will take a little more than that to beat the Subaru esp if it is a WRX."

Good comments.

Related and of interest, years ago in Hot Rod magazine they took a stock junkyard 400 engine out of a '73 LeMans. Then they spec'd out a series of modifications in an attempt to wring as much power per dollar possible out of the engine. First stage they cleaned it, painted it and changed the oil and filter then got it running on a engine dyno as a baseline. Second stage was a change to headers and metering rods on the stock Q-jet. Third stage was ignition mods. Fourth stage a cam and valvetrain. In the fifth stage they rebuilt the engine. Once fresh the next stage was to change the intake manifold. Here they made note the factory cast-iron intake was a very good match to the stock heads. That was why they performed exhaust, ignition and cam upgrades before turning their attention to the intake. It was then in stage six they changed to a Performer RPM intake.... result, the RPM intake combo performed about the same as the stocker at the bottom of the test range but pulled away in the midrange and on top end gaining 11 horsepower at a higher peak rpm, only after the prior changes..


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[JLMounce]

The TBI units are about the same height as most common carbs. Your issue is going to arise with the performer RPM. So what I'd do is measure the carb that's on it right now, then get the diminsions for the EFI you want to run as well as the added height of the RPM intake. That difference is how much of a drop base filter you're going to need to use.

There are a couple companies I believe that make a drop base for the trans am shaker. The issue you're going to run into there however is the fuel lines exiting the throttle body. Most people use a 45 degree fitting here as it keeps the fuel lines from being bent at an angle that could cause a kink. Because they jut out a ways from the throttle body, most drop base's will hit them as a result.

Here's what I'd do to combat that issue.

Run a corvette style fuel system with a pump in the gas tank. You use the corvette fuel filter which has an internal regulator set at 58psi where most of these systems run. You place this back by the tank and run the feed from the pump and the return from that fuel filter back to the tank. You then run a single fuel line, dead headed to the throttle body. You'll want to use several 90 degree AN fittings here to get the line and fitting as close to the body of the EFI unit as possible.

For ignition, you need to run resistor type plugs and RFI suppressed wires. Specifically the tach wire to the system needs to be routed as far away from the distributor, plugs and plug wires as possible. If you have to run it close, use some shielding on it.

Other notable things that help is proper oxygen sensor location and installation. Most of these kits come with an o2 bung that can be secured with clamps. These don't work well and only do so enough for you to drive the car to an exhaust shop and have it welded in. Don't rely on that thing sealing up well enough to provide accurate fueling.

The 02 Sensor should be placed in a position that it sees the maximum amount of cylinders firing, as early as possible after the exhaust leaves the cylinder. If you run headers, that means in the collector about an inch past the junction of the tubes. If you run manifolds with down pipes, you can place it a couple inches down from the manifold outlet.

There needs to be a minimum of 18" of sealed pipe aft of the oxygen sensor. You also need to verify that any gasket, exhaust coupling and the manifold or header is free of leaks. 90% of people that have trouble with these systems running poorly have vacuum and exhaust leaks that cause the system's sensors to receive false data and fuel incorrectly as a result.

That's about it though. It's all about the installation on these things.

As others' have noted, this change isn't going to let you outrun your wife's Subaru. I still think you'll enjoy the change though!

[grivera]

Not sure if OP already has the Sniper. If not, have you considered using a factory intake and the the Quadrajet version of the Sniper which is made for a spread-bore intake?

https://www.holley.com/products/fuel.../parts/550-869

[w72]

Thank you for the replies. I do not expect a power increase from EFI and an intake swap.

I have a set of Butler-prepped heads and intake ready to bolt on. Obviously, a cam swap is in order. Also have the PTFB drop-base air cleaner, I expect I will have to modify it for fuel line clearance. I plan to replace the tank with a unit from Tanks Inc. and run new hard lines to the front.

The Quadrajet version of the Sniper appears to be physically larger than the standard 4150 Sniper, giving even less room for lines under the air cleaner, though I'm sure it could work with the stock intake. The inlet and outlet situation on the QJ version doesn't seem to offer the same flexibility.

I know a lot of LS-swaps utilize the Corvette filter/regulator combo. I would prefer not to run the Sniper in a deadhead configuration, especially with the less-than-ideal set of 90* fittings that will be required for line clearance.

[Lee]

I have the FAST throttle body (2.0 style), Performer intake, and a factory housing, and my shaker fits o.k. I took the factory weatherstripping off, and replaced it with some softer, lower-profile foam strips. This is on a '73 T/A clone.

I also have Larry Navarro's WFO airfilter set up, but the factory housing gives me a slightly better fit with the Performer.

[joe69judge]

I put the Holley Sniper EFI (quadrajet style) systen with a MSD Dual Sync electronic controlled timing, stock intake, new gas tank kit all from Holley, on my 69 gto. The car is faster, runs smoother. and n more stalling at a light. It chirps every gear. It took a little while to understand and setup but well worth it.

[Singleton]

Originally Posted by w72

I would prefer not to run the Sniper in a deadhead configuration, especially with the less-than-ideal set of 90* fittings that will be required for line clearance.

If you're worried about reduced flow with 90 degree fittings, don't be.
https://www.youtube.com/watch?v=CvweWT5zwHs