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Old 2016-08-19
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Exclamation A Shaker That Scoops!

NMA Article: A Shaker That Scoops!

I have just made my ’76 Trans-Am’s shaker scoop functional!


First, some background: While all second generation (1970-81) Trans-Ams (well, except the ’80-’81 turbo models, which had an off-center hood blister) came with a shaker scoop (so named because it sat on the air cleaner and poked through the hood and shook with the vibrations of the engine) only the 1970-’72 cars had functional scoops from the factory. Uncle objected to the noise, you see — and killed the fun.


1973-up cars had their scoops boarded up.


Pontiac did a nice thing by making this very easy for owners to fix on the ’73-’76 cars, by installing a hint-hint “block-off plate” that satisfied Uncle but which was also easily removable. Just take out the three screws that held it in place and your shaker scooped.


Pontiac was always great about stuff like this (end-running Uncle) back in the day. The original 1964 GTO, for instance. You weren’t supposed to put big car engines in medium-sized cars. Pontiac, under the magnificent John DeLorean, did exactly that — and created the first true muscle car.


And the ’73-’74 SD-455 engine, too. Pontiac successfully (initially) smuggled this purpose-built, only slightly detuned race engine into mass production (and no need to “certify” it met federal emissions standards) by letting Uncle think it was just another 455, like the ones used in Safari station wagons and such.


Eventually, Uncle caught on.


Uncle also got wise to the (ho! ho!) “block off plate” and 1977-up Trans-Ams got a redesigned scoop with a molded-in rear section that had to be cut open, a much more delicate and difficult job.


Either way, whether removing the block-off plate or cutting the ’77-’81 scoops, the scoop could be made functional again — but crudely so. In contrast, the early (’70-’72) shakers had a flapper door that opened and closed to admit air to the engine instead of just a big gaping hole. It opened as the four barrel opened, the engine gulping air like a living thing. Performance increased and even better, the moan of the Quadrajet’s secondaries was no longer muffled. At idle, the hiss of engine vacuum was pleasantly menacing.


It was (and still is) possible to retrofit the factory ’70-’72 system to the ’73-76 Trans-Ams, which used the same hood scoop (’77-81 cars use an entirely different — smaller — shaker scoop with a bone line down the middle and the parts for the earlier cars don’t bolt on) but the factory components are both rare and expensive.


High four figures. That’s if you can even find them.


But — unpaid plug — you can now endow your post-’72 Trans-Am with a set-up very similar to what the factory offered, for a lot less money — and no snipe hunts at swap meets for NOS parts, either. Pontiac Plus (click here) will sell you a kit for your ’73-’76 or ’77-’81 Trans-Am that looks and functions like the factory system, just without the patina of NOS date codes and stampings. You can be operational in about half an hour, with basic hand tools.


And you can go either of two ways.


The first way is — my opinion — the coolest. And it’s also the least expensive (about $50) and by far the easiest. It’s a vacuum-actuated flapper that opens and closes in response to … engine vacuum. Engine off, the scoop is closed. Engine on, the scoop opens a little… and more and more the deeper you get on the gas.


The effect is enhanced by blocking off the underhood ductwork leading to the air cleaner so that all the engine’s air supply comes from outside, via the air-sucking shaker scoop. This enhances the pressure/vacuum signal and also, the outside air should be cooler — and so denser — and so contain more oxygen. Which ought to make more horsepower.


That was the whole point of having hood scoops, back in the day.


Also, there is the ram air effect.


Pontiac’s shaker was unusual, though, in that its air opening was rearward facing rather than facing into the wind. The idea behind it was that there was an area of low pressure at the base of the windshield and that placing the scoop opening there would allow less turbulent air to enter and provide more efficient “scooping.” Chevy used a similar Cowl Induction system on the ’67-69 Camaro Z28 and then again in 1980-’81, when it was called “Air Induction.” Whether it actually worked that way is debatable. But being able to watch the little flapper door snap open and closed was — and still is — a definite mood enhancer and one of the many qualities that gives an early Trans-Am its uniquely salty character.


Anyhow, the $50 kit is basically a functional flapper door and trim surround. To install, gently (take your time and be patient) pry out the factory epoxied-in bracket that the original block-off plate (’73’-76 models) bolted onto; after 40-something years, the epoxy will be brittle and (in my experience) it’s fairly easy to chip it out using a small flat blade screwdriver. Clean and lightly sand the area, then epoxy/glue in the new — functional — flapper assembly.


Let sit overnight; you’re done!


The second option is a rig that works very much like the factory original system. The door stays closed until the carburetor’s secondaries open up — or half-to-three-quarters throttle (whichever happens first). It uses electric solenoids and rods to open and close the door; the installation procedure is a bit more involved and of course, costs more.


But whichever way you go, though, your shaker will scoop once you’re done!


Comments?


www.ericpetersautos.com


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