IMHO: I’ve been around all sort of shakers, (both OEM and not), forced induction, hood scoops, you name it for a long time. With hands on experience, this is what I have surmised:
Factory/OEM scoops on the street, (and I’m using a very generic term here to cover shakers, scoops, etc), basically exist to serve only 4 functions:
1. An air inlet/extractor to reduce under hood temps
2. Force air into air cleaner housing
3. Purely cosmetic
4. Combo of one, some or all of the above
For this post, I’m going to focus on OEM type scoops; Induction systems from the “Muscle Car” era, etc, that I have experience with and what some of you folks might be familiar with
Mopar: Shaker: Definitely gets the air right into the air cleaner area. But it doesn’t do much for the under hood temps. In fact, the shakers very large, metal base practically covers the entire top of the engine, to include the distributor and does hinder air movement under the hood. Regardless, the air you are getting to the air cleaner is indeed fresh: All in all, just remember to close the doors when it’s raining, although direct water into the carb would be a somewhat rare occurrence. The entire set up is a little complex parts wise, takes allot of work to remove for basic maintenance type work and is heavy in weight. I’m not big fan of front facing, direct air into the air cleaner area type systems. But is better than the typical just under the hood type OEM type air filter assembly: Yes, I DO HAVE ONE on my 71 Cuda. Sex appeal with the Mopar shaker is %110
GM: Early (68/69) and real L88 hood (corvette) type air induction: One of the best out there IMHO: Pulls LOW pressure/cold air into the air cleaner assembly between the opening in the rear of the hood and the base of the windshield. No doors or extra hardware. Light in weight. No door solenoids or cables, easy access to get work done. Extra hood space between hood and engine really allows for convection type cooling of the engine, a plus.
Hood as seen on 69 Camaros, or 70-72 El Caminos/Chevelles: Works on same principle as the L88 example above, BUT: It does have a solenoid activated inlet door that opens upon accel. (Same with the early to mid 70’s vettes): It’s a very heavy system, but the door system is out of the way when you open the hood, so remaining air cleaner assembly is easy removed for work. Pulls in low pressure air from rear of hood where the air flap is . Some benefits of cooling engine bay, but marginal in this area
Trans am shakers: Late 60’s/early 70’s had a real solenoid, rear opening air flap to let in low pressure, cold air. Pretty effective set up. Shaker set up was easy to remove, shaker base was basically a stock OEM type GM set up. No real benefit of cooling engine bay. Later shakers did not have a rear activated door on the shaker, just a block off plate. Most guys just removed the block off plate that was there
These later shakers did have a cold air inlet by hose near the radiator cowl area that connected to the basically OEM type air cleaner base
