tbirdman

What was the purpose of the vacuum operated OAI? I understand how a OAI will add performance, but I don't understand why at idle for say you need the OAI closed off.

jensenracing77

It was likely for the people that didn't know any better. WOW, that looks cool, It must be fast!

Eddie Hansen

Wouldn't it also keep the oak closed when not running? To keep dirt and critters out? I dunno , I think Eric is probably right , I think the transam originally had the flapper working but that ended and they were just fixed closed, on the other hand as you say It does make more sense to have some kinda switch so in bad weather etc you could keep it closed?

rocketraider

The original W30 OAI systems were full-time outside air. Emissions regulations tightened in 1969 and temperature-controlled aircleaners were one solution toward reducing emissions especially on cold starts. The vacuum motors were put in so the engine would receive cold outside air only on full throttle and only after warmup. Keeping crap out of the aircleaner was a side benefit, because the 66-68 W30 suffered from icing. Factory recommended disconnecting the OAI hoses in winter.

In the last days of performance before the emission era all the carmakers followed this logic. Olds OAI, Pontiac Ram Air, Chevrolet Cowl Induction, Ford and Mopar Shaker, Hurst SC/Rambler- all had vacuum operated aircleaner flaps that operated "on demand". Buick was about the only one who didn't use it on their OAI, but that hood was really more show than go- it did very little for extra air to the engine due to aerodynamic airflow across the hood.

tbirdman

I didn't realize the OAI was both vacuum and temperature controlled. I thought about keeping crap, water etc out but at least on my 70 442 there is not a manual control from the driver's compartment.

MDchanic

The OAI itself is not temperature controlled, but if it were open all the time, it would prevent the temperature control that is built into the air cleaner from functioning.

- Eric

tbirdman

That makes sense. Thanks for all the replies and the explanation.

joe_padavano

Just to clarify, the federally-required hot air inlet to the air cleaner started with the 1968 model year, not 1969, which is why even 1968 cars have this feature in the snorkel. Engine HC emissions increase significantly when the choke is closed, so the sooner the engine warms up, the less it pollutes.

rocketraider

67 if you count Climatic Combustion Control.

joe_padavano

Good point, though that one wasn't federally mandated. The purpose was obviously the same.

rocketraider

And, unless I'm remembering wrong, Olds was the only one to have such a system in 1967. Which once again proves

oldsmobiledave

I believe Buick also shared this same or very similar air cleaner assembly in 1967 on their 1967 GS. I think the Bufford guys call it the "Star Wars" air cleaner.

Koda

I'm not sure the CCC should be considered a step ahead.

rocketraider

Although it looks similar to the Olds CCC aircleaner, I don't think the Star Wars aircleaner had CCC provision but it's admittedly been years since I've seen one up close.

CCC was the beginning of lean carburetion. The temperature control wasn't that big a deal if the flapper was working correctly and opened to cooler air when it was supposed to.

joe_padavano

You would be correct.