Bernhard

Has anyone ever tested the 68 duct V the 69 duct. I would think that the 68 duct would be worth some HP?

Thought's/tests/math ???

Octania

Either one has far more flow area than the carb at WOT, so I don't think it really matters much. It's the fact that your engine air is not coming from underhood that gives it the extra ooomph. Notice that pretty much ALL cars use that OAI feature now, they just don't advertise it. Kind of like how at first transistor radios proudly announced that on the face, and Fuel Injected cars had badges declaring so.

joe_padavano

And to add to Chris' post, the 4" corrugated duct tube causes far more restriction than the inlet scoop. Again, it's the temperature drop, not any "ram air" affect, that is increasing HP. I've seen published numbers in the range of 1 HP increase for each 7-10 deg F drop in inlet temperature.

Bernhard

I know the one local Olds racer that uses it says its worth 1mph but his is ducted to the high beam head lights and has 5"/4" spun aluminum duct reducer.
Thanks for the reply's.

davebw31

ALL: engineering said that @ 25 mph the 68-69 ram air system was already producing additional HP. I am sorry that Style Group and Sales Group decided to X that set up as it was supposed to be continued in to 70' model run. They cancelled it because they insisted that " the W-25 was more a visual hi-performance item then the under the bumper scoops and therefore more to sell cars"! Bullhockey!!!!!!!!!!!!!!!!!!!! The W-25 hood did not start making more HP until 70 mph.

BTW: the 69 had the same air flow in cfm's as the 68. The change was due to a little more clearance as there was some high warranty claims for damage to the scoop.

junior supercar

the W-25 hood isn't exactly light either

davebw31

junior supercar: 10-4 on that! I was at a NHRA National event and I was in the "tech line" when I spied Lattirmore four cars ahead of me, so I walked up and there is his 455 Supreme he was running as an SX. He was convincing the NHRA tech official that the ram air hood was factory and available as an option. It was an AFC (sic) repo. It must have shaved 50 or 60 lbs. off the frt. end!

Bernhard

Thanks for the reply good info on the 68/69 scoops

wmachine

Just to point out that Olds Engineering understood what they we doing, these special air induction systems from '66-'72 were initially called Outside Air Induction (OAI). There were no delusions of "ram" air.
The the term "Force-Air" was added in 1968 in promotion literature, while the technical side still used the OAI.
By 1970, marketing was getting an upper hand over engineering and the visually appealing W25 hood trumped any other more effective approach to force the air better. Truth is, none of the factory offerings from any of the car-makers were very effective. More modern tests have confirmed this. The basic problem is there is not a good place to grab air within a couple inches of the hood and front end profile.
It was pretty much a case of cool looks.

davebw31

Case in point: Look at the hood scoops on 67-70 GTO. Then in 71 a whole different approach as a redesigned frt. end with the hood scoops larger and just behind the leading and sloping frt. of the hood. My take is that it was the most efficient of all GM hood scoop designs.

ramrod31

I remember the hood came boxed up and it said 98 lbs