Datsun Roadster Forum-311s.org

So I noticed when I took my hood off that the hood scoop is all but blocked off by a sheet metal baffle located just inside the scoop opening. Anyone know why this was done? I assume it came from Datsun that way since a spare hood I have has the same thing. Is it advantageous to cut it out of there to increase cool air flow into the engine compartment and let heat out?

When the cars came from the factory, that baffle served the purpose of directing air towards the radiator. If it is flattened, then some ingenious PO smacked it. I have seen them removed, but don't know if there was an advantage to it. Now, if you wanted, you could make a plenum that mated to the hood and provided cold air ducting to the carbs - but that would be a lot of work.

A couple of years ago, there was a custom fiberglass hood on Ebay that had an open scoop. The front edge was a little higher than stock (not much though) and the scoop maintained that height to the rear of the hood - sort of a cowl induction look. I wonder who made it and if it helped expel hot air....

I always figured that the plate was there to provide stiffening to the scoop itself. The edge of the scoop would be the weakest point on the whole hood.

It wouldn't take much to put a serious bend right there, and I doubt the stainless trim would add much strength.

Well, it certainly does add strength, but my perspective was gained by studying the design of the plate. If it were only for reinforcement, then there would be no need to have the scoop open. The plate is made such that air comes in and is deflected downard. My thoughs are reinforced (in my mind anyway) by the fact that Nissan added the chin scoop to direct more air to the radiator.

Of course, I could be wrong....

Thanks for the feedback guys. I think I'll look into opening that scoop up to allow for more underhood cooling.

Dave,

DON"T DO IT!!!!!!! If you look carefully you will see that the hood scoop runs to the backside of the rad if you open this up what you will do is increase the engine bay pressure adversely affecting the amount of air going through the rad from the front. Remember that any medium( in this case air or the same applies to water) wants to go from an area of greater pressure ex. the front of the rad through the grill to an area of lessor pressure ...behind the rad or into the engine compartment.

I know myself and Bill Wessel both close this off completely( I don't think I would do this on a street roadster) for racing applications. In your case I would leave it alone. I even pop my hood against the hood pins to create a vent out the back and lower the pressure in the engine bay to get more flow through the rad.

Hope this Helps!

Russell

I have some doubts about how effective the hood scoop really is.

The airflow has to turn a very sharp corner as it flows over the crease in front of the hood scoop. This probably creates turbulent flow, and would reduce the flow going into the hood scoop. It's all just a theory though, and I generally agree that keepin the scoop at least partially blocked off is a "good thing."

With some over the road testing, with some pressure taps and manometers at a few locations, one could figure out what was going on with the airflow. Or, you could rent some wind tunnel time.

Regards,
Chris Coker
www.risensonracing.com

The question I ask is...
How Often do I go fast enough for this to make a difference for me? Then again, I don't have a problem with overheating (anymore).

The racers are correct on this one. Don't change what was originally engineered. Might we start to think that things were insufficiently engineered? Don't think so, that's why we have these Datsuns in the first place. (almost bought a 66 Midget with an A-series Datsun engine in yet, instead of my roadster)
The small opening has nothing to do with cooling or intake.
The small opening would allow radiating heat to escape while sitting still (a common Z car problem) but a totally closed opening would create stagnation pressure (and a big cushion shaped boundary layer) right at the scoop. With a bit of flow inward, the air stays more 'tucked'. I would bet that the air in the cockpit would change, possibly get more turbulent, if you plugged it. But, if ya lower the windshield like the racers, that's a whole new ballgame. After many years of VW tweaking, where we all added oil coolers but found that nearly all config's made oil temp go UP, leave the original engr'ing as is, they had reasons for all this.
Sorry, too many words. Fergus O

Thanks for all the input guys. My biggest concern is venting underhood heat. With an SR20-DET under there I'm going to be building up a lot of it. I went ahead and ceramic coated my exhaust manifold, turbo, and downpipe. I also wrapped the downpipe with header wrap. Hopefully, that will be sufficient. For now, I'll leave the scoop as it was designed and see what happens!

Dave,
How about finding someone to add louvers to the hood. A nice set of louvers could look good. I have been working on a Jaguar XK120 vintage race car and the owner found someone to louver his hood. It looks great. That would solve your underhood temp problems and give it a one-off look.

Will

SLOroadster wrote:Dave,
How about finding someone to add louvers to the hood. A nice set of louvers could look good.

You can do it yourself: http://www.lowbucktools.com/louver.html