Cold air intake

[Fairlady5150]

Looking for ideas for improving air intake on my 1968 1600, but I feel like it would be wasted time and money if I didn't bring in cooler air from outside the engine bay. I'm interested in your experiences with cold air intakes, whether kits or scratch-build. Would love to hear your thoughts / ideas, as well as see pics of your handiwork. Thanks in advance!

[Nissanman]

I have toyed with the same idea.
I have mocked up a cardboard template that is vertical at the carb to air cleaner base and runs from the chassis to the underside of the hood.
Plan to use some closed cell polyurethane foam on the top edge to seal against the under surface of the hood.
The front of the box would run up the inside of the engine bay to block off hot air from the the radiator.
Since I have removed the triangular brace adjacent to the starter motor, I was going to use that opening to channel air from the wheel well area up into the new box.
It won't be completely sealed because it isn't good idea to allow a cold air intake intake to get pressurised.
Still in the planning stage atm but when I get a few hours I will get moving on it......

[C.Costine]

Pretty much every under-hood pic of a racing roadster shows a cold air intake. I think that from what I have seen the main goal is to not draw air that has come through the radiator. If your roadster is tuned to the max and you have already installed headers and recurved your distributor and raised your compression it would make sense as a next step, as opposed to bigger projects such as stroking.

[spl310]

Is this a street car? Do you plan to race?

[Nissanman]

Yes and no.
We have very hot summers here in South Oz and when cruising the engine room gets very hot also.
Just a little pet project to squeeze a few more neddies out of the engine
I have experienced how much difference a cold air intake makes on my fuel injected P510 with an FJ20 engine so it will be worthwhile.
With our relaxed Historic Registration legislation it is now permitted to do such things

[SLOroadster]

Yes and no.
We have very hot summers here in South Oz and when cruising the engine room gets very hot also.
Just a little pet project to squeeze a few more neddies out of the engine
I have experienced how much difference a cold air intake makes on my fuel injected P510 with an FJ20 engine so it will be worthwhile.
With our relaxed Historic Registration legislation it is now permitted to do such things

What are Lou Mondellos thoughts? A cold air setup is not an easy thing to implement. At the very least you will likely be cutting holes in the inner fender. Fabricating a cold air box that will allow you to get to the carbs is another tough one. I guess it comes down to whether or not a few hp is worth hacking up the body?

Will

[Nissanman]

No, the way I intend to do it requires no body surgery at all.
As I said, I already have removed the triangular gusset to gain access to the starter so I intend to use that area for the intake and then duct the air to the sheet metal air box around the air cleaner.
Not 100% sealed but it will prevent the air cleaner from using the hot engine room air.

[RCMike]

Mine is 3 pieces. The left side of the radiator support has been removed. Air comes in through there. There is an aluminum piece that goes forward and right from the left side of the radiator to the grille to direct air into the opening. There in another aluminum piece with a 90* bend in it, mounted to the left flat bottom of the engine bay and to the radiator. This ends in a vertical only piece at the back to allow for engine movement.

Finally, there is a flat piece attached to the air horns, in plane with the vertical piece attached to the radiator.

None of this seals completely, but it will keep most of the hot air out, and allow for movement.

For more air at speed, remove headlight and put a 7 inch hose into the side of the engine bay from the headlight..

Screenshot_20190707-225857_Gallery.jpg

.

http://vimeo.com/257220179

[Gregs672000]

I'm about to leave on a trip through the north cascades or I'd see about pics, but I've done a few cold airbox versions over the years for the U20 with Dellorto or other such carbs. I've moved the rad over some toward the passenger side, cut the rad frame some to allow a large enough flex tube to feed through to an air box bolted to the carbs with velocity stacks. Worked fairly well, but agree with others about not pressurizing it. Now I simply run the same flex tube, and I made a simple hook that attaches to a round cone style air filter that is held in place next to the rad, channeling cold air through the filter through the flex tube that blows under the carbs which now use Ram Air foam socks on velocity stacks (whew, what a sentence!) Cooler air available to the carbs than without I believe. Impossible to know if it makes a noticeable difference, but this is a high compression motor and every bit helps.

First pic no filter or tube. Second you can make out the flex tube and filter. If needed I can get better pics later.

[Fairlady5150]

All very good responses, and serious food for thought. Thanks for your replies.

[CSP311]

For me, for airboxes on carbs, they could be restrictive. I have seen a couple that have been dynoed, and they loose a few hp rather that having an open (no box) system.

viewtopic.php?t=26116

Just over half way down. (NOT picking on this photo, just an example of a closed airbox). Most air from these comes from next to, or in front of the radiator. Fine. It is how the rear carb is fed with this cooler air that gets forgotten a bit. The air has to go through the filter (if an internal), around the first air trumpet and finally to the rear carb. All disrupted. This gets more disrupted, say running triples (6 trumpets) on a longer engine block. Even on a couple of stock Nissan air boxes, Nissan tried to address this, eg. the 260z has a separate passage at the bottom of the air box to feed the rear carb, and I have seen an option Nissan Bluebird metal airbox (with R series) that has a separate pipe feeding the rear. Airflow within the box is neglected in my view when people make something.

Some cold airboxes want to ram the air in, that is fine with injection/itbs, but carbs are designed to run much more at atmospheric.

I like the baffle system Mike has shown.

[cole455]

They did make an airbox for the roadster at one point. They didn’t make many, and I’m not sure how it drew its air (maybe a headlight bucket??). Kind of a cool niche piece, but not likely practical

[SLOroadster]

No, the way I intend to do it requires no body surgery at all.
As I said, I already have removed the triangular gusset to gain access to the starter so I intend to use that area for the intake and then duct the air to the sheet metal air box around the air cleaner.
Not 100% sealed but it will prevent the air cleaner from using the hot engine room air.

Well, here lies another issue, now you have introduced several 90 degree bends into the mix to get the cold air in, and had to route it next to the headers that will heat soak the snorkel (I say snorkel because I can't think of a better way to put it.) and thereby heat your incoming air likely as much as just leaving it to pull air in from the engine bay. The 90s will decrease the airflow into the box, and might also cause hotter air to enter than you'd get without it. Its one thing to pull air in from the front of the car, it will be cold, but to pull it from the wheel well, up past the exhaust, around the frame rail and in just seems like diminishing returns for the effort required.

If your car is right hand drive, you might have another option. Run the intake up from down above the idler box for the steering. This area is filled with the steering column on LHD cars, but that won't be in the way on a RHD car. You might have enough room to make it work. This would keep the air cold, from the front, and it will stay away from the heat of the headers.

Will

[Skyman]

I made this cold air intake a few year back. The intention of my project had changed. I would part with this if anyone was interested. You would need to figure out a way to clamp it together. I had some hardware for that I cannot find. There is enough room in there for some small stacks.

IMG_1042.jpg

IMG_1042.jpg

[redroadster]

Has anyone made the hood scoop functional ?
You might want to pull the hood and see what noticeable improvment you get