In need of opinions on "cold air intakes"

US cars with “six packs” only had to tune the center carb for idle, the other two kicked in when the throttles were opened, unlike multiple Webers where each barrel fed a single cylinder.


Wouldn’t the two Outboard Carbs be leaking a bit of air making the fore and aft cylinders run lean and the inboard cylinders run rich? I know this would only be during idle…

The outboard carbs had large diaphragm plates. The vacuum lines might even have been missing too. He blamed most of issues on bad intake gaskets. Think it’s a hagerty site on YouTube.

Probably. But the same would be true of a 4 bbl carb. I was surprised how off balance cylinders can be with various intakes and carbs. On Engine Masters they have sensors in all eight exhaust headers, and they find huge differences with some carb/intake setups.


You can make your own with water with some food coloring, a board and some clear tubing. Much safer than mercury. I made one to tune my Kawasaki 1000 cc engine. Normally you’d tune them to be equal but the service manual showed the center 2 needed to be 1/2 lower than the end cylinders.

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Manometers are very accurate, better than 4 gauges.

For example, 1/2” difference equals 0.018 psi.

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I graduated high school in 1970 and all through school, elementary, junior, and high school, we used mercury in school. I remember science teachers pouring it onto our hand so we could feel. Back then dimes were silver and our teaches often had us put a dime into the mercury to make it shinny as the mercury adhered to the dime and we could keep the dime… “We’ve come a long way baby…”

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There’s a relatively new film with the same title, Thunder Road, said to be a tribute to a Bruce Springsteen song. Not recommending, haven’t seen it, just saying.

Me, I’m totally into Humphrey Bogart films this weekend. Key Largo, Dark Passage, Treasure of the SM. & Casablanca of course.

The song “Thunder Road” was written and recorded by Bruce Springsteen is 1975. That song became the opening track on his album Born to Run.

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20+ years ago, I considered cold air intake for my 2004 4Runner. I visited k&n’s site and found power/torque diagrams with and without it. It turned out that ANY (quite miserable) effect is achieved after 4,500 RPM. This is not a motorcycle, it’s not a race car either so 4,500 (with red line @5,500) hardly ever happens. Another thought was: if cold air intake was really beneficial, all manufacturers would’ve installed them at the factory. Not the case. Therefore, pass.

In the '60’s some of us used “Cold Cans” this was a 3-pound coffee can that the gas hose was run to from the fuel pump. The can contained about 6-feet of copper hose that had been wrapped around a smaller can to create a “coil spring” like shape that fit into the coffee can. The hose then ran to the carburetor(s). The concept was that it would make the gas cold and more dense. We also piled ice on our intake manifold between runs expecting the cooler manifold allowed more dense air into the engine.

I retrospect, I do not believe it actually did any good, but it made us feel we were actually accomplishing something between races… At lest we did not try “water injection” (a J.C. Whitney Catalog favorite…).