The Stovebolt Site Forums The Shop Area Engine Shop air intake temperatures?

You guys made me curious about fuel & air temperatures.

Does anyone know the temperature range of air going into a stovebolt carburetor with an original style air filter?
How much higher than ambient?

Has anyone tried a cold air intake?

Here are calculator sheets i just made for estimating carburetor temperature, and another one for fuel temperature with a return line:
SMath worksheets

A return line should keep the lines and the tank at about equal temperature, but the carb runs substantially hotter than the rest of the fuel.
It looks like running a return system makes the supply side of the pump pretty much impervious to vapor lock (not sure about underbody temperatures though?). But depending on the air intake temperature, there is still potential for vapor lock temperatures in the carb itself. I found this link saying there's a high risk of vapor once the fuel get ~130-40F.


It would be interesting to input any temperature estimates you guys have, to see if this calculator is in the right ballpark or not.

If one preheats intake air with radiator air, it will run warmer than ambient air.

Ed

Has anyone tried a cold air intake?
Almost everything after 1970

A cold air intake on an engine with long manifold runners to the end cylinders like a stovebolt will result in massive differences in charge density between the end cylinders and the ones in the center due to fuel condensation in the manifold unless it's heated by conduction from the exhaust bolted to it. Contrary to popular opinion, the GM engineers in the 30's, 40's, and 50's were not a bunch of rubes who just fell off the turnip truck!
Jerry

GM used to have a thermostatic air cleaner on the L6 engines in the 70s and 80s. It was part of the anti-smog equipment. Anyway, I disconnected mine and I reconnected it again ASAP. Can you say "carb ice"! Warm air isn't so bad.

Hehe! I wish we had the roll on floor laughing smiley on this forum!

This seems like a good point and I am a fan of the stock exhaust manifold coupling.

I'd speculate that hot air makes carburetor happy up until the point where the float bowl reaches vapor locking temps ~130°F ... assuming a hot day with a return system and 90-100°F fuel going into the float bowl, the worksheet indicates that intake air should be limited no higher than ~150°F in order to prevent gas from overheating in the float bowl. On cooler days when the fuel entering the carb is cooler even higher intake temperatures are no problem.


This supports the reasoning of later engineers adding thermostatic intakes, though not sure if the temperature estimates of this calculator are any good.

Thermostatic air cleaner inlets, electronic ignition, and electrically heated automatic chokes, along with a lot of other "innovations" were mandated in the late 1960's to comply with increasingly strict exhaust emission rules, particularly during the first 5 minutes or so after a cold start. "Cold air" systems like the infamous K&N and others like it cater to gullible customers who believe that slightly denser air drawn from ahead of the radiator can be fed a richer mixture for an imaginary increase in horsepower. In reality, the air is so cold that the fuel tries to condense back into a liquid in the manifold runners, if it ever manages to evaporate at all. Diesels or turbocharged gas engines are a different breed of cat- - - - -cooler air can and does make more power, but only under very specific circumstances. Turbocharged stovebolts are about as scarce as a chicken with lips- - - - - -and about as practical as a windshield wiper on a duck's butt!
Jerry