[dataway]

Reposting this here as I accidentally posted it in the Body Shop section.

Anyway .. anyone have a decent idea of what underhood temps might be on a 60's Pontiac on a 90 degree summer day with the AC on?

Just the ambient temp, not in contact with the engine, or radiator.

Wondering what plastic materials I can use for making under hood parts.

Thanks

[Formulajones]

It's hot, here in Arizona anyway. Kind of hard to shoot ambient though as my infrared needs a solid target.

It will vary though depending on how hot you run the engine to start with.

I tend to think what ever you make from plastic will probably survive about as well as the rest of the plastic and rubber stuff under the hood.

[Brentco]

X2. As long as the parts aren’t contacting the engine, or sitting very close to the exhaust, it’s hard to imagine any kind of plastic melting just from the ambient temps.

That said, if you want a number, your best bet is probably to stick a thermometer in there and drive around on a hot day. Others may be able to share their measurements but there’s probably a fair degree of variability from car to car.

If you’re looking for just a ballpark I seem to remember Jim Hand quoting some numbers in his book’s discussion of cold air intakes.

[Steve C.]

It's been stated anything you can do to enhance cool air flow into the engine will be good for torque and horsepower across the entire rpm band. Remotely sourced inlet air is almost always cleaner and cooler than engine compartment air. Typically, colder air improves power approximately 1 percent for every 10-degrees drop in inlet-air-temperature.... at least that's what the internet says.


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[Formulajones]

Okay this peaked my interest.

I'm sticking a thermometer in the engine compartment for a few days while I drive around and check it periodically. May switch from car to car to see differences, if any.

On a side note, about the cold air intake stuff. I can tell you when I drive the Z around, or the Firebird, both with factory functional hoods, I can immediately pop the hood after a drive on a cool morning and the inside of the air cleaner where the filter is, the lid, all the parts that are enclosed within the rubber seal ingesting fresh outside air, are very cold to the touch. While the outside of the air cleaner base itself that is exposed to under hood temps is very warm, almost hot to the touch.

I've found that interesting given the whole air cleaner assembly is basically one piece, with part of it just sealed to outside air.

I've also got some data to back that up from the Chevelle and GTO, both functional hoods, where I can datalog and monitor IAT's with the Snipers on both cars and have found that pretty interesting how effective that is just driving around and dragstrip passes. But that's sort of an entire subject on it's own.

[dataway]

FJ, let me know what you find out.

When I was a kid and was going through the "airplane" phase of my GTO I had an underhood temp sender to a gauge panel in the car but I have long forgot what it said.

[Formulajones]

That sounds more sophisticated.
I'm just going to zip tie a simple thermometer under hood. Maybe try a couple different spots, off to the side out of fan flow, maybe firewall by distributor etc...

Although it's December and high temps this time of year are 50's and 60's so may not be as good of a test as June and 110 outside.

[Half-Inch Stud]

NJ Mineshaft air in Alabama today. Could be a sporty ride. Still no Mech cooling fan. Fan on bench for Spring install...maybe. Groundhog day starting now.

[Formulajones]

I'm going to have to run some errands and do some shopping. The thermometers I have here that I thought I could use only read up to 120. That's not going to be enough.

I'll see if I can find a digital version with a larger scale.

[78w72]

you can get a pretty accurate reading of under hood temps after going for a drive in the summer temps you want to check it in. fully warmed up engine on city streets at 30-40mph, then let it idle in your driveway or a parking lot for a few minutes...

pop the hood & use a infrared temp sensor pointed at adjacent items like a wheel well liner, underside of hood or other items in the areas where the plastic parts youre concerned with would be. will be as accurate as sticking a thermometer under the hood within +/- 1-2°

can also point at the thermostat housing or where the temp gauge sensor is to compare to the gauge reading.

[dataway]

I've got a thermistor sensor for my VOM .... I guess a person could just zip tie it to a brake like or something under the hood and run the wire out the back of the hood and through the driver side window ... then just check the VOM reading now and then.

Most good quality VOMs come with a thermistor sensor and cable about 3' long.