I did this today as an off-shoot to the aero efficiency yarn air flow tests by myself and JPhil recently.....my purpose was to attempt to measure underhood temps at Idle (hood closed) and at highway speeds...I tested my stock 1978 SA 4 speed
Instruments used:

!.Acurite oven thermometer..range 150-600 f
2. My old backpacking mercury thermometer range -40 f to +120 f....
Following pics show both...I used my the mercury thermometer to calibrate the oven thermometer below 150 at idle...I installed the oven thermometer at the firewall on drivers side...






The outside air ambient air temps today in El Cajon,Ca were 96 F with humidity at 42%...
!. Underhood at idle was 140 F (vette warmed up..hood closed...)
2.Highway at 75 mph after 8 miles was 150 F
3.Reduced speed to 55 and results were 137 F after 8 miles..I think my clutch fan kicked in and reduced temps...
When I stopped after test #2, I took surface readings as follows with my Raytek mini....
A.Air cleaner top= 149 F
B.firewall drivers side = 120 F
C.firewall passenger side = 122 F
D. Wiper motor...= 124 F
E. Inlet duct at radiator(surface only) = 109 F...was unable to get inlet/duct interior temps to carb with instruments I had...must think of something beyond range of my mercury thermometer...
My next underhood test will be my 69 502 Coupe with the L-88 hood..maybe tomorrow..

That's it until later...I also did an A/C interior test(inside cabin) while driving...this will be a separate thread later...but I started that test with cabin interior at 104 F to see how long it would take for my A/C system to pull temps down...
Rich

 

its actually pretty cool under the hood. i left a thermometer in the sunlight here in phoenix and it went up the like 140

 

I have used my Raytek Mini to get highway surface temps at ambient air temps of 100+ F...the surface temps on asphalt were around 130 F...my tire surface temps in those conditions were at 120 F..but not at any high speeds..think at 55-60 mph...

Rich

 

I'm sort of curious to the cabin temps myself with long tubes and no a/c

since thats what I'm dealing with

it's gotta be at least 120 in that cabin

 

same here... and I aint got no top.

 

Were those temps with the AC on or off? I think I would rather touch my headers than my AC compressor after it's been running for a bit.

 

Add headers and add about 50 degrees.

 

Corz..hang tough..I'll post my A/c results tonight..then tomorrow I'll test my 69 (no a/c) and get some good data for you.....good time for it here..hot as hell...105 today...

Edit: Long tubes ? Oh yeah !! Got those..3" all the way out thru Dynomax Turbo's...

 

I ran this "underhood" test without A/C on...it was 96 F this morning..and wanted to get a "feel" in the cabin without air on...not to bad at 40% humidity..

 

Actually,duals have less impact than a 2-1-2 system with the cat...I have duals on my 69(no A/C).Hedmons..and it is cooler in the footwells than my 78 with out air on...I'll explain why the difference in my 69 cabin test for Corz....tomorrow..
Rich

 

I can wait.. not like I have a motor in the stupid car anyway

 

I'm waiting till noon......want to get readings at same time I did the 78...it is only 75 F outside right now....(7:25 AM)

Here ya on the engine...good luck with that...

 

This is great information -- keep it coming!

 

Jeez, Rich, does this mean I'm gonna have to put 35 thermometers in places around my car just so I can one-up you again?
Interesting testing....I may actually do some underhood temp tests also, just to give us comparitve info....


John

 

Just got back..here is data: (Ambient outside air 98 F Humidity 51 % )

Engine at idle..driveway..
1.Engine compt at idle.(oven thermometer)..151 F (headers influenced this)
2.Air cleaner filter element(K&N) (Raytek)...140 F
3. Firewall..driver side(Raytek) 129 F

Highway test...drove 8 miles at 70 MPH...

1. Engine compt....130 F
2. Air cleaner element...126 F
3.Firewall driver side...122 F
4.Hood temp at Cowl opening..(underside)..110 F (took this just for info)
5.Exterior hood temp..by 427 emblem..128 F
When I did the yarn cowl test,I was convinced air was going into cowl off windshield at a high rate....seeing this temp data validates that..what I did not expect was that much of a temperature drop...-21 F !!!
Here is where I installed Oven gage...just to one side of cowl opening..



Interior cabin test..(no A/C on the 69)
1.Ambient inside before driving 96 F(Springfield digital)
2.Footwells before driving...92 F (Raytek)

Interior while driving using Raytek...
!.Ambient rose to 98 F (almost same as outside air)
2.Footwells rose to 96 F
Corz...under these same conditions running my 78 (A/C off) the footwells were 118-120 F !! The difference with the 69 is the splash shields with insulation under..my 78 does not have splash shields...but it will soon...

 

This morning when I stopped to check underhood temps..a guy stopped and said he seen me the other day with the yarn taped to the vette...

Get an oven thermometer that starts at 100 F..mine is marked from 150 upwards..but I had to calibrate(compare) readings with a separate instrument for readings below 150...
You also need A Raytek or similar device...on the 69,my air cleaner top is chrome..can't take readings with Raytek..so I took readings off the filter element...
Rich

 

looks like I gotta go dig up my shields and put them back on

thats just too g damned hot

 

Here are some pics from my 69....the insulation is foil backed on one side..






20 degree difference is huge when driving in 100 F weather...I'm putting the same plastic ones on the 78..Zip has them...don't know if the metal ones would get same results..???
Rich

 

well, I was talking to Sweethence and one of the best ways to get heat out of the cabin is to get side pipes.. I would assume that and the insulation would significantly drop cabin temps

 

No doubt in my mind...but you may transfer heat to your leg..