How to keep underhood temp down

[VinhZXT]

Hi all,

What can I do to keep the temp under the hood of my 280ZXT down? I have another 280ZXT (the Brucemobile) and the underhood temperature doesn't feel as hot as this one (Blue one). There aren't many differences between the 2 engines. On the blue one I stripped the insulation (paint) on the valve cover and the IC pipe coming out the compressor. These 2 items feel very hot after a 30 minutes drive. I did the same test on the yellow 280ZXT and it didn't feel hot. Also the yellow ZXT doesn't have the hood scoop that will intake cool air to cool down the turbo. While the blue one has one and yet it still feel alot hotter than the yellow ZXT. Anyone have any idea why? Thanks

[260DET]

Not terribly familiar with the 280ZX but most cars of that era had more than adequate air intake through the front, even if most of it went through the radiator. Any engine bay heat problem is therefore more likely to be a lack of air exit from the engine bay.

 

On my S30 turbo this was solved by adding two bonnet vents about 2/3 back, in the low air pressure area. Vents so positioned work when the car is stationary too.

 

All this probably does not help much with this particular problem but perhaps the theory can be applied somehow Plus you can always get the exhaust system done with a heat reducing coating.

[VinhZXT]

I saw a couple earlier post about that too and still thinking about that. The only problem is I have an 82-83 hood with the air intake scoop that will force air down to the bottom of the car. This same vent should allow heat to come out if the car stand still. I don't have AC in this car but I do have an IC in front. That shouldn't restrict incoming air that much. I am going to get a thermometer to compare the underhood temp between the 2 cars. The heat felt so hot and it just worries me a bit. My CAI is in the front of the radiator and so far it has not cause any major problem yet. BTW my water temp is not that hot. Still questioning why?

[Guest 305240]

Vinh, I've made a few trips into Calif and in the afternoon on the way back, my ZXT started to heat up both times. Especially when we stopped. It didn't really overheat, but the gauge shwed higher than normal.

 

On my 240 I'm building with a 5.0 in it, I'm running a custom grill which is larger than the stock one. Also a taurus 2 speed fan. I plan on running AC so I want it to run as cool as possible. I've got stainless vents in the hood as well as muffin fans installed in the fenderwells. One is behind the battery and the other is alongside the clutch master. I'm trying to do everything I can to keep the heat down. At least this way it can excape when in traffic and stop lights.

[VinhZXT]

305240,

I will continue to look for ways to relieve that hot air. I like the idea installing fan in the fender well. This should be perfect for me since I have 2 fender vents lol. Should be able to blow right thru those vents. I am also thinking of building a deflector at the bottom driver side to suck the air up from the ground and then the air from the hood scoop should push it down if the car is moving. This should relieve a little more than just leave it the way it is. There is a problem with this because if I go fast enough and the air doesn't push down fast enough my car will become a balloon and the front end will be push up. Maybe I should start out with a small deflector and test it out. I wish there is a way to blow some smoke into the engine while driving to see where the air will end up at.lol..

[Guest 305240]

Over on zcar.com there was quite a discussion about overheating. I know about the engine running cool as you are driving. I also know about the underhood temp rising when you are in traffic and stop lights. The way I figure it is if I can help the hot air in the engine bay excape, my car will be the better for it. When the 2 speed fan kicks into 2nd gear, I want a place for the heat to get out. Hence the hood vents, which look like louvers, and the 4" muffin fans. Those areas where the fans are actually act as air traps. No air circulating around the battery or master cyls. At least the muffin fans will help suck the air out. Interesting theory you have on the baloon...lol good luck. Keep us posted. BTW, love that Bruce Lee Z.

[260DET]

Agree with 305240, the important thing is to get the hot air out.

[Mike kZ]

The president of the Georgia Z club did the muffin fan thing, here is a write up:

 

http://www.georgiazclub.com/tips/ztech/v8cooling.htm

[VinhZXT]

Thanks for the link MikeKZ.

 

My car doesn't overheat at all. It's just the valve cover and the IC pipings and the intake were hot.. very hot.. For the intake manifold and the intake pipe coming out of the turbo to be hot I can understand because they are right next to the exhaust manifold. But for the valve cover to be hot I was questioning it. Anyway I thought about it a bit and here is my explanation for the valve cover to be hot. It is not absorbing the heat from the air it absorbed the heat directly from the head and actually releasing that heat. So if it's hot that means it is dissipating a lot of heat coming from the motor/head. In this case it is good that I stripped the paint on the valve cover so that it can release the heat better.

 

For the intake manifold it could be absorbing heat from both the motor/head and the exhaust manifold. The IC piping is absorbing heat from the exhaust manifold and the heat generate by the turbo. In this case the heat that cooking up the air inside it will be bad for my intake air. I would like to keep the temperature on both of these items down. I agree with you all that 1 way to minimize this is to vent the hot air under the hood and/or I can put some kind of insulation paint on both the intake and the IC pipes and the downpipe just like someone suggested. Thanks for all the replies guys..