Trying to cool engine bay

[surfingfreeman]

Thanks guys, great point, perhpa an electric fan mounted relatively high in the bay with ducting to blow the hot air out?

[So Cal Mark]

back in the days of carbed engines, several import brands had underhood fans, including the X1/9. I remember Landcruisers in particular having a fan that blew over the intake and carb. The problems aren't so much as when the car is going down the road as when it's idling or has just been shut off and is experiencing heat soak

[surfingfreeman]

Thanks mark, I have a 1988 FJ62 cruiser love it, what a great all round "SUV", thanks for the info, don't forget you still owe me a call

[RoyBatty]

Yeah, but come on guys, admit it.
Exhaust vents in the fenders have a lot more "cool factor".
And they dont require any electrical power !

[sptcoupe]

As Mark said, the problem of heat soak happens after the motor is turned off and the car is sitting. Vents in the engine bay don't help much under these condtions, especially vents lower down in the engine bay, as hot air rises and is unlikely to find its way out of those vents. They do lower the engine bay temp when underway, when there is positive air flow through the engine bay.

When stopped, the heat from the engine bay and the intake manifold causes the gas in the carb float bowl to expand, or percolate, and climb up the emulsion tube and pool on the throttle plates. It is not just rough starting that is the problem, but excessive raw gas washing the oil off the cylinder walls when you do re-start. Very bad for the rings and cylinder walls, and the oil itself as it gets more and more gas into it.

I am having a mild percolation porblem with the coupe right now, and I am running 7mm spacers. The inuslators/spacers help, and do reduce the heat soaking up from the the intake manifold to the carbs quite a bit (After sitting 5 mins, the manifold is hot to the touch, the carb bodies are just warm). Keep in mind that the coupe runs very cool when underway, even in heavy traffic, as I am running a 180 degree t-stat, and the only time I get percolation is after shutdown.

But the ambient air in the engine bay itself can cause percolation, in spite of the spacers under the carb. But percolation can also be a combo of engine bay heat and fuel, as in modern, enviro acceptable fuels, or RVP blended fuels.

Here is the issue: Reid Vapor Pressure (RVP) is a common measure of the volatility of gasoline. It is defined as the absolute vapor pressure exerted by a liquid at 100 °F (37.8 °C) as determined by a standardized test method.

The vapor pressure is important for the operation of gasoline powered, especially carbureted, vehicles. High levels of vaporization are desirable for winter starting and operation and lower levels are desirable in avoiding vapor lock during summer heat. In the wintertime, the RVP is mixed to cause high levels of vaporization, which means percolation of the fuel in the bowls will happen at much lower ambient air temps.

I just tried an an old hot rodders trick to prevent fuel vaporization. I added 1.5 gallons of 104 octane racing gas to a full tank of premium pump gas. I have only driven the coupe twice since I added the racing fuel, and had no percolation. The explanation I got is that the racing fuel lowers the vaporization levels if the fuel. I will continue to experiment, and I am hoping that maybe an off-the-shelf octane booster will do the same. I'll try that next and we'll see. Has anybody else tried this?

Meanwhile, I am also in the process of figuring out how to fit an underhood fan to blow air across the manifold for a few minutes after shut down, as I think that is the best and most practical solution.

[RoyBatty]

Only point of contention l have is that outlet vents would still be of benefit even after shutdown.
Expanding hot air can more easily escape from under the hood instead of being trapped to have more of a chance to heat soak the engine.

[fabspider]

Re: trying to cool engine bay all great ideas I will give a go at as I am having Vapor Lock on my 76 Spider I will also pop engine hood open & block it open a few inches to let the hot air escape while parked see if this will work The electric fan is a great idea but will need a timer switch or your battery will go dead! thnx for the help.

[majicwrench]

Not sure why you are trying so hard to cool under your hood, the biggest issue is going to come when you shut vehicle off and everyhot hot soaks. While on road tis always a large amount of air circulating.
Air is supposed to be coming thru your radiator, any hole you put in in front of car are going to interfere with that.
'To me this all sounds like a solution looking for a problem.
Keith

[TX82FIAT]

'To me this all sounds like a solution looking for a problem.

I agree that this is a 100% accurate statement on a stock car. However, if you have carb airflow or vapor issues or as this post started out,excess heat because of headers, the additional cooling solution may be required. When you take a car makin 102 HP and move it to a car making 150 HP some modifications beyond stock engeneering may be warranted. Most stock Spiders started life with head shield over the factory header. The mount for that shiled is removed with the old header. Therefore, if you do not shield items like the coil another approach may be needed.

I can tell you my car ran a lot better with the engine bay 10-15 degrees cooler after i increased the cold air with the holes to the side of the grill on the passenger side. Engine likes colder air.

[WYSpider]

When I'm done driving and park in the garage I always open my hood fully to cool the spider.

[majicwrench]

THe OP said it was getting warm under the hood, is this a problem?? It gets hot under hood. And engines like heat, heat reduces friction, burns off wastes in the oil. Intakes like cool air, just cause it is denser.
Some fuel inj engines ran little fans on the injectors to help cool em after shutdown too.
' Keith