I am getting quite a bit of heat build up under the hood with the new engine. Several problems are compounding the heat issue. First, the engine is so stinking big that the engine bay no longer has air flow. Where the 3.6 was smaller and further forward of the firewall to allow hot air to push straight back of the engine, the LT intake completely blocks the upper firewall opening and doesn’t allow hot air to continue down the trans tunnel. Second, the exhaust manifold is one cylinder bigger, and farther forward on the LT. Since the exhaust heat is more central in the engine bay, compared to the 3.6 exhaust location, heat tends to rise straight into the hood cavity and stay there. One of the biggest problems with heat build up under the hood is intake air temperature (IAT). High IAT number will rob the engine of performance. The misconception on the Jeep is the cold air intake (CAI) because the CAI does away with the factory air filter box and might add a plate to block off engine heat from the filter media. The problem is the plate that is used is not really doing anything to block heat, because when the plate gets hot it also radiates as bad as not having a plate. You are forced to use some sort of CAI design with an LS or LT swap because there is no such thing as a factory airbox for a V8. I used the RPM Extreme kit to do my LT swap and they include a really nice K&N oval filter and a slick airbox setup that will draw air from the passenger inner fender area. My IAT numbers have been acceptable with the RPM Extreme filter and airbox setup. The problem that I am fearing on trails in the future is that the connecting hose from the filter to the throttle body will become super heated with the engine compartment heat and report incorrect IAT numbers and skew my engine performance. All of this compiled information and what-ifs led me to look into a different hood design that would allow air to escape through hood vents. I am already running a power dome Rubicon 10th Anniversary hood, however the vents (that I cut open to make functional) are really small. They help but not enough. I looked at the Rough Country Vented Performance Hood, but didn’t really want to try to match the paint on my Jeep (again). I took a different approach and looked at my current hood design and noticed that the back of the hood has the potential to dump heat out the back and into the cowl opening. Seeing that this might be a chance to allow more heat to escape I drilled nine, one inch holes in a straight line along the back of the hood riser. I painted the bare metal and with the hood in a normal raised position you can’t even tell I changed anything. Now I have to wait for the rain to stop long enough to go drive around and use the temp gun to see if the back of the hood is exhausting hot air into the cowl. I will update this post at the bottom when I get more data.
