SHOP TALK: To Ruin A Perfectly Good Hood Or Not?

We’ve all had to make extremely hard decisions when it comes to our cars. Perhaps the most difficult ones are those that will affect the look of the car permanently. I recently faced this self-imposed dilemma when I considered incorporating CryO2 chilling in our family Pro Street Camaro.

Making the commitment to keep the air and fuel that was entering my combustion chamber cool was the easy part (the facts/reasoning for which I’ll share in a future article). Finding or making a dual-plenum top hat that would accommodate two 4” cold-air tubes that would serve as a home for the CryO2 air bulbs, was a bit of a challenge. After months of research and phone calls, though, my persistence paid off, and I found the right people to help bring my brainchild to fruition.

When all of the parts finally arrived, I wasted no time and began to “mock” everything up. My plan looked absolutely amazing on paper, but presented many obstacles. With an already high-rise Merlin intake, a 2” Edelbrock Spacer, Pro-System carb, and Spectre Dual Plenum top hat, there was no way the 572 and all of the above goodies were going to fit under my 6” VFN cowl hood. I’m a firm believer that necessity is the mother of invention, so there was no turning back. I was fully committed to getting the hood to work, whatever the cost.

This project is not an easy task to perform correctly by any means or under any circumstances. Sure, you could cut a giant hole in the hood and leave it or mate a “pro-stock” style snorkel over the hole, and call it a day. To add insult to injury, not only did I want to keep the somewhat stock looking hood, I also wanted it to open like it did when it was stock. This meant there would be some crazy compound angles to figure out as the hood was closing. The dimensions would change as the angle of the hood got closer to the cold air tubes and then once again when it was fully closed. This also meant that clearances would have to be cut in to manage the sweep of the hood as it pivoted down and around the projecting geometry of the plenum and tubes.

Anyone who has ever worked on door hinges knows exactly what I’m talking about here. Take a look at any door in your house, and you’ll see a slight inward angle on the leading edge of the door to compensate for the fact that the edge of the door travels in an arc that has a radius equal to the door width. That angle allows the leading edge of the door to clear the jamb and contact the door stop molding, while the outer edge is ever so slightly larger to maintain a presentable gap once the door is fully closed. The same phenomenon occurs on car door hinges. If you are building a car from scratch and fabbing hinges, then you know that the hinge pivot point has a critical impact on your leading edge door gap, and more importantly, avoiding collision with the fender, or in this case preventing the hood from colliding with the plenum. Perhaps the even more challenging part is that the tubes sit high enough in a few places, that they are actually more than halfway above the plane of the hood when closed – meaning that once the hood sweeps past the halfway point of the tube and rests in the fully closed position, the hole will tend to look too big in that area if not treated ever so carefully. It still has to clear during the sweep, but you don’t want a huge gap once closed. Quite the conundrum, but a fun challenge at that!

I saw it in my head and knew what I wanted, but there was no way to even begin this process without an extra pair of hands to somehow hold the hood in the spot your eyes told you would be the correct position. Knowing that engineering this was a bit out of my wheelhouse, I put out the gearhead distress signal to the only guy I would trust with such a task. My buddy Shawn is an old school gearhead like myself, with the added bonus of a college degree in engineering. I highly respect his intellect, and his ability to blend his two worlds together.

We both agreed that measurements needed to be taken but labored over where and how to begin. We eventually made a jig in the engine bay that we squared up with materials laying in the shop. We then taped up the cold air tubes and the dual plenum top hat, and set the hood nose down in place. It was a horrific site, to say the least, and scared me even more than I was before we started. Why was I scared you may ask? With the front of the hood resting in its place on the car, the hood clearance began at 2” off the fender and worked its way to well over 8” at the back. It’s not that the top hat was sitting too high, it was that the 4” cold air tubes run all the way to the front of the car. There was no way to use smaller tubes due to the CFM requirements this high-horsepower, big block would need.

This is where x-ray vision or the home shop x-ray machine would come in real handy. Ideally, we could trace the projection of the tubes onto the hood surface and begin cutting. Since neither of these were at our disposal, good old garage engineering and patience would have to do. We took what seemed like a hundred measurements of the hood, tubes and other reference points on the fenders to figure out what we called our home datum, or point of origin on both tubes. Using those same reference points, we were able to transfer the point of origin to the hood. This gave us the first point of entry at equal places relative to the tube. This was hypercritical because as close as the tubes are in size and location, they are not perfectly symmetrical. Even a degree or two off will change the clearance hole dramatically, so if we had assumed equal geometry on both sides it would have looked awful.

We both took very deep breaths and said a prayer, realizing the drill bit was loaded in the chuck, and we had approached the point of no return! Oh, and anyone who knows the 4th gen Camaro body well, you know that the hinges are waaaaaayyyyyy back in the cowl, making the sweep radius huge everywhere, so careful attention needed to be paid to the most forward geometry to ensure we avoided collisions during closure, but without over-clearancing for a poor final fit upon full-closure.

So the two of us stared at that hood, and at each other, and decided to check our measurements for the 101st time just to be sure. We took the hood off for the 1st of over 30 times that night and decided to begin surgery. I was so stressed that I handed the drill to Shawn and told him if anyone was going to ruin my perfectly good hood, it could not be me. After a few explicates, he agreed to drill the first hole that would enable us to see if we were in the ballpark with our measurements. We used a drill bit just big enough to stick a silver “Sharpie” marker in so we could make a mark on the freshly taped tubes. Let me tell you, as I watched that drill bit make contact with the fiberglass, I felt the full weight of my CryO2 chilling decision crashing down on me, and knew Project Hood Clearance was officially underway.

Before we proceed, it’s important to note that a few years back, Shawn moved to Florida so he could take a higher paying job and improve his family’s future. I still haven’t forgiven him for selfishly abandoning me. He will forever be my gearhead soul mate and having him 1,200 miles away is a hardship I’ve reluctantly learned to live with. So in order for my gearhead soul mate to help me with this project, he had to agree to my perfectly reasonable request, and fly in from Florida. Naturally he was on an extremely tight schedule, and therefore Project Hood Clearance had to be completed over the course of a sleepless night – just to make things a bit more interesting!

Back to the shop. The first hole has now been drilled, and we carefully placed the hood back on the car, setting it in place. We then removed the cap from the silver “Sharpie,” placed it in the new hole and scribbled a mark on what we hoped was the center of the right side cold air tube. Holding our breath, we lifted the hood off and smiled at the sight of our success. The mark was indeed in the exact spot our measurements had predicted. This achievement was precisely what we needed – it was like a B-12 shot giving us the confidence boost we needed to forge ahead.

We wasted no time and drilled four more holes (2 on each side of the original), and again were pleased to see our marks remained dead center on the tube. Just when you think it’s safe to keep drilling holes, Shawn says, “Get your air saw and a new blade.” After seeing the horror in my face he went on to explain that the tube was not flat it was round. Every 1/8” of tube that would stick out from the hole changed every measurement we originally took. The two hours of measuring we did were only good for drilling the first few holes in each side. The rest of the job would require many small cuts with the air saw and “eye-balling” it every step of the way.

We alternated between sides with every cut so we could get a true visual of where we were. It was exciting to slowly watch the gap between the hood and the fender slowly diminish. Taping the tubes and graphing our progress after every cut, proved to be the million-dollar idea. Each time we removed the hood, we saw where the next cut had to be. Shortly before sunrise, we had made 32 cuts on the driver side and 28 on the passenger. We feared cutting too much and ruining what was once a perfectly good hood. Making the 1/16” and 1/8” cuts was painstakingly slow, but kept us in check every step of the way.

In the end, Project Hood Clearance turned out to be a huge success. We pulled an all-nighter and were able to attach the hood to the hinges, opening and closing it with no problem whatsoever. Just as we were finishing up, my wife woke up and came out to the shop to see the fruits of our labor. She was blown away with how it turned out. She admitted that she could not see or imagine what we were trying to accomplish, and why it was going to be so difficult. After looking at it for a while she said, “it looks like the horns of a bull, you should call the car El Toro.” Shawn and I looked at each other and knew she was spot on, but the only problem is my daughter named the car Big Red a few years ago, in honor of its big tires, big block, and the fact that it is red. Given we already have Big Red license plates, decals, and signs for my shop, El Toro will have to be its middle name for now.

It’s always fun to watch people walk up to my car and hear them say, “Oh, look, a turbo car.” Then they get closer, can’t find any turbos, but notice the purge tubes and a few solenoids and say, “oh it’s a nitrous car.” That’s when I stand up and tell them it’s all motor, but I chill the air and fuel with CO2. Without fail the next thing they say is, “I love the way the hood fits over the tubes.” After thanking them, I share a little story about a good friend, a sleepless night, and the question of whether to ruin a perfectly good hood or not. Thank God it was “or not!”

Until next time….

Keep wrenching,

JT