Sound barriers

March 1, 2016 | By Staff

Question:

I’d like some advice regarding sound barriers, a crate engine, aluminum vs. cast iron heads, rack & pinion steering systems and garage floor sealers…

I want to use some sort of sound, heat and vibration barrier in the restoration of my ’57 Chevy 2-door hardtop. There’s no interior in the car now so this seems like a good time to insulate before a completely stock interior goes in.

There are a lot of materials out there like butyl with aluminum foil and sticky layers of varying thicknesses. Also what is butyl? I’ve seen products that resemble bubble wrap, vinyl, and bats that resemble the old jute material. Brands like Dynamat, HushMat and BuzzKil seem very popular.

Can you give a rundown of the different materials? I would like to put it on the doors, floors, roof, firewall and the trunk itself. Any recommendations would be greatly appreciated.

I also want to buy a Chevy small-block 383 crate engine since I already have purchased a brand-new in-the-box Edelbrock dual-quad setup with Thunder series carbs at a swap meet at a great savings. I feel that this size engine would be better suited with the dual carbs over a 350; what’s your take on this reasoning? I will also be using a Muncie four-speed trans and an axle with a 3:55 ratio.

Also a big question; what are the advantages of using aluminum cylinder heads over cast iron? I’m also considering switching my current factory manual steering to a more modern-type like power rack and pinion. Any opinion on this type of steering or should I also consider other types like the 600, 605 and 670 boxes?

In addition, I think the humidity in my one-car garage might be a little high. It has a concrete floor with two small cracks running diagonally. They don’t appear to be deep and are about 1 ⁄16 wide all the way across. Can you recommend any type of coating or sealant?

Thanks in advance for a great publication and I look forward every month for the arrival of Auto Restorer.

Answer:

Foil-backed sound and heat insulation can make a huge difference in climate comfort and noise reduction in your Chevy. If you want to go full zoot and don’t mind spending the money, a Dynamat kit for your car will work wonders. You will need the kit plus a roller and the cement and tape to do the job. There is very little cutting and fitting when you use a kit, and the results will be well worth the effort.

Personally, I have always just used Thermo Tec foil-backed jute-like sound proofing from the local auto supply along with 3M super-duty trim cement, and the results have been more than satisfactory. The stuff comes in 36” by 60” rolls and is moderately priced. When you install it you put the foil side toward the heat source. That means foil side down on floors, and toward the outside in tops and side panels. Use a utility knife to cut and fit the liner, and spray both the surface of the liner and the surface to be covered with the cement. Let it get tacky, and then press the liner in place.

Put
Be sure to put the foil side down on the floor of the car to insulate it from engine heat which goes under the car.

The most critical surfaces to cover are firewalls, tops and floors, with doors and side panels being secondary. I have also put it in the undersides of hoods to cut engine noise. Engine heat can radiate through a firewall and make your car insufferable on a hot day. The cooling system and toe board of your Chevy are designed to blow the engine heat back and down under the car, so floor insulation is a must. And then there is the radiant heat from the sun that makes it necessary to insulate the top before the headliner is installed.

I also like to use the expanding spray foam insulation available in rattle cans for shooting into channels, crevices and hard-to-get places. You just shoot it into a crevice and it expands to fit as it cures. Do not shoot it in the lower doorsills though. A certain amount of moisture always gets past the window rubber sweeps and will settle in the bottoms of the doors if the holes in the door bottoms are blocked. The holes were put by the factory to allow moisture to escape.

If you want to go for the best insulation available and don’t mind spending a little money, I suggest a Dynamat kit. You can reach them at:

Dynamat Hamilton, OH 45015 dynamat.com

As for the question what is butyl: It is a four-carbon alkyl radical or substituent group with general chemical formula C4H9 derived from either of the two isomers of butane. I am sure that description helps a lot.

Butyl rubber is a synthetic rubber, a copolymer of isobutylene with isoprene. Butyl rubber was invented in the early twentieth century, but it came into its own during World War II because of the shortage of natural rubber. Butyl is impermeable to moisture, and is not as prone to sun damage and rot as natural rubber. For interior insulation purposes I doubt that it is superior to other synthetic rubber or plastic liners though.

As for going with a 383 stroker motor, I suggest you get my book, “Building a Chevy Small Block For the Street,” published by Motorbooks (motorbooks. com). It covers every aspect of equipping, assembling and super-tuning such an engine for maximum power for street use. That includes head and cam choice, porting, carburetion, exhaust tuning and all the other aspects of putting together an engine that will knock your socks off but be reasonably well-behaved and dependable over the long haul.

You mentioned an Edelbrock twin four-barrel carburetion system that you have purchased, and I would advise you to keep in mind that all of the components of your new engine must be selected to work together. Otherwise, you may end up with a motor that won’t even perform as well as a stock one. A 383 with Sportsman heads and hot cam and valve train to match will require in the neighborhood of 680 cfm (cubic feet per minute) of air flow to run its best. More than that and you will end up with a big flat spot in the mid-range, and a mushy signal when you accelerate.

Also, I would check to see if your Edelbrock manifold is a dual-plane or single-plane type. A single-plane manifold will give you the ultimate horsepower, but it will be very peaky and will limit performance in the low- and mid-ranges to a certain extent. For street use a dual-plane manifold is preferable because it provides better performance at the rpm ranges you normally use on the street. To put it simply, a single-plane or plenum-type manifold is for racing. A dual-plane is better for street, or street and strip use.

As for going to a 383 versus a 350, the demand for the fuel/air mixture would not be that much greater, because the bore remains the same. All you have done by using the 400-cubic-inch crankshaft is added stroke. This will give you more bottom and mid-range torque.

Holly—a major manufacturer of carburetors for various applications—says that the major reason for complaints from customers is due to over-carburetion. Beyond what the engine needs, more is not better. The engine can only consume so much air and fuel no matter how much carburetion you give it. Your two four-barrel system sounds like a lot of carburetion for street use. To make it work you would want two small four barrels of 350 cfm. More than that and you will need a radical racing cam and some extensive head porting to make the engine inhale all those fumes.

Aluminum heads are used because aluminum transfers heat better than iron. With aluminum heads you can go a little higher on compression and you can worry less about overheating and pinging. They also weigh less than iron heads, but with a car as heavy as a tri-five Chevrolet that wouldn’t matter enough to be worth the expense just to save weight. Also, aluminum heads need to be installed correctly to avoid electrolysis which causes the heads to bond to the head studs, making them difficult to remove after a time.

Rack and pinion steering is simpler, lighter, and responds more directly than the original recirculating ball setup your Chevy came with. But a 1957 Chevrolet is not a sports car, and a complete rack and pinion system is an expensive alternative for what in my opinion is not much gain. Besides, I have it on good authority that the 600—605 steering boxes are prone to leaking.

With that big stroker motor under the hood you will want to go to wider tires, and they will cause the car to be harder to steer, making power steering a necessity. However, if you were going for serious drag racing you would not want power steering because that setup robs the engine of power. In that case, the standard, nonpower steering setup would be best. And in that case I would just go through the existing system and make sure everything is in good condition before putting the pedal to the metal.

Finally, think about it carefully before you go to one of those small sporty after-market steering wheels. The smaller the wheel, the harder it will be to turn. That’s why busses and trucks have huge wheels. Power steering is a must with that little wheel, and I would also do regular weight training in case the power steering fails or the engine quits because the car will be very difficult to turn under those circumstances.

A number of companies make kits with various steering ratios for whatever application you might want, but the installation should be done by someone who really knows steering systems because bump steer and misalignment can make for very dangerous handling. Installing rack and pinion also involves cutting your steering column and adding a rag universal joint, and that is a critical installation too. If the stock Tri-five steering system were heavy or problematic I might be persuaded to switch, but, unless you want a quicker response, I would leave things alone.

As for the humidity on your garage, I would certainly caulk those cracks with silicone sealer and paint the floor with an epoxy-based floor paint. Concrete does absorb water if not sealed. I would also make sure the garage door seals well. And if things get really damp, a dehumidifier might be in order. I use one in wet weather and it is startling how much moisture it can pull from the air during a three-day storm.