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Resto Tech Tip of the Month - May 2013

Mark Lundquist Dec 4, 2013
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Tip of the Month

In our March 2013 issue, we featured the installation of MSD’s new Atomic EFI fuel injection system on our ’65 Chevelle SS. At that time, preliminary results were excellent, but a long distance road test hadn’t yet been done. Since then the ZZ502/502-powered Chevelle has had a chance to pile on some miles checking for reliability, fuel mileage and driving experience. All three categories received an outstanding A+ grade. We drove the SS on a 205-mile road test comprised of mostly freeway driving, along with some city cruising. With the self-learning system doing its thing, the results were nothing short of amazing. Before the conversion, the ZZ502-equipped Chevelle got a best of 14.5 mpg in a mixed city and highway environment. With the MSD Atomic system, mileage came in at 19.8 mpg, with improvements in throttle response, hot and cold starts and idle quality. The long distance trip proved to be a pleasure. It has proven to be dead on reliable, leaving my Auto Club card a virgin.

Let It Bleed

First of all, let me thank you guys for a great magazine! It’s packed with useful information unlike most other magazines, which I call “one-sitters,” which means one bathroom break and you’re done with the magazine. I have been restoring a ’65 Impala SS. I had my uncle install an aftermarket disc brake conversion kit (this is my first build) and I’ve made a few mistakes, so the brakes were one thing I wanted to make sure was right). We tried bleeding the brakes a few times, but could never get pressure. He towed the car to a brake shop and they said that the kit was no good (the entire kit). I couldn’t understand how an entire kit could be bad.

After inspecting the car, I noticed he ran a brake line from all four sides of the master cylinder. Also, a friend of mine said that I needed a proportioning valve. I plugged up the two sides, installed the prop valve and also got a new distribution block for the conversion. I re-routed the lines and I still get no pressure. I had a buddy of mine check my work, and we bled the system and we still got no pressure. The calipers aren’t even moving. He thinks the booster is bad. Any ideas would relieve my frustration, please.

Shacoby Womack Sr.
Via email

Thanks for the kudos, Shacoby. We do our best to keep you informed while you’re, er, taking care of business.

Sorry you are having problems with the brakes on your Impala. Besides wiring and electrical problems, brakes can be a real pain especially after a disc brake conversion. Several things come to mind after reading your letter. First, check the brake pedal travel. Make sure the pedal is coming all the way back allowing the master cylinder piston to clear the fluid intake ports and draw in fluid. On more than one occasion, I have experienced the brake light switch being adjusted too far forward and interfering with the travel of the piston rod.

Another common problem is not bench bleeding the master cylinder before installing it on the car. This step includes bleeding the master on the bench to remove any air before it goes on the car. A simple tube and plastic fitting kit usually comes with the master cylinder kit to help you bleed the unit while returning the fluid to the reservoir until all the air is gone. This procedure will also show whether the cylinder is actually producing pressure to ensure the piston seals aren’t damaged. If the master doesn’t pump pressure after it is installed on the car, your problem is probably between the cylinder and the calipers.

I doubt the booster is the problem. The booster only aids in brake application. There is still a direct connection between the pedal and the master cylinder. Although it is much easier to bleed the system with the booster operating, it is not necessary. Forcing the fluid from the master through the calipers is accomplished by the method you are using. However, there are several tools to help you push or suck the fluid through the system. Everything from an air-operated cap installed on the master to push the fluid through to a vacuum canister attached to the bleeder screw on the calipers are available at some auto parts stores rental programs. Hopefully, these few suggestions will help you achieve the brakes you deserve. Let us know what you find.

Got a restoration question that’s been puzzling you? Send it to: [ m ] Super Chevy, Resto Tech, 9036 Brittany Way, Tampa, FL 33619. [ e ] [ f ] 813/675-3559



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