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Chevy Resto Tech - April 2014

Tip of the Month and Other Tech Advice

Mark Lundquist Mar 11, 2014
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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 ] 813-675-3557

Tip of the Month

We were invited recently to the monthly meeting of the Palm Springs Corvette Club. The event took place at the Mastershield facilities in Palm Desert, California. Mastershield installs paint protection film on just about anything that moves, including cars, trucks, boats, motorhomes—even helicopters. In fact, the 3M film was developed for the edge of helicopter blades to protect them from damage, especially in areas with a high concentration of ground debris. The film was later adapted by NASCAR to keep broken pieces attached to the car during major impacts, as well as protect the car from having to be painted after every race. Installed by a 3M certified professional, the film works every day and everywhere to keep these vulnerable areas of your car protected from the elements.

In the desert areas of the southwest where the Corvette owners from Palm Springs live, sand and road debris wreak havoc with front and side areas of their cars. Most have turned to installers like Mastershield to protect their rides. Installed correctly, the clear bras are virtually invisible and do little to change the appearance of the car. It came to mind that the idea of paint protection would go a long way on autocross cars that have become so popular today. Most courses can chew up a paint job in a hurry. The film can be cut by a CAD-powered printer for just about any car on the road today, and can also be custom fitted for any vehicle or hot rod.

Kits are available for anything, from just the front areas or the entire car. The mild custom 1966 Corvette you see in the accompanying picture is owned by a lady from the Corvette club who was afraid to drive her baby after the expensive paint job was completed until she discovered the benefits of a clear bra system. As you can see, the application is almost impossible to see, letting the quality of the body and paint shine through. Some years back we featured similar products in Super Chevy but we felt a repeat was in order with the improvements of the products available to protect your Bow Tie.

If you are an auto crosser or a drag racer, or just a proud Chevy owner who likes to drive, this simple solution to paint chips and damage might fit your needs. For any questions give Mastershield a call at 760-772-3075 or They are located a 78-015 Wildcat, Suite 102, Palm Desert, CA 92211. No matter where you are located, they would be glad to answer your questions about the protection available.

Timing is Everything

Here's the question.

I have a 383 in my Chevy and have two problems that might be related. The car has a mild hydraulic roller cam (.558/.558 lift and 238/242 degrees duration at .050) and a good set of aftermarket 190cc heads. The engine won't idle under 1,000 rpm, even when warmed up. Also, the idle speed tends to randomly move, both higher and lower. I think the problem is in the distributor. It is out of a ‘73 Impala. The shaft is really wobbly. Could these issues be related? The car runs really strong on the road, but it's confounding at stoplights and around town. Is this costing me any power?
James Champion
Via email

The set up doesn't sound problematic, and your cam choice should perform on the street with a quality idle with no problem. Your distributor, which I assume is a point type unit, would cause you timing problems if the shaft or breaker plate bushings were worn out. You need to start checking the basics in your search for the problem. Start with checking the timing with a timing light. With the engine running, check the timing at the damper and make note of the marks. Does it hold steady on the mark or does it jump around? If it jumps you either have a distributor problem or possibly a vacuum issue to the distributor.

Try unplugging the vacuum advance and see if the marks become stable. Centrifugal force can play havoc with the breaker plate and the rotor phasing causing unstable idle conditions if the components are worn out. I would recommend using ported vacuum to the distributor. Ported vacuum is above the throttle plates and doesn't come in until the throttle is opened.

Next check the actual vacuum gauge connected to any vacuum fitting on the intake manifold. It should read 14 inches or more. If it doesn't, the engine is probably not pulling enough vacuum to pull the fuel through the carb boosters below 1000 rpm. A low vacuum reading can be anything from retarded timing to an intake leak or tight valves. It might be worth it to pull the valve covers and check the valve adjustment. If the valve adjustment is too tight, the valves may not be closing all the way, contributing to low vacuum. After you readjust the valves, see if the vacuum comes in above 14 inches.

If all checks out okay, with the engine running try spraying WD-40 around the intake manifold, especially where it meets the cylinder heads. If you see a definite rpm change you might ha an intake leak. Try to keep the WD-40 concentrated around the manifold as the carb will pick up any overspray and give you a false reading.

Now that you have checked the main basics, hopefully you have found the problem. If not, I would still suspect the distributor itself. Sometime your first instinct will be correct.



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