Category Archives: Corvette Technical Answers

How To Put the Power Back in your C4 Corvette Power Windows

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DR-393

 

Why are the power windows so slow on my 1984 Corvette?

 


We get this question a lot. If you own a 1984-1986 C4 Corvette, you’ve probably noticed that your power windows are anything but powerful. ”Painfully slow” might be a more accurate description.  Chevrolet didn’t recognize the problem until mid-production in 1986 and then quickly fixed the flaw by introducing a second design window regulator.

So what about those of you who are stuck with the less powerful and unreliable first design window regulators? There’s an easy fix – and even better, it can be a do-it-yourself project!

Upgrade your 1984-1986 ribbon-style Corvette window regulators with Zip’s 1984-1996 Corvette Power Window Regulator and say goodbye to all of those annoying ribbon problems including broken ribbons, missing teeth or slow windows. You can also use this Corvette Part as a stock replacement for your 1987-1996 C4 Corvette to keep your windows working at their top performance.

Fully assembled and ready for installation, the regulator includes instructions and all necessary installation hardware.

Click here for Zip’s step-by-step installation guide, including pictures!

Purchase online at Zip Corvette Parts

 

Things To Consider Before Starting Your New “Old” Corvette

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This Corvette question comes from Jo Ann who inherited a 1981 Corvette.

I am inheriting my brother’s 1981 Corvette and it has been sitting in the driveway for over 5 years. It needs a lot of body work and a new passenger seat. The tires are slightly flat and are probably dry-rotted. We have not tried to start it up yet. Before we do, what advice can you give me before we try to start it up?

Prepare a Corvette for a Test Start

This is one of the most commonly asked questions in the restoration hobby. The real answer depends on your intentions for the Corvette. However, whether you are looking to make it a nice driver or a show winner, these initial steps will help you start the car and determine what you have to work with. All of this assumes the Corvette wasn’t parked for some serious motor issue, if you are unsure follow these steps until you hit a snag or need additional help.

We would begin by removing all of the spark plugs (remember to mark the wires so you get the firing order correct later) and pouring a table spoon or so of Marvel Mystery oil, motor oil, PB Blaster or any penetrent into each cylinder through the plug holes. Let this sit for a couple of days before you begin to rotate the motor.

Before reinstalling the plugs, try and spin the motor over by hand. If the motor does not turn by hand, remove the V-belts to check for a frozen accessory (Power Steering pump, AC Compressor etc.). If it still doesn’t turn over you may have a serious internal issue requiring professional help. If it does spin freely, replace the battery and try using the key to engage the starter to turn over the motor. If this works, great; if not then you need to begin diagnosing the Corvette’s starter system. For the purposes of this article we’ll assume the starter motor works. At this point you could reinstall the plugs or you could perform a compression check, which we recommend. Again, if the compression check reveals nothing out of the ordinary, proceed as follows. If not, more diagnosing is in order to determine what the problem is.

Before trying to start the engine, change the motor oil and filter, check that the throttle works properly (from the pedal to the carburetor, all of it, you don’t want to start a car and immediately rev it to the moon). You can check that there is coolant in the radiator, but plan on replacing it in the very near future. For now we are focusing on the start-up, once we get past that then draining and changing the coolant and checking the condition of the hoses and radiator will be a priority. If it turns out there are problems with the motor there is no need to spend money on these items now. Continue reading →

Corvette Wheel Offset & Back Spacing

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wheel-backspace-large-1

With so many different Corvette wheel designs on the market, finding the perfect set for your Corvette is not always as easy. At Zip, we take the guesswork out of the equation by listing the exact Corvette year a particular wheel set will fit. Of course this is assuming you Corvette has not been modified with aftermarket brake packages and/or body conversion kits. If your Corvette has been modified then you should be sure the wheels you are ordering are going to fit properly. To do so, you just need to understand wheel spacing terminology and use basic math skills. Let’s go over how to measure your wheels.

Wheel back Spacing is very simple and is often confused with the offset. To determine a wheel’s offset you must first find the wheels back space. The back space can be measured in inches but should be converted to millimeters before proceeding to find the offset. To find the back space place a straight edge across the rear of the wheel and measure to the mount pad. The distance equals the wheels back space, which in this case is 6.75″. Multiply the back space by 25.4 to convert the back space to mm (6.75″ x 25.4mm = 171mm).

Wheel offset is the distance between the centerline of the wheel to the wheel mount pad. It is measured in millimeters and the outcome can result in a zero, positive or negative measurement. To have a zero offset, the wheel mount pad must be even with the centerline of the wheel. A positive offset means that the mount pad is shifted past the centerline towards the face of the wheel, while a negative offset means the mount pad is shifted past the centerline towards the rear, or the brake side of the wheel. To determine the offset of a wheel you must first measure the overall width of the wheel. Lets say the wheel measurements are 18″ x 9.5″. Now convert the width to millimeters by multiplying the width by 25.4mm (9.5″ x 25.4mm = 241mm). Next divide the wheel width by 2 to determine the wheels centerline (241mm/2 = 121mm). With the centerline and back spacing of the wheel determined and converted to millimeters simply subtract the centerline from the back spacing for the offset (171mm – 121mm = +50mm).

Remember, we take into consideration every wheels backspace and offset before we offer a particular wheel for your Corvette. Each wheel set is listed for certain year applications because they are designed to fit properly to those models and are not guaranteed to work on Corvettes with modified body panels, suspension, brakes, etc.

For more information on which Corvette wheels are right for you feel free to Contact Us today.

How To Remove & Reinstall The Starter On A 1972 Corvette?

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This weeks Corvette question comes from Ray who owns a 1972 C3 Corvette.

How do I remove the starter from my 1972 Corvette?

1968-1982 Corvette Starter Mount
68-82 Corvette Starter Mount

The procedure for removing and installing the starter on a 1972 Corvette applies to all 1968-1982 Corvettes. It is not a difficult task to complete and only requires basic mechanical tools. To begin the removal first disconnect the battery cables (negative first) and raise the Corvette to an ideal working height. Next disconnect each wire at the solenoid terminals but be sure to reinstall the nuts after removing each wire as the thread sizes are different. If your Corvette has a big block, which included the starter solenoid shield you can now remove the front bracket upper bolt and remove the shield from the starter. For Corvettes equipped with the 350 engine you can now loosen the front bracket and remove the two mount bolts. You are now ready to remove the starter from the Corvette. After rotating the bracket away from your work space, lower the starter from the Corvette front first while holding it against the bellhousing.

Once you are ready to reinstall your Corvette’s Starter you can simply reverse the order of these instructions. Be sure to torque the mount bolts to 25-35 ft./lbs. first, followed by the starter brace bolt. Once correct operation of your Corvette’s starter is confirmed the removal and installation is complete.

Purchase online at Zip Corvette Parts

How Do You Adjust The Windshield Wipers On A 1993 C4 Corvette?

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This week’s Corvette question comes from Mike who owns a 1993 C4 Corvette.

How do I adjust the windshield wipers on my 1993 Corvette?

C4 Corvette Windshield Wipers
C4 Corvette Windshield Wipers

Despite their notoriety as a high-performance car and their innovations in design and technology, the C4 Corvettes had their fair share of imperfections. One common problem is with the C4 Corvette Windshield Wipers. Although only a minor flaw, the wipers on many of these Corvettes are not properly adjusted to rest beneath the hood when turned off. When the wipers do not park correctly, they can scrape the black paint on the window trim, resulting in unsightly scratch marks on the trim and blemishing the aesthetic appeal of the  vehicle. Fortunately, this minor problem can be easily corrected. All you need is a ratchet, 10mm socket, a flat-blade screwdriver, and no more than 20 minutes of your time. This simple adjustment will allow your Corvette’s wipers to rest below the hood line and prevent your Corvette’s window trim from being scratched again.

C4 Corvette Wiper Access Plate & Grill
C4 Corvette Wiper Access Plate

After opening the hood of your Corvette, look in the direction of the wipers where you will see the wiper transmission access plate. Remove the plate with a flat-blade screwdriver by carefully prying up on it. Not all C4 Corvettes have this plate, if you don’t simply remove the entire grill. Once the access plate or grill is removed you will have access to four retaining nuts. Loosen them with a 10mm socket but be sure not to remove them as reinstalling the nuts can be very difficult. Last, gently push the wiper arms towards the firewall. You will need to adjust both arms to avoid interference between them. Adjust the arms until they do not hit the windshield molding or they are below the hood line.

Once you have your Corvette’s windshield wipers adjusted properly you can tighten them down. Be sure not to over tighten or you could snap the stud on the linkage. Now check the adjustment. Close your Corvette’s hood and have someone spray water on the windshield while you operate the wipers. (Don’t operate the wipers without water on the windshield or you could permanently scratch the glass). Make sure the wipers are no longer hitting the windshield molding. Switch the wipers to high to check that they are not contacting each other or binding up. If they are contacting, then readjust them until they no longer contact each other. The same applies if they are still hitting your Corvette’s windshield molding. Once your adjustment is satisfactory, replace the access plate or grill and your job is done.