Tag: Tech Tip

Tech Tip: Ignition Coil Polarity Check on Early Model Vehicles – Randy Rundle @Underhood Service

Tech Tip: Ignition Coil Polarity Check on Early Model Vehicles – Randy Rundle @Underhood Service


Rundle’s Rules: Ignition Coil Polarity Check

Prior to 1956, the year when most all of the domestic auto manufacturers upgraded to 12-volt electrical systems using standardized negative ground designs, some of the electrical systems on cars and trucks were positive ground and some were negative ground.

Ford used positive ground, while General Motors used both.

Chevy trucks were negative ground, while GMC trucks used positive ground. There was and still is a lot of confusion concerning the polarity of electrical systems and how to properly connect the ignition coils, as well as the battery.

On classic and antique vehicles, you can test for correct polarity of the ignition coil by using a voltmeter.

Connect the negative lead to the (-) negative terminal and the positive lead to the engine block.
Set the meter on the highest volt range (these connections are the same whether you have a positive ground or negative ground electrical system).

The secondary winding’s polarity, which you are testing, is determined by the combined hookup of the battery and primary windings.

Crank the engine over (do not start it) and the needle of the voltmeter should show an upward swing to the plus or positive side (don’t worry about taking a reading).

If the needle swings down to the negative side and gives a negative reading, your coil is hooked up backward. To correct the polarity, simply reverse the coil primary leads.

A coil with reversed polarity will have about a 20% lower output, which may not show up at idle and low rpms, but can cause an engine to miss or stumble under load and at higher engine rpms.

This is why a technician who changes the points, condenser and other electrical components will still detect an engine miss.

The lesson here is, too often, it is “assumed” that the wiring is correct.

— Randy Rundle

Randy Rundle is the owner of Fifth Avenue Antique Auto Parts, Clay Center, KS, and services antique and classic vehicles. An author of six automotive technical books, Rundle has spent 20-plus years solving electrical, cooling and fuel-related problems on all types of antique and classic vehicles.

5 Reasons Why Your Stromberg Carburetor Leaks And Runs Poorly – @IrontrapGarage


Recently we have spent a lot of time rebuilding Stromberg carburetors for a few of the projects currently in the shop. While rebuilding them Steve and Matt found a few common issues that were found in the majority of the carbs. Matt decided to put together a video covering the common issues we found as a part of our hot rodding 101 series. Be sure to comment below if you have any other issues you seem to find with every Stromberg!

Improve Classic Car Braking (and Safety) With a Disc Brake and Dual-Circuit System Conversion – Jim Smart @Hemmings


The relationship we have with our classic cars tends to be a love/hate affair. We love the styling and the nostalgia of cool American iron from more than a half-century ago. However, suspension and braking systems are below par when you consider what’s sitting on showroom floors today. Drum brakes have their place, and obviously this arrangement is appropriate on a concours-restored show car where originality and show judging are paramount. However, if you drive your classic on a regular basis, maximizing your own safety and the safety of others depends upon getting your braking system up to date.

There was a time when you had to rummage through salvage yards to find a suitable disc brake package. These days, there’s a wealth of new disc brake kits for a wide variety of classic cars, from the Model T all the way up through the cars of the mid-20th century. Your decision should be based on what meets your personal needs and tastes. If your classic ride is a completely stock example, all you need are OEM-style front disc brakes, a dual-circuit master cylinder, new brake lines, and rear drum brakes.

Drum brakes have long been the mainstay of automotive braking systems. They perform quite well in rear axle positions yet are prone to fade when they get hot. When they get wet, friction is compromised and drum brakes can become unsafe. They also tend to lock up during hard braking.

If you have a performance-oriented model, or you’d just like a measure of braking performance beyond what the factory offered, the aftermarket may be able to assist. You may be surprised by the breadth of applications covered today, for both front and rear disc brakes.

Particularly important is the decision to convert your single-circuit hydraulic braking system to a dual system, meaning two separate circuits for the hydraulics fore and aft. American cars had single-circuit hydraulic braking systems prior to the 1967 model year, when dual braking systems became federally mandated. A dual-circuit braking system includes a two-chamber master cylinder, split between front and rear systems. The purpose of this is to maintain partial braking should there be a hydraulic system failure somewhere —a single leak should then affect only one circuit, not both as it does with a single-type system. In factory dual-circuit systems there is usually a pressure differential valve of some sort and a warning light to let you know you’ve lost either system. The pressure differential valve used on many vehicles has an internal “shuttle” valve that must be recentered once the trouble is corrected to turn the warning light out and enable proper bleeding of the system.

The humble drum brake is little more than C-shaped shoes/linings within a rotating drum. Because the front brakes do most of the work, the rear drums are there more as a backup for the fronts

Why opt for disc brakes? Drum brakes are prone to fading under hard use and, when wet, will often become seriously compromised. Disc brakes, on the other hand, are very effective stoppers.

They provide excellent braking force but are also more effective at dissipating heat, enabling them to endure severe use with good resistance to brake fade —the compromise in friction that occurs when the braking components become overheated. Even a front disc/rear drum system, with the split circuitry of a dual system, can offer a substantial improvement in braking performance and safety.

Most mainstream classic cars need little more than these cast-iron caliper, OEM-style disc brakes, and having them only in the front is usually a sufficient upgrade for normal driving. This is a Kelsey-Hayes four-piston front disc brake on a classic Mustang.

When you’re considering a disc brake upgrade, first determine if your car was ever available with disc brakes; if you determine it was not, investigate further to see if a system from a later version of your model offered discs. For example, a 1963 Plymouth was not offered with front disc brakes, but the parts from the right 1973 Plymouth could be adapted.

Of course, the aftermarket can simplify that process by providing whatever you might need for a disc conversion in kit form, eliminating the need to search out vintage parts from a salvage yard and the guesswork that can be involved in attempting to merge those items with your car. If you go this route, bear in mind that brake pad friction materials should be chosen based on the kind of driving you’re going to do. The daily commute or weekend getaway doesn’t call for hard friction materials designed for racing.

For a long time, six-cylinder Falcon, Comet, and Mustang owners couldn’t get front disc brakes. Only V-8 cars were available with them, and those models used five-lug wheels as opposed to the four-lug hubs found on six-cylinder models. However, given the intense demand in more recent years from six-cylinder owners, aftermarket companies answered the call with disc brake conversions for the inline-powered models. This example from SSBC-USA is a simple bolt-on kit you can install in a day.


Some years ago, asbestos was commonly used in brake shoes and pads, but when the health risks became clear, the material was phased out. When working on a vintage car, use caution with unknown friction materials —the brake shoes on a 50-year-old car may well be old enough to contain asbestos.

These days, we have three basic types of brake friction materials: Non-asbestos organic, semi-metallic, or ceramic for high-performance driving. Non-asbestos organic compounds are the most common type of brake friction material and are made from bonded organic fibers that retain shape by a resin or glue. Organic brake linings are made from a combination of several proven plant-derived fibers. Non-asbestos linings have a small amount of metallic content in them, typically brass to dissipate heat while contributing to abrasiveness (friction) for better stopping.

Affordable OEM-style disc brake kits are available for Ford, GM, Chrysler, and AMC classics from SSBC-USA (pictured here), CPP, Brake Performance, and LEED Brakes. They yield a factory-original appearance and will improve braking performance.

Read on

How to rebuild a vintage General Motors alternator – Rocky Rotella @Hemmings


When a hobbyist opens the hood of his or her vintage vehicle, the alternator generally isn’t what’s admired most. In fact, short of a charging system issue that forces action, the belt-driven voltage generator is so reliable that it can operate inconspicuously for years without maintenance. Nothing underhood is truly maintenance-free, however, and our Pontiac’s alternator proved just that. It wasn’t a charging issue that drew our attention. Instead, a persistent chatter at idle speed indicated something was amiss. A cursory check revealed that an internal bearing was beginning to fail, and without swift action it could leave us stranded.

For our ’76 Firebird’s 80-amp 10SI-series alternator, bearing replacement requires removal and disassembly. After disconnecting the battery and removing the alternator’s drive belt, electrical connections, and mounting hardware, it simply lifted out and away. On the workbench, we used a 15⁄16-inch wrench and 5 ⁄16-inch hex-wrench to remove the cooling fan retaining nut and lock washer, the fan, and its shaft spacer.

Our ’76 Firebird was originally equipped with a 10SI (or System Integrated)-series alternator developed and produced by GM’s Delco-Remy division in a variety of sizes and output ratings. While remanufactured 10SI alternators are typically stocked at local parts stores, we find originality important and decided to completely disassemble our Firebird’s original 80-amp unit and replace its shaft bushings. That then afforded us the opportunity to replace the internal electronics, essentially resulting in a complete alternator rebuild. Follow along to see how we did it.

A 3⁄8-inch socket was used to remove the four through-bolts that secure the alternator case halves together. The alternator assembly was then separated by lifting the halves apart.

Read on

Anybody can replace disc brake pads and rotors. Here’s how to do it the right way – Daniel Strohl @Hemmings


As the dominant choice for both front and rear brake systems for the last quarter-century, disc brakes offer a number of advantages over drums, including better serviceability. Without having to deal with return springs and adjustment wheels, a nice clean disc brake rotor and pad replacement should take about half the time a drum brake service requires.

But that’s not to say disc brake service doesn’t benefit from taking your time and paying attention to the details as you go along. Sure, you could breeze through and be back on the road in no time, but with a little bit of forethought you can get the best performance from your new brakes, avoid extensive damage, and make your next brake replacement go much smoother.

We followed along as tech columnist Jim O’Clair got his hands dirty replacing the brakes on a late-model Subaru and pointed out various tips, tricks, and other good advice for servicing pretty much any vehicle with disc brakes.

Hang The Caliper

While you should always inspect the brake hoses and the calipers when taking apart the disc brakes for service, it’s not always necessary to replace the hoses and calipers.

In those instances when you’re replacing just the rotors and pads, make sure to hang the caliper up and away from your workspace rather than just let it dangle by the hose. Brake hoses aren’t meant to be kinked or stretched, and dangling the caliper can do both, leading to damage

.While you could easily buy a caliper hanger set or devise a caliper hanger from zip ties, rope, or an old cloth, Jim fashioned one from a length of chain and a couple of hardware store S-hooks that he had laying around to make an easily adjustable, simple to use hanger. Make sure to hang the caliper from something sturdy and not from a brake line, hose, or fender liner.

Read on

12 essential automotive chemicals for your garage | DIY – Kyle Smith @Hagerty


I remember the days when you only needed a roll of duct tape and a lubricant in your toolbox. These days there are so many automotive chemicals it can make your head spin. Lubricants, penetrants, cleaners, adhesives; where do you start? In this DIY, Kyle Smith breaks down what he thinks are the essential chemicals you should always have handy in your garage. #DIY#KyleSmith#NeverStopDriving


  • Contents of this Video:
  • 0:00​ Intro
  • 0:47​ Multi-Purpose Grease
  • 1:22​ Threadlocker
  • 2:13​ Dielectric Grease
  • 2:52​ WD-40 & PB Blaster
  • 4:09​ Starting Fluid
  • 4:59​ White Lithium Grease
  • 5:38​ Carb Cleaner
  • 6:20​ SEM Solve (Paint Prep)
  • 7:10​ Brake Clean
  • 7:56​ Engine Degreaser
  • 8:32​ Glass Cleaner
  • 9:16​ Interior Cleaner
  • 9:37​ Outro

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Tech: How To Measure For Installing Larger Wheels And Tires – From Rod Authority


Always been a bit confusing for me working out wheel sizes, PCDs  and all that stuff!

Tech: How To Measure For Installing Larger Wheels And Tires

Wheels and tires can make or break the look of a car. You can have a clapped-out, rusty Camaro with a nice set of wheels, and it will typically look pretty cool. On the opposite end of the spectrum, a bad wheel choice can make a fully-restored and painted showpiece look less than spectacular.

This Rod Authority article  By Randy Bolig makes it a lot more simple to understand