Dealing with common issues in your trusty GM HEI (high energy ignition) distributor? Don’t worry, you’re not alone. Many classic GM muscle car owners face frustrating distributor problems that can leave your prized vehicle sitting lifeless in the garage.

Check for corroded or burnt HEI distributor cap

One of the most frequent culprits behind GM HEI distributor malfunctions is a corroded or burnt distributor cap. The cap is crucial for channeling the high voltage spark to the correct cylinder’s spark plug wire. But over years of heat cycles and moisture, the cap can become damaged. Inspect visually for cracks, carbon tracking or burned spots and use a cap tester to check for leakage.

Replace cap and rotor as a set

It’s wise to always replace the distributor cap and rotor together since they wear as a set. The rotor spins to distribute the spark, so a pitted or warped one causes misfires. And don’t forget new cap gaskets when reassembling!

Use dielectric grease

Adding dielectric grease to the cap’s terminals prevents corrosion and improves conductivity. It also helps the spark plug boot seals adhere better for a tight fit.

Inspect crack, wear of HEI distributor rotor

As mentioned above, the distributor rotor is spinning thousands of times per minute, enduring heat and friction. Inspect your HEI distributor’s rotor for any cracks, burned spots or excessive wear. If the tip is very worn, it can allow voltage to jump to the incorrect spark plug wire.

Check rotor spring and clips

While replacing the rotor, also check that the spring clips and mounting hardware are in good shape. The rotor has to snap firmly into place on the distributor shaft.

Replace faulty ignition coil in distributor

The ignition coil in an HEI distributor boosts the low 12V input voltage up to thousands of volts for the spark plugs. But over time, factors like heat cycling can cause internal winding damage. Use a multimeter to check coil primary and secondary resistance specs. Out of spec readings indicate it’s time for a new coil.

Inspect external ballast resistor

If your GM muscle car has an external ignition ballast resistor, check that first. A faulty resistor can cause low input voltage to the coil.

Examine HEI pickup coil and module

The magnetic pickup coil paired with the ignition control module are the brains of the HEI distributor. The pickup generates the signals for spark timing while the module amplifies voltage and switches the coil primary current.

Ensure air gap clearance

For accurate timing, the pickup coil air gap from the reluctor must be set properly. Use a feeler gauge to check the spec. Also inspect for cracked pickup coil insulation.

Test module and pickup

Use a digital multimeter to verify pickup coil resistance. Check for correct module input and output voltages. Intermittent issues can arise so it’s best to bench test if possible.

Check for loose, damaged spark plug wires

The high voltage spark has to traverse resistive spark plug wires to reach the plugs. Inspect along the length of each wire for cracks, burns or damaged insulation that allows voltage to leak out. Also ensure the boot seals firmly over the distributor cap towers and plugs.

Use dielectric grease

A bit of dielectric grease in the wire boots and on the plug end terminals significantly reduces resistance for a stronger spark. It also helps prevent moisture ingress.

Replace as a complete set

For best performance, install a fresh set of plug wires when servicing the distributor. Keep wire routing and lengths identical for correct firing order.

Replace worn distributor gear or shaft

The distributor shaft spins on a bushing and drives the gear that meshes with the camshaft. But excessive slop can develop over time. Check for up/down and side-to-side looseness by rocking the distributor body.

Consider bronze gear upgrade

An original nylon distributor gear wears rapidly from camshaft friction. An affordable bronze gear upgrade provides far greater durability and accuracy.

Check gear mesh backlash

Too much slop in the gear mesh allows timing to drift as rpms change. Use a dial indicator to precisely check the backlash spec.

Fix vacuum advance unit problems

Many GM V8 engines utilize vacuum advance to dynamically alter ignition timing. The diaphragm unit bolts to the distributor side. Check for cracked hoses, leaks, stuck advance plate or loose mount.

Test centrifugal advance

The counterweights and springs controlling the centrifugal advance can also wear out over time. Verify proper operation with a timing light at varying engine speeds.

Adjust vacuum canister if needed

To fine tune the vacuum advance, adjustable canisters are available. But check other potential vacuum leaks first before adjusting.

Inspect distributor advance weights and springs

Along with vacuum advance, centrifugal force on weights and springs controls ignition timing. But over decades of heating and cooling cycles, the springs can take a set or bind up.

Check for worn distributor shaft

Excessive play on the distributor shaft allows the weights to flutter at higher rpm. This varies timing erratically.

Consider an advance curve kit

Upgraded advance kits are available with higher spring pressures and multi-stage curves for a more ideal timing profile.

Clean and re-gap spark plugs to spec

Of course, don’t forget to check the final recipients of the spark – your spark plugs! Old plugs can be fouled or the gaps widened. Clean thoroughly and re-gap to factory spec for improved combustion.

Use anti-seize on plug threads

A small amount of anti-seize lubricant on the plug threads prevents galling in the aluminum heads when removing later.

Verify plug heat range

Make sure to consult your tune-up specs for the proper spark plug heat range. The wrong range can cause pre-ignition or fouling.

Verify proper ignition timing and adjust if needed

Finally, use a timing light with the engine warmed up to check the total advance timing. Incorrect total timing can cause performance or engine damage issues.

If the timing is off, you may need to adjust the timing tab on the distributor body to dial it in correctly after checking for binding advance mechanisms.

By methodically checking each component, you can often get your temperamental GM HEI distributor providing crisp, reliable spark once again. That means easier starts, smoother idle and loads of full-power fun cruising down the highway.

Having issues with your classic GM muscle car’s HEI distributor? Don’t despair. With some methodical troubleshooting and a few key replacement parts, you can have that high-energy ignition system sparking properly again.

Inspect crack, wear of HEI distributor rotor

The distributor rotor is an often overlooked component, but it’s spinning at engine speed every time you drive. So inspect yours closely for any cracks radiating from the center mounting hole or signs of excessive wear on the contact tips.

How can you tell if the rotor is excessively worn? Check the thickness of the rotor tip with a small ruler. If it’s worn below the manufacturer’s service limit, replacement is required to prevent misfires or crossed sparks to the wrong cylinder.

Why rotors matter

The rotor essentially switches each high voltage spark pulse to the correct spark plug wire in the firing order. So if the contact tip gets very thin from wear, it can allow voltage to jump to the wrong terminal, scrambling your engine’s ignition timing.

Always change distributor cap too

Any time you replace the rotor, it’s absolutely essential to also install a new distributor cap. They wear as a set and replacing only one component can cause driveability issues later.

Watch for warped or bent rotors

In addition to wear, inspect your HEI distributor rotor for any warping or visible wobble as it spins. Heat cycles over years can warp the rotor disc. This alters the crucial air gaps that the voltage must jump.

A bent rotor shaft prevents smooth spinning at high rpm. So gently check for any binding or tight spots when rotating the rotor by hand.

Check rotor spring and clips

The distributor rotor relies on firm spring tension to hold it tightly on the shaft. But over many heat cycles, the spring can lose its “springiness” and allow sloppy rotor fitment.

Carefully inspect your HEI distributor rotor’s mounting spring clips for any cracked, brittle or distorted areas. Also check the spring tabs for signs of fatigue or cracking.

Why a tight rotor matters

With a loose rotor, the centrifugal forces at higher rpm can cause it to lift slightly off the shaft and wobble. This allows the spark timing to waver and drift.

Don’t forget new clips

Be sure to install new spring clips and hardware along with the new rotor for proper retention. Reusing old worn clips defeats the purpose.

Check shaft wear

While you have the rotor off, inspect the distributor shaft condition as well. Excessive wear allows the rotor to wobble. A new bushing or shaft may be needed in severe cases.

Replace faulty ignition coil in distributor

Without a properly functioning ignition coil, your HEI distributor can’t provide adequate voltage for healthy spark plug firing. But coils can fail after years of countless heat cycles and vibration.

How can you test your coil? Use a multimeter to check the primary and secondary resistance values first. Out of specification readings indicate potential winding issues requiring coil replacement.

Watch for overheating damage

Ignition coils are filled with insulating varnish that can boil out after overheating episodes. This leads to shorted windings down the road. So be sure to solve any engine overheating problems promptly.

Consider upgrading to a hotter coil

For even better spark energy, consider upgrading to a high performance coil matched with performance plug wires. Just verify it has the proper primary resistance for your HEI distributor system.

Check for loose, damaged spark plug wires

Your HEI distributor relies on ignition wires to channel the high voltage pulses to each spark plug. But worn, damaged insulation allows the voltage to leak away before reaching its target.

Carefully inspect each distributor wire by hand, looking for any cracking,carbon tracking or burns. Also ensure the rubber boots seal tightly over the distributor cap towers and plug ends.

Why wire resistance matters

Higher resistance in the plug wires causes voltage losses. This robs combustion power and can even prevent the engine from starting.

Consider a wire upgrade

Many opt for performance spiral core wires when servicing an HEI distributor. The tighter coil windings reduce resistance for a hotter spark. Just match the wire set length to OEM for proper firing order.

With some methodical inspection and replacement of worn components, you can have your HEI distributor running like new again. Then it’s time to hit the road and enjoy some carefree cruising in your classic!

Replace faulty ignition coil in distributor

Having ignition issues with your GM HEI distributor? I feel your pain. Dealing with a faulty distributor can leave you stranded and frustrated. But don’t despair, my friend – with a few simple repairs, you can get your ride back on the road. Stick with me and I’ll walk you through the most common GM HEI distributor problems, along with the fixes that’ll have you cruising again in no time.

First up – the dreaded ignition coil failure. This little baby is at the heart of providing juice to your ignition system. When it goes kaput, your engine’s gotta no spark, compadre. Replacing a damaged ignition coil is pretty straightforward, hermano. Just remove the distributor cap and rotor to access the coil. Disconnect the electrical lead and mounting bracket, then swap in a new coil. Be sure to connect the new coil properly and replace the cap and rotor before starting ‘er up. That should get your ignition firing again.

Next up on the hit list – corroded distributor wiring and connectors. Over time, moisture and grime can work their way into the wiring harness leading to the distributor, causing corrosion and loose connections. The hei distributor plug and terminals are especially prone to corrosion. Loose wiring prevents proper current flow, leaving your engine stumbling for power. The fix? Carefully inspect the distributor wire harness, connectors, and terminals. Clean any corrosion, replace damaged wires, re-seat connections, and apply dielectric grease to prevent future issues. Taking time to troubleshoot and repair shoddy distributor wiring can really pay off down the road.

Now onto a sneaky one – worn distributor shaft bearings. These little bushings allow the distributor shaft to spin freely. But wear and tear eventually takes its toll, causing excessive shaft play. The resulting timing fluctuations can make your engine run rough, stall, or not start. Thankfully, rebuilding the distributor to replace worn shaft bearings is a straightforward DIY project. Distributor overhaul kits include new bushings, seals, and hardware. With the distributor removed, simply disassemble, clean, and reassemble with the new parts. Don’t forget to check the gear while you’re in there. Voila – with the fresh bearings installed, your distributor will spin freely once again.

Speaking of spinning, let’s chat about the distributor shaft itself. If the distributor gear becomes damaged or excessively worn, it can throw off your ignition timing. Symptoms include rough idle, hesitation under acceleration, backfiring, hard starting, and poor performance. Inspect the distributor gear for chipped, broken, or excessively worn teeth. If it’s toast, the only remedy is to replace the shaft or the entire distributor. A quick swap and you’ll be back in sync.

Now for one that really gets my goat – sloppy distributor cap and rotor. These engine staples endure heat, vibration, and wear. Eventually carbon tracks, corrosion, and cracks can develop, allowing voltage to leak. Hard starting, misfires, and rough running can quickly ensue. Luckily, a new cap and rotor set is cheap insurance. I recommend replacing them proactively every 30k miles. The improvement in engine performance and reliability will speak for itself.

Of course, we can’t discuss distributor issues without mentioning everyone’s favorite – the faulty ignition module. This little brain behind the scenes controls the timing of the spark. When it malfunctions, the engine loses its firepower. Warning signs include intermittent stalling, no starts, and flashing check engine light with ignition-related codes. Sadly, modules don’t repair well – replacement is the only cure. Swapping in a new module should have you up and running again lickety-split.

One more wire-related issue to highlight – worn or damaged spark plug wires. These critical conduits deliver juice from the coil to the plugs. Cracks, corrosion, and leakage problems can leave your engine misfiring like Grandpa’s old .22. Replacing worn plug wires restores voltage delivery for smooth running. I recommend hei distributor wire connector replacement every 50k miles.

Well, that about wraps up our tune-up on common GM HEI distributor repairs. With a little DIY determination, you can diagnose and fix most issues yourself. Just follow proper precautions and safety steps. Take your time, get the right replacement parts, and be meticulous during reassembly. Before you know it, your ride will be running right again. Here’s to happy motoring and putting these annoying distributor problems in the rearview mirror!

Examine HEI pickup coil and module

Experiencing some gremlin in your GM HEI distributor? Say it ain’t so! But don’t sweat it, we’ll get to the bottom of this lickety-split. When your distributor starts acting up, there’s a couple of key components to inspect – the pickup coil and ignition module. Stay tuned and I’ll walk you through why these fellas can cause issues, and how to examine them to get back on the road.

Let’s dive into the pickup coil first, compadre. This little inducer coil generates the voltage needed to fire the ignition module and distribute the spark. It’s essentially the activator for the entire ignition system. If the pickup coil is damaged or not generating sufficient voltage, your distributor can’t do its thing. The engine may not start, or will run rough and lack power. Weak pickup coils are often caused by shorted or corroded windings, or loose connections. Time for some troubleshooting, hermano!

First, visually inspect the pickup coil wires and connections. Look for any corrosion or loose hei distributor plugs. Clean and reseat any questionable connections. Next, use a multimeter to test the pickup coil resistance – you should get a reading between 800-1400 ohms. Out of spec means it’s time for a new pickup coil. While you’re test driving, check for erratic voltage readings that indicate a flaky coil winding.

If the pickup checks out, the next suspect is the ignition module. This little brain controls the ignition timing and spark distribution. When it fails, the engine loses its firepower. Symptoms include rough idle, stalling, hard starting, misfires, and flashing check engine light. Unfortunately modules don’t repair well – replacement is the fix.

Accessing the module may require some disassembly. Remove the distributor cap and rotor to gain entry. Disconnect the electrical connectors and any mounting hardware to free up the module. Take care not to damage internal parts during removal. When installing the new module, follow the manufacturer’s directions closely. Reconnect all distributor wire connectors and reassemble precisely.

While you have the distributor opened up, inspect for any cracked hei distributor wires or damaged components. Check that the magnetic rotor moves freely. Clean any debris and relube if needed. Proper alignment is critical for the distributor to operate smoothly.

An easy test for module issues is to connect a known-good spare module, or swap yours into a running vehicle. If the problems disappear with the new module, you’ve found the culprit. No guesswork required!

Now let’s chat about preventive maintenance. To maximize module life, use dielectric grease on all electrical connections to reduce corrosion. Install a distributor cap with built-in ignition noise filter. Keep connections clean and tight. And consider proactive module replacement around 100k miles.

For pickup coils, inspect wire condition and connections periodically. Look for damage to coil windings or insulation. Measure pickup resistance yearly – out of spec means replacement time. And apply protective conformal coating to resist moisture damage.

With age, heat cycling, vibration, and wear, both modules and pickup coils eventually fail. But with diligent inspection, testing, and maintenance you can prolong their lifespan significantly. Identify problems early, replace components proactively, and take steps to protect your investment.

Well amigos, that just about wraps up our tune-up on examining your HEI pickup coil and ignition module. With consistent TLC, these key components should provide thousands of miles of faithful service. Here’s to smooth sailing ahead! Vaya con Dios!

Check for loose, damaged spark plug wires

Got a misfiring engine? Having ignition issues with your classic GM ride? Don’t sweat it, amigos. Inspecting your spark plug wires should be high on your troubleshooting checklist. Let’s rap about how to check for loose wire connections and damaged plug wires causing problems in your HEI distributor.

Those sparky spark plug wires have one simple job – reliably deliver voltage from the distributor to the plugs to ignite that sweet combustion. But wear and tear over miles of operation can take a toll. Cracked insulation, corrosion, and loose wire connections or boots allow voltage to leak out rather than reach the plugs. The resulting misfires and poor performance can leave you scratching your head.

During inspection, carefully examine each plug wire from tip to tip. Look for any cracks, abrasions, or melted areas in the insulation, especially near the wire terminals. Then follow the length of each wire, checking for corrosion buildup and damage. Give each spark plug boot a gentle tug to confirm tight connections. Loose boots can definitely contribute to misfires. While you’re probing around, ensure the distributor wire connections and hei distributor plug are also snug.

It’s ideal to use a multimeter to test plug wire resistance for any out-of-spec readings. But you can also test for faults using an inexpensive spark tester tool. Simply clip it over each wire while cranking the engine. An erratic or weak spark indicates that cylinder is missing fire. Swap wires with a known good cylinder to confirm the problem wire.

If you discover any questionable wires, the best bet is simply to replace the entire set. Trying to patch cords or mix and match can cause further headaches. Complete plug wire sets are affordable and give you peace of mind knowing all connections are mint.

While installing the new plug wires, follow the factory routing exactly. Correct firing order is critical for smooth running. Apply dielectric grease inside the spark plug boots and distributor cap tower contacts to prevent corrosion. And always connect and disconnect wires by the boot – never pull on the wire itself. This avoids putting stress on the connections.

Be methodical when positioning and connecting each new wire. Loose connections or crossover will have you right back in the same sputtering boat. Take your time to guarantee everything is routed properly and firmly attached. Your engine will thank you with that sweet steady idle and crisp acceleration.

As preventive maintenance, I recommend inspecting plug wires closely every tune-up and replacing them proactively every 50-60k miles. Quality wires constructed with spiral core suppression will provide superior spark delivery and radio noise reduction. Refrain from cheaping out on el cheapo plug wires – you get what you pay for.

While you have the distributor open for wire replacement, it’s smart to examine other components for wear. Carefully check the distributor wire harness, cap, and rotor for cracks or corrosion. Ensure the rotor spins freely with no binding. Clean any gunk buildup and lubricate if needed. Proper cleaning and lubrication go a long way for smooth operation.

Be sure to reinstall the distributor cap and rotor precisely aligned – incorrect orientation can throw off timing. Always connect all distributor wire connectors securely. Don’t leave any loose ends that could vibrate free. Precision and care here make all the difference.

Well compadres, that wraps up today’s tune-up on checking spark plug wires to keep your GM HEI distributor running right. With diligent inspection and proactive replacement, you’ll keep the voltage flowing and avoid being stranded. Here’s to smooth cruising ahead under blue skies! Adios amigos!

Replace worn distributor gear or shaft

Uh oh, is your distributor gear looking a little worse for wear? No worries, we’ll get that fixed up. Let’s chat about inspecting and replacing a worn drive gear or damaged shaft to get your GM HEI distributor back in fighting shape.

That small drive gear on the bottom of the distributor shaft serves one critical purpose – turning the oil pump to lubricate your engine. If the gear teeth become excessively worn, chipped, or broken, it can’t properly mesh with the camshaft gear to spin the pump. Lack of oil flow means big trouble in little China.

Symptoms that the drive gear or shaft are damaged include low oil pressure, dirty oil, oil leaks, tapping or knocking noises, and excess play or wobble in the shaft. If you suspect issues, it’s inspection time, amigos.

Start by carefully examining the drive gear teeth. Look for abnormal wear, heavy scuffing, chipping, or missing cogs. Give the distributor shaft a gentle wiggle – excessive shaft play indicates worn bushings or bearings. If damage is confirmed, replacement will be needed to restore proper function.

For drive gear replacement, the distributor must be removed from the engine. This gives access to disassemble the distributor and lift off the drive gear. Clean any grime from the shaft and coat with fresh lubricant. The new gear slides into place and locks onto the shaft. Reassemble precisely – proper shaft/gear alignment is critical. Don’t forget to reconnect the distributor wire connectors and hei distributor plug.

If the entire shaft is damaged, a full distributor replacement may be needed. Transfer any usable parts like the cap and coil to the new unit. Install the fresh distributor with care, ensuring the drive gear mesh is aligned properly. Reconnect all hei distributor wire harnesses in their original locations.

While you have the distributor out, inspect the whole assembly for wear. Look for sloppy shaft play, worn bushings, cracked housing, damaged trigger wheel, or corrosion. Rebuild kits are affordable insurance to refresh worn components.

Pro tip: When reinstalling the distributor, be sure it’s fully seated on the camshaft before tightening down the hold down clamp. An out-of-sync distributor can cause major timing issues resulting in poor performance.

To maximize drive gear life, maintain proper lubrication and minimize contamination. Change oil regularly and use the recommended weight. If you spot seal leaks, repair promptly to prevent oil loss. Keep the distributor housing clean by wiping down the exterior periodically.

Preventative maintenance also pays dividends. Consider replacing the drive gear proactively every 60-80k miles or during major engine work. Upgrade to a hardened steel gear if suitable. This improves durability and longevity compared to plastic factory gears.

While inspecting the drive gear, check the full distributor shaft for up/down and side/side play. If the shaft wobbles excessively in the bushings, a rebuild should be scheduled soon. Don’t wait for complete failure – that could really leave you stranded.

There you have it amigos – a tune-up on inspecting and replacing worn drive gears and distributor shafts. With close monitoring and preventive replacement, you can keep this critical component engaged for the long haul. Here’s to happy motoring ahead!

Fix vacuum advance unit problems

Got an engine that’s idling rough or stumbling under acceleration? The culprit could be issues with your distributor vacuum advance unit. Let’s rap about diagnosing problems with this emissions-era component and getting your timing back on track.

The vacuum advance uses manifold vacuum to dynamically adjust ignition timing based on engine load. At idle and low rpm it advances timing for smoother running. Under heavier throttle it disengages for full spark output. Malfunctions cause incorrect advance, running issues, and check engine lights.

Symptoms of vacuum advance troubles include rough idle, stalling, hesitation, backfiring, lack of power, and engine codes for timing or fuel trim faults. If you suspect issues, it’s time to test the unit.

Start with a visual inspection of the vacuum advance on the side of the distributor. Look for cracked hoses, loose fittings, or a leaky diaphragm. Confirm the vacuum nipple is clean and hose is firmly attached. Give the advance arm a wiggle – it should move freely without binding.

Use a hand-held vacuum pump to test diaphragm and spring function. At 15-20 inches of vacuum, the mechanism should smoothly advance. If movement is sticky or limited, cleaning or replacement may be needed.

To remove the advance, detach the vacuum hose and remove the retaining screw or clip. Disconnect any electrical leads from the distributor wire harness. Lift off the advance plate and withdraw the diaphragm/spring assembly.

Thoroughly clean the advance cavity and components of debris. Inspect closely for cracks, dried out diaphragm, and broken springs. Any defects mean replacement time. Reinstall the cleaned or new parts in reverse order, taking care not to bend the advance plate.

While you have the distributor opened up, inspect and clean the points if equipped. Check the rotor and distributor wire connectors for damage. And ensure the vacuum hose fitting is leak-free.

If surging, backfiring, or rough running continue after testing the unit, the problem may lie elsewhere. Verify base and centrifugal timing are correct using a timing light. Inspect the distributor Advance Stop Bushing – if missing or broken, timing will be erratic.

Check for vacuum leaks downstream from the advance unit, as this can provide false vacuum readings. Common sources include carb gaskets, EGR valves, and brake booster leaks.

On HEI distributors, verify the vacuum canister is getting 12v power from the correct terminals. Swapping in a known good vacuum canister can help diagnose electrical faults.

To maximize vacuum advance life, use a fuel filter to catch contaminants before they reach the inlet nipple. Annual cleaning keeps the diaphragm flexing freely. And check adjustment periodically – the spec is typically around 10-15 degrees advanced.

There you have it friends – a tune-up on diagnosing and repairing faulty vacuum advance systems. Keep that vacuum timed just right for smooth cruising ahead. Your engine will run quiet as a church mouse and happy as a clam. Adios for now!

Inspect distributor advance weights and springs

If your classic GM muscle car is suffering from poor performance, rough idle, or misfiring at higher RPMs, the issue may lie with the distributor advance system. The heart of this system is the advance weights and springs inside the distributor, which control the ignition timing. After years of use, these components can become worn, bent, or corroded, disrupting the finely tuned advance curve.

Advance weights are attached to the distributor shaft and fly outwards under centrifugal force as the engine RPMs increase. This rotates the top plate inside the distributor, advancing the ignition timing. Springs counter this force and determine the rate of advance. Weaker or damaged springs can cause too much advance too soon, while stronger springs retard the timing. Bent weights may hang up or bind, preventing normal advance.

Inspecting and correcting issues with the advance system is crucial for restoring proper ignition timing. Here are 7 must-know steps for DIYers:

1. Remove the distributor cap and rotor

Before inspecting the advance mechanism, the cap and rotor must be removed. Label and disconnect all spark plug wires for proper reinstallation. Remove the hold-down bolt or clamp and lift the distributor cap off. Then remove the rotor by gently prying it from the shaft.

2. Check for binding, sluggishness

Manually rotate the distributor shaft through its full range of motion. Closely watch the weights for binding or sticking at any point. The weights should move smoothly outward when spun. Any hesitation means the advance system is hanging up.

3. Look for worn advance slots

Inspect where the advance weights pivot inside their slots. Excessive clearance indicates worn slots. Proper fit is around 0.001-0.003 inches. Any binding in the mechanism is likely due to excessively worn slots.

4. Check springs for fatigue or stretching

Weak or unevenly stretched springs can be diagnosed by comparing the installed height to a new spring. Examine for cracked or bent ends which may rub on the hub or shaft. If any are questionable, replacement is advised.

5. Inspect weights condition and movement

Closely check each advance weight for signs of wear, bending, or rubbing that inhibits free movement. Any binding, looseness, or corrosion pits will disrupt the advance curve. Advance weights must be replaced in sets to maintain balance.

6. Look for slop in weight pivots

A noticeable up/down slop or play indicates a worn pivot. To check, move the weights up and down while holding the base. If you feel excessive movement, new advance components may be needed.

7. Lube pivot points and shaft

A light lubricant on the advance weight pivots, spring ends, and distributor shaft allows smoother interaction and prevents binding. Use a high quality lightweight oil, not grease which can collect grit.

Periodically inspecting and correcting issues with advance system components is essential to maintain proper ignition timing as the engine RPMs change. Worn or damaged weights, sluggish springs, and sloppy pivots can all cause miss or hesitation issues. Careful DIY inspection and replacement of faulty parts restores smooth engine performance.

Rather than live with poor drivability and mileage, take time to inspect key distributor advance weights and springs. Your classic GM muscle machine will reward you with that crisp, seamless throttle response once again.

Some other common GM HEI distributor issues include:

• Corroded or loose wiring connections
• Cracked distributor cap allowing arcing
• Excessively worn cap, rotor, or ignition coil
• Binding advance system
• Incorrect ignition timing settings
• Weak or intermittent pickup coil signal

By carefully inspecting the cap, wires, advance system, and electrical components, many HEI problems can be corrected before resorting to replacement. Proper maintenance and tune-up procedures will help your HEI distributor provide reliable high-voltage spark for thousands of miles.

Clean and re-gap spark plugs to spec

Is your classic GM muscle car misfiring or suffering from poor performance? The culprit may be worn or fouled spark plugs. Restoring strong spark output requires periodic spark plug inspection, cleaning, and re-gapping.

Over time, spark plug gaps can increase through normal electrode erosion. Wider gaps can result in weak sparking, cross-firing, and combustion inconsistency. Shorter gaps cause premature firing. Deposits that build up on plugs also disrupt the spark.

For optimal ignition, spark plugs must fire at precise moments dictated by the distributor. Maintaining proper plug gap spacing is crucial to engine timing and performance.

Here are 7 key steps for DIY cleaning and re-gapping of spark plugs:

1. Remove plugs and inspect

Carefully detach the spark plug wires, then unthread the plugs from the cylinder head. Check for heavy carbon buildup and examine the electrode’s condition. Severe erosion indicates a need for replacement.

2. Clean deposits from plug

Use a wire brush or media blaster to remove carbon fouling from plug tip. Ensure the insulator, terminal, and gasket sealing areas are also cleaned of debris before reinstalling.

3. Check gap against spec

Use a round wire feeler gauge to measure the existing gap width between the side and center electrodes. The proper gap spacing for most HEI systems is around 0.035-0.045 inches.

4. Adjust gap if needed

Carefully bend the outer electrode to widen or narrow the gap to align with manufacturer specifications, if needed. Be cautious not to damage the electrode or ceramic insulator.

5. Check that gap is even

Always check the gap on both sides of the center electrode for uniformity after adjusting. The caliper-style feeler gauge is ideal for verification.

6. Clean threads and reinstall

Use a thread chaser to clean any debris from the spark plug threads. Apply anti-seize compound. Then carefully thread plugs back into the cylinder head to the specified torque.

7. Reconnect wires

Reattach the spark plug wires in the original firing order. Double check connections are fully seated to avoid crossfire.

Properly gapped and cleaned spark plugs will restore strong, consistent sparks for great performance. Weak or sporadic sparks from fouled or wide-gapped plugs are common causes of miss or hesitation in HEI engines.

Some other common GM HEI ignition issues include:

• Faulty ignition coil
• Cracked distributor cap
• Corroded plug wires
• Worn rotor or points
• Binding advance weights
• Incorrect ignition timing

Regular plug inspections and tune-up maintenance helps detect issues before they cause driveability problems. With properly gapped and seated spark plugs, your HEI distributor can keep delivering powerful sparks for maximum horsepower.

Verify proper ignition timing and adjust if needed

Is your classic GM V8 stumbling off idle or lacking power? Incorrect ignition timing could be the culprit. Verifying and adjusting the timing is a crucial tune-up step for peak performance.

The ignition timing mark on the harmonic balancer needs to precisely line up with the timing pointer at the correct moment. Off by a few degrees, and acceleration can suffer along with fuel economy.

Here are 7 key steps for DIYers to check and adjust ignition timing on a GM HEI distributor:

1. Warm up the engine

Timing must be set with the engine fully warmed up. Cold timing settings will be off. Get up to normal operating temperature before adjusting.

2. Connect timing light

Hook up a timing light following the directions. Disable any vacuum advance and disconnect EGR to check base timing only.

3. Aim at timing marks

Aim the timing light at the balancer timing marks with the engine at idle. The light flashes each time the number 1 cylinder fires.

4. Note ignition timing number

Check where the balancer mark lines up relative to the pointer on timing cover. Compare to factory spec for base idle timing, usually around 10 degrees BTDC.

5. Loosen distributor clamp

If timing needs adjustment, loosen the distributor clamp just enough so it will turn by hand. Do not remove completely.

6. Rotate distributor body

While watching the timing mark, carefully turn the distributor body to align marks to spec. Clockwise retards timing; counterclockwise advances it.

7. Secure distributor

Once dialed in accurately, secure the distributor clamp nut. Recheck with timing light and adjust as needed.

Properly set timing is crucial for crisp throttle response and optimal power. Advancing too much causes pre-ignition; retarding too far weakens low end torque.

Other common HEI ignition issues include:

• Faulty pickup coil or module
• Corroded wires and bad grounds
• Worn or fouled spark plugs
• Cracked distributor cap
• Binding advance weights

Regularly verifying timing with tune-ups helps avoid flat spots and poor performance. Dialing in the timing marks precisely keeps your HEI distributor providing maximum spark energy for great drivability.