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Views: 0 Author: Site Editor Publish Time: 2025-05-21 Origin: Site
Spark plug wires carry high-voltage electricity from the ignition coil to spark plugs. These wires must handle heat, vibration, and electricity without fail. Crimping matters. It connects the wire to terminals. Done right, it keeps the engine firing clean. Done wrong, it causes misfires, rough idle, poor fuel economy, and wear on ignition components. A tight, strong crimp using a quality wire crimper means steady power and longer part life.
Pre-assembled kits can fail. Universal kits often don’t match engine specs. Crimping custom wires ensures perfect fit, better resistance, and clean routing. Whether building a race car, tuning a street rod, or fixing a daily driver, proper crimping ensures performance and reliability. It also adds to the satisfaction of a DIY job well done.
To do the job right, gather these:
| Tool/Material | Purpose |
|---|---|
| Wire crimper | Compresses terminal onto wire |
| Spark plug wire stripper | Removes jacket cleanly |
| Dielectric grease | Prevents corrosion inside boots |
| Replacement terminals | Choose single or double crimp |
| Boots (plug and coil ends) | Protects connection |
| Razor blade or trimming tool | Precise cuts |
| Multimeter | Tests continuity and resistance |
| Heat shrink tubing (optional) | Adds sealing and strain relief |
Top choices for wire crimper include MSD Pro Crimp, ratcheting styles, or Pertronix crimp tools. Don’t skip the dielectric grease. It keeps boots clean and dry, and prevents arcing. Heat shrink can help keep moisture out and add a clean look to wires.
Single crimp: Folds conductor over jacket. One crimp point. Easy for beginners.
Double crimp: One crimp for conductor, one for insulation. Stronger, more secure.
| Terminal Type | Color | Use |
|---|---|---|
| Single | Brass | Basic kits, older engines |
| Double | Silver | Performance, high-vibration setups |
Socket style (common in older systems)
HEI (High Energy Ignition, GM-style)
Coil pack terminals
Power sports variants (dirt bikes, ATVs)
Straight
45-degree
90-degree
HEI snap-on
Choose boot angle based on clearance needs, heat sources, and routing plans. Right boot shape reduces strain and makes service easier.
Slide boot onto wire first. Grease inside lightly. Use dielectric grease. Makes install easier. Forgetting this step means redoing your crimp.
Use spark plug wire stripper. Remove outer jacket carefully. Leave 3/4 inch for single crimp. Leave 1/2 inch for double crimp. Don’t nick inner conductor. Don’t leave strands loose. It’s vital to retain conductor integrity for low resistance.
Rotate blade gently. Don’t cut too deep.
Keep wires clean and straight.
Trim jacket only. Leave core intact.
For single crimp: fold conductor strands back over insulation. Keeps it centered. Builds strength. Don’t twist too tight. Uniform folding helps secure the crimp.
Place terminal saddle over wire. For double crimp: conductor fits in front pocket, jacket in rear pocket. Align it carefully. No stray strands. Correct alignment avoids weak crimps.
Insert terminal into correct slot on wire crimper. Squeeze handles firmly. Don’t stop halfway. Use even pressure. Crimp once. Don’t wiggle. Crimp should grip wire tight without crushing. A quality wire crimper ensures consistency.
Crimp conductor first. Then insulation. Use marked sections of wire crimper. Strong double crimp stops pull-out. Finish with clean shape. Feel the click and inspect both ends. Good crimp should be flat and even.
Use multimeter. Check continuity. Set to ohms. Touch probe to terminal, then plug end. Resistance should be under 5,000 ohms/foot. No reading? Crimp failed. Redo it. Better to fix now than diagnose misfires later.
Slide boot up over terminal. Rotate while pushing. Use dielectric grease again. Prevents sticking. Keeps water and dirt out. Boot must fully seat. Hear or feel click on HEI boots. Tug lightly to ensure full engagement.
Boot not seated? Wire may arc. Misfires begin. Double-check fit before moving on.
Set to resistance mode. Test every wire end-to-end. Resistance should be:
Under 10,000 ohms total for long wires
Under 5,000 ohms for short wires
High reading? Check crimp. Check conductor. Try again if needed.
Loose wires
No continuity
Gaps in terminal
Poor engine performance
Bad crimps kill spark. Don’t ignore poor tests. Fix before running engine.
| Mistake | Result |
|---|---|
| Over-stripping | Weak grip, exposed wire |
| Under-stripping | Terminal won’t fit |
| Wrong terminal type | Loose fit, arcing |
| Improper conductor folding | Weak spark, poor contact |
| Low crimp pressure | Terminal falls off |
| Forgetting to slide boot | Can’t install after crimping |
Use practice wires before working on final set. Mistakes cost time and engine health.
| Type | Pros | Cons |
|---|---|---|
| Bulk wire | Full custom fit | Needs full crimping |
| Semi-terminated | Pre-crimped on one side | Still needs correct length cut |
Carbon core: Common. Resists EMI. Moderate resistance.
Spiral core: Performance choice. Low resistance. Flexible.
Solid copper: Very low resistance. Not for EFI cars.
HEI terminals need HEI boots. Socket-style use round plug boots. Match engine, distributor, and coil end. Using mismatched parts causes poor fit, voltage leaks, and bad ignition.
Summit Racing
Jegs
Amazon
Manufacturer direct: MSD, Accel, Pertronix
Choose quality over price. Cheap tools break. Cheap wire burns. A reliable wire crimper lasts decades and ensures perfect crimps every time.
No. Crimps lose grip after use. Always use new terminals.
Just long enough to reach with slack. Avoid tight bends. Measure each one. Keep routing clean and away from exhaust.
Technically yes, but never recommended. Pliers crush. Poor crimps cause misfires. A proper wire crimper ensures safe connections.
Every 30,000 to 50,000 miles. Or when cracked, burnt, or failing resistance tests. Always test before replacing.
It prevents corrosion. Keeps boots sealed. Eases future removal. Always use it. One small dab can save hours later.
MSD YouTube: Pro Crimp Tool demo
Pertronix install video
Summit Racing blog: Choosing spark plug wires
Holley Tech: Spark plug wire tech tips
Instruction PDFs from manufacturers
Forums like LS1Tech, FordMuscle, and The H.A.M.B.
Crimping your own spark plug wires is easy with the right wire crimper. You save money. Get perfect fit. Boost performance. Avoid misfires. Whether you use single crimp or double crimp terminals, prep right and crimp tight. Measure resistance. Use dielectric grease. Don’t rush.
Building clean ignition wires takes care. But the reward is smoother idle, quicker starts, and reliable power. Got questions? Drop them below. Share your experience. Let's build better wires together.
If you’re building a custom harness or upgrading your engine bay, mastering your wire crimper technique brings professional-level results to any garage project.
