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HOT ROD RESCUE: 1966 Chevelle with Starter & Ignition Problems

Marlan Davis Dec 22, 2017
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The Combo

Kenosha, Wisconsin's Dave Miracle has been into cars since high school. Like many of us, he took time off to raise three kids—that is, until he discovered a bare-bones 1966 Chevelle that had laid dormant in a friend's garage for 20 years. "Even though it was basically just a shell with a bunch of parts and boxes, it was too good a deal to pass up," Miracle relates. About the only drivetrain part remaining was the original factory 3.73:1 12-bolt Posi rearend. Sparing no effort, Miracle had the frame and control arms powdercoated. "Everything went tenfold from there: all-new interior, suspension and brakes, glass and trim, fluid lines, and stainless-steel bolts throughout. I wanted a no-hassle street driver but with plenty of get up and go, so I went for a 496ci Rat motor from Ateco Engine in Illinois. Behind it is a TCI TH400 and 2,800-rpm-stall torque converter."

Kenosha, Wisconsin's Dave Miracle has been into cars since high school. Like many of us, he took time off to raise three kids—that is, until he discovered a bare-bones 1966 Chevelle that had laid dormant in a friend's garage for 20 years. "Even though it was basically just a shell with a bunch of parts and boxes, it was too good a deal to pass up," Miracle relates. About the only drivetrain part remaining was the original factory 3.73:1 12-bolt Posi rearend. Sparing no effort, Miracle had the frame and control arms powdercoated. "Everything went tenfold from there: all-new interior, suspension and brakes, glass and trim, fluid lines, and stainless-steel bolts throughout. I wanted a no-hassle street driver but with plenty of get up and go, so I went for a 496ci Rat motor from Ateco Engine in Illinois. Behind it is a TCI TH400 and 2,800-rpm-stall torque converter."

The Problem

"Realizing that I was not the person who took the car apart," Miracle continues, "I thought putting it back together would be the most difficult part of the project—but I was wrong. When the car was done, it would slow down on cranking. When you released the ignition key when it did start, it felt like a kick in the teeth. There was a screaming sound as if you kept the ignition key in crank too long after the engine started. Sometimes it would backfire. This could happen at any time, but was worst after the car heated up. Everything was brand new with all the good parts, so I first thought there was something wrong with the tune."

Key

The lettered callouts at the beginning of each line below refer to the photo above. Any numbers or range of numbers at the end of a category line refer to numbered drawings and photos in the rest of this article below.

A] Starter/flexplate gear mesh (0108)

B] Voltage tests, wiring changes (0910)

C] Better grounds and terminals (1119)

D] AWG 6 charging wire (20)

E] Remove ignition resistor wire

F] Clean out bulkhead connector (21)

The Mechanical Diagnosis and Fix

One of our go-to rescue shops, Norm Brandes' Westech Automotive, is a stone's throw away from Kenosha. When Brandes got the car, he confirmed the slow cranking and starter kick-back. Was it just a tuning issue like the owner thought? "These symptoms can occur if the timing was excessively retarded," Brandes explains, "So we started by putting in a reasonable base timing of 12 degrees at the crank. That didn't help at all, so we suspected a mechanical or electrical issue. Miracle's Powermaster gear-reduction ministarter should have had more than enough cranking torque to get the job done."

Brandes first checked for mechanical interference between the starter drive pinion and flexplate ring gear. He discovered chipped flexplate ring-gear teeth, a sure sign of a mechanical issue. Mechanical causes of drive pinion-to-ring-gear bind may include:

  • Wrong tooth-engagement depth clearance between the crown of the drive-pinion gear and the root of the flexplate gear. On the Chevelle, this clearance was within spec.

Summit Racing

  • Wrong clearance between the back of the flexplate ring gear and the front edge of the teeth on the starter pinion. In the engaged position, the drive-pinion gear should be nearly on-center with the flexplate ring gear, but on the Chevelle, it was too far forward. To correct the for-and-aft engagement clearance problem as well as assess the starter's physical condition, Brandes shipped the starter to Powermaster in nearby Chicago for inspection. Even though the flexplate ring gear was shelled, Powermaster determined it was physically OK. As Brandes puts it, "We expected damage after all the abuse, but the Powermaster turns out to be the Plymouth Rock of starters!" Powermaster's techs corrected this problem by adding an extra internal shim.

  • Excessive flexplate runout. While rotating the flexplate, Brandes also noticed the clearance amount between the flexplate ring gear and the front edge of the teeth on the starter pinion had also changed slightly. Sure enough, an initial runout check revealed a way out-of-spec flexplate. That said, relaxing tension by backing off the torque converter mounting-bolt nuts brought flexplate runout within spec, indicating the problem was really with the converter. Believe it or not, the height of one converter mounting-pad turned out to be shorter than the other two—easily solved by shimming the short pad to equal the height of the other two pads. The old flexplate with its chipped teeth was replaced by a Scat externally balanced Chevy 454 SFI-certified flexplate.

The Electrical Diagnosis

The starter was no longer screaming and kicking back, but cranking remained slow and lazy. Electrical gremlins like this are hard to find because they appear fine at rest or under a light load, but generate high resistance under heavy amperage draws. Powermaster engineer Dave McILvaine showed up with a handful of digital multimeters to figure out where the ignition and charging circuit was losing current. Starting at Miracle's trunk-mounted battery, he checked the charging and cranking system for voltage drop on each side of every connector, terminal, and junction while cranking the engine. This includes the often-overlooked grounds, which are part of the full circuit.

These tests must be performed with the battery fully charged to 12.6 volts. To be sure you're not just seeing a battery surface charge, turn on your headlights for 2 minutes with the engine off. Shut everything down. If the static (no-draw) charge is still 12.5 volts, you're good to go. If not, you may have a battery issue. Downstream from the battery, a 0.10.3V drop across most connectors is acceptable; anything more is cause for concern. Collectively, under crank at the starter solenoid battery (B+) terminal, you should see a minimum 1010.5 volts (see electrical diagram, illustration 10). On the Chevelle, voltage sagged as low as 7 volts at the B+ terminal and the readings fluctuated. "We were getting inconsistent high-voltage drop from poor grounds and bad crimps," McILvaine says.

However, the long "Solenoid S" ignition cranking circuit that runs from the starter "B+" terminal to the alternator charge wire, ignition switch, neutral safety switch, and back to the S terminal—often a problem on old GM cars—surprisingly checked out OK once the master firewall bulkhead connector was purged of excess sealing goop.

As for the battery cables and charge wires, Miracle's No. 2 AWG battery cable size was sufficient for the system, but he was still relying on the original factory 12-gauge alternator charging wires with a much more powerful, late-model, 105-amp CS130 one-wire alternator, an upgrade Miracle installed to support high-draw modern accessories including air conditioning, electric fans, and an electric fuel pump. And the ignition wasn't operating at full power because the MSD standalone breakerless distributor was still receiving current through the original 1966 ballast-resistor wire. Like GM's big-cap HEI, the MSD unit must receive a full 12 volts at crank and at least 13.7 volts in Run to be all it can be.

The Fix: Electrical

Ground integrity was compromised by a powdercoated frame and sheetmetal ground screws. Westech installed rivet nuts—blind, self-upsetting, internally threaded inserts—in the frame to serve as ground-terminal hook-ups. Brandes says the install process using his hydraulic setting tool provides great metal-to-metal contact, while the rivet nut's full-length "real" threads permit use of standard bolts and washers. NAPA's electrically conductive Sil-Glyde multipurpose, silicone-based lubricant further enhanced ground integrity.

Miracle's battery cable terminals were too small for the cable size, and poorly crimped. The terminals were cut off and replaced with high-quality, crimp-style terminals using a quality crimping tool. Two additional ground straps were added to positively tie the engine to the frame.

Powermaster offers preterminated alternator charge-wires; a new 6-gauge charge wire was run independently from the solenoid B+ circuit to the alternator. The original 12-gauge factory charge wires were left intact to support the existing harness connections and distribution scheme that fans out from the (typical for old Chevys) horn relay busbar. Overlaying the factory red wires instead of disturbing or replacing them also kept the stock ammeter working, though it does read slightly high.

The stock ballast-resistor-wire-to-coil-positive-"run" wire was replaced by a standard 12-gauge high-temp GXL wire, ensuring full-power ignition output; no longer required, the old solenoid R-terminal bypass wire was eliminated. Parts Hound sells the weird Twin Lock terminal needed for the firewall bulkhead connector end of the new wire.

The Results

It's a Miracle! Once Westech whipped the battery cables, grounds, and charging wires into shape so Powermaster's ministarter could crank at its full 200lb-ft capacity, the Chevelle now starts right up with minimal cranking duration and no kickback. The engine also runs a lot smoother now that the ignition runs at full power.

Lessons Learned

Powdercoated frames look cool, but require that extra attention be paid to ground integrity. Sheetmetal screws do not make for a good ground point. "If you take care of the grounds, 90 percent of your electrical gremlins go away," Brandes says. "Voltage drop adds up, so pay attention to every terminal and connector in the system. Beware of poor terminations!"

Need Junk Fixed? If your car has a gremlin that just won't quit, you could be chosen for Hot Rod to the Rescue. Email us at pitstop@HotRod.com and put "Rescue" in the subject line. Include a description of your problem, a photo, your location, and a daytime phone number.

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