The first thing to let go on my 1990 Corvette Z51 after buying it used with 69,000-plus miles on the clock was the starter, but it didn’t happen all at once. That would have made it too easy to diagnose the fault. It was a sneaky, intermittent problem that at first seemed like ensuring the clutch pedal was fully depressed was all it took to start, but then the problem grew worse.
Having never owned a Corvette newer than a 1959 model I imagined the ’90’s problem was due to some modern-age DOT safety requirement like having a clutch pedal safety switch, so I located it and wired a bypass. This seemed to solve the problem for a few days. Then one early Sunday morning at the Balboa car show it reared its ugly head again. The beauty of a stick shift is they’re easy to start with a bum starter or a dead battery.
A friend and I pushed it to a fast roll then I hopped in and popped the clutch. A few blocks later the ’90 Z51 stalled so I had to crowd source a couple of obliging tourist lads from the crosswalk to help me push-start it away from a green light on Balboa Blvd. From there, I drove straight home and put the ’90 up on jack stands.
The RPO Z51 (VIN code J) with a German-made ZF six-speed manual transmission utilizes a Delco-Remy gear reduction starter (PN 10455702) whereas automatic transmission equipped cars (VIN code 8) use a conventional Delco-Remy starter. The Delco-Remy reduction drive starter is smaller in size, weighs less and offers more cranking power than the conventional Delco-Remy starter.
When my Delco-Remy starter motor worked it cranked briskly, as it should, so the starter solenoid was suspect. Similar to the disc in a conventional starter, the copper plunger contacts in the reduction starter’s solenoid tend to wear out prematurely.
I learned solenoid rebuild kits are not readily available anymore. In the search for Delco-Remy model number 10455702 replacement parts I ran across CVR High-Performance Racing Products (Arnprior, Ontario, Canada) and its Protorque Ultra starter. It was the impressive specifications of the CVR starter (PN 9323) versus sourcing a rebuilt Delco-Remy that inspired the upgrade. Vette
1. As a matter of safety, the first step was to disconnect the negative terminal (ground) at the battery.
2. Again it’s about safety. We devised a method on how to raise one side and plant it on jack stands then do the same to the other side, followed by shaking the car to test its stability.
3. The Delco-Remy starter was disconnected electrically and then unbolted and dropped down.
4. The Delco-Remy starter (left) puts out 1.4kW of power compared to the CVR Protorque Ultra’s 2.52kW, confirmed with an included test sheet.
5. The oil filter needs to be removed in order to remove the gravel shield (the flat tin sheet between the bellhousing and the oil pan).
6. Here’s where the last bolt needed to remove the gravel shield hides. Now is a great opportunity to change the motor oil.
7. Look for broken or chipped teeth on the flywheel. Next, clearances need to be adjusted.
8. Important! To adjust the starter-pinion-to-flywheel clearance the pinion was held in an engaged position with a tie-wrap.
9. Using masking tape helps to hold the bolts in place, freeing the hands to tighten the bolts.
10. Center a pinion tooth and check the clearance. The clearance should be 0.030-0.060 inch. Check clearances at least three locations 120-degrees apart.
11. The starter motor rotates (adjusts) on the mounting flange to allow clearance for exhaust and oil pan clearance.
12. Sans starter motor, bolt the mounting flange on top of (over) the gravel shield and mark where the gravel shield needs to be trimmed.
13. This photo show the area marked with a Sharpie that needs to be cut out.
14. Clamping the gravel shield in a vice held it steady while we cut out area using an electric hacksaw.
15. The final shaping and cleanup work was done with a mill file.
16. With the CVR starter in the properly aligned position there wasn’t a need to lengthen the factory wiring.
17. We replaced the wire terminals and repaired (re-covered) worn insulation with Painless Performance Classic Braid.
18. The CVR Hitachi-type reduction starter (PN 9323) can be used to replace a conventional Delco-Remy starter on a VIN code 8 C4.
Photos by John Gilbert