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Reman Revelation - Remanufactured and Rebuilt Corvette Alternators and Starters

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A look at remanufactured and rebuilt Corvette alternators and starters.

by Hib Halverson
Copyright 1996, 1997 Shark Communications
No Use Without Permission

I’m a value-conscious Corvette enthusiast. No way I could afford owing America’s Sports Car if I was not. Part of this value-consciousness shows when I replace certain parts on my car. Sometimes, I may pass on new pieces and take something that is remanufactured. Don’t choke on your coffee, but this holds true even for some high-performance applications.

Out of ignorance, many people apply the words "rebuilt" and "remanufactured" interchangeably. However, they describe significantly different procedures.

When something is rebuilt; the unit is disassembled. Its components are cleaned, examined and parts that are inoperative or worn past a specific point are replaced. Then, the piece of equipment is reassembled and put back in service.

An important characteristic of remanufacturing is that it’s done on an assembly line with many aspects of the process and some of the quality control testing being automated. This precludes previously-grouped parts being reassembled together. Obviously, remanufacturing is a more comprehensive process. Units are disassembled to their most basic parts. Everything is cleaned and inspected. Some pieces are tested and reworked. In certain cases, parts are improved via engineering upgrades. Non-wearing parts maybe reused but anything that wears is replaced with new or refinished pieces. Finally, the device is reassembled. The result is, essentially, a "zero-time" part.

Almost anything in a Corvette, even the whole car, can be "rebuilt." However, remanufacturing is only done to certain subsystems that lend themselves to the process. While some rebuilt parts can be as good as remanufactured pieces, in the price-competitive, consumer mass markets; reman parts are often a better value.

Two of the most familiar "reman" parts are alternators and starters. We thought it would be interesting to take a look at examples of these items from two distinct sources: an original equipment manufacturer, in this case, GM’s ACDelco brand, and an aftermarket giant, Robert Bosch Corporation.

We started our evaluation by ordering a bunch of remanufactured alternators and starters from each. Some I took some apart for inspection and others I ran on test vehicles. Mainly, I tested for proper fit, initial quality and reliability. The reality of publishing deadlines precluded any long-term durability testing, however, given the market conditions under which these products are sold; I expect 50,000 mile durability from any, up-market reman part. Obviously, problems do occur so each company warranties their parts.

Remanufactured by the Manufacturer

The General Motors Service Part Operations ACDelco brand is a given when discussing remanufactured alternators and starters for any Chevrolet because its suppliers, Delphi Energy and Engine Management Systems (alternators) and Delco-Remy America (starters) are also the original equipment (OE) manufacturers of some of those items.

ACDelco sells about 1.3 million reman alternators annually with those for Corvettes done at a factory in Anderson, Indiana. It also markets about 800,000 starters remanufactured at plants in Indiana, Michigan and Mississippi.

"Delcotron" alternators have been OE on Corvette since 1963 and ACD has reman units for most applications up to 1996. The only model years not supported are ’84 and ’85, which used an unusual alternator configuration which we will discuss later.

Delco-Remy (once a GM Division but today, a spin-off corporation) built OE Corvette starters from 1953 to 1987. ACDelco Reman has starters for virtually all ’60-’87 Corvette engines along with, interestingly, units for ’54 and ’55 sixes. However, a disappointing omission is coverage for any Corvette built after ’87.

I disassembled and examined the parts of both an ACDelco Reman 10SI alternator (MY69-81) and a 15SI (MY82). Using a Mac Tools ET332 digital multimeter, I performed simple tests discussed in either the 1971 Chevrolet Chassis Overhaul Manual or the 1982 Corvette Service Manual to its components and found, expectedly, that the rotor, stator, rectifier bridge and voltage regulator passed with flying colors. The factory service manuals I got from Ecklers.

The slip rings were properly finished, their diameters measured within specifications and run-out measured significantly under OE specs. I observed better-than-original quality bearings. Clearly, remanufacturing using today’s processes and parts allows ACDelco Reman to be, in the case of SI Delcotrons, better than original.

In preparation for this story, we talked with Bob Snider, an engineer at Delphi. He told us that SI-series alternators get new bearings having the latest improvements. The bearing bores in the housings undergo a knurl operation if they gauge oversize. Most hardware is new. No housings are reused if threaded holes are stripped, with the exception of that for the drive belt tension adjustment bolt. When necessary, it will be repaired with a thread insert. Slip rings are remachined or replaced as needed. Because of improved processes, the current slip-ring run-out specification (.001-in or less) is below that of the OE spec (.003 or less) used while the SI-series was still being built new.

Snider explained that Delphi uses contemporary, industry-standard quality control processes, including statistical process control (SPC), in the remanufacture of alternators. There are advantages in having been the OEM of any Chevrolet alternator it remanufactures. For example, 100% of the SI-series voltage regulators and rectifier bridges are tested on the same equipment used when SIs were in production.

I installed and road tested a ACDelco Reman CS130, used on Corvettes from 1986 to 1991 along with a multitude of other Chevrolets from 1987 to date. It was identical in appearance to the unit I removed and it bolted-on easily. I added a new drive belt, then put the car back in service. To date, it’s run about 8500 miles trouble-free.

Bob Snider said that Early CS130s used a slip-ring end bearing that was 8mm in width. Reman units, regardless of core vintage, are fitted with more durable 10mm bearings. Additionally, remans are fitted with an improved drive-end bearing developed recently for new units. To test CS-series Delcotrons, Delphi uses the same test rigs used in the production of new units. All rotors and stators are tested prior to reassembly. After reassembly output current is bench-tested at both low and high speeds. Snider also revealed that engineers working with the reman side recently devised a modified test procedure that improved reliability and durability and was adopted for OE production.

The more powerful, CS144 Delcotron is used on Corvettes from 1992 to date. I tore down and inspected one for a 1995 LT5. The stator, rectifier bridge, voltage regulator and brush assembly were new parts. The slip-rings were immaculately finished and virtually zero run-out. I suspect that the rotor was new or low-time-used. Both bearings were new as was all the hardware. I tested some of the CS144s electrical components with the Mac ET332 using procedures I found in the 1995 Corvette Service Manual. The rotor, stator, and rectifier bridge were OK.

I installed and road tested another reman CS144 on a ’92 LT1. The LT1 unit was the expected, simple bolt-on and has seen about 3000 trouble-free miles.

I ran an ACDelco Reman SD300 starter on an ’82 Collector’s Editor. In this case, a replacement starter was required due to failure of the OE unit after 14 years and 71,000 miles. Again, the installation was a simple bolt-on. Shimming, required in some cases with reman starters, was not necessary. At press time, the starter has run about 10,000 miles without a problem.

A second ACD SD300 for a ’76 was disassembled for inspection. Commutator diameter was 1.690-1.691, well above the 1.625-in. Delco-Remy cites as its discard diameter. Bushings were new and lubricated. Brushes were new. The starter solenoid was fitted with a new contact plate, cap, seal and terminal hardware. All reused parts were clean. All hardware was new.

Bottom line: Our evaluation of ACDelco Reman alternators and starters was favorable. They are suitable for any Corvette application except a matching-numbers restoration. Our only disappointment is that, because of some limitations in coverage, not all Corvette owners can enjoy these benefits.

The Aftermarket Giant

The Robert Bosch Corporation’s "Premium Quality Reman" brand is one of the most comprehensive lines of remanufactured alternators and starters for Corvettes. While Bosch is usually associated with electrical parts for foreign cars, they supply parts for domestics, too. If you doubt that, open the hood of any C4 and you will probably find Bosch switches and relays. Bosch remanufacture alternators and starters for the U.S. market at a factory in Lithia Springs, Georgia. We asked for annual production data, but Bosch refused our request.

Bosch Reman alternator support for Corvette starts with 1963 and goes right up to 1996. Starter availability does not go back as far, starting in 1965, but carries to ’96. With such consistent coverage, clearly, Bosch intends to be a major player in the domestic reman parts market.

The Bosch Quality System is used worldwide at all Bosch facilities. The specifics of the program are proprietary. However, Bosch spokesperson, Fred Padgett, told us that the system incorporates industry-standard QC techniques that are altered or combined in a manner that meets Bosch’s needs. Padgett also told us that the engineering group responsible for remanufactured products conducts regular durability tests and "benchmark" studies of Bosch Reman alternators and starters. The purpose of this is to see how aftermarket parts compare to OE as well as to see what can be done to remedy reliability/durability problems inherent with some OE designs.

I disassembled a Bosch remanufactured 10SI and ran the same Overhaul Manual tests with the Mac ET332. The parts tested met specifications. Some of what I saw in the 10SI was up to our expectations. However, I was surprised at a few deficiencies.

I saw more used hardware than I would have expected. Two of four housing bolts had damaged threads. If this alternator were disassembled during its life, it is possible that the stripped bolts could cause failure of the threads in the drive-end housing.

Both insulated bolts holding the voltage regulator and brush holder to the slip-ring end housing were used. One had cracked insulation which surprised us as grounding of this bolt causes failure of the alternator.

The rotor was originally manufactured with what appeared to be resin-coated paper surrounding its windings. The paper was breaking apart in "flakes" which I could pull away with our fingers. I wondered if a large piece of the stuff breaking loose while the unit is running at high speed could damage the alternator in some way.

I road-tested a Bosch Premium Reman 15SI alternator on an ’82 Collector’s Edition. The installation was trouble-free with connections, and mounts being identical to the OE part I removed. So far this ’82 has gone about 2500 miles with no problems.

I disassembled a Bosch Reman SD-300 starter used on Corvette up to 1987. The quality was not what I expected. Both armature bushings, while new parts, were not sufficiently lubricated. The commutator’s diameter was inconsistent enough that its "hour-glass" shape was visually apparent. It varied .018-in. across the width traversed by the brushes. In press information, Bosch lists a specification of .05-mm (.0019-in.) for accuracy in machining of commutators. The unit I examined missed that figure by a considerable margin.

I examined a Bosch Reman CS130 Delcotron which is not designed for field servicing. Fixtures, specific to a factory environment, are used for assembly. Consequently, I did not open-up this unit as doing so would damage some internal parts. However, using a bright light and a magnifying glass I was able to examine its exterior and some of its internals.

A lack of identifying marks on the slip-ring end housing and differences in appearance from two other CS130s fitting the same application indicated that this unit had new end housings not manufactured by GM. All hardware was new. The slip-ring end bearing was new. The voltage regulator appeared new. I popped-off the plastic shield that covers the soldered connections between the stator and the rectifier bridge and looked inside. The rectifier bridge, the rectifier/regulator cooling fan and the rotor looked new. Bosch appears to be doing an outstanding job remanufacturing CS130s.

We ordered a Bosch reman starter for the ’90-’95 LT5s. It is typical of the Nippondenso gear-reduction units used on Corvettes since 1988. However, due to its location between the cylinder heads; its mounting plate is different than those of L98 or LT1 starters.

I removed the solenoid cap to find internals indicating the solenoid was new. I removed the armature end plate to find new brushes and a new bearing on the commutator end. The commutator was properly machined and its diameter measured 1.178-in. across its width. I was unable to disassemble the gear reduction section without destroying the screws holding it together. All hardware I could see was new.

Bottom line: our evaluation of Bosch’s Premium Reman line had mixed results. I found problems with a 10 SI alternator. I found significant problems with an SD300 starter that might result in limited reliability and durability. However, both the CS130 and 15SI Delcotrons and the LT5 starter appeared to be top-quality, remanufactured parts.

Reman Warranties and Price Comparison

Obviously, AC Delco and Bosch warrant their respective brands of remanufactured alternators and starters. ACD offers 12 months or 12,000 miles, whichever comes first. Bosch has a 12-month warranty with no mileage restriction. In either case, the customer deals directly with the retailer for warranty claims and only the parts are covered.

Bosch also has a 24-month, limited, road service plan. If a Bosch Premium Remanufactured alternator or starter fails in its first two-years of service, the buyer is eligible for emergency road service that is provided at Bosch expense. The plan is activated by the customer calling Bosch’s 24-hour-a-day, toll-free phone number listed on the back of the warranty card.

Being a value-concious Corvette owner also means understanding price-competitiveness. For this story, we did a little canvassing of list prices for Corvette applications of different vintages. These prices were current as of the summer of 1996.

MY Type ACD Bosch


10SI alternator




SD300 starter




15SI alternator




CS130 alternator




CS144 alternator



Clearly, Bosch is more competitive with list prices. However, these reman parts are available for varying-degress-less than list price at many places. We encourage you to shop local prices. Examples of sources for ACDelco Reman are: your GM Dealer as well as Trak Auto, Hi-Lo Auto Parts and Parts America. Sources for Bosch Reman are: Trak Auto and NAPA. Interestingly, Trak offers its own limited lifetime warranty on the two brands. Lastly, in both cases, there are thousands of traditional auto parts jobbers that carry one or both of these brands.

The Matching-Numbers Rebuild

One area where large re manufacturers are not to be found is high-end rebuilds of existing alternators and starters for restorations. Small, specialized operations do this kind of work. To find one with a credible track record, we used "VetteNet," the Internet mail list for Corvette enthusiasts. Subscribe to VetteNet by sending an email to: listserv@asuvm.inre.asu.edu. In the body of the email, type the words "subscribe vettes" then add your name and send it. In a day or two, you will get a reply explaining how the list works. "VN" is an invaluable resource for Corvette technical information.

We queried VetteNet and got back several replies from restoration-oriented subscribers, the majority of which cited John Pirkle of Augusta, Georgia as an excellent source for matching-numbers rebuilds.

In 1988, Pirkle retired from the Army and purchased a ’63 Roadster to restore. Having trouble finding the correct parts for his project and having knowledge of electrical systems through his military service; he decided to go into business restoring Corvette electrical items and started Masters City Classic Car Parts.

He and son, John Jr, an ASE-certified Electrical Technician, have a thriving operation that employees four people. Masters City has 6000+ alternator and starter cores in stock. All restorations are done to Bloomington or NCRS standards.

A Pirkle restoration of a 1963-’68 DN-series or SI-series Delcotron starts with disassembly. End housings are restored to OE appearance. All hardware is cleaned, inspected and, if serviceable, it is replated. Stators and rotors are tested. Then, they are cleaned and dipped in the same caramel-colored varnish that was OE at the time of manufacture. Slip-rings are finished with 400 grit sandpaper and run-out is held to .002-in.

With DNs, the Pirkles use diodes that are correctly date-coded using ink of the proper type and color. The housings are then reassembled using new brushes, bearings, diode bridge insulators and the new diodes. With the SIs the process is similar except a new rectifier bridge and diode trio are installed.

The housings are joined, the correct pulley and fan are attached then, the unit is bench-tested. Lastly, using the correct ink, the proper inspection or broadcast code is stamped on the drive-end housing.

I examined a Perkle-restored DN-series for a ’63 with a special high performance engine and a SI for a ’74 base engine with air. With the 10SI, I tested components as I did with ACD and Bosch units. With the DN, I tested the rotor, stator and diodes according to the 1963 Corvette Shop Manual. No problems were found during these tests.

All hardware was new or replated. Diodes, rectifier s and the brush assemblies were new. Rotors and stators were fastidiously clean and varnish-dipped. I noted that the housings of both Delcotrons were similar in appearance and feel to a new unit of the same vintage. I asked John Sr. about this and he said that the specifics of their cleaning process are proprietary, but volunteered that they did not use any acid dips. He added that any abrasive cleaning is not grit blasting and uses a finer media than is typical of that used by mainstream re manufacturers.

In summary, we were impressed with the two restored Delcotrons supplied by the Pirkles and feel that their products would be suitable for any restoration where dead-nuts accuracy is required.


ACDelco Reman Parts
See your local GM Dealer or ACDelco Parts Retailer.

Bosch Reman Parts
See your local Bosch Retailer

PO Box 5637
Titusville, FL 32783-5637

Mac Tools
4635 Hilton Corporate Dr.
Columbus, OH 43232-0940


Masters City Classic Car Parts
3706 Merion Dr.
Augusta, GA 30907

ACD’s SI-to-CS Conversion

The advent of computer engine controls on Corvettes in the 1980 and ’81 model years and an overdrive automatic transmission in MY82 forced increased alternator output. The reasons were higher electrical demands of the new electronics and the lower engine speeds in high gear making alternators put out less. Simply changing pulleys would increase low speed output but compromise alternator reliability at high engine speeds.

The ’81s used a 70-amp, 10SI Delcotron. The following year, in response to this growing problem, GM introduced the 15SI which had the same maximum output but in a larger package with a bit more low-speed output. The introduction of the ’84 car brought even higher electrical system demands making the low speed output problem even worse, so the alternator changed again, this time, to the more powerful, but quite rare, 97-amp, 17SI. Part-way through the model year, output was increased to 108A. During MY85, GM again bumped the 17SI to 120-amps.

In three years Delco had near-doubled alternator output to compliment low-rpm engines, overdrive transmissions and tall axle ratios. However, the 17SI really wasn’t a good solution. It was big, heavy and had an electrical design dating to 1969 that was only marginally effective in addressing the low speed output issue. Additionally, it was expensive to produce as its only use was on a couple hundred thousand Corvettes, Cadillacs, Aston Martins, Rolls Royces and specialized pieces of off-highway equipment.

Fortunately, a clean-sheet-of-paper alternator development had been underway for several years. For 1986, Corvettes and, strangely enough, four-cylinder Camaros (we can’t imagine who’d have bought such a slug), were first to get the new, 105-amp, CS130 Delcotron. By 1988 all GM cars used the CS-series.

Though the CS130 (for "Charging System with 130mm diameter stator") had less maximum output, it’s low-speed output equaled and idle output exceeded the 17SI. All this performance came in a package that weighed 30% less, was 3/4-in. smaller in diameter, used 60% less internal fasteners, had a better voltage regulator system, had increased durability and was less noisy, both audibly and electrically. These improvements were achieved through three major design features.

First, the rotor and stator have more windings than the SI-series. Additionally the type of wire and the windings ratio are optimized for higher output at low speeds.

Next, there is less air gap between the rotor and stator. Just a .001-in. reduction in gap increases output by several amps. The CS-series has many times less air gap than most SIs. However, less gap required more than just a change in rotor and stator sizes. To work with less clearance between rotor and stator, the CS130 had to have bearings and other parts that would maintain a more stable relationship over the life of the alternator. This need drove new bearing designs, improved techniques for manufacturing housings, rotors and stators as well as the development of special assembly processes and tools.

The third CS advantage is a regulator design that improves low-speed output, provides a "cleaner" current to sensitive engine computer circuits and reduces radio frequency interference.

Several years ago, Delphi Energy and Engine Management Systems designed wiring adapters that allow either a CS130 or it’s more powerful sibling, the CS144, to be retrofitted to a variety of ’69-’85 engines on which SIs were OE. With remanufactured 17SIs available in limited quantities and the CSes offering so many improvements; prime candidates for this "SI-to-CS Conversion" are 1984 and 1985 Corvettes.

We retrofitted a 120-amp, ACDelco reman CS144 (p/n 321-368) to an ’84 originally equipped with a 97-amp 17SI. One modification is required with this installation: the 17SI’s five-groove, Corvette pulley must be installed on the CS144. If you are doing the SI-to-CS converson to an ’85, use a slightly different CS144 (p/n 321-567), otherwise, take the same steps.

Most likely, an impact wrench will be used to change the pulley. Do not overtorque the pulley nut. Overtightening results in certain damage to the alternator. Tighten the nut to 70-75 ft/lb. Most 1/2-in drive impacts will generate twice-to-three times that much torque. Our advice is to use a 3/8-in drive impact and verify tightening torque before use.

At presstime Delphi told us that it was considering making available to ACDelco remanufactured CS144s for retrofit kits specific to ’84/’85 Corvettes. These units would not require a pulley swap and the kits would include the correct wiring adapter (p/n 8078).

To install the CS144, disconnect the negative battery cable, disconnect the alternator wires, remove the 17SI and bolt on the CS144. Under the bolt that holds the rear support bracket to the alternator, add two washers. Install the ACD wiring adapter (p/n 8078), reconnect the alternator wires then reconnect the battery. The job takes about an hour.

Similar conversions can be done on pre-’84 cars, too. Why might that be necessary? How about aftermarket electrical accessories…specifically, powerful audio equipment; high-wattage driving lights; high-output, capacitive-discharge ignitions or high-flow, electric cooling fans?

There are two ACDelco Reman, 105-amp CS130s (p/ns 321-333, and -396) and one 124-amp, CS144 (p/n 321-371) we suggest for SI-series replacement on ’69-’82 Corvettes.

The CS130 is slightly smaller than the 10SI. Because the above-listed CS130s have the same 6.6-in mounting-hole, center-to-center distance as the 10SI; they are an ideal choice for many pre-’82 retrofit applications and must be used where alternator mounting is tight, such as ’69-’74 big-blocks with power steering. In most cases the SI drive pulley will have to be installed on the CS. The two CS130s discussed will bolt right into the SI mounts. In some cases, fabrication of a rear support bracket may be required. Some changes in hardware may be necessary.

The CS144 is the size of a 15/17SI. Where the highest maximum output is required, if it will fit; opt for the CS144. When a CS144 is used in place of a 10SI, modification of mounts, as well as rear support brackets maybe necessary.

The same ACD wiring adapter for ’84/’85 conversions is the one most ’69-’82s will use. However, cars having 35 or more ohms resistance in the alternator "exciter" line, need a different adapter (p/n 8077). The adapter selection is an issue because CS Delcotrons require a higher exciter-line resistance than do SIs. A CS run without adequate resistance will eventually fail.

If you are unsure which adapter to use, measure the resistance of the exciter line. Disconnect the positive battery cable and the alternator plug. Connect an ohm meter between the #1 terminal on the plug end of the alternator harness and the end of the positive battery cable. Turn the ignition key to the "on" position and read the ohmmeter. If resistance is less than 35 ohms, use adapter #8078. If it’s between 35-350 ohms, use #8077. If it’s more than 350 ohms, you have excessive resistance somewhere in that circuit which needs to be repaired, first.

The last wiring issue in a SI-to-CS conversion is the alternator supply line that connects to the Delcotron’s "batt" post. As late as 1979, the 37-amp and 42-amp 10SIs were used on Corvettes. If one was to install a CS on a car originally equipped with such an anemic unit, the high resistance of a small diameter charging wire would be a problem.

From 1969 up to the mid-’70s Corvette alternator charge lines ran from the alternator to the horn relay then halfway around the engine compartment and down to the starter solenoid. Often, this circuit was a mix of 10- and 12-gauge wire. For a CS conversion, we strongly suggest using an 8-ga. charge wire.

Consult a factory wiring diagram appropriate for your model year to verify charging system wire sizes. Modification of the car’s charging circuitry is probably going to be necessary for safety and alternator efficiency.

--H. Halverson