Hib Halverson's Big Block From Hell Series

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Part 9 ... The Big-Block from Hell, Halfway

by Hib Halverson

As magazine project cars go, VETTE's Big-Block from Hell is like that damn pink Energizer Bunny; it's still around. Part Nine marks a kind of half-way point, so we decided to show what the car looks like. BBfH, like any half-finished project, isn't the best looking thing in the VETTE Magazine garage...it's kinda like the kid with a face only a mother could love.

The car still has a gray hood and those ugly black patches on the rear fenders. Okay, okay...but at least we took off the cheesy-looking worn out tires. The BBfH budget won't tolerate new paint quite yet, but we did order a new set of Goodyears.

The car came to us several years ago with 16-inch Etoile wheels and 255/50VR16s. At this point, the fronts were of unknown age, had cracked sidewalls and almost no tread. Though we'd replaced the rears in Part Five (VETTE, May '91); they were down to the cords after many 1/4-mile blasts.

We stuck on a new set of 255/50ZR16 Eagle ZR-Ss. We try to not compromise BBfH's performance and that means the most aggressive, yet streetable (enough tread for occasional driving in the rain), tire we can get. Goodyear has a soft, "S-compound" version of the GS-C, but it's not streetable as it's really a race tire with a minimum "tread" to satisfy SCCA's World Challenge rules.

Not so the ZR-S. Derived from the VR-S, Goodyear's original soft compound, street tire, its tread is not quite as deep as a typical passenger car tire, but it's still a full tread that you can safely drive in the wet. It also uses the old VR/ZR casing which is more rigid than the GS-C.

ZR-S tires are hard to get because Goodyear doesn't publicize them. Nevertheless, they're available by special order and are listed in Goodyear's catalog. If you want the highest performance, streetable tire you can buy and will accept the ride quality penalty they bring; find a friendly Goodyear dealer who will special order for you.

The rest of BBfH's exterior needs help. The car came with had flared fenders. The fronts are okay, but the rears are, like...so ugly. The previous owner, a total geek we suppose, installed rear fenders so large that, to fill the wheel wells, he used wheels with too much offset. The style of the rear fenders is pretty obtuse in the way the rear section of the flares curve back and down, leaving an open space behind the rear wheels. Those black patches on the front of each rear fender (undoubtedly there to deal with rocks kicked up by the front tires) have got to go along with that functional, but really cheap looking, front air dam!

Though the existing paint ("Sunflower Yellow," a stock color) is acceptable for being seven years old, there are cracks and chips that need to be repaired. Most of the bright work was blacked-out by the previous owner using a thermo-set coating applied by Kal Gard. Most of the Kal-Garded pieces have stood the test of time very well. However, the door handle plates and the front bumper/grille assembly (areas that see a lot of wear due to constant handling or abrasion from road debris) need to be "re-blacked out". A more chip and abrasion resistant choice for those items may be the Jet Hot Coating we have on the car's headers. It is available in semi-gloss black.

The Reddi Kilowatt meets BBfH

In Part Seven, we changed the cooling system around (VETTE, Feb. '93). After nearly a thousand test miles, most everything works well. The Griffin aluminum radiator we installed turned out to be a particularly good modification. The LT5 electric fan package also has proven a wise move.

The only problem was a fan relay assembly made by Hayden consisting of: a temperature probe that is pushed between the radiator fins, a relay having a fan-on-temperature adjustment and a wiring harness. The probe turns the relay on and off, depending on what fan-on temperature you select with the adjustment. The relay, in turn, controls the fans.

The first problem came with the temperature probe. It would not stay in place. After it fell out a few times, we attached it to the radiator inlet with several wraps of 3M "27 Glass Cloth Electrical Tape." 3M 27 is Class B insulated to 266°F and is for use on wiring in oven controls, furnace switches and other hot areas.

About a month after we went to press with the radiator article, the relay began to malfunction. First, if the fans were running, they wouldn't quit when the ignition was turned off...we had to pull the fuse. Later, the problem deteriorated such that whenever the ignition was on and regardless of coolant temperature the fans came on and wouldn't go off. The solution was removal of Hayden's pieces.

GM cars using electric fans not controlled by the powertrain control module (PCM), use a temperature sensitive switch screwed into the engine's cooling system to actuate a relay that turns on the fans. The Chevrolet Raceshop's Mark McPhail suggested we take that route and sent us a switch (p/n 3053190) used on some GM export products. This unit has the lowest fan-on temperature, 203°F, of any GM fan switch we've found. We added a tee to the heater outlet on the engine and screwed the switch into it. We hooked it up using a "Connector Replacement Pack" (p/n Chevrolet 12102621 or Delco PT308). Lastly, we added a relay assembly (p/n 30101) made by Perfect Performance Products for use with electric fans.

Why all this talk of relays? A relay uses a small current in one circuit to control a large current in another. Typically, high current devices (such as electric fans, which in BBfH's case, pull up to 20 amps) are controlled by relays.

The relay assembly we used (p/n 30401), called a "Fan-Thom," is marketed by Perfect Performance in their "Painless Wiring" line of electrical products for street rod builders. Though its instructions say to wire it using a mechanical switch in the battery circuit to actuate the relay; we set it up such that power flows from ignition switch, to the relay, then to the fan switch. When the coolant reaches 203°F, the fan switch grounds. Power flows through the relay which turns on the fans.

Another trick piece from Perfect Performance we mentioned briefly in Part 7 and was recommended to us by Scott Leon, the Corvette Development group's resident Technician at the GM Desert Proving Ground. Most GM electric fans have "Metri-pack" connections. Perfect has a weatherproof, in-line, 30 amp fuse holder (p/n 432) that is based on a Metri-pack. We soldered two of these into the fan harness, removed their caps and fuses, then plugged them into our fans. This was a hell of a lot cheaper than buying a ZR-1 fan harness and more durable than using four spade connectors.

Back in Part 5, we installed an MSD 6A capacitive discharge ignition amplifier. We wired it to an adjacent terminal block connected, via eight gauge wires, to the battery cable junction on the starter and to ground. We hooked one side of each fan connector to that terminal block and grounded the other.

We have the MSD (5-7 amps) and the fans (15-20 amps) powered by our 8ga. line from the starter. We might add some auxiliary lighting (8 amps) and some high-power sound system pieces (as much as 10 amps) in the future. We needed to increase the charging system's capacity. Sometime in the car's life, the stock, 42 amp Delco 10SI alternator was replaced with a 63 amp 10SI. Even with that, at idle with the fans on, the battery was not charging. At night, with headlights and fans on; the rate of discharge was substantial.

An obvious solution is speeding up the alternator with a different pulley to increase its output at low engine speeds. However, with the BBfH's 6800 rpm red line, at high engine speeds, the alternator would be spinning real fast...perhaps exceeding its safety margin. The reason hi-po engines have large pulleys is to slow the alternator down so it isn't damaged by high engine speeds.

We needed an alternator capable of higher output at low speeds with a large pulley. Finding one was simple, thanks to the miracle of GM interchangeability. The Delco CS130, used on Corvettes from 1986 to 1991, just about bolts on and it's rated at 105 amps. We found the CS130 is slightly smaller than the 10SI but it has the same 6.6-in mounting-hole, center-to-center distance as the 10SI. It is an ideal choice for many pre-'82 retrofit applications and must be used where alternator mounting is tight, such as the Big-Block from Hell and all '69-'74 big-blocks with power steering. In most cases the SI drive pulley will have to be installed on the CS. There are two ACDelco, remanufactured, 105-amp CS130s (p/ns 321-333, and -396) that right into the SI mounts. In some cases, fabrication of a rear support bracket may be required. Some changes in hardware may be necessary.

With such a large increase in alternator output, we recommend an increase in the size of the alternator charge wire. The stock alternator charge line ran from the alternator, to a junction on the left-front inner fender, rearward to the firewall, across the firewall and to a junction with the positive battery cable on the starter solenoid. Changing all that to 8ga. would have meant a major rewiring, so we eliminated the wire from the alternator to the first junction and replaced it with an 8ga. wire from the new alternator to the + connection on our auxiliary terminal block in front of the radiator.

Trivia buffs familiar with the '71 Corvette wiring harness will note that wiring the alternator that way puts it out of the circuitry coupled to the car's ammeter so any charging will not be shown on the gauge...nor will the load from the MSD and the fans. Of course, since the gauge only goes to 40 amps, output over that would peg, and perhaps damage, the gauge.

Up until 1977, Corvettes used ammeters, however, they're like never balancing your checkbook: you see the money go in and out, but never know how much you have. Ammeters indicate which way current is flowing, but say little about the condition of the battery itself.

A voltmeter is a better choice and, since 1977, all Corvettes have had voltmeters, so we installed an Auto Meter, Pro-Comp Voltmeter (p/n 5491) into the Big-Block from Hell.

Voltmeters are better indicators of electrical system status. Nominal battery voltage is 12.6 volts and nominal alternator output is 13.5-14.5 volts. Two simple rules for voltmeters: 1) key off and no accessories running or lights on; you should see about 12.6 volts. 2) engine running and warmed up; you should see 13.5-14.5. As long as the electrical system voltage stays within those limits most of the time (ie: only temporary readings outside those ranges) the electrical system condition is, in most cases, acceptable.

While MSD 6A's are excellent ignition amplifiers, any capacitive discharge ignition unit emits interference, both radio frequency (r.f.), radiated by the amplifier and the spark plug wires, and electrical "noise" transmitted through the wires of the car's electrical system. If you have a good stereo, the r.f. is a tough problem with a Corvette because of the fiberglass body. We deal with that by using MSD's Heat Guarded Heli-Core spark plug wires (p/n 31778) and locating the 6A box as far from the radio as possible...in front of the radiator. To suppress interference that comes through the car's electrical system, we wired an MSD Noise Filter (p/n 8830) in parallel with the power lines feeding the 6A and the fans.

Cooling Hell's Fire

In the Dec. '92 VETTE, the "Techside" column discussed ways to reduce heat radiated from the exhaust system into the interior. This month, we took some of our advice and shipped the car's exhaust headers to Jet Hot Coatings for application of their ceramic, thermal barrier coating. Treating the headers with Jet Hot does three things: 1) it provides a barrier to thermal radiation so heat stays in the exhaust and goes out the tailpipe, 2) it eliminates corrosion and 3) it gives headers a decorative appearance...in our case, we chose Jet Hot's "High Luster" finish, one of several they offer.

When we reinstalled the headers, we used Fel-Pro Performance header gaskets (p/n 1410), certainly one of the durable types of gaskets available for use with tube headers.

An ageless problem are header bolts that loosen. An interesting solution are positive-locking bolts made by Stage 8 Fasteners. They are nickel-plated, 12-point, grade-8 bolts that accept a 12-pt. splined retainer. The retainer butts up against the header pipe preventing the bolt from loosening. An E-clip fits into a groove machined into the bolt head and locks the retainer in place. Stage 8 bolts will not loosen unless the clip and retainer are removed.

We installed a set these bolts (p/n 8912-A) on the BBfH eliminating problems with loose header bolts...forever. One thing though, make sure you put the retainer on the bolt such that it will inhibit counterclockwise (loosening) rotation . Trust me, it's easy to get this backwards.

Also in the Dec. '92 "Techside" we talked about exhaust wrap. We removed the car's tailpipes and wrapped the exhaust system between the center crossmember and the mufflers with Thermo-Tec "Header Wrap" (p/n 11002). We secured the wrap with Thermo-Tec's "Snap Strap" kit (p/n 13001). This operation will reduce heat radiated from the tailpipes through the floor and into the interior. Lastly, to a few places where the exhaust headers come very close to the floor in the foot well areas adjacent to the transmission tunnel, we bonded sections of Thermo-Tec "Aluminized Heat Barrier" (p/n 14001) using 3M Weatherstrip Adhesive.

What Next?

For months we've talked about an oil cooler installation we were going to do. Originally to be part of February's cooling system story substantial delays forced on us by the closure of BSE Inc., to which we contracted for the work, had us postpone the oil cooler deal. Then, we got sidetracked with the steering system (VETTE Mar. '92) and this month's electrical and exhaust system work, so the oil cooler installation is still in a holding pattern. We will try and make that the next part of the series.

Farther down the road, we'll have a transmission and rear axle update. We plan piece on ride and handling. We'll discuss interior work, a stereo installation, and last, but certainly not least, maybe a bodywork story.

Stay tuned.


see your ACDelco dealers
Auto Meter Products, Inc.
413 W. Elm St.
Sycamore, IL 60178
Autotronic Controls Corp. (MSD)
1490 Henry Brennan Dr.
El Paso, TX 79936
Chevrolet Motor Division
Delco Products Division
see you local dealer
Jet Hot Coatings
55 E. Front St.
Bridgeport, PA 19045
Kal-Gard Coating and Manufacturing Co.
16616 Schoenborn St.
Sepulveda, CA 91343
Perfect Performance Products
Suite 114
8851 W. Freeway
Fort Worth, TX 76116
Stage 8 Fasteners
15 Chestnut Av.
San Rafael, CA 94901
470 Hwy 250
Greenwich OH 44837

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