Hib Halverson's Big Block From Hell Series

Hib Halverson's Big Block From Hell Series

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Part 5 ... The Big-Block from Hell, The Sequel - Ha! Would we forget the BBfH! Not a chance!

by Hib Halverson

Once just an engine project; it's now project car, so we took a break to regroup. The engine built for the July through October 1990 issues of Vette was named the "Edelbrock 454." However, the series was titled "454 From Hell"–but often, we referred to it as "Big-Block from Hell" or just "BBfH".

Were you confused? We were, too!

Now the engine is done and we're moving on to the rest of the car, so we settled on one name.

In the October issue, we finished our dynamometer testing. The Edelbrock dyno room staff of Curt Hooker, Robert Jung, Mike Eddy, Mark Gray and Matt Compton had done well. With 479 hp at 5000 rpm and 514 lb/ft. torque at 4500 rpm, the Edelbrock 454 was a devilish combination.

For the first installment of Big-Block from Hell: "the whole car series" we're reinstalling the engine into the '71 Coupe we introduced you to back in July of 1990.

Initial Steps

With the engine hot from the final run on the Super Flow 901 dynamometer, Matt Compton ran a cylinder leakage test to measure the amount of "blow-by," a good gauge of ring seal. Leakage averaged 3%, low for an engine that had seen nearly 100 wide-open-throttle runs on the dyno. Obviously, the Childs and Albert ZGS ring set we used is quite durable. Curt Hooker, who heads the dyno room staff, removed the oil pan for inspection. If rod bearing problems occur, they begin at the crankshaft's third rod bearing journal, so we pulled number five and six rod caps. The C&A bearing shells looked like they'd never been run.

The final test in the October '90 issue was done with a single four-barrel on a Torker II-O intake manifold. Edelbrock's Mark Gray replaced that with the C66, dual four-barrel manifold also tested that issue. Previously, I sent the Edelbrock C66 to Tech Line Coatings for treatment. Its underside was coated with "Thermal Barrier" that reduces heat transfer and sheds hot oil. The upper side was shot with "Thermal Dispersant" which promotes heat transfer and is responsible for the manifold's black color. The cooler the manifold runs, the more power we get; so we're making it hard for heat to get in through the bottom and easy for it to radiate away through the top. Additionally, we tried an idea that some Pro Stock drag racers use. Tech Line treated the C66's port walls with "Dry Film Lubricant" . Dyno tests (other than ours) have shown slight performance gains from this process. It decreases fuel puddling on the floors of the ports that happens when fuel condenses out of the mixture. It is unclear why DFL acts as it does but, Tech Line's Leonard Warren believes the coating "…changes the surface characteristics of the port wall just enough such that turbulence in the air flow is increased at no loss to velocity."

On the dyno, the knock sensor for the Edelbrock Ignition Computer was screwed into the block's right-side water jacket drain plug hole. The car's frame interferes with that location, so the sensor was moved to one of the threaded holes in the C66's water crossover. The Ignition Computer is designed for proper operation with the sensor in either location. Mark bolted on the C66 with a set of Edelbrock manifold bolts (p/n 8564).

For the dyno tests we fitted our 454 with a McLeod aluminum flywheel. To complete the flywheel/clutch assembly, we used an idea pioneered by Chevrolet on the Corvette in the early '70s: a dual-disc clutch. Unfortunately, the technology wasn't ready then and those units had problems. The option was discontinued after a short run.

Twenty years later, reliable, dual-disc clutches are a reality. The McLeod Street Twin (p/n 63109027) is attractive for easy pedal effort. Since two discs have twice the friction area of a single-plate clutch; our dual-disc requires less spring pressure to handle the BBfH's 514 lbs/ft. of torque. That reduces pedal effort. The Street Twin, though sharing the concept used by Chevrolet two decades ago, is quite different in its execution. Rather than using a diaphragm pressure plate, it combines the best of the Borg/Beck and the Long lever-type pressure plate designs. Next come a pair of discs with non-asbestos facings and a steel floater plate. McLeod's "constant-run" throwout bearing (p/n 16010), similar to those used on '84-'88 cars, completes the package

The clutch height and floater position are set with shims selected during assembly at McLeod. Since I marked them earlier, I had no reassembly problems. Get the shims mixed up and the clutch will not work properly. If that happens, consult McLeod Industries for information on resetting the shim packs. I lined up the discs, floater, pressure plate and the proper shim packs using a McLeod alignment tool (p/n 105313). Pressure plate nuts were tightened to 35 ft/lbs.

A Street Twin in a '63-'82 needs a bit more clutch fork travel than does a stock clutch. To get that, I eliminated free play with the constant run bearing and optimized clutch release fork geometry. The right geometry has the clutch fork fulcrum as close to the pressure plate as possible. You want .030-.060 inch minimum clearance between the highest part of the pressure plate and the fork. View this by turning the crankshaft and looking through the clutch fork hole. Fork geometry is altered by changing the length of the clutch fork mounting stud. Do not use an "adjustable" clutch stud. With the '63-'82 clutch fork and the Street Twin, the ideal dimension is outside the range of most adjustables.

I found the ideal stud length between that of Chevrolet's 1.375-inch (p/n 3887159) and 1.480-inch (p/n 3729000) studs. I selected a flat washer that would fit into the bell housing's clutch stud recess and had Edelbrock's machine shop drill its inside diameter to fit over the stud's threads. I installed the spacer-equipped stud and found geometry ideal. Now, I had another problem: the washer had spaced the head of the stud above the transmission mounting surface…nothing a brief session with the belt sander would not cure.

Mark Gray bolted-on the bell housing while I filled the Big-Block from Hell's M21 with Red Line MTL, a synthetic oil for manual transmissions detailed in the November 1990 "Trick Ideas" column. Mark added the gear box then slipped the output yoke in place to prevent oil leakage during engine installation. I got the "honor" of steam cleaning the engine compartment. We pushed the '71 Coupe out back of Edelbrock's dyno room. I fired the steam cleaner and got gnarly on all that grease and grime!

The last task prior to dropping the Edelbrock 454 into place was some electrical work that was far easier with the engine out. In 1971, Corvettes had a positive cable running from the battery to the starter but the system was grounded through the frame. From an electrical standpoint; it is better to have a negative battery cable, so I made one up from eight feet of #2 welding cable and a couple of copper lugs…total cost about $15.50. I routed it, using cable ties, parallel to the positive cable.

I installed the same MSD-6A capacitive discharge ignition amplifier we used on the dyno in front of the radiator where it would stay cool and, as CD's can be effective transmitters of ignition noise, would be as far from the radio as possible. I had a fabricator make a mounting plate for the -6A from .125-inch 3003 sheet aluminum.

Because the ignition amp is up front and the battery is behind the seats; the -6A box's power leads were too short. I ran 8-gauge power and ground wires from the starter and negative battery cable connections to a terminal block next to the MSD, cut the -6A's wires short and attached them to the block.

Using Velcro strips, Doug Stalter of Edelbrock's Electronics Department mounted the Edelbrock Ignition Computer and Ignition Controller on the back of the passenger side, dashboard trim panel. These devices were detailed in the October and November 1990 issues of this magazine. Their wires and the hose for the Ignition Computer's vacuum sensor were run though existing firewall openings. The Computer's display head was Velcro'ed to the trim plate above the center console instrumentation. Under the hood, Doug wired the MSD to the Computer's wiring harness using Delco-Packard Weather Pack connectors. Lastly, we adjusted the Ignition Computer's rev limiter function by removing the top of the Computer module and setting the rev limiter "DIP" switches for 6500 rpm.

We were using a McLeod Mini Super Starter (p/n 810152) which has only two connections (a factory unit has three), so we eliminated the starter bypass line which runs from the solenoid to the ignition coil. The Edelbrock 454 will be fitted with headers and consequently, the area around the starter will get pretty hot. I wrapped the last 18-inches of the starter harness with 3M Glass Cloth Electrical Tape. This material is durable up to 266°F and is can be found at electrical supply houses or industrial hardware stores.

Engine Installation

After nine months of work on this project, putting the engine back in the BBfH was a little anticlimactic. Mark Gray fitted two new Chevrolet motor mounts (p/n 6258154) then, using Edelbrock's 5 ton hoist, Mark, Mike Eddy and myself dropped her in.

A brief pause to say, "Finally!" and we were back to work with on a myriad of tasks; the first of which was exhaust headers. Finding under-chassis units offering adequate ground clearance on a Corvette can be difficult. Doug Thorley Headers, on special order, offers an excellent set of headers (p/n 360) having two-inch diameter, 34-36 inch long primaries and a 3.5-inch diameter collector. They were not a bolt-on as the mounting flanges had to be relieved for clearance around our B&B Performance 12-point head bolts and we had to dimple the #2 pipe in two places: 1) to clear the frame member holding the passenger side motor mount and 2) the nut on the upper idler arm attachment bolt. Nevertheless, short of custom building (at great expense) a set of headers; I see the Thorley pieces as best choice. For connection to the car's existing three-inch exhaust system and Flowmaster mufflers; we relied on Bob Krause who runs Edelbrock's Tubular Exhaust System division. He welded up a set of nifty adapters that made bolting up the system a snap.

Next Mr. Gray installed the McLeod starter, a gear-reduction unit that is lighter and provides more starting torque than a factory unit. It comes with shims to adjust starter-to-flywheel distance which must be optimized for long starter life. Instructions explaining this are included. The clutch linkage, gear shifter and driveshaft were returned to their respective locations and Mark added a K&N Oil Filter (p/n 07-0029). We set the car on the ground to add other engine accessories beginning with an aluminum water pump (p/n14058915) from the Chevrolet Raceshop's Power Catalog. It is not a direct replacement but was our choice for reduced weight and to replace a worn stock pump. It has a smaller diameter shaft than the stocker. Rather than change our Corvette fan clutch and water pump pulley, Edelbrock's machine shop made an adapter bushing to fit over the fan pilot. If you are going to use this pump, you must either use a bushing or a fan clutch and pulley of the smaller diameter. Do not run the stock Corvette clutch and pulley without an adapter or catastrophic failure of the water pump shaft will occur. Following the water pump were: the clutch fan assembly, power steering pump and hoses, alternator and wiring, associated bracketry, fan belts and heater hoses.

Mark set number one piston at 20-degrees before top dead center then installed the distributor. The unit we are using is a stock Chevrolet, ball-bearing, tach. drive distributor (p/n 1111263) as modified for the October '90 issue with a mechanical advance lockout plate (part of the Edelbrock Ignition Computer hardware) and a MSD Cap-A-Dapt Kit (p/n 8420). Mark connected the wires from the distributor to the Ignition Computer, reinstalled the set of MSD Heat Guarded Heli-Core spark plug wires (p/n 31778) used on the dyno and added a MSD Wire Separator Kit (p/n 8846). Completing the ignition system were NGK R5674-7 V-Power Racing spark plugs.

The carburetors on the C66 were the same two run for the October article: Edelbrock 600 cfm four-barrels (p/n 1405) with only two changes–first, Curt Hooker fitted the rear carburetor with an electric choke kit (p/n 1478). This will make the engine in the Big-Block from Hell as easy to start as your grandma's Caprice Classic. Secondly, I replaced the race-type throttle linkage used for our dyno sessions with an Edelbrock progressive linkage (p/n 7094). The engine starts, idles and runs at low-speed on the rear carburetor. As one starts to give BBfH the boot; the front unit's primaries begin operation. Once both sets of primaries are flowing a lot of air, the air valve secondaries in both Edelbrocks open up. Progressive operation makes a dual four-barrel engine smooth as a kitten when we're "just cruisin.'" but, if we're" giving religion" to offending Ford drivers; we get all 480 horsepower. Say your prayers… blue oval boys!

It Runs!

I filled the cooling system with water and two bottles of Red Line Water Wetter cooling system additive. This product inhibits corrosion and promotes heat transfer to the coolant. Mark Gray added eight quarts of Red Line Synthetic 40 weight Racing Oil. Curt Hooker made preliminary idle speed and mixture adjustments to the Edelbrock 1405s and prefilled the float bowls using a squirt can. Then, the moment of truth: With the entire Edelbrock dyno room crew as spectators, I pumped the gas twice and turned the key…

Ree-ee-ee…Brap, rumble rumble, rumpty rump rump rumpty…etc.. The Edelbrock 454 settled down to a 1200 rpm fast idle. Robert Jung, who ran the dyno for our October tests, retarded the timing slightly and we all stepped back and listened while the Big-Block from Hell warmed up. Once temperature reached about 180°F I rechecked the coolant level. Our electronics expert, Mr. Stalter, disconnected the Ignition Computer from the Ignition Controller. This allows the engine to run on initial advance only and is the only way you can set the timing. Using one of MSD's Timing Lights (p/n 8990), Robert set the initial advance to 10° after which the Computer was reconnected.

The front carburetor's idle speed adjustment was set so the throttle plates were just cracked open and its idle mixture screws were screwed one turn out. The front unit must be configured this way for smooth transition between rear-primaries-only and front-and-rear-primaries-together operation. We set idle speed on the rear carb for 700-750 rpm, then, using a vacuum gauge, adjusted its mixture screws for highest vacuum. After resetting the idle to 700-750, Robert rapped the BBfH's 454 a couple of times. Throttle response was fearsome and the noise when all eight barrels kicked in, was oh so good!

Shakedown and More.

Impatience was getting the best of me and a look under the car showed no leaks. It was time for a maiden voyage. Sans a hood and air filters, I took the car once up and down the side street adjacent to Edelbrock's manufacturing plant. It was obvious just on this part- throttle jaunt that the Big Block from Hell was going to be "sporting" to drive.

Back on the rack, we discovered minor leaks at the oil pressure line's connection to the engine block and from the transmission. These were fixed by 1) rerouting the oil line and treating it to a new fitting and 2) draining some of the MTL out of the transmission…it had not been level when I filled it and ended up overfull.

Doug Stalter reappeared on the scene with a prototype version of Edelbrock's "Rich/Lean" indicator (RLI) which will soon be available through their dealers. This product consists of a heated oxygen sensor and a display head having a series of red, yellow and green light emitting diodes (LED's). The O2 sensor output runs the LED's, the number illuminated being indicative of the engine's air/fuel ratio in real time. This device would make dialing-in the Edelbrock 1405's a snap. Once again, Edelbrock's exhaust whiz, Mr. Krause, showed up with his welding gear and added a bung to the driver's side header adapter into which he screwed the O2 sensor. Doug wired the RLI and installed its display head next to the Ignition Computer unit above the center console gauges.

We fired the Edelbrock 454 to check the operation of the RLI and to set the Ignition Computer's knock sensor threshold adjustment. The adjusting screw is accessed through a hole in the top cover of the Computer. Run the engine at 3000 rpm then let off the throttle abruptly. On deceleration, the engine makes enough mechanical noise to trigger the knock sensor which turns on the display head's red light. If you don't get a quick blink of the red light, turn the adjusting screw counterclockwise until you do. As we were now through with adjustments to the Ignition Computer, the passenger side trim panel with the Edelbrock ignition boxes in place was reinstalled.

We had to find a hood as the stocker was not going to clear our dual-quad set-up. The place to look for fiberglass is in the Eckler's catalog and I found a number of choices. Purists would probably want a '68-'69 L88/ZL1 unit but, I dare to be different! Eckler's lists a hood (p/n 10418) that fits a '68-'72 but has the style of the '73-'75 hood, which I prefer, along with more induction system clearance and elimination of the wiper door. Plates are riveted to underside reinforcements for easy installation of latches and hinges. Eckler's 'glass has top-quality Gelcoat; the best in resins and fiberglass mat; along with being formed in Eckler's own heavy duty molds.

Our only alteration to the hood was removal of its rear bulkhead to make a functional cold air hood. I transferred the hood latch assembly from the stock hood, added two new hinges (p/n 3912639, left and 3912640, right) then dropped it in place. Adjustment of the hinges and latch mechanism was a simple process because of a clear explanation in Eckler's instructions. As a paint job is farther down the road in this project, for now, we'll leave the hood gray.

The final modification to the car for this month was an air box/air filter assembly for the carburetors. I wanted a cold air induction unit that would both serve as an air filter and, through the hole we cut in the rear of the bulge, would provide outside air to the carburetors. This was a difficult task. Even though the Eckler's hood had four-inches of extra clearance, with the height of the Edelbrock C66 and the three-inch tall air filter we'd use to get adequate air flow; there wasn't a lot of space. We had a fabricator built an air box that would be the envy of any Winston Cup race team. It was hand-formed and heli-arc welded from .050-inch, 3003 sheet aluminum stock. It covers both Edelbrocks, has a forward slope to match the hood's contour and is fitted with a K&N Filtercharger (p/n E-1910) air filter. The air filter top was built out of .125-inch 3003. To complete this work of art, we sealed the outside edge of the air box to the bottom of the hood with weatherstrip from Ace Hardware.

Runnin' with the Big Dogs

They say: if you can't do that, "Stay on the porch." Well, since porches are places for Porsches and Fords; we want the Big Block from Hell to be one of the big dogs. The first task was to dial-in the Edelbrock 1405s using the Rich/Lean Indicator. I spent time running the car at cruise speeds and moderate acceleration. The RLI showed at part throttle the 1405s were running a bit rich. To lean the mixture back a bit, Curt Hooker suggested a primary metering rod and jet change from 7052 rod/102 jet to 7352/98.

I checked knock sensor operation by buying five gallons cheap gas. Combine that with a warm day and sure enough, I got a bit of detonation. The engine rattled once, the red light on the Ignition Computer's display head came on, the knock avoidance feature retarded the timing and the knock went away. The Edelbrock Computer was was doing exactly what it was intended to do… keeping spark timing at the optimum value under all conditions. It is interesting that even with this engine's 10:1 compression ratio, I can drive on cheap gas. The Computer's detonation avoidance feature, the polished combustion chambers of our DeGroff cylinder heads, a 180° thermostat and the carburetors breathing cool, outside air must be helping.

Now it was time to lean on the BBfH a bit. After installing colder, NGK 5674-8 plugs, I took the car to our usual test venue and began some easy quarter-file passes limiting the engine to 4500 rpm. The feel of the BBfH is pure big-block Corvette, "only…" (to steal one of Dave McLellan's famous utterances) "…more so!" Five hundred fifteen pounds/feet of torque made it painfully obvious that the car's existing rear tires, five-year old, 255/50VR16s weren't cutting it. The car wouldn't hook in first and it was even firing the tires in second. Years of L.A. smog had hardened the rubber to the point of near no adhesion. I ordered a set of fresh Goodyears ZR Eagles, specifying showroom stock, S-Compound race rubber shaved to 3/32-inch tread depth. The only thing that would be better are slicks, but this is a street car and only fools run slicks on the street.

New tires mounted, it was back to the track. The tire deal worked as the car picked up a tenth. After a few more passes, the car's feel and the RLI readout was telling us that, at wide-open-throttle, the mixture was a bit lean. This made sense as, when we leaned cruise mixture, WOT mixture got leaner as well. We had just started changing secondary jets on the Edelbrock 1405s when a rainstorm washed away our drag strip test day. We averaged the last five passes. For comparison, the car's drag strip performance before modification is also printed:

Pre-BBfH: 13.74/ 109.4

Big-Block from Hell: 12.98/116.9

We were not able to do another session before press time so, in the next installment of the Big-Block from Hell; we'll have the rest of our testing for you. I expect that we'll knock a few more tenths off the car's times by dialing in the secondary jetting and learning more about how to deal with the Edelbrock 454's prodigious mid-range torque on the starting line. It'd be nice to see the car in the 12.6s-.7s at 120 mph. Considering 3.36 rear gears and street tires, I'd be happy with that.


At this point in the Big Block from Hell project, Edelbrock's role will take a lower profile. They will continue to support the BBfH with occasional fine tuning or updates of their products. Vette would like to thank Vic Edelbrock and his hard working staff for all they have done in the past six months. They performed beyond the call of duty for a magazine project and we attribute that to Vic's enthusiasm for Corvettes.

In the next part of this series, we'll cover modifications to improve and/or restore the car's cooling system. We will also add an oil cooler and the car is just too damn hot inside so we'll work on "thermal management".

Stay tuned!

Autotronic Controls Corp. (MSD)
1490 Henry Brennan Dr.
El Paso, TX 79936
Chevrolet Raceshop
see your local Chevrolet dealer
Eckler Div. of Smart Choice
Box 5637
Titusville, FL 32783-5637
Edelbrock Corporation
2700 California St.
Torrance, CA 90503
Tech Line Coatings, Inc.
559 W. Mane St.
Gas City, ID 46933
317 674 0054
Goodyear Tire and Rubber Co.
see your local
Goodyear Tire store
Mark DeGroff's
Cylinder Head Service
and Machine Shop
18736 Parthenia Unit 2
Northridge, CA 91324
McLeod Industries
1600 Sierra Madre Circle
Placentia, CA 92870
NGK Spark Plugs, USA
22 Mauchly
Irvine CA 92618
Red Line Synthetic Oil
6100 Egret Court
Benicia CA 94510
800 624 7958

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