Big Block from Hell
Part 1 ... Just One More Time
by Hib Halverson
We together with Edelbrock for one last Big-Block Build up
Part 1, Short Block Preparation
True enthusiasts of Big-Block Corvettes are a rarity. Oh sure, lots of people have a fixation on the cars with the big, Mark IV engines but for many of them these days the car must be 100% original and because of sky-high value or mechanical problems like 11:1 compression and poor fuel, "driving" the Big-Block means in and out of an enclosed trailer.
Others are just into owning "prestige" like the loudmouth we all have seen at Corvette club meetings who hits any single women with the line, "Hi. My names Bob. I got a Big-Block." Of course, Bob, the scumbag that he is, never admits he hasnt had the car out in two years because he doesnt have insurance. Whats worse, hes working a deal with a Japanese collector to sell the Corvette so he can by a 300ZX. What a dork, eh?
To these folks I say: 1) Zora Duntov intended big blocks to be driven and driven hard. Those who dont are wimps 2) So what if its not original! 3) Anyone who sells a classic Corvette to the Japs is doing his part to undermine this country.
That editorializing done, those not offended and still reading are the ones I intended reach, anyway: the hot rodders, the fast drivers, the true rat motor Corvette enthusiasts. If thats you; stay tuned because we, along with friends in the performance aftermarket, are about to begin series of articles where we perform some street-high-performance magic on a 71 Coupe and end up with a pretty damn fast car.
The first part of this project (we havent named it yetalthough we thought about "The Big-Block from Hell" your suggestions are encouraged), which well do over the next few months will be modification of the 454 cubic inch, Mark IV Chevrolet engine. Initially, well stay conservative with moderate compression, a mild cam and modified oval-port, cast iron "low-performance" heads. This will result in a state of tune that makes for a practical, street driven big-block. We are looking for 430-440 hp and 490-510 lbs/ft. torque. The mild cam and heads will give us snappy throttle response and a mid-range that will have ZR-1 drivers envious. Later in the project with some changes in transmission and final drive ratio, perhaps, we might just challenge the ZR-1 hmm, "Devils Duel: ZR-1 vs. modified Big-Block." perhaps that idea has some potential.
Lastly, we have the future in mind. Although we will start conservatively in our selection of camshaft and heads, the rest of the engine will be built with parts and techniques used by top builders of all-out racing engines durability will be of utmost concern. Thus, as we progress in this series, we will be able to explore things like 7000 rpm roller lifter cams, aluminum heads, Weber carburetors or fuel injection let your mind wander.
Setting the Stage
As hot rodding Big-Block Corvettes is a rare art nowadays, you may be reading, perhaps, this magazines last in-depth look at rat motor hot rodding. Thus, the organization assembling our 454 had to be a person or persons who 1) has a well-known and unquestioned reputation in the high performance field 2) is capable of assembling a top-quality, street high performance engine and 3) is a Corvette enthusiast. This tall order left us a small group from which to choose. Fortunately, the individual at the top of the list listened to about three sentences of our pitch then said "Deal me in."
Vic Edelbrock is not only a mover and a shaker in the performance aftermarket but he is a Corvette fan. He owns three. The most famous is the ex-Bob Bondurant 63 Z06 Coupe that was the scourge of SCCA racing on the West Coast in the mid-60s. Vic vintage races the car and it was the subject of a feature in our 3/89 issue. Mr. Edelbrock also owns an 80 that is a street hi-po work of art. It has a 425hp, all-aluminum small-block that sports just about every piece Edelbrock makes along with nitrous oxide and a Nash five-speed. Vics "sedate" daily driver/touring unit is an 87 Roadster.
Edelbrocks Research and Development Facility in Torrance California is a performance enthusiasts dream. Besides Vettes, inside were: a rare Lister/Chevrolet, Vics newest vintage race car, undergoing preparation for the 1990 season; a restored 40s-style Midget originally owned by Vic Edelbrock Sr. and raced by Roger Ward and, of course, the famous Edelbrock "Fun Team," 38-foot offshore race boat with two, 1100hp twin-turbocharged big-blocks for power. Enough ohing and ahing, let the work begin
Our 71 Coupe, a two-owner car with 72,000 miles on the clock, was rolled in the R&D shop and, in an afternoon, Edelbrock Technicians Mike Eddy and Mark Gray had the cars LS-5 454/365 sitting on the floor. This engine was original except for: a Melling 396-S camshaft; a L-88/ZL-1 oil pump; a distributor with a modified advance curve; a Rochester Quadrajet altered to optimize fuel curve; a K&N air filter element; MSD cap, rotor and ignition wires; a set of NGK R5674-6 V-Power racing spark plugs and a crankcase full of Red Line 10W-40 synthetic oil. The chassis was equipped with: a 3.36:1 Positraction axle, M21 close-ratio four-speed, 255/50VR16 tires and a 3-inch, high performance exhaust system with Flowmaster street mufflers. Just before engine removal, I tested the car. Quarter mile times averaged 13.74 sec. at 109.4 mph.
Gray and Eddy installed the engine onto one of Edelbrocks Superflow 901 dynamometers and Director of Testing, Curt Hooker, ran tests to gauge the 454s health. The engine produced 353 gross horsepower at 5000 rpm and 435 lbs/ft. torque at 3500. In 1971, Chevrolet rated this engine at 365 hp@4800 and 465 lbs/ft@3200. Our numbers are down due to the engines age. Power and torque peaks moved up slightly, probably a function of the more aggressive camshaft profile. Power dropped sharply at 5500 rpm due to valve float caused by high-mileage valve springs.
Disassembly began with all accessories being cleaned and some set aside for possible reuse. The oil pan, intake and exhaust manifolds, and distributor would not be reused and were stored. The stock crankshaft and connecting rods were sold and all else was discarded leaving us a 71 LS5 two-bolt-main-bearing bare block (c/n 3963512) and two bare heads (c/n 3993820).
The block was shipped to Evans Speed Equipment. Owned by Gene Ohly, it is recognized as the finest machine shop doing engine work in the Western U.S. All freeze plugs and oil passage plugs were removed and the block was hot tanked and pressure tested. Evans first modification was a four-bolt main conversion using semi-finished, Chevrolet Raceshop main caps (p/n 140153344 req., p/n 141031561 req.) listed in the Chevrolet Power Manual. This process requires quite a bit of specialized machine work along with align boring once the caps are fitted. The conversion was done by Dick New who handles those tasks at Evans.
Gene Ohly bored each cylinder to 4.276 inches then milled the cylinder head decks .007" to get them parallel to the crankshaft centerline and perpendicular to the cylinders. The block height now fixed at 9.785", we ordered pistons.
The Edelbrock 454 will be fitted with forged racing pistons custom-built for this project by Bill Miller Engineering. A specific piston allowed us to pick our compression ratio and gave us higher quality, more durability and lighter weight than off-the-shelf units. BME pistons are machined from 2618 T-61 aluminum forgings on CNC milling equipment and go through 15 major quality-control steps. They are for use with a 1/16-1/16-3/16 ring package and full-floating wrist pins retained by double-Spiralox. Their domes were sized for a 9.7:1 compression ratio which will allow operation on 92-octane unleaded fuel. Wrist pins were also supplied by BME. Mr. Miller himself pinfitted all eight of our pistons before they were shipped to Evans.
Piston suppliers give specific instructions as to how piston diameter is to be measured. This is a critical point as piston-to-bore clearance is dependent on accurate measurement. BME pistons are to be measured 90° to the pin bore and 1/2-inch below the oil ring groove. Measurement is done with a 4"-5" micrometer and piston diameter varied only five ten-thousandths of an inch.
Bill Miller suggests, for street high performance use, his pistons have .007"-.008" piston-bore clearance. Evans honed the cylinders to get that figure. About .004"-.005" was taken out of each cylinder in two stages by Evans Sunnen CK10 honing machine. The final step removed .001" with 400 grit stones. During this process, Evans CK10 expert, Andy Cazares, had a torque plate and head gasket bolted to each deck to duplicate the effect tightened head bolts have on cylinder roundness.
After final hone, bores were 4.2797"-4.2803" which, with the 454s four-inch stroke, will have our engine displacing just a hair over 460 cubic inches. New Childs and Albert cam bearings (p/n C-4540) were fitted and the block was shipped to Vettes West Coast shop for deburringI like to get my hands dirty, too, you see!
Deburring is done to: 1) to remove sharp edges that can start stress cracks 2) to remove casting "flash" that could later break loose and fall into the engine and 3) to smooth surfaces inside the lifter valley to promote oil drain back. On the outside of the block, only sharp edges and flash were deburred. Casting numbers and other symbols were left as is. Block deburring takes about three hours if you have proper materials. I used a die grinder fitted with either sanding cartridge rolls or small sanding discs in 60-grit suppled by Standard Abrasives Incorporated.
Another task related to deburring is clearing the water passages on the head decks of scale and casting flash. The large square passages at the rear of the block usually require a lot of attention. Cooling will be improved if restriction to water flow in these passages is removed. The best way to do this is with a carbide rotary file in a die grinder.
A Chevrolet Raceshop, LS-6/L-S7 454 crankshaft was ordered. This unit (p/n 3963523) is forged from 1053 steel, has nitride heat treated bearing journals and is cross drilled for improved oiling. It was sent to Evans Speed to be Magnafluxed and straightened. Next, I got my turn with the crank for deburring and polishing. Then, it went back to Evans to have its oil holes chamfered and bearing journals micropolished. At this point the block and crank were moved to Edelbrock in preparation for assembly. Edelbrocks Mike Eddy was in charge of this job. At times Curt Hooker and engine, builder Robert Jung, lent a hand.
This teams first task was relieving the block. This standard big-block race engine trick involves grinding bevels at the top of each cylinder adjacent to the spaces occupied by the valves when they are open. The intent is to unshroud the valves thereby improving airflow when the valves are just opening or near closing. A Fel-Pro Pro 8180PT1 head gasket that has the right size reliefs and is used as a template. Trace around each cylinder with machinists blue. At the center of each relief, a mark is made a point on the cylinder wall that is a distance below the deck .100" less than the measurement between the top of the piston and the top of the first ring. Make lines from that mark to the edges of traced areas on the deck then fill this in with bluing. Start grinding at the horizontal center of the blued area and grind until you reach the bottom of the vertical mark. After that, grind sideways each direction until the blued material is gone. Curt Hooker used a die grinder fitted with a carbide rotary file for this. The markings must be done carefully and the grinder operated with a steady hand. A serious mistake will cost you a block. Needless to say, Mr. Hooker is a big-block master and completed this with the greatest of ease.
Mike took over and cleaned our 454 block (inside, outside and all oil passages) first, with solvent and then, hot water and Tide. A high pressure blow dry was next. Cleaning the block has been beat to death in every engine story ever written. However, I can not stress the importance of a block thats absolutely spotless before assembly. After scrubbing, the block was painted inside with Rustoleum brown primer to seal the pores of the cast iron and outside with, what else Chevrolet Orange.
Adjusting clearances between moving parts for best performance is a big part of the task many call "blueprinting" and is the major difference between a true street high performance or race engine and a stocker. Optimizing clearances is time consuming and expensive but pays off in significant power and durability gains.
Our first step was to set the piston ring gaps. We are using a Childs and Albert ZGS ring set (p/n RS42Zx4.285). ZGS stands for Zero Gap Second and means that the second compression ring is C&As unique "tortureous leak-path" design. The ZGS rings main advantage is reduced cylinder leakage. Leak testing a properly assembled, ZGS-equipped engine shows only about 1-2% leakage rather than the 5-8% usually seen in a new engine.
C&A rings, like many brands sold for hi-po and racing use are oversized. The user trims the ends of the compression rings to get the proper end gap. Robert Jung set the ring gaps using a C&A Precision Ring Filer. Once he had trimmed to the point of nearing the ideal figure, he checked the gap by squaring the ring one-inch down in the cylinder with a piston, then measuring the gap with a feeler gauge. Small amounts of additional filing and a couple checks with the feeler had the gaps set to C&A specifications of .015" for the top ring while the ZGS ring and the oil rings require no trimming.
Mike Eddy took over to install a main bearing cap Stud Kit from B&B Performance Sales (p/n 3316) in the block. B&B manufacturers a multitude of hardware items intended for race engine use. All their stuff is top quality and the choice of many Winston Cup engine builders. The Main Stud Kit is designed with center studs that mount a windage tray. B&B Main Studs are machined from 8740 chromoly steel, have rolled threads, are heat-treated and black oxidized.
We used Childs and Albert main and rod bearings. They are a tri-metal design but differ from other bearings of that type in that they are continuously cast and are of bronze-lead-indium composition. As a result, they are capable of sustaining higher loads than conventional tri-metal bearings. Lead-indium bearings are slowly being recognized as the best choice for performance applications.
Edelbrock practice is to check clearances using a micrometer for crankshaft bearing journals and a dial bore gauge for the bearing diameter. Lacking a bore gauge, an inside micrometer is acceptable. Under no circumstances should clearances be checked with "Plastigauge." Its readings vary too much for high performance engine work.
It was during this checking process that we discovered all crankshaft journals to be .0007"-.0013" undersize. Although the crank was micropolished, that only removes a ten-thousandth of an inch of material at worst, so apparently some Raceshop cranks are machined undersized. Mike Eddy had to use C&A, .001" undersized main bearing shells (p/n M-4540-001) to get our clearances to the .0024"-.0030" that is considered ideal by Edelbrock.
We passed on Chevrolet rods in favor of a premium-quality, racing connecting rod. LS-7 rods are good starting point, however the amount of preparation work necessary to prepare them for high performance and racing use equals or exceeds the price of an aftermarket race rod.
The aftermarket pieces we choose for the Edelbrock 454 were Crowerods. Made by the Crower Cams and Equipment Company, these units (p/n 91010B) are an I-beam design which eliminates unnecessary weight while delivering exceptional strength. They are machined from billets of 4340 chromoly steel, hand deburred, grit-blasted then fitted with H-11 alloy steel, D-head through-bolts. Crowerods are the most durable connecting rod available for the big-block Chevrolet and, in their small-block V8 size, are the choice of may Winston Cup engine builders. A tribute to Crowers craftsmanship is that both Evans Gene Ohly and Edelbrocks Curt Hooker said that no preparation work is necessary with a Crowerod just set bearing clearances and go.
Again, we had to use "one-under" C&A bearings (p/n R-4540-001) in the Crowerods to get Edelbrocks desired .0023"-.0025" clearance with the undersize Chevrolet crank. Next, rod side clearance was checked. This is done by fitting two rods to a crank journal then measuring the space between them with a feeler gauge. Mike Eddys measurement was .028" which is more than the .025" maximum recommended in the Chevrolet Power Manual and the .018" suggested by Edelbrock. We checked the thickness of the Crowerods big ends and found them right on at 0.990". On measuring the LS-7 cranks journal widths, we found all to be .008"-.010" over the nominal 2.00" width. This problem proved to be impractical to remedy as the only solutions were: start over with another crankshaft or have Crower make a special set of "wider" rods. Both solutions were prohibitively expensive.
We decided to go with the .028" side clearance. This would not affect durability but it would leave us with an oil control problem as a possibility. With large side clearances a lot of oil will be sprayed onto the camshaft and the cylinder walls. We decided to rely on an Edelbrock lifter valley shield and standard tension C&A oil rings to help with oil control.
After talking with Curt Hooker and Gene Ohly, I think Chevrolet has a rather large manufacturing tolerance for their big-block crankshafts. Perhaps, the units that are closest to ideal journal diameters and rod journal widths are used in Chevrolet Raceshop 454 LS-6/LS-7 Engine Assemblies and Cylinder Block Assemblies. Others that are just a bit under on the journals and/or wide on the rod journals, but otherwise serviceable, are fed into the Service Part Operations network. This is not an ideal situation but, nevertheless, acceptable to Chevrolet when judged for cost effectiveness. Perhaps its time for Chevrolet to tighten manufacturing tolerances a bit. They can do it with cranks for LT-5s so why cant they do it with cranks for Mark IVs?
The Balancing Act and the Friction Fight
Balancing is an important part of the modification process and is done for two reasons: 1) to reduce vibration and main bearing wear caused by dynamic imbalance and 2) reduce differences in weights of reciprocating parts. All balance work was done by Evans Speed Equipment. The weights of the rod and piston assemblies were equalized. The crankshaft, harmonic damper and flywheel were dynamically balanced as a unit on a Stewart-Warner stroboscopic balancing machine. Bob weights were used to simulate the mass of the rod/piston assemblies. If necessary the crankshaft counterweights, flywheel and harmonic damper were drilled to remove material enough to achieve balance. Although not the case with our engine, sometimes weight will have to be added. This is done by drilling holes in the cranks counterweights then filling them with a metal of higher mass such as Tungsten.
Friction is the eternal enemy of an internal combustion engine. It causes an engine to work harder and eventually wear out. Needless to say, anything done to reduce friction pays off in longer life and more power.
In the late-60s, molybdenum, thermosetting (or "dry-film"), antifriction coatings were developed for aerospace applications. About 15-years after the aerospace industry developed these coatings, the quest for increased power and durability in motorsport had race engine builders trying them.
In some race engines built for oval track use and equipped with many coated parts, as much as a 5% horsepower gain have been realized. Today, use of of dry-film lubricant coatings is perhaps more widespread than one would think. Many race engine builders using them will not admit to it they look at them as a competitive edge to be kept secret. I wanted to coat some of the 454s parts, however, considering the expense of coating, I selected a limited program focused on increasing durability rather than a large power increase.
We contacted G&L Coating in San Marcos, California. They work with the Kal Gard Coating and Manufacturing Co (the originator of the process) in developing coatings for the automotive market. Molybdenum, or just "moly", is an excellent extreme pressure lubricant. When used by G&L in a thermoset coating, moly is combined with other load-bearing lubricants and mixed with a liquid bonding agent. The mix is applied to a part with a spray gun then is cured in a oven. What is left is a thin layer (typically .0002-.0005-inch) of antifriction coating that is bonded to the part.
G&Ls owner, Leonard Warren, recommended that we coat our engines camshaft, distributor drive gear, oil pump internal parts, main and rod bearing shells and the skirts of our BME pistons with their DFL0221 material. All of those parts are very friction-sensitive items and coating them offers durability gains.
G&L suggests burnishing all parts treated with DFL0221 with a Standard Abrasives General Purpose grade BriteRite pad before use. The amount of burnishing is important. You dont want so much that the coating is completely removed however, you want to remove the upper levels of the coating. The best way to to rub a bit, wash the part in solvent then look for the minute scratches the BriteRite leaves in the coating. If, in spots you can just begin to see the metal under the coating, done burnish any more. Additionally, on the very edges of the part (this is a particularly good clue on bearing shells) the coating will be rubbed away.
Begin Final Assembly
Were getting down to the wire with this months installment of the Edelbrock 454 story. At this point, all the "prelims" are done. The block is cleaned one more time and Mike Eddy begins putting things together.
The C&A upper main bearing shells are installed into the block. Some Red Line Synthetic Assembly Lube thinned with a little of Red Lines 15W40 Break In Oil was smeared on the shells then the crank was set in place. Each main cap was fitted with a bearing, more lube was put on those shells and the main caps were set in place. Every main cap stud nut was tightened to 90 ft./lbs. The tightening of each cap was done in a sequence at 40-60-80 then 90 ft/lbs. of torque.
The rear main bearing is also the thrust bearing so, to insure the thrust surfaces of the two rear main shells were positioned correctly, before tightening the rear cap; the crankshaft is forced all the way rearward. This is done using a screwdriver between the number three cap and a crank throw to pry the crank back. After the last cap was in place Mike checked thrust clearance with a dial indicator. It was .006", acceptable for street high performance applications.
Legend has it the next thing an engine builder is to do is to spin the crankthe idea being that any bearing problem or a bent crank will prevent it from spinning freely. Of course, the blueprinting process will uncover any problem long before assembly reaches this pointhowever, there is that satisfaction of spinning that crank, noting how smoothly it moves then, standing back and saying, "Now thats going to be one hell of a motor!"
Ill admit to enjoying that ritual. Next month, well finish assembling the short block then take a look at cylinder head modifications.
Performance Sales, Inc.
Crower Cams and
|Red Line Synthetic Oil
6100 Egret Court
Benicia CA 94510
800 624 7958
|Standard Abrasives, Inc.
4201 Guardian St.
Simi Valley CA 93063
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