Big Block from Hell
Part 6 ... One step forward then, two back
by Hib Halverson
In Part Six of Our
Series, Its One step forward
then, two back.
Ten months have passed since Vette published an article on our in-your-face, 1971, big-block Coupe. Now, thats a pretty long break for a project series and Ive taken a lot of flak for that.
Editor: "Ah yea, Halverson ah, youve been screwing around with that car for six months, are you going to have an article this year or next?"
Girlfriend: "I thought we were gonna take a trip in that car this summer. But, nooooooo youre working on it all the time. Why cant you just fix it so it runs?"
Neighbor: "Hey bud, do ya ever drive that thing or is it a parts car. Heh, heh, ha, ha."
Truth is, life with BBfH has been anything but easy. Once we got the engine in, problems began. Every time we took a step forward, we then took two back.
Issue One: Low/No Oil Pressure under braking.
We ended the last installment of BBfH in the May 1991 issue with some 1/4 mile acceleration tests. Our best on street tires was 12.98/116.9. With deadline approaching we went to press with that article and continued to test at the drag strip and later, over our favorite set of twisties.
Then came the first obstacle. Under acceleration or cornering, the oil pressure was rock solid at 60-65 psi. Hit the brakes, and it would drop to zero. No rocket scientist was needed to figure we had a problem with either oil level or baffling in the oil pan. We rolled the car into Vettes Western Technical Facility, put it up on jack stands and began working on the problem.
Those following the series know wed fitted the 454 in the Big-Block from Hell with an eight-quart, wet-sump, road racing oil pan from Milodon, Inc. First, we called Milodon and confirmed the pan held eight quarts. Next, we drained the oil. To get every last drop, we jacked the car way high in front and let the oil drain overnight. The next day we changed the K&N Oil Filter (p/n 07-0029) and filled the engine with nine quarts (eight for the pan, one for the filter) of Red Line 10W40 Synthetic Oil. A brief test showed, regrettably, nothing changed.
We removed the Milodon oil pan, the Milodon windage tray, the Milodon oil pump and the Milodon oil pump pickup. We sent this stuff back to the manufacturer with a request that they check for anything that could cause oil flow away from the pump pick up during braking. Ten days later, Milodon called saying that all looked good. They also said there was probably an oiling system problem " unique to our engine " and to solve that and try their parts again.
A careful inspection of the engines lower end found no problems. The 454 was assembled at the Edelbrock Corporation, so we reviewed assembly records with Curt Hooker and Robert Jung, the people in charge of BBfH assembly. Again, no anomalies were found.
Two weeks later, working on a long shot that removal and replacement of the oil pan, tray and pump unit would fix our difficulties; the Milodon pieces were reinstalled, the crankcase was refilled and we went out for another road test.
We hit the brakes; the oil pressure dropped. I found it hard to believe that an oil pan assembly, supposedly designed for road racing, would have a problem like this, but our test data was pretty convincing.
Again, BBfH was in our shop up on stands and we removed the Milodon pieces. We dusted off the stock pan, tray, pump and pick-up (in storage since removal 18 months before) and reinstalled the production Chevrolet hardware. We filled the engine with five quarts of Red Line 10W-40 and went out for a test. Under maximum braking (just to the point of wheel lockup from 60 mph) the oil pressure was 60-65 psi.
Youd think my patience with Milodon pans would have worn thin by now. However, in a weak moment, I called Milodon and suggested the problems stemmed from a design defect. I offered to help solve the problem by using the Big-Block from Hell for further tests. The only restriction was that any design change made to solve the oil pressure loss must be put into production, so anyone buying the big-block Corvette pan would have the benefit of the change. They said that was ok and to return the parts.
After three weeks, I got a call saying the pieces had been modified such that, Milodon assured us, our problems would be over. However, when asked if these changes, should they eliminate the oil pressure drop, were to be applied to all their big-block, road race pans; the Milodon representative told us that no changes would be made in their manufacturing.
This was where Vette Magazine and Milodon parted ways. As there was no point testing something readers couldnt buy; we let them keep their oil pan. At this writing we are using the production Corvette pan assembly. Perhaps we should have just used the stock stuff to begin with such is the benefit of hindsight, eh?
Now comes the nastiest tasting part of the crow
I was a mistake to go to press with our story in the May 1991 issue before we had finished testing the car. If we had waited, wed have known about the problem with the Milodon pan sooner. We apologize for that.
If there are readers who tried the Milodon big-block, wet sump, road race oil pan assembly as we did; we suggest you contact Milodon for a refund. If you cant get satisfaction, contact us; we will make sure your problems are discussed in print.
Issue Two: the Diesel Corvette
About a week after Edelbrock installed the engine for the May 91 issue, we had to add a quart of oil. Shortly thereafter, it was weird, but we added oil, again. While playing oil pan switcheroo, we drained and refilled the crankcase a bunch of times. Undoubtedly we spilled oil or, we could have lost count of how much wed put in. Nevertheless, I was amazed when BBfH needed yet a third quart of oil in less than a month. Whats worse, there had been a few times Id seen smoke out the exhaust.
It appeared, especially once we got the stock pan back on (done with the draining and refilling drill), as if the engine was burning too much oil. As a final confirmation, I filled the crankcase, drove the car 103.9 miles then carefully measured the oil I added just a little bit less than one quart.
Geez, the Big-Block from Hell was a diesel! The problem was with either: 1) rings or cylinder walls or 2) valve seals and/or valve guides. As the valve guide scenario was easiest to fix; we began with that.
I contacted Mark DeGroffs Cylinder Head Service, who did all the head work for the project. Mark DeGroff was skeptical of any problem with the heads, but agreed to change the valve stem seals at no charge, if wed bring the car to his shop. Afterwards, I ran another oil use test. No change.
Back at our shop, we pulled the heads and had DeGroff replace the stock guides with K-Line bronze inserts, set the valve stem-to-guide clearance at minimum acceptable dimensions and add, yet another set of stem seals. Once more Mark completed all work asked for by Vette at no charge in spite of feeling the problem was not with his cylinder heads. I ran another test and found, the engine was still sucking oil, big time.
DeGroffs work had been flawless originally and his efforts with this problem reconfirmed our feeling that his shop is one of the best cylinder head emporiums in the country. You havent heard the last of Mark DeGroffs excellent service in this magazine.
This left us with the rings or cylinder walls as the culprit. After the oil pan problems and pulling the heads; now, the engine would have to come out. The "BBfH" name started as a play on words Car and Driver used one time to describe the ZR-1, however "Big-Block from Hell", by now, was certainly an accurate description.
Edelbrock Corporations President, Vic Edelbrock, again stepped up to help. He offered the services of Curt Hooker and the dyno room crew (the same bunch that had served us so well when we built the engine in 1990) to disassemble, repair, reassemble then dyno test the engine if we were willing to do the removal/replacement at our shop. If the problem was with Edelbrocks initial work, theyd do the rebuild free. If it was a problem with someone elses work or parts, wed pay only for the engine work. The dyno testing would be a trade-out as Edelbrock needed to try out the final prototype of a new, big-block, intake manifold. All this was a deal we could not refuse.
I rang up good friend and fellow Corvette enthusiast, Gary Petersen, to give me a hand with pulling the engine, and we started the next morning. That night the 454 was sitting on the ground in our shop. The following day, I hauled the engine to Edelbrocks facility in Torrance in a 1991 K3500, big-block, extended-cab, dualie, four-wheel drive pick-up (think we got a serious enough truck?!) on loan from Chevrolets PR fleet.
A day later, I had the first of two, memorable phone conversations with Childs and Albert, the piston ring manufacturer we used for the original engine build-up in 1990. I called to advise them we might have a problem with their rings. I was astounded when they replied, "Were pretty sure we sent you the wrong parts."
After talking to them, I was a bit frustrated, " pretty sure ?! wrong parts!? Geez, thats just peachy!" I thought. Hell, the motor was using a quart of oil every hundred miles I was very sure we had the wrong parts!
Childs and Albert introduced their "ZGS" ring sets with a second compression ring having a vertical face. That is appropriate for drag race engines that spend little time in part throttle/high vacuum operation. It would be expected that C&A would engineer the ZGS ring sets that way as many of their customers are drag racers.
However, with vertical-faced second rings, if theres any significant manifold vacuum; oil is pulled past rings and into the combustion chamber. Street cars, road racers and anything else that runs at part-throttle need a second ring with a tapered-face. As the piston moves on the down-stroke, a tapered-face, second ring assists the oil ring in scraping oil down the cylinder wall.
Once Childs and Albert began to sell ZGS ring sets for street use, the oil consumption problem may have surfaced and they changed the second ring to a tapered-face. In talking with C&A, it was unclear how we received the wrong parts, but I speculate that there may have been some old stock (vertical-face second) in their warehouse that we got by mistake.
Two days later, Curt Hooker and I were looking at the the guts of the BBfHs 454 spread out on the bench in Edelbrocks engine assembly room. It was easy to see from the wear pattern that the second compression rings, indeed, had vertical faces.
I would have gladly installed Childs and Alberts tapered-face ZGS ring set, but on a second call to them, I asked, since it was their mistake that caused our problems, if they were interested in sharing the expense of the engine work. Their reply was a firm "No". When I UPSed the used rings to them for inspection, I also sent back a second unused set I had bought for another engine project. In an accompanying letter, I requested a refund on the second set of rings. At press time, more than months later, I have yet to receive that refund. In my opinion, Childs and Albert wins no prizes for customer service.
Bill Miller, who owns Bill Miller Engineering, the manufacturer who supplied the 10:1 forged pistons for the engine build-up series, had been aware of our difficulties and asked to see the pistons and rings once we had the engine apart. A week later, on trip to Northern California, I took a swing into Nevada and stopped by BME in Carson City, Nevada.
Millers pistons are top quality and, expectedly, were no worse for wear other than a little burned oil scum on their tops. However, as Bill looked at the top compression rings under a magnifier, he said "Well, your ring ends have been butting not real bad, but they have been butting. See (I looked through the magnifier) You can tell from the burnished ends. Not only were you sucking oil because of the second compression rings, but once the top rings butted; you began loosing compression. Perhaps C&As ring gap recommendations were a bit too tight for your engine."
Most of us know that insufficient ring gap causes the ring ends to touch. Many think, when that happens, the rings just get tight in the cylinder. What actually takes place is worse. Once the ring can no longer expand in the conventional manner; it deforms into a wave shape. The top ring is the major contributor to cylinder sealing. Once it gets wavy; compression loss begins.
"You know, Halverson," Miller mused as he continued to examine the rings, "you got too many problems, here. I think you ought to switch to Speed Pro. If theyre good enough for my Top Fuel car they ought to be good enough for your Big Block from Hell."
Putting down the magnifier, he changed the subject, "Okay, time for dinner. I stayed late so Vette Magazine is buying, right? How bout Mexican?"
What a concept! After a killer burrito and a couple bottles of Dos Equis, I definitely felt better.
We ordered a set of Speed Pro piston rings (p/n R9745-035) from the Sealed Power Corporation. This ring set is a 1/16-1/16-3/16ths configuration with a moly-filled top ring, a ductile-iron tapered-face (yes, yes!) second compression ring and a standard-tension oil ring.
New rings meant honing the cylinders and to save time, we honed by hand. There is but one tool to use for this and thats the Flex-Hone. Edelbrocks Robert Jung used a variable speed, 1/2-inch chuck, electric drill and a 320-grit, 4 1/4-inch Flex-Hone (p/n GBD 4.250x320SC) to do the job.
The key to a good honing before a re-ring job is getting the correct cross-hatch pattern on the cylinder walls. Remember that classic movie "Honey, I Shrunk the Kids"? Imagine yourself as that small. Youve rappelled down the cylinder and are looking closely at the cylinder wall. The hone cuts hundreds of grooves (Feel them?) in the cylinder walls. Because the hone moves up-and-down as it rotates, the grooves are in two, helical patterns. The patterns cross each other to form a multitude of diamond shapes that are critical for good ring seating and (Dont get your clothes greasy!) oil retention when I say "oil retention", thats just the tiny bit of oil that lubricates the rings, not a quart every hundred miles!
The diamond shapes make up the cross-hatch pattern. The key variable is (got your protractor out?) the angle between the two sets of helical grooves. Sealed Power suggests a 20°-30° from horizontal, cross-hatch angle and a drill speed of 200-450 rpm. Getting the proper angle depends on how rapidly you move the drill up-and-down. Believe me, this technique takes practice, but engine aces like Edelbrocks Robert Jung have the procedure down pat.
Once wed Flex-Honed the cylinders, we were ready for reassembly. All parts were washed. Though wed had trouble with rings and customer service, the Childs and Albert bearings we used previously showed virtually no wear, so we reinstalled them. We attribute the lack of wear to use of Red Line Synthetic Oil and the fact that C&As bearings are made by Vandervell whose engine bearings are excellent products.
The LS-7 crank was dropped in and the mains torqued to specification. The BME pistons, pins and our Crowerods were put back together with new double-Spiralocks. The Speed Pro rings were gapped (.018" for the top ring and .012" for the second) then installed, the rod bearings were added and the piston/rod assemblies were pushed in place using the same B&B Tapered Ring Compressor (p/n 4145) wed left at Edelbrock at 18-months before. Next came the camshaft.
Originally, we used an Edelbrock "Torker-Plus" flat tappet, hydraulic cam. This unit is relatively inexpensive and is an excellent choice for a high performance street engine. We were perfectly satisfied with the Torker-Plus, but, as we didnt want to spend this whole article cryin the blues, I decided wed try a new camshaft.
A couple of steps up the performance ladder, but certainly more costly, are roller lifter cams intended for street use. Edelbrock does not market street rollers so we turned to Crane Cams for help. The camshaft they suggested is a bit more aggressive than the Torker-Plus, but is actually fairly mild as far as street rollers go.
Edelbrock Torker-Plus Crane Hi-Roller
Duration at .050" liftint./exh. 224°/232° 234°/244°
Valve liftInt./Exh. .527"/.553" .567"/.567"
Valve lash .022"/.022"
With a conventional flat tappet camshaft, as the cam rotates, the lifter slides over the cam lobe. The more aggressive the cam profile, the stronger the valve springs must be to keep the lifter in contact with the lobe and prevent the valves from bouncing on the seat when they close. However, with the sliding action of a flat tappet cam, there are limits to maximum spring pressure that are set by lubrication and materials that is, the stronger the springs, the harder the lifter rubs on the lobe and the tougher it is to lubricate and keep the metal of the cam from wearing.
The advantage to a roller lifter camshaft is that the lifter rolls over the cam lobe rather than sliding over it which greatly reduces problems with lubrications. As a result, roller cam profiles can use valve springs of higher rates and, because of the stronger valve springs, can have more radical profiles.
Now, youll notice in our chart above that the Crane roller is really not that much more in duration (+10°) or lift (+.040"/+.014") than the Edelbrock Torker-Plus. The significant difference, which we cant show as we do not have Edelbrocks or Cranes complete cam profile information, is in how rapidly the valves open and close. Because a roller cam moves the valves more quickly, even though duration and lift figures appear similar; the total valve "event" is larger. If the valve event is larger, more air and fuel gets into the engine and more power comes out. If all this is too technical, just trust me and look at our dynamometer results later in the story.
Robert Jung installed the cam per instructions Crane supplied. A quick check with the degree wheel showed that Cranes quality control was right on. The Edelbrock Performer Link roller timing chain (p/n 7810) used in the original build-up was in fine shape, so we reused it. Roller cams are more liable to move back-and-forth in the block. There must be some device to control this, so a Crane Needle Bearing Spacer (p/n 99165-1) was installed on the front of the cam sprocket.
Cranes "Professional Series" roller lifters (p/n 13542-16) are a relatively new addition to their product line. One difference between them and Cranes standard roller lifters is lighter weight. Though its questionable whether we need lighter valve train pieces right now; if we ever get to "Stage II" with this engine; well need that to get the engine to safely rev higher.
The heads had been sent over to Mark DeGroffs to have Crane valve seals, valve springs, retainers and locks (p/ns 99822-16, 99895-16, 99955-16 and 99098-1) installed. As Mark had just done the guides, nothing else was necessary and the heads were returned to Edelbrock. Robert Jung fitted the engine with Fel-Pro PermaTorque/Blue Stripe head gaskets (p/n 1017-1) then bolted on the DeGroff heads.
Crane push rods (p/n 13634-16) added along with the Edelbrock Camshaft Oiler (p/n 8098) we used before. Robert reinstalled the Edelbrock C66, dual four-barrel intake manifold using a set of Fel-Pro intake gaskets (p/n 1212). They have the "Printoseal" feature, silicone rubber beads around the intake ports and water crossover, which make future tear downs a snap as the gaskets can be easily removed. Last to go on the engine were our Edelbrock "Red Rocker" needle-bearing rocker arms, valve covers with Fel-Pro gaskets and our pair of Edelbrock, 600 cfm, Performer Series four-barrel carburetors.
Back in the Saddle Again.
During Part Four of this series (Oct. 90 Vette) we spent a week testing this engine, so Edelbrocks dynamometer cell #2 was a familiar place. We hooked the engine up to the dyno fluid delivery lines and instrumentation then, as BBfHs ignition system stayed with the car; we installed Edelbrocks dynamometer ignition system. On went the dyno headers and in went a set of NGK R5674-9 V-Power Racing Spark Plugs. We filled the crankcase oil and fired that mother up.
The long period of fast-idle to break-in a flat tappet camshaft is unnecessary with a roller, so we ran the engine long enough to reach operating temperature. Robert Jung shut the motor off and adjusted the valves.
He fired it again and ran the 454 for about 30 minutes at speeds of 2000-3000 rpm and with light to moderate load to seat the rings. During the ring seating process synthetic oil is not the best choice be used because it is so good at lubrication, the rings take a longer time to seat. A good quality petroleum-base oil can be used to shorten the ring seating period.
Once the engine had run long enough for the Speed Pro rings to seat, we shut it off, changed to Red Line grade 30 Synthetic Race Oil and began our test sequence, the first part of which was several dyno pulls to check carburetor jetting. Expectedly, the cam change had us altering the jetting somewhat. We installed #92 jets in both ends of each carburetor and the primary metering rods ended up 6552s. Now, it was time to run hard with the Big-Block from Hells 454.
Robert Jung, started the engine. He programmed Edelbrocks Super Flow 901 computerized dyno for a 2500-6500 rpm step-test while engine warmed. He scanned the 901s console and, after seeing all looked good, he asked, "Are we ready?"
"Beat on that sucker," I answered.
Our ears were treated to the wail of a 454 hard at work making big torque and power numbers. As we were now using a mechanical lifter roller camshaft, Robert wound the engine tighter than before. The peak figures are in bold type.
BBfH Stage 1, w. Torker-Plus BBfH Stage 1A, w. Hi-Roller
RPM torque horsepower torque horsepower
2500 460.1 219.0 489.6 233.1
3000 506.2 289.1 491.3 289.6
3500 505.5 336.9 523.0 348.5
4000 513.3 390.9 511.0 389.2
4500 513.7 440.1 524.6 449.5
5000 503.7 479.5 521.0 496.0
5500 453.9 475.3 498.8 522.4
6000 406.9 464.9 461.0 526.7
6500 395.5 489.5
There are a some conclusions to be drawn from our dyno run: 1) In the mid-range, up to about 4000 rpm, where most street driving is done; the Torker-Plus flat tappet hydraulic cam is comparable to a roller. This is an important consideration if you are building a big-block on a budget. 2) If you have the bucks for a roller, there is a payoff above 5000 rpm. For us it was 47 horses at 5500 and 61 at 6000 and 3) the Crane street roller, in spite of more lift and duration than the Torker-Plus, maintains good torque down low. This motor should be fun to drive!
Once again, Edelbrocks assembly work and dyno testing made a substantial contribution to the Big-Block from Hell project. We appreciate Vic Edelbrocks interest in Vette and its readers.
On the Road, Again.
Chevrolet PR loaned us another pick-up, this time a 1991 K1500 four-wheel drive short bed, to haul the engine back to the our Western Technical Facility. Both times we borrowed trucks, we have gotten the superb C/K series pick-ups; one, a big-block/automatic and the other a small-block/five speed. These trucks drive nice, ride like cars and easily met our freight-carrying needs handily.
Once again, Gary Petersen was on hand at WTF to help and, over a weekend, we had the engine back in the car and running. Previously, however, we competed a few jobs on the chassis. First, we took the Street Twin, dual-disc clutch and flywheel assembly back to its manufacturer, McLeod Industries, and had it switched from a 168-tooth to a 153-tooth flywheel. This allowed us to move the starter closer to the block, gaining us some additional clearance between the starter and the number four exhaust header tube which, with the old set-up, had to be crushed to about half its normal diameter. We took the header to Pro Chassis, a top-quality race car builder and our main fabricator for projects, to have a new, #4 tube bent and welded in place of the squished unit.
We partially disassembled the cars Muncie M21 four-speed to repair a leak then filled it with Red Line MTL, a synthetic lubricant for manual transmissions. We upgraded the fuel system with a Holley electric fuel pump (p/n 12-802) and adjustable fuel pressure regulator (p/n 12-803). These two come as a unit and are racing quality pieces of equipment. The pump is capable of 14 psi, so the regulator must be used with carburetors. The recommended pressure for Edelbrock Performer Series four-barrels is 6-6.5 psi. We had a fabricator build us a neat little bracket to hold the pump and this assembly was installed near the fuel tank. A note of caution: with the Holley pump pressurizing the fuel system to 14 psi downstream of the regulator, any flexible connections between pump and regulator should use either braided stainless-steel hose and AN-type fittings or the high-quality rubber fuel hose recommend for use with late model, fuel injected engines and screw-type hose clamps.
Lastly, we had Doug Moody of Edelbrocks Electronics Department alter the software in our Edelbrock Ignition Computer such that the rev limiter kicks in at 6800 rpm rather than the 6200 rpm limit we used with the hydraulic cam.
Once the car was running, we began a series of easy driving tests to make sure we had no leaks, that the fuel system changes were working and, most importantly, the oil burning problem was solved. In the second week of testing, I ran the car through the same 103.9 mile oil use test I did before. This time, things were looking up. The car used no oil and, at this writing several hundred miles later, we have yet to add any. Obviously the hot ticket in a high-performance street Corvette engine are Speed Pro rings with a tapered-face second.
Finally all the weenie driving was over. It was time to take the car to the drag strip and see what all this effort had done to the cars quarter mile times. Strip conditions were as follows: traction, fair to good; temperature, 70°F and altitude, 300 feet. The BBfH was raced with street tires, a 3.36:1 rear end and a close ratio four-speed manual transmission. In road tests, Vette normally power-shifts manuals. However, the Muncie in the BBfH is 72,000+ mile unit thats never been rebuilt. Considering the engines torque and that we didnt want to break the trans; we did not power shift.
First, we made half a dozen no-time passes to 1) sort out the progressive throttle linkage on the two four-barrels, 2) determine shift points and 3) learn how to get the car to leave best. Then, we ran five passes for time. I threw out the quickest and slowest and averaged the middle three. The car ran 12.57/122.6.
Seems as though the Big-Block from Hell project is back on track, eh? Well be back in a few months, I hope, with more.
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