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Chevy 566ci Big-Block Build and Test

Go-To Power: Building a 566-cube 850hp Chevy for the street

Steve Dulcich Dec 16, 2016
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When some guys consider the AMSOIL Engine Masters Challenge, they often envision wild, custom, one-off engines. Some will imagine engines built strictly for the event and dyno results. Granted, there are some exceptions; however, for the most part we get real street or race powerplants, just as capable in a car as they are on the pump. The fact is, the vast majority of the competition engines are built with a street or race application in mind after the event. Such is the case with this 566-cube big-block Chevy. As builder Eric Roycroft relates, “This isn’t a wild, one-off Engine Masters Challenge engine. It is the type of Chevy that can readily be duplicated.” No, it’s not your dad’s 427 or 454, but it is indicative of what can be bolted together with today’s mainstream aftermarket parts. The power potential here is what makes the big Chevy today’s go-to high-horsepower source.

Regular Street

Eric Roycroft is a man familiar with the annual AMSOIL Engine Masters Challenge competition, having a history of coming to the competition with straightforward, but formidable engine combinations. Looking at the multiclass event for 2015, there was a broad choice on just what type of engine to build, and a decision to make on just where he might best fit in. This time the decision was helped by the fact that he pretty much had the required weapon locked, loaded, and nearly ready for action right in his garage. As Eric tells it, “I had about 80 percent of the parts on hand to make a competitive big-block Chevy, so it seemed like a practical choice. Most of the short-block was there to build a 566-cube combination, using a 4.600-inch bore and 4.250-inch stroke. I had the Dart block, the Scat crank and rods, and even a good set of heads to go with it.”

“I knew it would be good for its size, but in reality it was too big for the competition. If I was starting from scratch, and building specifically for the competition, I would have gone 100 cubes smaller. I did know that this is a very good combination that makes good power. It is a very common combination, and I didn’t have a lot of time. I had a good chance to win unless someone came in with a smaller engine that was really good. If I tried to make it smaller, the heads would be too big and I’d have to change everything and just about start over. I just had Diamond make some changes to their stocking pistons to meet my compression ratio needs, and I did piston-guide the rods because I think that is worth some hp, but the short-block is really run-of-the-mill.”

This bore and stroke formula is popular due to the readily available Dart big-bore block. The 4.600-inch bores dwarf what can be done with a production Chevy block, and it has the beef to handle all the power and rpm you can throw at it. The short-block was assembled with off-the-shelf aftermarket parts, including a Scat 4.250-inch crank, Scat 6.350-inch rods, King engine bearings on both the rods and mains, Total Seal Gapless Top rings, and a replacement-style Melling oil pump. Roycroft wasn’t jiving us when he said the bottom end was simple.

850 Horsepower Big Block Chevy 024 2/24

Heads, Induction, and Cam

To top the big-inch bottom end, Roycroft once again kept it simple and took advantage of parts he had on hand. As Eric details, “I have had these Pro Topline heads for years. In fact, I think they quit making them. Since I had them I figured I might as well use them, and they seemed like a good match to the engine. I bought them from a buddy, and it is a shame they don’t make them anymore because they are really good heads.” The large 360cc intake port heads definitely have the capacity to handle the cubes. Roycroft filled the bare head castings with 2.300/1.900-inch Manley valves. Other than a valve job, and a minor blend of the machine work into the bowls, the heads were otherwise unmodified—neither ported nor flow-tested.

To complement the cylinder heads, an Edelbrock Super Victor intake was selected and once again used with very few modifications, other than minor blending of the plenum entrance. This intake comes with the size and capacity to handle a big-inch Chevy right out of the box. Carb expert Dale Cubic reworked the 1250 Holley Dominator carburetor. As Eric explained, “I sent him a 1250 carb and he put on his metering blocks, performed his magic, and sent it in to me with his calibration sheet. I didn’t have to do anything to it. I put it on the engine and made some minor jetting adjustments and it was right on. We did tune it in competition because of the difference in the air in Ohio compared to Georgia where I live, but that’s it. I use Dale because he is good at what he does and you can expect it to be right on. It wasn’t too trick, just a basic job.”

Once the long-block was assembled it was left alone, but the camshaft was an area where Eric experimented. As he tells us, “I tried three cams in it all with very close lift and duration specs, with the difference being the lobe. Initially, I got two cams. I felt the intake runners on the heads were a little big, which leads to lower air speed, so that steered the cam specs. We took a little bit of a guess on it based on previous experience, and started with a pair of cams from Competition Cams. The first cam we tried was a less intense and slower lobe, but it turned out to be the better of the two. I wanted to try again, so I sent the other cam to be re-ground with yet another lobe profile, but once again it wasn’t as good as the first. We changed the lobe we used and what I thought would be better wasn’t. One had a quicker opening but it was worse on power. Why that was the case, I never determined. I ended up just using the one that worked. What I learned was what you think will work may not work.” The cam specs ended up at 260/260-degrees duration at 0.050, with 0.792-inch lift delivered via Trend pushrods operating 1.8:1 WW Engineering shaft rockers. The cam was ground on a 104-degree lobe separation angle and is driven by a Jesel beltdrive system.

Dyno Time

The engine had a chance to show its capabilities in competition at the 2015 Engine Masters Challenge, hosted by the University of Northwestern Ohio. Here it was pitted against stiff competition, coincidentally including another 566-cube Chevy with the same basic bottom-end configuration. It is against the dyno where the huge power potential of these big Chevys really shows. The big displacement translated to big torque, with 664 lb-ft showing right at the bottom of the curve at 3,000 rpm, rising to a peak of 777 lb-ft by 4,900 rpm. That is torque that will get you moving in a hurry. On the power side of the equation, the engine certainly wasn’t short, pounding out a stout 851 hp at 6,500 rpm. Keep in mind, those power numbers came about without expensive custom porting or one-off race parts. This 566 is just a great example of the kind of power a well-executed, serious, but basic big-block Chevy is capable of. That just goes to show why the big-block Chevy has become the go-to engine in just about any application where serious power is needed.

850 Horsepower Big Block Chevy 002 3/24

1. This 566-cube Chevy big-block is built on a stout foundation, featuring a Dart Siamese-bore block allowing a bore size of 4.600-inch to be easily accommodated. Note the hefty four-bolt main structure. A Scat 4.250-inch crank and Scat rods complete the bottom end. Bearings are by King.

850 Horsepower Big Block Chevy 003 4/24

2. Filling the bores are Diamond pistons, where they were ordered as shelf parts from Diamond with a modified dome to provide a compression ratio of 11.4:1. The 6.350-inch H-beam Scat rods come with ARP bolts.

850 Horsepower Big Block Chevy 004 5/24

3. A profile view shows the very short skirt of the 1.325-inch compression height Diamond pistons. Note that the piston pin protrudes into the oil ring groove, requiring an oil ring support rail. Rings are Total Seal Gapless Tops, in a 0.043/0.043/3mm package.

850 Horsepower Big Block Chevy 005 6/24

4. The pistons feature vertical gas ports to aid ring seal under compression. The pistons achieve a zero deck height, which provides a 0.040-inch quench clearance with a Fel-Pro composition head gasket.

850 Horsepower Big Block Chevy 006 7/24

5. A Moroso deep-sump pan contains the AMSOIL 5w20 motor oil. Note the integral louvered windage tray. The oil pump is a stock replacement Melling unit.

850 Horsepower Big Block Chevy 007 8/24

6. Heads are a used set of Pro Topline 360cc cylinder heads, which are no longer manufactured. Note the support bar for a set of WW Engineering shaft-mounted rocker arms.

850 Horsepower Big Block Chevy 008 9/24

7. The heads came to Eric as bare castings, which he filled with Manley 2.300/1.900-inch valves. The chambers measure 119 cc to give a compression ratio of 11.4:1. Other than a minor blending of the valve job machine work, the heads remained as-cast, with no further porting or flow bench work.

850 Horsepower Big Block Chevy 009 10/24

8. Lunati solid roller lifters are worked by a custom Comp cam. Eric tried three cam profiles, surprisingly finding the least aggressive made the most power. Note the screens epoxied into the drain-back areas to catch any debris from a failed part.

850 Horsepower Big Block Chevy 010 11/24

9. Here we see the mechanics of the valvetrian. Eric gives high praise to the Lunati solid roller lifters as a great value. The WW Engineering rockers deliver a ratio of 1.8:1, and mount to sturdy shaft supports. Trend formed pushrods set the standard in the industry.

850 Horsepower Big Block Chevy 011 12/24

10. Here we see the assembled valvetrain. The shaft-mounted arrangement is much less prone to deflection and false motion than the stock stud-mounted setup, improving rpm capability while allowing much higher spring loads.

850 Horsepower Big Block Chevy 012 13/24

11. Taking the load off the valvetrain at high rpm are Manley titanium retainers and locks, holding stout PAC #1247 springs installed at 2.050-inch.

850 Horsepower Big Block Chevy 013 14/24

12. A Dale Cubic-modified Holley 1250 Dominator carb works with an Edelbrock Super Victor intake to mix the air and fuel and send it to the generously sized intake ports.

850 Horsepower Big Block Chevy 014 15/24

13. The three-circuit carb was reworked internally by Dale Cubic and features their proprietary metering blocks. Also visible are the flanged boosters.

850 Horsepower Big Block Chevy 015 16/24

14. The Edelbrock Super Victor (PN 2927) intake has the capacity to feed a large-displacement Chevy big-block. The manifold was mostly as-delivered, with minor plenum blending being the only modification.

850 Horsepower Big Block Chevy 016 17/24

15. Fitted beneath the carb was a Wilson open manifold spacer. Spacers add plenum volume, changing the characteristics of the intake manifold and the power curve itself. This provides an easy tuning point for the induction system.

850 Horsepower Big Block Chevy 017 18/24

16. Up front you see an armada of MSD ignition components, including the HVC II coil, front-mounted billet distributor, and crank trigger. Note the Meziere electric water pump and Innovators West damper.

850 Horsepower Big Block Chevy 018 19/24

17. The ignition timing is fixed without a curve, handled by the rock-steady MSD crank trigger arrangement. This gives error and scatter-free ignition timing, and is adjusted by moving the pick-up unit on the graduated bracket.

850 Horsepower Big Block Chevy 019 20/24

18. The distributor itself, working with a crank trigger, is free of all timing duties. It simply routes the spark to the appropriate cylinder, and the only consideration is proper phasing. It is driven by a cogged belt from the crank.

850 Horsepower Big Block Chevy 020 21/24

19. Headers are from Dynatech, and feature stepped primary tubes with a merge collector comprising the secondary. Note the unusually long collector required to mate with the exhaust system in the dyno cell.

850 Horsepower Big Block Chevy 021 22/24

20. Contributing to the good looks of Eric’s Chevy big-block are these faux carbon-fiber valve covers. We have to say Roycroft’s Chevy was one well detailed piece.

850 Horsepower Big Block Chevy 022 23/24

21. On the dyno, the big Chevy produced a huge torque curve topping out at 777 lb-ft at just 4,900 rpm, while recording 851 hp at 6,500. Those are stout numbers for a single four-barrel Chevy big-block capable of running on pump gas.

850 Horsepower Big Block Chevy 023 24/24

22. The team of Eric Roycroft, Gerry Stone, and Dale Cubic had much to be proud of at the 2015 Engine Masters Challenge, earning a runner-up finish with a very basic combination.

Technical Specifications
Roycroft 566ci Chevy Big-Block
Builder: Eric Roycroft
Bore: 4.600 inch
Stroke: 4.250 inch
CID: 566 ci
Block: Dart
Deck height: 9.8 inches
Compression ratio: 11.4:1
Engine fasteners: Dart and ARP
Crankshaft: Scat
Camshaft: Comp solid roller
Cam journal: OEM
Timing chain: Jesel belt
Lifters: Lunati
Lifter diameter: 0.842 inch
Pushrods: Trend
Valvesprings: PAC 1247
Installed height: 2.050 inch
Retainers/locks: Manley titanium
Intake duration: 260 degrees @ 0.050
Intake lift: 0.792 inch
Exhaust duration: 260 degrees @ 0.050
Exhaust lift: 0.792 inch
Rocker arms: WW Engineering 1.8:1
Lobe separation: 104 degrees
Installed centerline: 104 degrees
Top ring: Total Seal 0.043
Second ring: Total Seal 0.043
Oil ring: Total Seal 3mm
Pistons: Diamond
Gas ports: Vertical
Main fasteners: Dart
Main bearings: King
Rods: Scat
Rod length: 6.350 inch
Rod bearings: King
Main bearing clearance: 0.0032 inch
Rod bearing clearance: 0.0027 inch
Cylinder heads: Pro Topline
Combustion chamber volume: 119 cc
Intake valve diameter: 2.300 inch
Exhaust valve diameter: 1.900 inch
Cylinder head gaskets: Fel-Pro composition
Piston quench clearance: 0.040 inch
Intake manifold: Edelbrock Super Victor
Carburetor: Dale Cubic 1250
Carb spacer: Wilson
Header: Dynatech
Ignition: MSD
Distributor: MSD front-mount
Spark plug wires: MSD
Damper: Innovators West
Water pump: Meziere
Oil pan: Morsoso
Oil pump: Melling
Fuel: VP 101 Unleaded
Engine oil: AMSOIL 5w20

Dyno Results
566 Chevy Big-Block: Built by Eric Roycroft
Tested At UNOH: SuperFlow DTS Powermark Dyno
RPM Torque Horsepower
3000 664 379
3100 682 403
3200 703 428
3300 714 449
3400 718 465
3500 718 479
3600 719 493
3700 717 505
3800 712 515
3900 710 527
4000 719 548
4100 736 575
4200 748 598
4300 757 620
4400 763 639
4500 767 657
4600 768 672
4700 769 688
4800 774 707
4900 777 725
5000 776 738
5100 774 752
5200 772 764
5300 768 775
5400 768 789
5500 766 803
5600 761 811
5700 758 822
5800 752 830
5900 744 835
6000 736 841
6100 725 842
6200 713 841
6300 704 844
6400 695 847
6500 687 851
6600 676 850
6700 663 846
6800 651 842
6900 637 836
7000 622 829

Sources

AMSOIL
Superior, WI 54880
800-956-5695
www.amsoil.com
Manley Performance Products
Lakewood, NJ 08701
732-905-3366
http://www.manleyperformance.com
Dart Machinery
Troy, MI 48084
248-362-1188
www.dartheads.com
VP Racing Fuels
San Antonio, TX 78265
210-635-7744
www.vpracingfuels.com
Wilson Manifolds
Ft. Lauderdale, FL
954-771-6216
http://www.wilsonmanifolds.com
Melling Engine Parts
Jackson, MI 49204
517-787-8172
http://www.melling.com
Meziere Enterprises
Escondido, CA 92029
800-208-1755
meziere
Innovators West
Salina, KS 67401
785-825-6166
http://www.innovatorswest.com
Pac Racing
Southfield, MI 48034
866-799-9417
http://www.racingsprings.com/
Moroso Performance Products
Guilford, CT 06437
203-453-6571
www.moroso.com
Jesel
Lakewood, NJ 08701
732-901-1800
www.jesel.com
King Engine Bearings
Cedar Grove, NJ 07009
800-772-3670
www.kingbearings.com
Scat Crankshafts
Redondo Beach, CA 90278
310-370-5501
www.scatcrankshafts.com
Federal-Mogul
Southfield, MI 48034
248-354-7700
www.federal-mogul.com
Dynatech Headers
Boonville, IN 47601
800-848-5850
http://www.dynatechheaders.com
Total Seal
Phoenix, AZ
(800) 874-2753
totalseal.com
Edelbrock
Torrance, CA 90503
310-781-2222
www.edelbrock.com
Diamond Racing Pistons
877-552-2112
http://www.diamondracing.net
Competition Cams
800-999-0853
http://www.compcams.com
MSD Ignition
915-857-5200
www.msdignition.com
ARP
Ventura, CA 93003
800-826-3045
www.ARP-BOLTS.COM

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