Shaver Specialty Service is a company known nationwide for their reputation in engine building. While the guys at Shaver build a wide variety of engines for everything from street to drag racing, these guys have gained special notoriety for their famed Chevrolet sprint car engines. Ron Shaver is no stranger to making horsepower, and to that point the big-block Chevrolet featured here was assembled to compete in our annual engine building competition, the 2006 Engine Masters Challenge. While Shaver's big-block proved to be the most powerful Chevrolet entry, it's interesting to note that to fit within the 434 cubic-inch displacement specification for the contest, Shaver's engine relied on a near stock production bore and stroke configuration. On that basis, this engine is essentially a traditional 427 Chevrolet engine bored 0.035-over. While that might be true, a deeper look at the combination shows that this engine is anything but ordinary. What does it take to make 700 hp from a 10.5:1 compression, pump gas, 427? A close examination of Shaver's engine reveals the details.
The Engine Masters Challenge is open to any traditional domestic V-8 engine type. We asked Shaver why he decided to build a big-block Chevy. He responded: "I had all the bits and looked at everything else. And, I'm a Chevy guy. I knew about that CHI Ford head and thought we could probably hang with it. Those Ford heads have a really small port, but it moves a lot of air. I thought we really had a shot with it, but got a little bamboozled by Kaase, because he and I did some preliminary running and we were really close. Except he wasn't letting all the cats out of the bag, while I had them all out on the floor and he shot 'em. But that won't happen again. I thought about running a small-block, but what discouraged me is that I didn't think I could get there without a rollover head. The reason I didn't go with a rollover head is because no one makes one with a standard exhaust pattern. That was a problem because I had to meet that criteria for the rules. I would have done better with my rollover motor, we knew that, but I couldn't get there from here with the manifold and exhaust port."
The Bottom EndWhile the trend in past Engine Masters' competitions seemed to favor smaller bores, the 427 Chevy was definitely an engine known for a large bore-to-stroke ratio. Shaver investigated the possibilities. As he explains: "We tried to go over-square and it just shrouded the valves so badly, we didn't think it would make it. I know from talking to other competitors, they were up against the same thing, so there was a limit on how much stroke could practically be put into it." Shaver selected a World Merlin iron block for his foundation, and filled it with some of the nicest parts in the industry.
The crank is a Bryant billet piece, and it's a work of art. Shaver related, "His cranks are the best in the world, I mean there are other nice cranks, but I grew up with him, so I'm a little biased-but they really are good cranks."
The main journals are standard big-block Chevrolet, and the rod journals are 2.100 inch. Unlike some competitors, Shaver didn't go crazy with journal size reduction. Shaver elaborated, "You don't need to with a lower speed engine. From testing, we've found the parasitic loss at 6,500 rpm is negligible. You really don't see a lot of that until the higher rpm, but when you go above 8,500 rpm it really starts going on the cube. From 7,800 to 8,000, the drag is still comparatively low, and then it really starts drawing the horsepower. I have a 50hp motor turning it, and it may draw 13 hp at 8,000 rpm; and by the time you get to 8,900 rpm, you're drawing 50 hp. So the drag starts to go up quick. There's a lot of stuff that goes on with the parasitic losses, but in the rpm range of this contest, from 2,500 to 6,500 rpm, it's not doing much."
Pistons are Mahle, and come with a phosphate coating, with a friction-reducing skirt coating. Shaver enthusiastically stated: "The Mahle piston is something, I have to say that it's really good."
The ring pack consists of Total Seal's regular 0.043-inch moly rings at the top, a cast-iron L-shaped scraper ring in the second groove, and SSU50 oil rings. Interestingly, Shaver uses a tighter ring gap on the second ring than the top: "Yeah, we're kind of old-school there and stay with the hottest ring bigger than the coldest ring."
We noticed a few close edges on the piston tops, and inquired about the quench clearance. Shaver disclosed: "We had the piston-to-head [clearance] running pretty tight, and it was slightly touching on a few edges, as can be seen by the marks on the pistons, but the actual quench was set at .042 inch."
Heads, Cam, InductionAs nice as the short-block may be, making big power with any engine relies on an equally impressive top-end package and a complimentary camshaft. By Shaver's description, the heads are exceptional, with moderately sized runners offering up staggering flow. These heads are fitted with large 2.300-inch intake valves, and 1.860-inch exhaust valves. The heads flow 375-380 cfm at .700-inch lift, and 350 cfm at .500 inches. Shaver gave us the lowdown: "The heads are Brodix raised oval ports CNC ported by Weldtech and then modified by HVH. We were afraid that we were already on the big side. The port size on the runners is 300 cc, and we were afraid that might be almost too big; and it ended up being too big, in my opinion. They're not huge for a big-block by any means, but our 408s are making almost 900 hp, and those heads are only 280cc port volume."
The manifold is a Brodix. Shaver elaborated on the induction: "HVH really modified the hell out of the Brodix intake. We used a Carb Shop 4150 Holley, with a fancy adapter that HVH made for us. I've got some really neat adapters and spacers that I tried, but this was the best overall."
A stout solid roller cam from Crane was also part of the plan, and an important player in the overall power-producing character of the engine. Commenting on the cam, Shaver told us, "We had a wider cam in it, and ran a 112 [degree] center, and it had about 210 to 212 psi of cranking pressure. With the 110 center we gained pressure and the engine was just a happier guy. The cam phasing was tried all over the place; an installed centerline of 106 degrees is where it ended up making the best average power." Shaver continued, "These engines are really sensitive to carburetors and manifolds; and again, the cam is a key. The lobe centers on the cam are really important. I think there is more left with another cam combination. We did try a few different cams, but I think we got going down the wrong avenue, because we were making big horsepower, and then we had to back up. We were at over 720 horses, and we finally backed up to about 700, and got our best average power that way."
For headers, Shaver ran a set of Hooker 2-inch primary headers, but as with the heads, Shaver would have liked to explore the potential of smaller ports. Shaver explained: "I'm not sure that I couldn't have made them smaller, but when you talk big-block in something you can buy, you'll find very little under two inches. I know some guys had very good success with 1 7/8-inch headers."
Any time you can make over 1.6 hp per cubic inch, you know you have a real engine on your hands. Making it on pump gas at only 6,500 rpm takes a real mastery of internal combustion science. Shaver has been doing it for years, and there are definitely things to learn by studying this man's combination.
|THE POWER NUMBERS |
|DTS ENGINE DYNO |
TESTED AT WORLD PRODUCTS
|RPM ||TQ ||HP |
|2,600 ||477 ||236 |
|2,800 ||489 ||261 |
|3,000 ||490 ||280 |
|3,200 ||489 ||298 |
|3,400 ||485 ||314 |
|3,600 ||478 ||328 |
|3,800 ||476 ||344 |
|4,000 ||488 ||372 |
|4,200 ||517 ||414 |
|4,400 ||545 ||457 |
|4,600 ||565 ||495 |
|RPM ||TQ ||HP |
|4,800 ||583 ||533 |
|5,000 ||590 ||562 |
|5,200 ||591 ||585 |
|5,400 ||594 ||611 |
|5,600 ||602 ||642 |
|5,800 ||606 ||669 |
|6,000 ||600 ||686 |
|6,200 ||585 ||690 |
|6,400 ||570 ||695 |
|6,500 ||563 ||697 |
What's A "Rollover" Head?It's one of the most effective modifications common in the old days when modifying small-block Chevrolet engines was giving those old iron heads a heavy dose of angle milling. Back then, choices in aftermarket heads were limited, and this approach had definite performance value, particularly in building race engines. Angle milling is done by tilting the head in the mill to take more material off the plug side of the head. With the Chevy's steep 23-degree factory valve angle, the chamber is deeper than most, and angle milling reduces the chamber volume much more effectively, while taking less material off the decks than flat milling. Much smaller final chamber volumes are possible. Angle milling also had the effect of rolling the axis of the heads, which helped straighten the valve angle, improving flow. The down side was extensive correction to the manifold flange, which would then need corrective milling to align with the manifold. The head bolts would usually need to be spot faced on the mill to correct the contact surface with the head fasteners, and sometimes the bolt holes themselves would need reworking to prevent binding.
These days, aftermarket manufactures are already wise to these tricks, and rollover heads refer to cylinder heads that are configured much like the old-school custom-angle mill pieces, with a shallower valve angle and smaller chambers. The difference is that these "rollover" heads are machined with the "rollover" valve-to-deck angle as part of the design, so the heads bolt-on without any special machining.
|VITAL SPECS: |
|SHAVER SPECIALTY SERVICE |
|434-INCH BIG-BLOCK CHEVROLET |
|Bore: ||4.285-inch |
|Stroke: ||3.750-inch |
|CID: ||434 cubic inches |
|Compression ratio: ||10.5:1 |
|Camshaft: ||Crane solid roller |
|Cam duration: ||256/260 degrees |
|@ 0.050-inch tappet rise |
|Valve lift: || .820/.780-inch |
|Rocker ratio: ||1.8:1 |
|Lobe separation: ||110 degrees |
|Installed centerline: ||106 degrees |
|Top ring: || .043-inch Total Seal |
|Top ring gap: || .016-inch |
|Second ring: ||1/16-inch Total Seal |
|Second ring gap: || .012-inch |
|Oil ring: ||3/16-inch (9-lb drag) |
|Piston: ||Mahle |
|Quench clearance: || .042-inch |
|Block: ||World |
|Crankshaft: ||Bryant, billet |
|Rods: ||Eagle 6.800-inch |
|Main journal: ||standard BBC |
|Rod journal: ||2.100-inch |
|Cylinder head: ||300cc Brodix oval raised port; |
Weldtech CNC; HVH
|Peak intake flow: ||375 cfm at .700 inch lift |
|Intake valve diameter: ||2.300-inch |
|Exhaust valve diameter: ||1.86-inch |
|Intake manifold: ||Brodix, Ported by HVH |
|Carburetor: ||Carb Shop Holley 4150 |
|Carb spacer: ||HVH |
|Header: ||Hooker 2-inch primary |
|Ignition: ||MSD |